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Olejarz A, Faltusová M, Börger L, Güldenpfennig J, Jarský V, Ježek M, Mortlock E, Silovský V, Podgórski T. Worse sleep and increased energy expenditure yet no movement changes in sub-urban wild boar experiencing an influx of human visitors (anthropulse) during the COVID-19 pandemic. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 879:163106. [PMID: 36966827 PMCID: PMC10038670 DOI: 10.1016/j.scitotenv.2023.163106] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/29/2022] [Revised: 03/14/2023] [Accepted: 03/23/2023] [Indexed: 05/17/2023]
Abstract
Expansion of urban areas, landscape transformation and increasing human outdoor activities strongly affect wildlife behaviour. The outbreak of the COVID-19 pandemic in particular led to drastic changes in human behaviour, exposing wildlife around the world to either reduced or increased human presence, potentially altering animal behaviour. Here, we investigate behavioural responses of wild boar (Sus scrofa) to changing numbers of human visitors to a suburban forest near Prague, Czech Republic, during the first 2.5 years of the COVID-19 epidemic (April 2019-November 2021). We used bio-logging and movement data of 63 GPS-collared wild boar and human visitation data based on an automatic counter installed in the field. We hypothesised that higher levels of human leisure activity will have a disturbing effect on wild boar behaviour manifested in increased movements and ranging, energy spent, and disrupted sleep patterns. Interestingly, whilst the number of people visiting the forest varied by two orders of magnitude (from 36 to 3431 people weekly), even high levels of human presence (>2000 visitors per week) did not affect weekly distance travelled, home range size, and maximum displacement of wild boar. Instead, individuals spent 41 % more energy at high levels of human presence (>2000 visitors per week), with more erratic sleep patterns, characterised by shorter and more frequent sleeping bouts. Our results highlight multifaceted effects of increased human activities ('anthropulses'), such as those related to COVID-19 countermeasures, on animal behaviour. High human pressure may not affect animal movements or habitat use, especially in highly adaptable species such as wild boar, but may disrupt animal activity rhythms, with potentially detrimental fitness consequences. Such subtle behavioural responses can be overlooked if using only standard tracking technology.
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Affiliation(s)
- Astrid Olejarz
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic.
| | - Monika Faltusová
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic
| | - Luca Börger
- Department of Biosciences, Swansea University, Singleton Park, Swansea SA2 8PP, Wales, UK
| | - Justine Güldenpfennig
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic
| | - Vilém Jarský
- Department of Forestry and Wood Economics, Faculty of Forestry and Wood Sciences, Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic
| | - Miloš Ježek
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic
| | - Euan Mortlock
- School of Biological Sciences, Queen's University Belfast, 19 Chlorine Gardens, Belfast BT95DL, Northern Ireland, UK
| | - Václav Silovský
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic
| | - Tomasz Podgórski
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences,Czech University of Life Sciences, Kamýcká 129, Prague 6-Suchdol, 165 00, Czech Republic; Mammal Research Institute, Polish Academy of Sciences, Stoczek 1, 17-230 Białowieża, Poland
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2
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Kendall-Bar JM, Williams TM, Mukherji R, Lozano DA, Pitman JK, Holser RR, Keates T, Beltran RS, Robinson PW, Crocker DE, Adachi T, Lyamin OI, Vyssotski AL, Costa DP. Brain activity of diving seals reveals short sleep cycles at depth. Science 2023; 380:260-265. [PMID: 37079694 DOI: 10.1126/science.adf0566] [Citation(s) in RCA: 13] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/22/2023]
Abstract
Sleep is a crucial part of the daily activity patterns of mammals. However, in marine species that spend months or entire lifetimes at sea, the location, timing, and duration of sleep may be constrained. To understand how marine mammals satisfy their daily sleep requirements while at sea, we monitored electroencephalographic activity in wild northern elephant seals (Mirounga angustirostris) diving in Monterey Bay, California. Brain-wave patterns showed that seals took short (less than 20 minutes) naps while diving (maximum depth 377 meters; 104 sleeping dives). Linking these patterns to accelerometry and the time-depth profiles of 334 free-ranging seals (514,406 sleeping dives) revealed a North Pacific sleepscape in which seals averaged only 2 hours of sleep per day for 7 months, rivaling the record for the least sleep among all mammals, which is currently held by the African elephant (about 2 hours per day).
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Affiliation(s)
- Jessica M Kendall-Bar
- Scripps Institution of Oceanography, University of California San Diego, San Diego, CA, USA
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Terrie M Williams
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Ritika Mukherji
- Department of Neuroscience, University of Oxford, Oxford, UK
| | - Daniel A Lozano
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | | | - Rachel R Holser
- Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Theresa Keates
- Ocean Sciences Department, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Roxanne S Beltran
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Patrick W Robinson
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Daniel E Crocker
- Department of Biology, Sonoma State University, Rohnert Park, CA, USA
| | - Taiki Adachi
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
| | - Oleg I Lyamin
- Semel Institute for Neuroscience and Human Behavior, University of California Los Angeles, Los Angeles, CA, USA
- A.N. Severtsov Institute of Ecology and Evolution, Moscow, Russia
| | - Alexei L Vyssotski
- Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Daniel P Costa
- Ecology and Evolutionary Biology, University of California Santa Cruz, Santa Cruz, CA, USA
- Institute of Marine Sciences, University of California Santa Cruz, Santa Cruz, CA, USA
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3
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Harding CD, Yovel Y, Peirson SN, Hackett TD, Vyazovskiy VV. Re-examining extreme sleep duration in bats: implications for sleep phylogeny, ecology, and function. Sleep 2022; 45:zsac064. [PMID: 35279722 PMCID: PMC9366634 DOI: 10.1093/sleep/zsac064] [Citation(s) in RCA: 9] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2021] [Revised: 02/17/2022] [Indexed: 11/23/2022] Open
Abstract
Bats, quoted as sleeping for up to 20 h a day, are an often used example of extreme sleep duration amongst mammals. Given that duration has historically been one of the primary metrics featured in comparative studies of sleep, it is important that species specific sleep durations are well founded. Here, we re-examined the evidence for the characterization of bats as extreme sleepers and discuss whether it provides a useful representation of the sleep behavior of Chiroptera. Although there are a wealth of activity data to suggest that the diurnal cycle of bats is dominated by rest, estimates of sleep time generated from electrophysiological analyses suggest considerable interspecific variation, ranging from 83% to a more moderate 61% of the 24 h day spent asleep. Temperature-dependent changes in the duration and electroencephalographic profile of sleep suggest that bats represent a unique model for investigating the relationship between sleep and torpor. Further sources of intra-specific variation in sleep duration, including the impact of artificial laboratory environments and sleep intensity, remain unexplored. Future studies conducted in naturalistic environments, using larger sample sizes and relying on a pre-determined set of defining criteria will undoubtedly provide novel insights into sleep in bats and other species.
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Affiliation(s)
- Christian D Harding
- Department of Physiology Anatomy and Genetics, Sir Jules Thorn Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
| | - Yossi Yovel
- School of Zoology, Faculty of Life Sciences, Tel-Aviv University, Tel-Aviv, Israel
- Sagol School of Neuroscience, Tel-Aviv University, Tel-Aviv, Israel
| | - Stuart N Peirson
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
- Nuffield Department of Clinical Neurosciences, Sir Jules Thorn Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, UK
| | | | - Vladyslav V Vyazovskiy
- Department of Physiology Anatomy and Genetics, Sir Jules Thorn Sleep and Circadian Neuroscience Institute, University of Oxford, Oxford, UK
- The Kavli Institute for Nanoscience Discovery, Oxford, UK
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4
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Smeltzer EA, Stead SM, Li MF, Samson D, Kumpan LT, Teichroeb JA. Social sleepers: The effects of social status on sleep in terrestrial mammals. Horm Behav 2022; 143:105181. [PMID: 35594742 DOI: 10.1016/j.yhbeh.2022.105181] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 04/12/2022] [Accepted: 04/22/2022] [Indexed: 11/18/2022]
Abstract
Social status among group-living mammals can impact access to resources, such as water, food, social support, and mating opportunities, and this differential access to resources can have fitness consequences. Here, we propose that an animal's social status impacts their access to sleep opportunities, as social status may predict when an animal sleeps, where they sleep, who they sleep with, and how well they sleep. Our review of terrestrial mammals examines how sleep architecture and intensity may be impacted by (1) sleeping conditions and (2) the social experience during wakefulness. Sleeping positions vary in thermoregulatory properties, protection from predators, and exposure to parasites. Thus, if dominant individuals have priority of access to sleeping positions, they may benefit from higher quality sleeping conditions and, in turn, better sleep. With respect to waking experiences, we discuss the impacts of stress on sleep, as it has been established that specific social statuses can be characterized by stress-related physiological profiles. While much research has focused on how dominance hierarchies impact access to resources like food and mating opportunities, differential access to sleep opportunities among mammals has been largely ignored despite its potential fitness consequences.
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Affiliation(s)
- E A Smeltzer
- Department of Anthropology, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - S M Stead
- Department of Anthropology, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada.
| | - M F Li
- Department of Anthropology, University of Toronto, 19 Russell St., Toronto, Ontario M5S 2S2, Canada
| | - D Samson
- Department of Anthropology, University of Toronto Mississauga, 3359 Mississauga Rd., Mississauga, Ontario L5L 1C6, Canada
| | - L T Kumpan
- Department of Anthropology, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
| | - J A Teichroeb
- Department of Anthropology, University of Toronto Scarborough, 1265 Military Trail, Scarborough, Ontario M1C 1A4, Canada
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5
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Reicher V, Bálint A, Újváry D, Gácsi M. Non-invasive sleep EEG measurement in hand raised wolves. Sci Rep 2022; 12:9792. [PMID: 35697910 PMCID: PMC9191399 DOI: 10.1038/s41598-022-13643-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2021] [Accepted: 05/17/2022] [Indexed: 11/10/2022] Open
Abstract
Sleep research greatly benefits from comparative studies to understand the underlying physiological and environmental factors affecting the different features of sleep, also informing us about the possible evolutionary changes shaping them. Recently, the domestic dog became an exceedingly valuable model species in sleep studies, as the use of non-invasive polysomnography methodologies enables direct comparison with human sleep data. In this study, we applied the same polysomnography protocol to record the sleep of dog’s closest wild relative, the wolf. We measured the sleep of seven captive (six young and one senior), extensively socialized wolves using a fully non-invasive sleep EEG methodology, originally developed for family dogs. We provide the first descriptive analysis of the sleep macrostructure and NREM spectral power density of wolves using a completely non-invasive methodology. For (non-statistical) comparison, we included the same sleep data of similarly aged dogs. Although our sample size was inadequate to perform statistical analyses, we suggest that it may form the basis of an international, multi-site collection of similar samples using our methodology, allowing for generalizable, unbiased conclusions. As we managed to register both macrostructural and spectral sleep data, our procedure appears to be suitable for collecting valid data in other species too, increasing the comparability of non-invasive sleep studies.
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Affiliation(s)
- Vivien Reicher
- Department of Ethology, Doctoral School of Biology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary. .,MTA-ELTE Comparative Ethology Research Group, Budapest, Hungary.
| | - Anna Bálint
- MTA-ELTE Comparative Ethology Research Group, Budapest, Hungary
| | - Dóra Újváry
- Department of Ethology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
| | - Márta Gácsi
- MTA-ELTE Comparative Ethology Research Group, Budapest, Hungary.,Department of Ethology, Institute of Biology, Eötvös Loránd University, Budapest, Hungary
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6
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Loftus JC, Harel R, Núñez CL, Crofoot MC. Ecological and social pressures interfere with homeostatic sleep regulation in the wild. eLife 2022; 11:73695. [PMID: 35229719 PMCID: PMC8887896 DOI: 10.7554/elife.73695] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2021] [Accepted: 01/18/2022] [Indexed: 12/12/2022] Open
Abstract
Sleep is fundamental to the health and fitness of all animals. The physiological importance of sleep is underscored by the central role of homeostasis in determining sleep investment – following periods of sleep deprivation, individuals experience longer and more intense sleep bouts. Yet, most sleep research has been conducted in highly controlled settings, removed from evolutionarily relevant contexts that may hinder the maintenance of sleep homeostasis. Using triaxial accelerometry and GPS to track the sleep patterns of a group of wild baboons (Papio anubis), we found that ecological and social pressures indeed interfere with homeostatic sleep regulation. Baboons sacrificed time spent sleeping when in less familiar locations and when sleeping in proximity to more group-mates, regardless of how long they had slept the prior night or how much they had physically exerted themselves the preceding day. Further, they did not appear to compensate for lost sleep via more intense sleep bouts. We found that the collective dynamics characteristic of social animal groups persist into the sleep period, as baboons exhibited synchronized patterns of waking throughout the night, particularly with nearby group-mates. Thus, for animals whose fitness depends critically on avoiding predation and developing social relationships, maintaining sleep homeostasis may be only secondary to remaining vigilant when sleeping in risky habitats and interacting with group-mates during the night. Our results highlight the importance of studying sleep in ecologically relevant contexts, where the adaptive function of sleep patterns directly reflects the complex trade-offs that have guided its evolution.
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Affiliation(s)
- J Carter Loftus
- Department of Anthropology, University of California, Davis, Davis, United States.,Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Konstanz, Germany.,Department of Biology, University of Konstanz, Konstanz, Germany.,Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany.,Mpala Research Centre, Nanyuki, Kenya.,Animal Behavior Graduate Group, University of California, Davis, Davis, United States
| | - Roi Harel
- Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Konstanz, Germany.,Mpala Research Centre, Nanyuki, Kenya
| | - Chase L Núñez
- Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Konstanz, Germany.,Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany.,Mpala Research Centre, Nanyuki, Kenya
| | - Margaret C Crofoot
- Department of Anthropology, University of California, Davis, Davis, United States.,Department for the Ecology of Animal Societies, Max Planck Institute of Animal Behavior, Konstanz, Germany.,Department of Biology, University of Konstanz, Konstanz, Germany.,Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Konstanz, Germany.,Mpala Research Centre, Nanyuki, Kenya.,Animal Behavior Graduate Group, University of California, Davis, Davis, United States
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7
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Shukla I, Kilpatrick AM, Beltran RS. Variation in resting strategies across trophic levels and habitats in mammals. Ecol Evol 2021; 11:14405-14415. [PMID: 34765115 PMCID: PMC8571619 DOI: 10.1002/ece3.8073] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2021] [Revised: 07/26/2021] [Accepted: 08/18/2021] [Indexed: 12/30/2022] Open
Abstract
Mammals must carefully balance rest with other behaviors that influence fitness (e.g., foraging, finding a mate) while minimizing predation risk. However, factors influencing resting strategies and the degree to which resting strategies are driven by the activities of predators and/or prey remain largely unknown. Our goal was to examine how mammalian resting strategies varied with trophic level, body mass, and habitat. We reviewed findings from 127 publications and classified the resting strategies of terrestrial and aquatic mammalian species into three categories: social (e.g., resting in groups), temporal (e.g., resting during the day), or spatial (e.g., resting in burrows). Temporal strategies were most common (54% of cases), but the prevalence of strategies varied with body mass and among trophic levels. Specifically, lower trophic levels and smaller species such as rodents and lagomorphs used more spatial and social resting strategies, whereas top predators and larger species used mostly temporal resting strategies. Resting strategies also varied among habitat types (e.g., rainforest vs. grassland), but this was primarily because closely related species shared both habitats and resting strategies. Human presence also affected resting strategies at all trophic levels but most strongly influenced top predators through shifts in rest timing. Human-induced behavioral changes in rest patterns cascade to modify behaviors across multiple trophic levels. These findings advance our fundamental understanding of natural history and ecology in wild animals and provide a roadmap for future comparative studies.
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Affiliation(s)
- Ishana Shukla
- Ecology and Evolutionary BiologyUniversity of CaliforniaSanta CruzCAUSA
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8
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Mohanty NP, Wagener C, Herrel A, Thaker M. The ecology of sleep in non-avian reptiles. Biol Rev Camb Philos Soc 2021; 97:505-526. [PMID: 34708504 DOI: 10.1111/brv.12808] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2021] [Revised: 10/10/2021] [Accepted: 10/18/2021] [Indexed: 01/10/2023]
Abstract
Sleep is ubiquitous in the animal kingdom and yet displays considerable variation in its extent and form in the wild. Ecological factors, such as predation, competition, and microclimate, therefore are likely to play a strong role in shaping characteristics of sleep. Despite the potential for ecological factors to influence various aspects of sleep, the ecological context of sleep in non-avian reptiles remains understudied and without systematic direction. In this review, we examine multiple aspects of reptilian sleep, including (i) habitat selection (sleep sites and their spatio-temporal distribution), (ii) individual-level traits, such as behaviour (sleep postures), morphology (limb morphometrics and body colour), and physiology (sleep architecture), as well as (iii) inter-individual interactions (intra- and inter-specific). Throughout, we discuss the evidence of predation, competition, and thermoregulation in influencing sleep traits and the possible evolutionary consequences of these sleep traits for reptile sociality, morphological specialisation, and habitat partitioning. We also review the ways in which sleep ecology interacts with urbanisation, biological invasions, and climate change. Overall, we not only provide a systematic evaluation of the conceptual and taxonomic biases in the existing literature on reptilian sleep, but also use this opportunity to organise the various ecological hypotheses for sleep characteristics. By highlighting the gaps and providing a prospectus of research directions, our review sets the stage for understanding sleep ecology in the natural world.
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Affiliation(s)
- Nitya P Mohanty
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India
| | - Carla Wagener
- Centre for Invasion Biology, Department of Botany and Zoology, Stellenbosch University, Stellenbosch, Western Cape, 7600, South Africa
| | - Anthony Herrel
- Département Adaptations du Vivant, MECADEV UMR7179 CNRS/MNHN, Paris, France
| | - Maria Thaker
- Centre for Ecological Sciences, Indian Institute of Science, Bangalore, 560 012, India
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9
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Castro-Sa MJ, Dias-Silva RH, Barnett AA. Cathemeral activity by brown-throated three-toed sloths (Bradypus variegatus) in central Amazonian flooded igapó forests. CAN J ZOOL 2021. [DOI: 10.1139/cjz-2020-0177] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Both biotic and abiotic factors are important for maintaining the activity cycles of animals and may determine the most advantageous periods for eating, moving, and sleeping. Although the solar day–night cycle is among the most central of abiotic variables, a number of species are active both day and night. Three-toed sloth (genus Bradypus Linnaeus, 1758) populations across the Neotropics show this pattern, with activity occurring at various times within the 24 h cycle. In the current study, we used radio-tracking techniques to investigate the daily temporal patterning of brown-throated three-toed sloth (Bradypus variegatus Schinz, 1825) displacement in Amazonian flooded igapó forest and compared the results with populations studied in other habitats. We concluded that igapó sloths are cathemeral, and discussed that environmental temperature, nutritional needs and the presence of predators may be the main factors influencing their activity pattern.
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Affiliation(s)
- Matheus J. Castro-Sa
- Ecology Post-graduate Program, National Amazon Research Institute, Avenida André Araújo, 2.936 - Petrópolis, Manaus, Amazonas, Brazil
| | - Renann H.P. Dias-Silva
- Zoology Post-graduate Program, Universidade Federal do Amazonas, Avenida Gal. Rodrigo Otávio Jordão Ramos, 3000, Sector South Manaus, Amazonas, Brazil
| | - Adrian A. Barnett
- Amazon Mammals Research Group, National Amazon Research Institute, Avenida André Araújo, 2.936 - Petrópolis, Manaus, Amazonas, Brazil
- Zoology Department, Federal University of Pernambuco, Recife, Pernambuco, Brazil
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10
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Harrison XA. A brief introduction to the analysis of time-series data from biologging studies. Philos Trans R Soc Lond B Biol Sci 2021; 376:20200227. [PMID: 34176325 PMCID: PMC8237163 DOI: 10.1098/rstb.2020.0227] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/29/2021] [Indexed: 12/24/2022] Open
Abstract
Recent advances in tagging and biologging technology have yielded unprecedented insights into wild animal physiology. However, time-series data from such wild tracking studies present numerous analytical challenges owing to their unique nature, often exhibiting strong autocorrelation within and among samples, low samples sizes and complicated random effect structures. Gleaning robust quantitative estimates from these physiological data, and, therefore, accurate insights into the life histories of the animals they pertain to, requires careful and thoughtful application of existing statistical tools. Using a combination of both simulated and real datasets, I highlight the key pitfalls associated with analysing physiological data from wild monitoring studies, and investigate issues of optimal study design, statistical power, and model precision and accuracy. I also recommend best practice approaches for dealing with their inherent limitations. This work will provide a concise, accessible roadmap for researchers looking to maximize the yield of information from complex and hard-won biologging datasets. This article is part of the theme issue 'Measuring physiology in free-living animals (Part II)'.
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Affiliation(s)
- Xavier A. Harrison
- Centre for Ecology and Conservation, University of Exeter, Penryn TR10 9FE, UK
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11
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Williams CL, Hindle AG. Field Physiology: Studying Organismal Function in the Natural Environment. Compr Physiol 2021; 11:1979-2015. [PMID: 34190338 DOI: 10.1002/cphy.c200005] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
Continuous physiological measurements collected in field settings are essential to understand baseline, free-ranging physiology, physiological range and variability, and the physiological responses of organisms to disturbances. This article presents a current summary of the available technologies to continuously measure the direct physiological parameters in the field at high-resolution/instantaneous timescales from freely behaving animals. There is a particular focus on advantages versus disadvantages of available methods as well as emerging technologies "on the horizon" that may have been validated in captive or laboratory-based scenarios but have yet to be applied in the wild. Systems to record physiological variables from free-ranging animals are reviewed, including radio (VHF/UFH) telemetry, acoustic telemetry, and dataloggers. Physiological parameters that have been continuously measured in the field are addressed in seven sections including heart rate and electrocardiography (ECG); electromyography (EMG); electroencephalography (EEG); body temperature; respiratory, blood, and muscle oxygen; gastric pH and motility; and blood pressure and flow. The primary focal sections are heart rate and temperature as these can be, and have been, extensively studied in free-ranging organisms. Predicted aspects of future innovation in physiological monitoring are also discussed. The article concludes with an overview of best practices and points to consider regarding experimental designs, cautions, and effects on animals. © 2021 American Physiological Society. Compr Physiol 11:1979-2015, 2021.
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Affiliation(s)
- Cassondra L Williams
- National Marine Mammal Foundation, San Diego, California, USA.,Department of Ecology and Evolutionary Biology, School of Biological Science, University of California Irvine, Irvine, California, USA
| | - Allyson G Hindle
- School of Life Sciences, University of Nevada Las Vegas, Las Vegas, Nevada, USA
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12
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Lyamin OI, Kibalnikov AS, Siegel JM. Sleep in ostrich chicks (Struthio camelus). Sleep 2021; 44:6010143. [PMID: 33249508 DOI: 10.1093/sleep/zsaa259] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 11/03/2020] [Indexed: 11/12/2022] Open
Abstract
It has been reported that adult ostriches displayed the longest episodes of rapid eye movement (REM) sleep (up to 5 min) and more REM sleep (24% of the nighttime) than any other bird species. If the mammalian ontogenetic trend exists in the ostrich, then the amounts of REM and the duration of sleep episodes in young ostriches may be greater than those reported in adults. We investigated sleep in 1.5-3.5 month old ostrich chicks. Recordings were conducted during nighttime (20:00-08:00), the main sleep period in ostriches, which are diurnal. The polygrams were scored in 4-s epochs for waking, non-rapid eye movement (NREM) sleep and REM sleep, as in other bird studies. REM sleep in ostrich chicks occurred during both cortical EEG activation and during slow waves, as was described in adult ostriches. The chicks spent 69.3% ± 1.5% of the night in NREM sleep. REM sleep occupied 14.1% ± 1.8% of the night or 16.8% ± 2.0% of nighttime sleep. Episodes of REM sleep lasted on average 10 ± 1 s and ranged between 4 and 40 s. Therefore, the total amount and duration of REM sleep episodes in ostrich chicks were substantially smaller than reported in adult ostriches while the amounts of NREM sleep did not greatly differ. The developmental profile of REM sleep ontogenesis in the ostrich may be remarkably different from what has been reported in all studied mammals and birds.
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Affiliation(s)
- Oleg I Lyamin
- Department of Psychiatry, University of California Los Angeles, Los Angeles, CA.,Greater Los Angeles Healthcare System, North Hills, CA.,A.N. Severtsov Institute of Ecology and Evolution, Russian Academy of Sciences, Moscow, Russia
| | | | - Jerome M Siegel
- Department of Psychiatry, University of California Los Angeles, Los Angeles, CA.,Greater Los Angeles Healthcare System, North Hills, CA
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Sleep in two free-roaming blue wildebeest ( Connochaetes taurinus), with observations on the agreement of polysomnographic and actigraphic techniques. IBRO Neurosci Rep 2021; 10:142-152. [PMID: 34179868 PMCID: PMC8211919 DOI: 10.1016/j.ibneur.2021.02.005] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2020] [Accepted: 02/09/2021] [Indexed: 12/28/2022] Open
Abstract
Most studies examining sleep in mammals are done under controlled conditions in laboratory/zoological facilities with few studies being conducted in their natural environment. It is not always possible to record sleep polysomnographically (PSG) from animals in their natural environments, as PSG is invasive, requiring the surgical implantation of electrodes on the surface of the brain. In contrast, actigraphy (ACT) has been shown to be a minimally-invasive method to objectively measure overall sleep times in some mammals, although not revealing specific sleep states. The aim of this study is two-fold, first, to measure sleep polysomnographically in free-roaming blue wildebeest (Connochaetes taurinus) under the most natural conditions possible, and second, to establish the degree of concordance between ACT and PSG recordings undertaken simultaneously in the same individuals. Here we examined sleep in the blue wildebeest, in a naturalistic setting, using both polysomnography (PSG) and actigraphy (ACT). PSG showed that total sleep time (TST) in the blue wildebeest for a 24-h period was 4.53 h (±0.12 h), 4.26 h (±0.11 h) spent in slow wave (non-REM) sleep and 0.28 h (±0.01 h) spent in rapid eye movement (REM) sleep, with 19.47 h (±0.12 h) spent in Wake. ACT showed that the blue wildebeest spent 19.23 h (±0.18 h) Active and 4.77 h (±0.18 h) Inactive. For both animals studied, a fair agreement between the two techniques for sleep scoring was observed, with approximately 45% of corresponding epochs analyzed being scored as both sleep (using PSG) and inactive (using ACT).
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Iotchev IB, Kubinyi E. Shared and unique features of mammalian sleep spindles - insights from new and old animal models. Biol Rev Camb Philos Soc 2021; 96:1021-1034. [PMID: 33533183 DOI: 10.1111/brv.12688] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2020] [Revised: 01/19/2021] [Accepted: 01/20/2021] [Indexed: 11/29/2022]
Abstract
Sleep spindles are phasic events observed in mammalian non-rapid eye movement sleep. They are relevant today in the study of memory consolidation, sleep quality, mental health and ageing. We argue that our advanced understanding of their mechanisms has not exhausted the utility and need for animal model work. This is both because some topics, like cognitive ageing, have not yet been addressed sufficiently in comparative efforts and because the evolutionary history of this oscillation is still poorly understood. Comparisons across species often are either limited to referencing the classical cat and rodent models, or are over-inclusive, uncritically including reports of sleep spindles in rarely studied animals. In this review, we discuss the emergence of new (dog and sheep) models for sleep spindles and compare the strengths and shortcomings of new and old models based on the three validation criteria for animal models - face, predictive, and construct validity. We conclude that an emphasis on cognitive ageing might dictate the future of comparative sleep spindle studies, a development that is already becoming visible in studies on dogs. Moreover, reconstructing the evolutionary history of sleep spindles will require more stringent criteria for their identification, across more species. In particular, a stronger emphasis on construct and predictive validity can help verify if spindle-like events in other species are actual sleep spindles. Work in accordance with such stricter validation suggests that sleep spindles display more universally shared features, like defining frequency, than previously thought.
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Affiliation(s)
- Ivaylo Borislavov Iotchev
- Department of Ethology, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest, 1117, Hungary
| | - Eniko Kubinyi
- Department of Ethology, ELTE Eötvös Loránd University, Pázmány Péter sétány 1/C, Budapest, 1117, Hungary
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de Miranda EB, Kenup CF, Campbell-Thompson E, Vargas FH, Muela A, Watson R, Peres CA, Downs CT. High moon brightness and low ambient temperatures affect sloth predation by harpy eagles. PeerJ 2020; 8:e9756. [PMID: 32913676 PMCID: PMC7456529 DOI: 10.7717/peerj.9756] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2020] [Accepted: 07/28/2020] [Indexed: 11/20/2022] Open
Abstract
BACKGROUND Climate plays a key role in the life histories of tropical vertebrates. However, tropical forests are only weakly seasonal compared with temperate and boreal regions. For species with limited ability to control core body temperature, even mild climatic variation can determine major behavioural outcomes, such as foraging and predator avoidance. In tropical forests, sloths are the arboreal vertebrate attaining the greatest biomass density, but their capacity to regulate body temperature is limited, relying on behavioural adaptations to thermoregulate. Sloths are largely or strictly nocturnal, and depend on crypsis to avoid predation. The harpy eagle (Harpia harpyja) is a sloth-specialist and exerts strong top-down control over its prey species. Yet the role of environmental variables on the regulation of predator-prey interactions between sloths and harpy eagles are unknown. The harpy eagle is considered Near Threatened. This motivated a comprehensive effort to reintroduce this species into parts of Mesoamerica. This effort incidentally enabled us to understand the prey profile of harpy eagles over multiple seasons. METHODS Our study was conducted between 2003 and 2009 at Soberanía National Park, Panamá. Telemetered harpy eagles were seen hunting and feeding on individual prey species. For each predation event, field assistants systematically recorded the species killed. We analysed the effects of climatic conditions and vegetation phenology on the prey species profile of harpy eagles using generalised linear mixed models. RESULTS Here we show that sloth predation by harpy eagles was negatively affected by nocturnal ambient light (i.e. bright moonshine) and positively affected by seasonally cool temperatures. We suggest that the first ensured low detectability conditions for sloths foraging at night and the second posed a thermally unsuitable climate that forced sloths to forage under riskier daylight. We showed that even moderate seasonal variation in temperature can influence the relationship between a keystone tropical forest predator and a dominant prey item. Therefore, predator-prey ecology in the tropics can be modulated by subtle changes in environmental conditions. The seasonal effects shown here suggest important demographic consequences for sloths, which are under top-down regulation from harpy eagle predation, perhaps limiting their geographic distribution at higher latitudes.
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Affiliation(s)
- Everton B.P. de Miranda
- School of Life Sciences, Centre for Functional Biodiversity, University of KwaZulu-Natal, Pietermaritzburg, Pietermaritzburg, KwaZulu-Natal, South Africa
| | - Caio F. Kenup
- Wildlife and Ecology Group, Massey University, Palmerston North, New Zealand
| | | | | | | | | | - Carlos A. Peres
- School of Environmental Sciences, University of East Anglia, Norwich, UK
- Departamento de Sistemática e Ecologia, Universidade Federal da Paraíba, João Pessoa, Brazil
| | - Colleen T. Downs
- School of Life Sciences, Centre for Functional Biodiversity, University of KwaZulu-Natal, Pietermaritzburg, Pietermaritzburg, KwaZulu-Natal, South Africa
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Ungurean G, van der Meij J, Rattenborg NC, Lesku JA. Evolution and plasticity of sleep. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2019.12.013] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
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17
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Reinhardt KD. Wild primate sleep: understanding sleep in an ecological context. CURRENT OPINION IN PHYSIOLOGY 2020. [DOI: 10.1016/j.cophys.2020.04.002] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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van Hasselt SJ, Rusche M, Vyssotski AL, Verhulst S, Rattenborg NC, Meerlo P. Sleep Time in the European Starling Is Strongly Affected by Night Length and Moon Phase. Curr Biol 2020; 30:1664-1671.e2. [PMID: 32197088 DOI: 10.1016/j.cub.2020.02.052] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2019] [Revised: 02/13/2020] [Accepted: 02/18/2020] [Indexed: 12/21/2022]
Abstract
Sleep is considered to be of crucial importance for performance and health, yet much of what we know about sleep is based on studies in a few mammalian model species under strictly controlled laboratory conditions. Data on sleep in different species under more natural conditions may yield new insights in the regulation and functions of sleep. We therefore performed a study with miniature electroencephalogram (EEG) data loggers in starlings under semi-natural conditions, group housed in a large outdoor enclosure with natural temperature and light. The birds showed a striking 5-h difference in the daily amount of non-rapid-eye-movement (NREM) sleep between winter and summer. This variation in the amount of NREM sleep was best explained by night length. Most sleep occurred during the night, but when summer nights became short, the animals displayed mid-day naps. The decay of NREM sleep spectral power in the slow-wave range (1.1-4.3 Hz) was steeper in the short nights than in the longer nights, which suggests that birds in summer have higher sleep pressure. Additionally, sleep was affected by moon phase, with 2 h of NREM sleep less during full moon. The starlings displayed very little rapid-eye-movement (REM) sleep, adding up to 1.3% of total sleep time. In conclusion, this study demonstrates a pronounced phenotypical flexibility in sleep in starlings under semi-natural conditions and shows that environmental factors have a major impact on the organization of sleep and wakefulness.
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Affiliation(s)
- Sjoerd J van Hasselt
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 Groningen, the Netherlands
| | - Maria Rusche
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 Groningen, the Netherlands; Avian Sleep Group, Max Planck Institute for Ornithology, Haus 5, Seewiesen 82319, Germany
| | - Alexei L Vyssotski
- Institute of Neuroinformatics, University of Zurich, Winterthurerstr. 190, 8057 Zurich, Switzerland
| | - Simon Verhulst
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 Groningen, the Netherlands
| | - Niels C Rattenborg
- Avian Sleep Group, Max Planck Institute for Ornithology, Haus 5, Seewiesen 82319, Germany
| | - Peter Meerlo
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, Nijenborgh 7, 9747 Groningen, the Netherlands.
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Characterizing Sleep Spindles in Sheep. eNeuro 2020; 7:ENEURO.0410-19.2020. [PMID: 32122958 PMCID: PMC7082130 DOI: 10.1523/eneuro.0410-19.2020] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2019] [Revised: 01/13/2020] [Accepted: 01/14/2020] [Indexed: 01/10/2023] Open
Abstract
Sleep spindles are distinctive transient patterns of brain activity that typically occur during non-rapid eye movement (NREM) sleep in humans and other mammals. Thought to be important for the consolidation of learning, they may also be useful for indicating the progression of aging and neurodegenerative diseases. The aim of this study was to characterize sleep spindles in sheep (Ovis aries). We recorded electroencephalographs wirelessly from six sheep over a continuous period containing 2 nights and a day. We detected and characterized spindles using an automated algorithm. We found that sheep sleep spindles fell within the classical range seen in humans (10–16 Hz), but we did not see a further separation into fast and slow bands. Spindles were detected predominantly during NREM sleep. Spindle characteristics (frequency, duration, density, topography) varied between individuals, but were similar within individuals between nights. Spindles that occurred during NREM sleep in daytime were indistinguishable from those found during NREM sleep at night. Surprisingly, we also detected numerous spindle-like events during unequivocal periods of wake during the day. These events were mainly local (detected at single sites), and their characteristics differed from spindles detected during sleep. These “wake spindles” are likely to be events that are commonly categorized as “spontaneous alpha activity” during wake. We speculate that wake and sleep spindles are generated via different mechanisms, and that wake spindles play a role in cognitive processes that occur during the daytime.
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Burger AL, Fennessy J, Fennessy S, Dierkes PW. Nightly selection of resting sites and group behavior reveal antipredator strategies in giraffe. Ecol Evol 2020; 10:2917-2927. [PMID: 32211165 PMCID: PMC7083675 DOI: 10.1002/ece3.6106] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 01/21/2020] [Accepted: 01/27/2020] [Indexed: 12/28/2022] Open
Abstract
This study presents the first findings on nocturnal behavior patterns of wild Angolan giraffe. We characterized their nocturnal behavior and analyzed the influence of ecological factors such as group size, season, and habitat use. Giraffe were observed using night vision systems and thermal imaging cameras on Okapuka Ranch, Namibia. A total of 77 giraffe were observed during 24 nights over two distinct periods-July-August 2016 (dry season) and February-March 2017 (wet season). Photoperiod had a marked influence on their activity and moving behavior. At dusk, giraffe reduced the time spent moving and increasingly lay down and slept at the onset of darkness. Body postures that likely correspond to rapid eye movement (REM) sleep posture (RSP) were observed 15.8 ± 18.3 min after giraffe sat down. Season had a significant effect with longer RSP phases during the dry season (dry: 155.2 ± 191.1 s, n = 79; wet: 85.8 ± 94.9 s, n = 73). Further analyses of the influence of social behavior patterns did not show an effect of group size on RSP lengths. When a group of giraffe spent time at a specific resting site, several individuals were alert (vigilant) while other group members sat down or took up RSP. Simultaneous RSP events within a group were rarely observed. Resting sites were characterized by single trees or sparse bushes on open areas allowing for good visibility in a relatively sheltered location.
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Affiliation(s)
- Anna Lena Burger
- Bioscience Education and Zoo BiologyGoethe University FrankfurtFrankfurt am MainGermany
| | - Julian Fennessy
- Giraffe Conservation FoundationWindhoekNamibia
- School of Biological, Earth and Environmental SciencesUniversity of New South WalesSydneyNSWAustralia
| | | | - Paul W. Dierkes
- Bioscience Education and Zoo BiologyGoethe University FrankfurtFrankfurt am MainGermany
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22
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Siegel JM. Sleep under evolutionarily relevant conditions. Sleep Med 2020; 67:244-245. [PMID: 32035745 DOI: 10.1016/j.sleep.2020.01.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Affiliation(s)
- Jerome M Siegel
- Semel Institute and Brain Research Institute, University of California, Los Angeles, CA, 90095, USA; VA Greater Los Angeles Healthcare System, 16111 Plummer St, Los Angeles 91343, USA.
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van der Meij J, Martinez-Gonzalez D, Beckers GJL, Rattenborg NC. Intra-"cortical" activity during avian non-REM and REM sleep: variant and invariant traits between birds and mammals. Sleep 2019; 42:5195213. [PMID: 30462347 DOI: 10.1093/sleep/zsy230] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2018] [Accepted: 11/19/2018] [Indexed: 01/23/2023] Open
Abstract
Several mammalian-based theories propose that the varying patterns of neuronal activity occurring in wakefulness and sleep reflect different modes of information processing. Neocortical slow-waves, hippocampal sharp-wave ripples, and thalamocortical spindles occurring during mammalian non-rapid eye-movement (NREM) sleep are proposed to play a role in systems-level memory consolidation. Birds show similar NREM and REM (rapid eye-movement) sleep stages to mammals; however, it is unclear whether all neurophysiological rhythms implicated in mammalian memory consolidation are also present. Moreover, it is unknown whether the propagation of slow-waves described in the mammalian neocortex occurs in the avian "cortex" during natural NREM sleep. We used a 32-channel silicon probe connected to a transmitter to make intracerebral recordings of the visual hyperpallium and thalamus in naturally sleeping pigeons (Columba livia). As in the mammalian neocortex, slow-waves during NREM sleep propagated through the hyperpallium. Propagation primarily occurred in the thalamic input layers of the hyperpallium, regions that also showed the greatest slow-wave activity (SWA). Spindles were not detected in both the visual hyperpallium, including regions receiving thalamic input, and thalamus, using a recording method that readily detects spindles in mammals. Interestingly, during REM sleep fast gamma bursts in the hyperpallium (when present) were restricted to the thalamic input layers. In addition, unlike mice, the decrease in SWA from NREM to REM sleep was the greatest in these layers. Taken together, these variant and invariant neurophysiological aspects of avian and mammalian sleep suggest that there may be associated mechanistic and functional similarities and differences between avian and mammalian sleep.
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Affiliation(s)
- Jacqueline van der Meij
- Avian Sleep Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-Strasse, Seewiesen, Germany
| | - Dolores Martinez-Gonzalez
- Avian Sleep Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-Strasse, Seewiesen, Germany
| | - Gabriël J L Beckers
- Cognitive Neurobiology and Helmholtz Institute, Utrecht University, Yalelaan, CM Utrecht, The Netherlands
| | - Niels C Rattenborg
- Avian Sleep Group, Max Planck Institute for Ornithology, Eberhard-Gwinner-Strasse, Seewiesen, Germany
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Beckwith EJ, French AS. Sleep in Drosophila and Its Context. Front Physiol 2019; 10:1167. [PMID: 31572216 PMCID: PMC6749028 DOI: 10.3389/fphys.2019.01167] [Citation(s) in RCA: 38] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2019] [Accepted: 08/29/2019] [Indexed: 12/17/2022] Open
Abstract
A prominent idea emerging from the study of sleep is that this key behavioural state is regulated in a complex fashion by ecologically and physiologically relevant environmental factors. This concept implies that sleep, as a behaviour, is plastic and can be regulated by external agents and changes in internal state. Drosophila melanogaster constitutes a resourceful model system to study behaviour. In the year 2000, the utility of the fly to study sleep was realised, and has since extensively contributed to this exciting field. At the centre of this review, we will discuss studies showing that temperature, food availability/quality, and interactions with conspecifics can regulate sleep. Indeed the relationship can be reciprocal and sleep perturbation can also affect feeding and social interaction. In particular, different environmental temperatures as well as gradual changes in temperature regulate when, and how much flies sleep. Moreover, the satiation/starvation status of an individual dictates the balance between sleep and foraging. Nutritional composition of diet also has a direct impact on sleep amount and its fragmentation. Likewise, aggression between males, courtship, sexual arousal, mating, and interactions within large groups of animals has an acute and long-lasting effect on sleep amount and quality. Importantly, the genes and neuronal circuits that relay information about the external environment and internal state to sleep centres are starting to be elucidated in the fly and are the focus of this review. In conclusion, sleep, as with most behaviours, needs the full commitment of the individual, preventing participation in other vital activities. A vast array of behaviours that are modulated by external and internal factors compete with the need to sleep and thus have a significant role in regulating it.
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Affiliation(s)
- Esteban J Beckwith
- Department of Life Sciences, Imperial College London, London, United Kingdom
| | - Alice S French
- Department of Life Sciences, Imperial College London, London, United Kingdom
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Avoiding Beach’s Boojum Effect: Enhancing bench to bedside translation with field to laboratory considerations in optimal animal models. Neurosci Biobehav Rev 2019; 104:191-196. [DOI: 10.1016/j.neubiorev.2019.06.034] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/24/2019] [Revised: 05/15/2019] [Accepted: 06/24/2019] [Indexed: 11/23/2022]
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Reinhardt KD, Vyazovskiy VV, Hernandez-Aguilar RA, Imron MA, Nekaris KAI. Environment shapes sleep patterns in a wild nocturnal primate. Sci Rep 2019; 9:9939. [PMID: 31289296 PMCID: PMC6616475 DOI: 10.1038/s41598-019-45852-2] [Citation(s) in RCA: 56] [Impact Index Per Article: 11.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/07/2019] [Accepted: 06/12/2019] [Indexed: 11/09/2022] Open
Abstract
Among primates, the suborder Haplorhini is considered to have evolved a consolidated monophasic sleep pattern, with diurnal species requiring a shorter sleep duration than nocturnal species. Only a few primate species have been systematically studied in their natural habitat where environmental variables, including temperature and light, have a major influence on sleep and activity patterns. Here we report the first sleep study on a nocturnal primate performed in the wild. We fitted seven wild Javan slow lorises (Nycticebus javanicus) in West Java, Indonesia with accelerometers that collected activity data, and installed climate loggers in each individual’s home range to collect ambient temperature readings (over 321 days in total). All individuals showed a strictly nocturnal pattern of activity and displayed a striking synchronisation of onset and cessation of activity in relation to sunset and sunrise. The longest consolidated rest episodes were typically clustered near the beginning and towards the end of the light period, and this pattern was inversely related to daily fluctuations of the ambient temperature. The striking relationship between daily activity patterns, light levels and temperature suggests a major role of the environment in shaping the daily architecture of waking and sleep. We concluded that well-known phenotypic variability in daily sleep amount and architecture across species may represent an adaptation to changes in the environment. Our data suggest that the consolidated monophasic sleep patterns shaped by environmental pressures observed in slow lorises represent phylogenetic inertia in the evolution of sleep patterns in humans.
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Affiliation(s)
- Kathleen D Reinhardt
- Nocturnal Primate Research Group, Oxford Brookes University, Oxford, United Kingdom. .,Center for Ecological and Evolutionary Synthesis, University of Oslo, Oslo, Norway.
| | - Vladyslav V Vyazovskiy
- Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford, United Kingdom.
| | - R Adriana Hernandez-Aguilar
- Center for Ecological and Evolutionary Synthesis, University of Oslo, Oslo, Norway.,Department of Social Psychologyand Quantitative Psychology, Faculty of Psychology, University of Barcelona, Barcelona, Spain
| | - Muhammad Ali Imron
- Department of Forest Resources Conservation, Faculty of Forestry, Universitas Gadjah Mada, Yogyakarta, Indonesia
| | - K Anne-Isola Nekaris
- Nocturnal Primate Research Group, Oxford Brookes University, Oxford, United Kingdom
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ONEIROS, a new miniature standalone device for recording sleep electrophysiology, physiology, temperatures and behavior in the lab and field. J Neurosci Methods 2019; 316:103-116. [DOI: 10.1016/j.jneumeth.2018.08.030] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 07/27/2018] [Accepted: 08/31/2018] [Indexed: 11/23/2022]
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Interacting circadian and homeostatic processes with opportunity cost: A mathematical model of sleep with application to two mammalian species. PLoS One 2018; 13:e0208043. [PMID: 30540805 PMCID: PMC6291086 DOI: 10.1371/journal.pone.0208043] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2018] [Accepted: 11/09/2018] [Indexed: 11/18/2022] Open
Abstract
This paper introduces a new model of sleep for mammals. It extends the classic ‘two-process’ model of sleep to account for differences in external circumstances. We apply this model to previously-collected data on elephants and sloths, comparing sleep patterns in the wild with sleep patterns in captivity. We find that the model does very well in explaining sleeping patterns for both types of animals, in both the captive state and in the wild state.
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Tisdale RK, Lesku JA, Beckers GJL, Vyssotski AL, Rattenborg NC. The low-down on sleeping down low: pigeons shift to lighter forms of sleep when sleeping near the ground. J Exp Biol 2018; 221:221/19/jeb182634. [DOI: 10.1242/jeb.182634] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/12/2018] [Accepted: 07/30/2018] [Indexed: 12/21/2022]
Abstract
ABSTRACT
Sleep in birds is composed of two distinct sub-states, remarkably similar to mammalian slow-wave sleep (SWS) and rapid eye movement (REM) sleep. However, it is unclear whether all aspects of mammalian sleep are present in birds. We examined whether birds suppress REM sleep in response to changes in sleeping conditions that presumably evoke an increase in perceived predation risk, as observed previously in rodents. Although pigeons sometimes sleep on the ground, they prefer to sleep on elevated perches at night, probably to avoid nocturnal mammalian ground predators. Few studies to date have investigated how roosting sites affect sleep architecture. We compared sleep in captive pigeons on days with and without access to high perches. On the first (baseline) day, low and high perches were available; on the second day, the high perches were removed; and on the third (recovery) day, the high perches were returned. The total time spent sleeping did not vary significantly between conditions; however, the time spent in REM sleep declined on the low-perch night and increased above baseline when the pigeons slept on the high perch during the recovery night. Although the amount of SWS did not vary significantly between conditions, SWS intensity was lower on the low-perch night, particularly early in the night. The similarity of these responses between birds and mammals suggests that REM sleep is influenced by at least some ecological factors in a similar manner in both groups of animals.
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Affiliation(s)
- Ryan K. Tisdale
- Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany
| | - John A. Lesku
- School of Life Sciences, La Trobe University, Melbourne 3086, Australia
| | - Gabriel J. L. Beckers
- Cognitive Neurobiology and Helmholtz Institute, Utrecht University, Utrecht 3584 CM, The Netherlands
| | - Alexei L. Vyssotski
- Institute of Neuroinformatics, University of Zürich/ETH Zürich, Zürich 8057, Switzerland
| | - Niels C. Rattenborg
- Avian Sleep Group, Max Planck Institute for Ornithology, Seewiesen 82319, Germany
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Lyamin OI, Kosenko PO, Korneva SM, Vyssotski AL, Mukhametov LM, Siegel JM. Fur Seals Suppress REM Sleep for Very Long Periods without Subsequent Rebound. Curr Biol 2018; 28:2000-2005.e2. [PMID: 29887309 DOI: 10.1016/j.cub.2018.05.022] [Citation(s) in RCA: 65] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2018] [Revised: 02/26/2018] [Accepted: 05/08/2018] [Indexed: 11/17/2022]
Abstract
Virtually all land mammals and birds have two sleep states: slow-wave sleep (SWS) and rapid eye movement (REM) sleep [1, 2]. After deprivation of REM sleep by repeated awakenings, mammals increase REM sleep time [3], supporting the idea that REM sleep is homeostatically regulated. Some evidence suggests that periods of REM sleep deprivation for a week or more cause physiological dysfunction and eventual death [4, 5]. However, separating the effects of REM sleep loss from the stress of repeated awakening is difficult [2, 6]. The northern fur seal (Callorhinus ursinus) is a semiaquatic mammal [7]. It can sleep on land and in seawater. The fur seal is unique in showing both the bilateral SWS seen in most mammals and the asymmetric sleep previously reported in cetaceans [8]. Here we show that when the fur seal stays in seawater, where it spends most of its life [7], it goes without or greatly reduces REM sleep for days or weeks. After this nearly complete elimination of REM, it displays minimal or no REM rebound upon returning to baseline conditions. Our data are consistent with the hypothesis that REM sleep may serve to reverse the reduced brain temperature and metabolism effects of bilateral nonREM sleep, a state that is greatly reduced when the fur seal is in the seawater, rather than REM sleep being directly homeostatically regulated. This can explain the absence of REM sleep in the dolphin and other cetaceans and its increasing proportion as the end of the sleep period approaches in humans and other mammals.
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Affiliation(s)
- Oleg I Lyamin
- Department of Psychiatry and Biobehavioral Sciences and Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA; A.N. Severtsov Institute of Ecology and Evolution, RAS, Moscow, Russia; Utrish Dolphinarium, Moscow, Russia.
| | | | | | - Alexei L Vyssotski
- Institute of Neuroinformatics, University of Zurich and Swiss Federal Institute of Technology (ETH), Zurich, Switzerland
| | - Lev M Mukhametov
- A.N. Severtsov Institute of Ecology and Evolution, RAS, Moscow, Russia; Utrish Dolphinarium, Moscow, Russia
| | - Jerome M Siegel
- Department of Psychiatry and Biobehavioral Sciences and Brain Research Institute, University of California, Los Angeles, Los Angeles, CA, USA.
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Aulsebrook AE, Jones TM, Mulder RA, Lesku JA. Impacts of artificial light at night on sleep: A review and prospectus. JOURNAL OF EXPERIMENTAL ZOOLOGY PART 2018; 329:409-418. [PMID: 29869374 DOI: 10.1002/jez.2189] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/12/2018] [Revised: 05/10/2018] [Accepted: 05/22/2018] [Indexed: 12/13/2022]
Abstract
Natural cycles of light and darkness govern the timing of most aspects of animal behavior and physiology. Artificial light at night (ALAN)-a recent and pervasive form of pollution-can mask natural photoperiodic cues and interfere with biological rhythms. One such rhythm vulnerable to perturbation is the sleep-wake cycle. ALAN may greatly influence sleep in humans and wildlife, particularly in animals that sleep predominantly at night. There has been some recent evidence for impacts of ALAN on sleep, but critical questions remain. Some of these can be addressed by adopting approaches already entrenched in sleep research. In this paper, we review the current evidence for impacts of ALAN on sleep, highlight gaps in our understanding, and suggest opportunities for future research.
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Affiliation(s)
- Anne E Aulsebrook
- The University of Melbourne, School of BioSciences, Melbourne, Victoria, Australia
| | - Therésa M Jones
- The University of Melbourne, School of BioSciences, Melbourne, Victoria, Australia
| | - Raoul A Mulder
- The University of Melbourne, School of BioSciences, Melbourne, Victoria, Australia
| | - John A Lesku
- La Trobe University, School of Life Sciences, Melbourne, Victoria, Australia
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Rattenborg NC, de la Iglesia HO, Kempenaers B, Lesku JA, Meerlo P, Scriba MF. Sleep research goes wild: new methods and approaches to investigate the ecology, evolution and functions of sleep. Philos Trans R Soc Lond B Biol Sci 2018; 372:rstb.2016.0251. [PMID: 28993495 DOI: 10.1098/rstb.2016.0251] [Citation(s) in RCA: 64] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 03/22/2017] [Indexed: 11/12/2022] Open
Abstract
Despite being a prominent aspect of animal life, sleep and its functions remain poorly understood. As with any biological process, the functions of sleep can only be fully understood when examined in the ecological context in which they evolved. Owing to technological constraints, until recently, sleep has primarily been examined in the artificial laboratory environment. However, new tools are enabling researchers to study sleep behaviour and neurophysiology in the wild. Here, we summarize the various methods that have enabled sleep researchers to go wild, their strengths and weaknesses, and the discoveries resulting from these first steps outside the laboratory. The initial studies to 'go wild' have revealed a wealth of interindividual variation in sleep, and shown that sleep duration is not even fixed within an individual, but instead varies in response to an assortment of ecological demands. Determining the costs and benefits of this inter- and intraindividual variation in sleep may reveal clues to the functions of sleep. Perhaps the greatest surprise from these initial studies is that the reduction in neurobehavioural performance resulting from sleep loss demonstrated in the laboratory is not an obligatory outcome of reduced sleep in the wild.This article is part of the themed issue 'Wild clocks: integrating chronobiology and ecology to understand timekeeping in free-living animals'.
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Affiliation(s)
- Niels C Rattenborg
- Avian Sleep Group, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | | | - Bart Kempenaers
- Department of Behavioral Ecology and Evolutionary Genetics, Max Planck Institute for Ornithology, 82319 Seewiesen, Germany
| | - John A Lesku
- School of Life Sciences, La Trobe University, Melbourne 3086, Victoria, Australia
| | - Peter Meerlo
- Groningen Institute for Evolutionary Life Sciences, University of Groningen, 9700 Groningen, The Netherlands
| | - Madeleine F Scriba
- Department of Ecology and Evolution, University of Lausanne, 1015 Lausanne, Switzerland
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Davimes JG, Alagaili AN, Bhagwandin A, Bertelsen MF, Mohammed OB, Bennett NC, Manger PR, Gravett N. Seasonal variations in sleep of free-ranging Arabian oryx (Oryx leucoryx) under natural hyperarid conditions. Sleep 2018; 41:4883370. [DOI: 10.1093/sleep/zsy038] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2017] [Indexed: 11/13/2022] Open
Affiliation(s)
- Joshua G Davimes
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
| | - Abdulaziz N Alagaili
- Department of Zoology, KSU Mammals Research Chair, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Adhil Bhagwandin
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
| | - Mads F Bertelsen
- Centre for Zoo and Wild Animal Health, Copenhagen Zoo, Frederiksberg, Denmark
| | - Osama B Mohammed
- Department of Zoology, KSU Mammals Research Chair, College of Science, King Saud University, Riyadh, Saudi Arabia
| | - Nigel C Bennett
- South African Research Chair of Mammal Behavioural Ecology and Physiology, University of Pretoria, Pretoria, South Africa
| | - Paul R Manger
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
| | - Nadine Gravett
- School of Anatomical Sciences, Faculty of Health Sciences, University of the Witwatersrand, Parktown, Johannesburg, Republic of South Africa
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Abstract
Despite decades of intense study, the functions of sleep are still shrouded in mystery. The difficulty in understanding these functions can be at least partly attributed to the varied manifestations of sleep in different animals. Daily sleep duration can range from 4-20 hrs among mammals, and sleep can manifest throughout the brain, or it can alternate over time between cerebral hemispheres, depending on the species. Ecological factors are likely to have shaped these and other sleep behaviors during evolution by altering the properties of conserved arousal circuits in the brain. Nonetheless, core functions of sleep are likely to have arisen early and to have persisted to the present day in diverse organisms. This review will discuss the evolutionary forces that may be responsible for phylogenetic differences in sleep and the potential core functions that sleep fulfills.
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Affiliation(s)
- William J Joiner
- Department of Pharmacology, University of California San Diego, La Jolla, CA 92093-0636, USA; Biomedical Sciences Graduate Program, University of California San Diego, La Jolla, CA 92093-0636, USA; Neurosciences Graduate Program, University of California San Diego, La Jolla, CA 92093-0636, USA; Center for Circadian Biology, University of California San Diego, La Jolla, CA 92093-0636, USA.
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Bio-logging, new technologies to study conservation physiology on the move: a case study on annual survival of Himalayan vultures. J Comp Physiol A Neuroethol Sens Neural Behav Physiol 2017; 203:531-542. [PMID: 28612235 PMCID: PMC5522509 DOI: 10.1007/s00359-017-1180-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2017] [Revised: 05/01/2017] [Accepted: 05/04/2017] [Indexed: 12/31/2022]
Abstract
Bio-logging, the on-animal deployment of miniaturised electronic data recorders, allows for the study of location, body position, and physiology of individuals throughout their ontogeny. For terrestrial animals, 1 Hz GPS-position, 3D-body acceleration, and ambient temperature provide standard data to link to the physiology of life histories. Environmental context is added at ever finer scales using remote sensing earth observation data. Here we showcase the use of such bio-logging approaches in a conservation physiology study on endangered Himalayan vultures (Gyps himalayensis). We determine environmental, behavioural, and physiological causes of survival in immature birds that roam from wintering sites in India, Bhutan, and Nepal towards summer areas in Tibet and Mongolia. Five of 18 immature griffons died during one year. Individuals that died had failed to migrate sufficiently far northward (>1500 km) in spring. Individuals likely died if they flew against headwinds from the north or were less able to find thermal updrafts. Surviving individuals migrated to cold and dry areas with low population density. We highlight flight experience, long distance movements, and remote places with low human population as factors critical for the survival of Himalayan vultures. High-resolution bio-logging studies can advance conservation management by pinpointing where and why migratory animals have problems and die.
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Sleep Ecophysiology: Integrating Neuroscience and Ecology. Trends Ecol Evol 2016; 31:590-599. [DOI: 10.1016/j.tree.2016.05.004] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2016] [Revised: 05/09/2016] [Accepted: 05/10/2016] [Indexed: 10/21/2022]
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Mader EC, Mader ACL. Sleep as spatiotemporal integration of biological processes that evolved to periodically reinforce neurodynamic and metabolic homeostasis: The 2m3d paradigm of sleep. J Neurol Sci 2016; 367:63-80. [PMID: 27423566 DOI: 10.1016/j.jns.2016.05.025] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2016] [Revised: 05/12/2016] [Accepted: 05/13/2016] [Indexed: 11/19/2022]
Abstract
Sleep continues to perplex scientists and researchers. Despite decades of sleep research, we still lack a clear understanding of the biological functions and evolution of sleep. In this review, we will examine sleep from a functional and phylogenetic perspective and describe some important conceptual gaps in understanding sleep. Classical theories of the biology and evolution of sleep emphasize sensory activation, energy balance, and metabolic homeostasis. Advances in electrophysiology, functional neuroimaging, and neuroplasticity allow us to view sleep within the framework of neural dynamics. With this paradigm shift, we have come to realize the importance of neurodynamic homeostasis in shaping the biology of sleep. Evidently, animals sleep to achieve neurodynamic and metabolic homeostasis. We are not aware of any framework for understanding sleep where neurodynamic, metabolic, homeostatic, chronophasic, and afferent variables are all taken into account. This motivated us to propose the two-mode three-drive (2m3d) paradigm of sleep. In the 2m3d paradigm, local neurodynamic/metabolic (N/M) processes switch between two modes-m0 and m1-in response to three drives-afferent, chronophasic, and homeostatic. The spatiotemporal integration of local m0/m1 operations gives rise to the global states of sleep and wakefulness. As a framework of evolution, the 2m3d paradigm allows us to view sleep as a robust adaptive strategy that evolved so animals can periodically reinforce neurodynamic and metabolic homeostasis while remaining sensitive to their internal and external environment.
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Affiliation(s)
- Edward Claro Mader
- Louisiana State University Health Sciences Center, Department of Neurology, New Orleans, LA 70112, USA.
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Libourel PA, Herrel A. Sleep in amphibians and reptiles: a review and a preliminary analysis of evolutionary patterns. Biol Rev Camb Philos Soc 2015; 91:833-66. [DOI: 10.1111/brv.12197] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2014] [Revised: 04/22/2015] [Accepted: 04/28/2015] [Indexed: 01/18/2023]
Affiliation(s)
- Paul-Antoine Libourel
- SLEEP - Physiopathologie des Réseaux Neuronaux du Cycle Sommeil, Centre de Recherche en Neurosciences de Lyon, Inserm U1028 - CNRS UMR5292, Faculté de Médecine Laennec; 7 rue Guillaume Paradin 69372 Lyon Cedex 08 France
| | - Anthony Herrel
- Département d'Ecologie et de Gestion de la Biodiversité; UMR 7179 C.N.R.S/M.N.H.N.; 57 rue Cuvier, Case Postale 55 75231 Paris Cedex 05 France
- Evolutionary Morphology of Vertebrates; Ghent University; K.L. Ledeganckstraat 35 B-9000 Gent Belgium
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