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Kohles JE, Page RA, Wikelski M, Dechmann DKN. Seasonal shifts in insect ephemerality drive bat foraging effort. Curr Biol 2024; 34:3241-3248.e3. [PMID: 38942018 DOI: 10.1016/j.cub.2024.05.074] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2023] [Revised: 03/11/2024] [Accepted: 05/31/2024] [Indexed: 06/30/2024]
Abstract
Animal foraging is fundamentally shaped by food distribution and availability.1 However, the quantification of spatiotemporal food distribution is rare2 but crucial to explain variation in foraging behavior among species, populations, or individuals. Clumped but ephemeral food sources enable rapid energy intake but require increased effort to find,3 can generate variable foraging success,4 and force animals to forage more efficiently. We quantified seasonal shifts in the availability of such resources to test the proximate effects of food distribution on changes in movement patterns. The neotropical lesser bulldog bat (Noctilio albiventris) forages in a seasonal environment on emerging aquatic insects, whose numbers peak shortly after dusk.5,6 We GPS-tracked bats and quantified nocturnal insect distribution in their foraging area using floating camera traps across wet and dry seasons. Surprisingly, insects were 75% less abundant and swarms were 60% shorter lived (more ephemeral) in the wet season. As a result, wet season bats had to fly twice as far (total and maximum distance fromroost distances) and 45% longer (duration) per night. Within foraging bouts, wet season bats spent less time in each insect patch and searched longer for subsequent patches, reflecting increased temporal ephemerality and decreased spatial predictability of insects. Our results highlight the tight link between foraging effort and spatiotemporal distribution of food and the influence of constraints imposed by reproduction on behavioral flexibility and adaptations to the highly dynamic resource landscapes of mobile prey.7,8 Examining foraging behavior in light of spatiotemporal dynamics of resources can help predict how animals respond to shifts in food availability caused by escalating environmental changes.
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Affiliation(s)
- Jenna E Kohles
- Max Planck Institute of Animal Behavior, Department of Migration, Am Obstberg 1, Radolfzell 78315, Germany; Centre for the Advanced Study of Collective Behaviour, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany; Department of Biology, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany; Smithsonian Tropical Research Institute, Luis Clement Avenue, Bldg. 401 Tupper, Ancon, Panama 0843-03092, Republic of Panama.
| | - Rachel A Page
- Smithsonian Tropical Research Institute, Luis Clement Avenue, Bldg. 401 Tupper, Ancon, Panama 0843-03092, Republic of Panama
| | - Martin Wikelski
- Max Planck Institute of Animal Behavior, Department of Migration, Am Obstberg 1, Radolfzell 78315, Germany; Department of Biology, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany
| | - Dina K N Dechmann
- Max Planck Institute of Animal Behavior, Department of Migration, Am Obstberg 1, Radolfzell 78315, Germany; Department of Biology, University of Konstanz, Universitätsstraße 10, Konstanz 78464, Germany; Smithsonian Tropical Research Institute, Luis Clement Avenue, Bldg. 401 Tupper, Ancon, Panama 0843-03092, Republic of Panama
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Ramp C, Lesage V, Ollier A, Auger-Méthé M, Sears R. Migratory movements of fin whales from the Gulf of St. Lawrence challenge our understanding of the Northwest Atlantic stock structure. Sci Rep 2024; 14:11472. [PMID: 38769407 PMCID: PMC11106244 DOI: 10.1038/s41598-024-62173-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2024] [Accepted: 05/14/2024] [Indexed: 05/22/2024] Open
Abstract
Fin whales, Balenoptera physalus, are capital breeders, having the potential to separate breeding and feeding both spatially and temporally. Fin whales occur throughout the Northwest Atlantic, but stock structure and seasonal movements remain unclear. By deploying satellite transmitters on 28 individuals, we examine movement patterns within and beyond the Gulf of St. Lawrence (GSL), Canada, and challenge the current understanding of stock structure. Eight individuals left the GSL in autumn, with five tags persisting into January. Migration patterns of these whales showed considerable variation in timing and trajectory, with movements extending south to 24°N, and thus beyond the assumed distribution limit of the species in the Northwest Atlantic. A rapid return to the Scotian Shelf or Gulf of Maine was observed from several whales after incursions in southern waters, suggesting that fin whales in the Northwest Atlantic may not have a common winter destination that fits the definition of a breeding ground. Area-restricted search (ARS) behavior dominated fin whale activities during summer (92%) and fall (72%), with persistence into the winter (56%); ARS occurred at multiple locations in the GSL, Scotian Shelf and Shelf edge, and near seamounts of the North Atlantic, having characteristics consistent with foraging areas.
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Affiliation(s)
- Christian Ramp
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, 850 Route de la mer,, Mont Joli, QC, G5H 3Z4, Canada.
| | - Veronique Lesage
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, 850 Route de la mer,, Mont Joli, QC, G5H 3Z4, Canada
| | - Angélique Ollier
- Fisheries and Oceans Canada, Maurice Lamontagne Institute, 850 Route de la mer,, Mont Joli, QC, G5H 3Z4, Canada
| | - Marie Auger-Méthé
- Institute for the Oceans and Fisheries, AERL, 2202 Main Mall, University of British Columbia, Vancouver, V6T 1Z4, Canada
- Department of Statistics, ESB, 2207 Main Mall, University of British Columbia, Vancouver, V6T 1Z4, Canada
| | - Richard Sears
- Mingan Island Cetacean Study, 285 rue Green, St Lambert, QC, J4P 1T3, Canada
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Nowak BVR, Bowen WD, den Heyer CE, Lang SLC, Lidgard DC. Ontogeny of movement patterns in naïve grey seal pups inhabiting a complex continental shelf ecosystem. PLoS One 2023; 18:e0290707. [PMID: 37756252 PMCID: PMC10529606 DOI: 10.1371/journal.pone.0290707] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2022] [Accepted: 08/14/2023] [Indexed: 09/29/2023] Open
Abstract
Most vertebrate offspring must transition from the relative security of parental care (nutrition and protection) to independent foraging. Offspring face many challenges during this critical period, particularly in species where parental care ends at weaning, such as the grey seal (Halichoerus grypus). We studied the development of movement behaviour in naïve grey seal pups from their first trips to sea to about five months of age. Twenty-five (12 males and 13 females) newly-weaned pups were fitted with satellite-linked GPS tags on Sable Island, Nova Scotia, Canada in January 2016. The influence of fixed effects (pup size, sex, week) and the random effect of pup identity on trip characteristics were examined. Movement behaviour was analyzed using a move persistence mixed-effects model. Habitat use was highly variable among individuals and covered much of the geographic distribution of the population. Unlike older juveniles, subadults, and adults in this population, most naïve pups used multiple haulout sites to begin and end trips. There was little evidence of area-restricted search behaviour during trips, suggesting that naïve pups were using an opportunistic foraging tactic that may result in more variable foraging success than that of older, experienced animals. Naïve pups made longer trips with longer haulout durations between them than observed for older greys seals. Males and females differed in some trip characteristics, but sex effects were small over the first few months of life. Offspring size at weaning was not a useful predictor of trip characteristics. Move persistence of grey seal pups was initially high and then decreased over time as individuals gained experience. Both intrinsic and extrinsic factors were influential on the movements of grey seal pups. Greater body length at weaning, longer duration spent on shore after weaning, shallower water column depth, and farther distance from shore were all associated with lower move persistence. Female grey seal pups had lower move persistence than males. Overall, the movements of naïve grey seal pups during the first few months of life were characterized by extensive exploration, but move persistence decreased over time suggesting they may be using an exploration-refinement foraging tactic.
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Affiliation(s)
- Benia V. R. Nowak
- Biology Department, Life Science Centre Dalhousie University, Halifax, Nova Scotia, Canada
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
| | - W. Don Bowen
- Biology Department, Life Science Centre Dalhousie University, Halifax, Nova Scotia, Canada
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
| | - Cornelia E. den Heyer
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
| | - Shelley L. C. Lang
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
- Northwest Atlantic Fisheries Centre, St. John’s, Newfoundland, Canada
| | - Damian C. Lidgard
- Biology Department, Life Science Centre Dalhousie University, Halifax, Nova Scotia, Canada
- Population Ecology Division, Bedford Institute of Oceanography, Dartmouth, Nova Scotia, Canada
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Shuert CR, Hussey NE, Marcoux M, Heide-Jørgensen MP, Dietz R, Auger-Méthé M. Divergent migration routes reveal contrasting energy-minimization strategies to deal with differing resource predictability. MOVEMENT ECOLOGY 2023; 11:31. [PMID: 37280701 DOI: 10.1186/s40462-023-00397-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/23/2023] [Accepted: 05/30/2023] [Indexed: 06/08/2023]
Abstract
BACKGROUND Seasonal long-distance movements are a common feature in many taxa allowing animals to deal with seasonal habitats and life-history demands. Many species use different strategies to prioritize time- or energy-minimization, sometimes employing stop-over behaviours to offset the physiological burden of the directed movement associated with migratory behaviour. Migratory strategies are often limited by life-history and environmental constraints, but can also be modulated by the predictability of resources en route. While theory on population-wide strategies (e.g. energy-minimization) are well studied, there are increasing evidence for individual-level variation in movement patterns indicative of finer scale differences in migration strategies. METHODS We aimed to explore sources of individual variation in migration strategies for long-distance migrators using satellite telemetry location data from 41 narwhal spanning a 21-year period. Specifically, we aimed to determine and define the long-distance movement strategies adopted and how environmental variables may modulate these movements. Fine-scale movement behaviours were characterized using move-persistence models, where changes in move-persistence, highlighting autocorrelation in a movement trajectory, were evaluated against potential modulating environmental covariates. Areas of low move-persistence, indicative of area-restricted search-type behaviours, were deemed to indicate evidence of stop-overs along the migratory route. RESULTS Here, we demonstrate two divergent migratory tactics to maintain a similar overall energy-minimization strategy within a single population of narwhal. Narwhal migrating offshore exhibited more tortuous movement trajectories overall with no evidence of spatially-consistent stop-over locations across individuals. Nearshore migrating narwhal undertook more directed routes, contrasted by spatially-explicit stop-over behaviour in highly-productive fjord and canyon systems along the coast of Baffin Island for periods of several days to several weeks. CONCLUSIONS Within a single population, divergent migratory tactics can achieve a similar overall energy-minimizing strategy within a species as a response to differing trade-offs between predictable and unpredictable resources. Our methodological approach, which revealed the modulators of fine-scale migratory movements and predicted regional stop-over sites, is widely applicable to a variety of other aquatic and terrestrial species. Quantifying marine migration strategies will be key for adaptive conservation in the face of climate change and ever increasing human pressures.
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Affiliation(s)
- Courtney R Shuert
- Department of Integrative Biology, University of Windsor, Windsor, ON, N9B 3P4, Canada.
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, R3T 2N6, Canada.
| | - Nigel E Hussey
- Department of Integrative Biology, University of Windsor, Windsor, ON, N9B 3P4, Canada
| | - Marianne Marcoux
- Fisheries and Oceans Canada, Freshwater Institute, Winnipeg, MB, R3T 2N6, Canada
| | | | - Rune Dietz
- Department of Ecoscience, Aarhus University, Frederiksborgvej 399, 4000, Roskilde, Denmark
| | - Marie Auger-Méthé
- Institute for the Oceans & Fisheries, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
- Department of Statistics, University of British Columbia, Vancouver, BC, V6T 1Z4, Canada
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