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Brighton CH, Zusi L, McGowan KA, Kinniry M, Kloepper LN, Taylor GK. Aerial attack strategies of hawks hunting bats, and the adaptive benefits of swarming. Behav Ecol 2021; 32:464-476. [PMID: 34104109 PMCID: PMC8177810 DOI: 10.1093/beheco/araa145] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/08/2020] [Revised: 12/03/2020] [Accepted: 12/14/2020] [Indexed: 11/12/2022] Open
Abstract
Aggregation can reduce an individual’s predation risk, by decreasing predator hunting efficiency or displacing predation onto others. Here, we explore how the behaviors of predator and prey influence catch success and predation risk in Swainson’s hawks Buteo swainsoni attacking swarming Brazilian free-tailed bats Tadarida brasiliensis on emergence. Lone bats including stragglers have a high relative risk of predation, representing ~5% of the catch but ~0.2% of the population. Attacks on the column were no less successful than attacks on lone bats, so hunting efficiency is not decreased by group vigilance or confusion. Instead, lone bats were attacked disproportionately often, representing ~10% of all attacks. Swarming therefore displaces the burden of predation onto bats outside the column—whether as isolated wanderers not benefitting from dilution through attack abatement, or as peripheral stragglers suffering marginal predation and possible selfish herd effects. In contrast, the hawks’ catch success depended only on the attack maneuvers that they employed, with the odds of success being more than trebled in attacks involving a high-speed stoop or rolling grab. Most attacks involved one of these two maneuvers, which therefore represent alternative rather than complementary tactics. Hence, whereas a bat’s survival depends on maintaining column formation, a hawk’s success does not depend on attacking lone bats—even though their tendency to do so is sufficient to explain the adaptive benefits of their prey’s aggregation behavior. A hawk’s success instead depends on the flight maneuvers it deploys, including the high-speed stoop that is characteristic of many raptors. Swarming bats emerging from a massive desert roost reduce their predation risk by maintaining tight column formation, because the hawks that predate them attack peripheral stragglers and isolated wanderers disproportionately. Whereas a bat’s predation risk depends on maintaining its position within the column, the catch success of a hawk depends on how it maneuvers itself to attack, and is maximized by executing a high-speed dive or rolling grab maneuver.
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Affiliation(s)
| | - Lillias Zusi
- Department of Biological Sciences, 100 Galvin Life Science Center, Notre Dame, IN, USA
| | - Kathryn A McGowan
- Department of Biological Sciences, 100 Galvin Life Science Center, Notre Dame, IN, USA
| | - Morgan Kinniry
- Department of Biological Sciences, 100 Galvin Life Science Center, Notre Dame, IN, USA
| | - Laura N Kloepper
- Department of Biological Sciences, 100 Galvin Life Science Center, Notre Dame, IN, USA
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Genoud M, Isler K, Martin RD. Comparative analyses of basal rate of metabolism in mammals: data selection does matter. Biol Rev Camb Philos Soc 2017; 93:404-438. [PMID: 28752629 DOI: 10.1111/brv.12350] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2016] [Revised: 05/29/2017] [Accepted: 06/05/2017] [Indexed: 12/21/2022]
Abstract
Basal rate of metabolism (BMR) is a physiological parameter that should be measured under strictly defined experimental conditions. In comparative analyses among mammals BMR is widely used as an index of the intensity of the metabolic machinery or as a proxy for energy expenditure. Many databases with BMR values for mammals are available, but the criteria used to select metabolic data as BMR estimates have often varied and the potential effect of this variability has rarely been questioned. We provide a new, expanded BMR database reflecting compliance with standard criteria (resting, postabsorptive state; thermal neutrality; adult, non-reproductive status for females) and examine potential effects of differential selectivity on the results of comparative analyses. The database includes 1739 different entries for 817 species of mammals, compiled from the original sources. It provides information permitting assessment of the validity of each estimate and presents the value closest to a proper BMR for each entry. Using different selection criteria, several alternative data sets were extracted and used in comparative analyses of (i) the scaling of BMR to body mass and (ii) the relationship between brain mass and BMR. It was expected that results would be especially dependent on selection criteria with small sample sizes and with relatively weak relationships. Phylogenetically informed regression (phylogenetic generalized least squares, PGLS) was applied to the alternative data sets for several different clades (Mammalia, Eutheria, Metatheria, or individual orders). For Mammalia, a 'subsampling procedure' was also applied, in which random subsamples of different sample sizes were taken from each original data set and successively analysed. In each case, two data sets with identical sample size and species, but comprising BMR data with different degrees of reliability, were compared. Selection criteria had minor effects on scaling equations computed for large clades (Mammalia, Eutheria, Metatheria), although less-reliable estimates of BMR were generally about 12-20% larger than more-reliable ones. Larger effects were found with more-limited clades, such as sciuromorph rodents. For the relationship between BMR and brain mass the results of comparative analyses were found to depend strongly on the data set used, especially with more-limited, order-level clades. In fact, with small sample sizes (e.g. <100) results often appeared erratic. Subsampling revealed that sample size has a non-linear effect on the probability of a zero slope for a given relationship. Depending on the species included, results could differ dramatically, especially with small sample sizes. Overall, our findings indicate a need for due diligence when selecting BMR estimates and caution regarding results (even if seemingly significant) with small sample sizes.
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Affiliation(s)
- Michel Genoud
- Department of Ecology and Evolution, University of Lausanne, CH-1015, Lausanne, Switzerland.,Division of Conservation Biology, Institute of Ecology and Evolution, Department of Biology, University of Bern, CH-3012, Bern, Switzerland
| | - Karin Isler
- Department of Anthropology, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
| | - Robert D Martin
- Integrative Research Center, The Field Museum, Chicago, IL, 60605-2496, U.S.A.,Institute of Evolutionary Medicine, University of Zürich-Irchel, CH-8057, Zürich, Switzerland
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O'Shea TJ, Cryan PM, Cunningham AA, Fooks AR, Hayman DTS, Luis AD, Peel AJ, Plowright RK, Wood JLN. Bat flight and zoonotic viruses. Emerg Infect Dis 2014; 20:741-5. [PMID: 24750692 PMCID: PMC4012789 DOI: 10.3201/eid2005.130539] [Citation(s) in RCA: 210] [Impact Index Per Article: 21.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
High metabolism and body temperatures of flying bats might enable them to host many viruses. Bats are sources of high viral diversity and high-profile zoonotic viruses worldwide. Although apparently not pathogenic in their reservoir hosts, some viruses from bats severely affect other mammals, including humans. Examples include severe acute respiratory syndrome coronaviruses, Ebola and Marburg viruses, and Nipah and Hendra viruses. Factors underlying high viral diversity in bats are the subject of speculation. We hypothesize that flight, a factor common to all bats but to no other mammals, provides an intensive selective force for coexistence with viral parasites through a daily cycle that elevates metabolism and body temperature analogous to the febrile response in other mammals. On an evolutionary scale, this host–virus interaction might have resulted in the large diversity of zoonotic viruses in bats, possibly through bat viruses adapting to be more tolerant of the fever response and less virulent to their natural hosts.
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Reichard JD, Fellows SR, Frank AJ, Kunz TH. Thermoregulation during flight: body temperature and sensible heat transfer in free-ranging Brazilian free-tailed bats (Tadarida brasiliensis). Physiol Biochem Zool 2010; 83:885-97. [PMID: 21034204 DOI: 10.1086/657253] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Bat wings are important for thermoregulation, but their role in heat balance during flight is largely unknown. More than 80% of the energy consumed during flight generates heat as a by-product, and thus it is expected that bat wings should dissipate large amounts of heat to prevent hyperthermia. We measured rectal (T(r)) and surface (T(s)) temperatures of Brazilian free-tailed bats (Tadarida brasiliensis) as they emerged from and returned to their daytime roosts and calculated sensible heat transfer for different body regions (head, body, wings, and tail membrane). Bats' T(r) decreased from 36.8°C during emergence flights to 34.4°C during returns, and T(s) scaled positively with ambient temperature (T(a)). Total radiative heat loss from bats was significantly greater for a radiative sink to the night sky than for a sink with temperature equal to T(a). We found that free-ranging Brazilian free-tailed bats, on average, do not dissipate heat from their wings by convection but instead dissipate radiative heat (L) to the cloudless night sky during flight ([Formula: see text] W). However, within the range of T(a) measured in this study, T. brasiliensis experienced net heat loss between evening emergence and return flights. Regional hypothermia reduces heat loss from wings that are exposed to potentially high convective fluxes. Additional research is needed to establish the role of wings in evaporative cooling during flight in bats.
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Affiliation(s)
- Jonathan D Reichard
- Center for Ecology and Conservation Biology, Department of Biology, Boston University, Boston, Massachusetts 02215, USA.
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Reichard JD, Prajapati SI, Austad SN, Keller C, Kunz TH. Thermal windows on Brazilian free-tailed bats facilitate thermoregulation during prolonged flight. Integr Comp Biol 2010; 50:358-70. [PMID: 20811514 DOI: 10.1093/icb/icq033] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
The Brazilian free-tailed bat (Tadarida brasiliensis) experiences challenging thermal conditions while roosting in hot caves, flying during warm daylight conditions, and foraging at cool high altitudes. Using thermal infrared cameras, we identified hot spots along the flanks of free-ranging Brazilian free-tailed bats, ventral to the extended wings. These hot spots are absent in syntopic cave myotis (Myotis velifer), a species that forages over relatively short distances, and does not engage in long-distance migration. We hypothesized that the hot spots, or "radiators," on Brazilian free-tailed bats may be adaptations for migration, particularly in this long-distance, high-flying species. We examined the vasculature of radiators on Brazilian free-tailed bats with transillumination to characterize the unique arrangements of arteries and veins that are positioned perpendicular to the body in the proximal region of the wing. We hypothesized that these radiators aid in maintaining heat balance by flushing the uninsulated thermal window with warm blood, thereby dissipating heat while bats are flying under warm conditions, but shunting blood away and conserving heat when they are flying in cooler air at high altitudes. We also examined fluid-preserved specimens representing 122 species from 15 of 18 chiropteran families and radiators appeared present only in species in the family Molossidae, including both sedentary and migratory species and subspecies. Thus, the radiator appears to be a unique trait that may facilitate energy balance and water balance during sustained dispersal, foraging, and long-distance migration.
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Affiliation(s)
- Jonathan D Reichard
- Center for Ecology and Conservation Biology, Department of Biology, Boston University, Boston, MA, 02215, USA.
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Pretzlaff I, Kerth G, Dausmann KH. Communally breeding bats use physiological and behavioural adjustments to optimise daily energy expenditure. THE SCIENCE OF NATURE - NATURWISSENSCHAFTEN 2010; 97:353-63. [PMID: 20143039 PMCID: PMC2841750 DOI: 10.1007/s00114-010-0647-1] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 11/09/2009] [Revised: 12/30/2009] [Accepted: 01/04/2010] [Indexed: 12/04/2022]
Abstract
Small endotherms must change roosting and thermoregulatory behaviour in response to changes in ambient conditions if they are to achieve positive energy balance. In social species, for example many bats, energy expenditure is influenced by environmental conditions, such as ambient temperature, and also by social thermoregulation. Direct measurements of daily fluctuations in metabolic rates in response to ambient and behavioural variables in the field have not been technologically feasible until recently. During different reproductive periods, we investigated the relationships between ambient temperature, group size and energy expenditure in wild maternity colonies of Bechstein's bats (Myotis bechsteinii). Bats used behavioural and physiological adjustments to regulate energy expenditure. Whether bats maintained normothermia or used torpor, the number of bats in the roosts as well changed with reproductive status and ambient temperature. During pregnancy and lactation, bats remained mostly normothermic and daily group sizes were relatively large, presumably to participate in the energetic benefits of social thermoregulation. In contrast, smaller groups were formed on days when bats used torpor, which occurred mostly during the post-lactation period. Thus, we were able to demonstrate on wild animals under natural conditions the significance of behavioural and physiological flexibility for optimal thermoregulatory behaviour in small endotherms.
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Affiliation(s)
- Iris Pretzlaff
- Department of Animal Ecology and Conservation, Biocentre Grindel, University of Hamburg, Martin-Luther-King Platz 3, 20146, Hamburg, Germany.
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Hamilton TH, Barth RH, Rubinoff I. THE ENVIRONMENTAL CONTROL OF INSULAR VARIATION IN BIRD SPECIES ABUNDANCE. Proc Natl Acad Sci U S A 2006; 52:132-40. [PMID: 16591186 PMCID: PMC300585 DOI: 10.1073/pnas.52.1.132] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- T H Hamilton
- DEPARTMENT OF ZOOLOGY, UNIVERSITY OF TEXAS, AUSTIN
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Soriano PJ, Ruiz A, Arends A. PHYSIOLOGICAL RESPONSES TO AMBIENT TEMPERATURE MANIPULATION BY THREE SPECIES OF BATS FROM ANDEAN CLOUD FORESTS. J Mammal 2002. [DOI: 10.1644/1545-1542(2002)083<0445:prtatm>2.0.co;2] [Citation(s) in RCA: 40] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022] Open
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Abstract
Examination of genotypes of female-pup nursing pairs taken from large maternity colonies of the Mexican free-tailed bat in Texas demonstrates that nursing is nonrandom and selective along genetic (kinship) lines. This is contrary to previous reports that nursing in these colonies is indiscriminate. Although nursing is nonrandom, an estimated 17 percent of the females sampled were nursing pups that could not be their offspring. This "nonparental" nursing is an apparent result of the difficulties females face in consistently relocating and selectively nursing their own pups within these enormous colonies.
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Pagels JF. Temperature regulation, body weight and changes in total body fat of the free-tailed bat, Tadarida brasiliensis cynocephala (Le Conte). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1975; 50:237-46. [PMID: 234324 DOI: 10.1016/0300-9629(75)90005-5] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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Pagels JF. The effects of short and prolonged cold exposure on arousal in the free-tailed bat, Tadarida brasiliensis cynocephala (Le conte). COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1972; 42:559-67. [PMID: 4404384 DOI: 10.1016/0300-9629(72)90134-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Studier EH, O'Farrell MJ. Biology of Myotis thysanodes and M. lucifugus (Chiroptera: Vespertilionidae). I. Thermoregulation. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY. A, COMPARATIVE PHYSIOLOGY 1972; 41:567-95. [PMID: 4401731 DOI: 10.1016/0300-9629(72)90014-x] [Citation(s) in RCA: 57] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Studier EH, Wilson DE. Thermoregulation in some neotropical bats. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY 1970; 34:251-62. [PMID: 5426562 DOI: 10.1016/0010-406x(70)90164-7] [Citation(s) in RCA: 28] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Wang LC, Hudson JW. Some physiological aspects of temperature regulation in the normothermic and torpid hispid pocket mouse, Perognathus hispidus. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY 1970; 32:275-93. [PMID: 5417459 DOI: 10.1016/0010-406x(70)90941-2] [Citation(s) in RCA: 40] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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McNab BK. The economics of temperature regulation in neotropical bats. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY 1969; 31:227-68. [PMID: 5353570 DOI: 10.1016/0010-406x(69)91651-x] [Citation(s) in RCA: 170] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Morrison P, McNab BK. Temperature regulation in some Brazilian phyllostomid bats. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY 1967; 21:207-21. [PMID: 6033838 DOI: 10.1016/0010-406x(67)90130-2] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Leitner P, Nelson JE. Body temperature, oxygen consumption and heart rate in the Australian false vampire bat, Macroderma gigas. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY 1967; 21:65-74. [PMID: 6033844 DOI: 10.1016/0010-406x(67)90115-6] [Citation(s) in RCA: 34] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
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Leitner P. Body temperature, oxygen consumption, heart rate and shivering in the California mastiff bat, Eumops perotis. ACTA ACUST UNITED AC 1966. [DOI: 10.1016/0010-406x(66)90152-6] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Tucker VA. Oxygen consumption, thermal conductance, and torpor in the California pocket mouse Perognathus californicus. J Cell Physiol 1965; 65:393-403. [PMID: 5836969 DOI: 10.1002/jcp.1030650313] [Citation(s) in RCA: 79] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023]
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