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Wilson LN, Gardner JD, Wilson JP, Farnsworth A, Perry ZR, Druckenmiller PS, Erickson GM, Organ CL. Global latitudinal gradients and the evolution of body size in dinosaurs and mammals. Nat Commun 2024; 15:2864. [PMID: 38580657 PMCID: PMC10997647 DOI: 10.1038/s41467-024-46843-2] [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: 01/05/2024] [Accepted: 03/12/2024] [Indexed: 04/07/2024] Open
Abstract
Global climate patterns fundamentally shape the distribution of species and ecosystems. For example, Bergmann's rule predicts that homeothermic animals, including birds and mammals, inhabiting cooler climates are generally larger than close relatives from warmer climates. The modern world, however, lacks the comparative data needed to evaluate such macroecological rules rigorously. Here, we test for Bergmann's rule in Mesozoic dinosaurs and mammaliaforms that radiated within relatively temperate global climate regimes. We develop a phylogenetic model that accounts for biases in the fossil record and allows for variable evolutionary dispersal rates. Our analysis also includes new fossil data from the extreme high-latitude Late Cretaceous Arctic Prince Creek Formation. We find no evidence for Bergmann's rule in Mesozoic dinosaurs or mammaliaforms, the ancestors of extant homeothermic birds and mammals. When our model is applied to thousands of extant dinosaur (bird) and mammal species, we find that body size evolution remains independent of latitude. A modest temperature effect is found in extant, but not in Mesozoic, birds, suggesting that body size evolution in modern birds was influenced by Bergmann's rule during Cenozoic climatic change. Our study provides a general approach for studying macroecological rules, highlighting the fossil record's power to address longstanding ecological principles.
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Affiliation(s)
- Lauren N Wilson
- University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA.
- Department of Geosciences, University of Alaska, Fairbanks, AK, 99775, USA.
| | - Jacob D Gardner
- School of Biological Sciences, University of Reading, Reading, RG6 6EX, UK.
| | - John P Wilson
- Department of Earth Sciences, Montana State University, Bozeman, MT, 59715, USA
| | - Alex Farnsworth
- School of Geographical Sciences, University of Bristol, University Road, Bristol, BS8 1RL, UK
- State Key Laboratory of Tibetan Plateau Earth System, Resources and Environment (TPESRE), Institute of Tibetan Plateau Research, Chinese Academy of Sciences, Beijing, 100101, China
| | - Zackary R Perry
- University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
- Department of Geosciences, University of Alaska, Fairbanks, AK, 99775, USA
| | - Patrick S Druckenmiller
- University of Alaska Museum, 1962 Yukon Drive, Fairbanks, AK, 99775, USA
- Department of Geosciences, University of Alaska, Fairbanks, AK, 99775, USA
| | - Gregory M Erickson
- Department of Biological Science, Florida State University, Tallahassee, FL, 32306, USA
| | - Chris L Organ
- School of Biological Sciences, University of Reading, Reading, RG6 6EX, UK.
- Department of Earth Sciences, Montana State University, Bozeman, MT, 59715, USA.
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Kellner A, Atwood TC, Douglas DC, Breck SW, Wittemyer G. High winds and melting sea ice trigger landward movement in a polar bear population of concern. Ecosphere 2023. [DOI: 10.1002/ecs2.4420] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/12/2023] Open
Affiliation(s)
- Annie Kellner
- Graduate Degree Program in Ecology Colorado State University Fort Collins Colorado USA
- Department of Fish, Wildlife, and Conservation Biology Colorado State University Fort Collins Colorado USA
| | - Todd C. Atwood
- U.S. Geological Survey Alaska Science Center Anchorage Alaska USA
| | | | - Stewart W. Breck
- USDA‐WS‐National Wildlife Research Center Fort Collins Colorado USA
| | - George Wittemyer
- Graduate Degree Program in Ecology Colorado State University Fort Collins Colorado USA
- Department of Fish, Wildlife, and Conservation Biology Colorado State University Fort Collins Colorado USA
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Rode KD, Douglas D, Atwood T, Durner G, Wilson R, Pagano A. Observed and forecasted changes in land use by polar bears in the Beaufort and Chukchi Seas, 1985–2040. Glob Ecol Conserv 2022. [DOI: 10.1016/j.gecco.2022.e02319] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Togunov RR, Derocher AE, Lunn NJ, Auger-Méthé M. Drivers of polar bear behavior and the possible effects of prey availability on foraging strategy. MOVEMENT ECOLOGY 2022; 10:50. [PMID: 36384775 PMCID: PMC9670556 DOI: 10.1186/s40462-022-00351-4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2022] [Accepted: 11/09/2022] [Indexed: 06/05/2023]
Abstract
BACKGROUND Change in behavior is one of the earliest responses to variation in habitat suitability. It is therefore important to understand the conditions that promote different behaviors, particularly in areas undergoing environmental change. Animal movement is tightly linked to behavior and remote tracking can be used to study ethology when direct observation is not possible. METHODS We used movement data from 14 polar bears (Ursus maritimus) in Hudson Bay, Canada, during the foraging season (January-June), when bears inhabit the sea ice. We developed an error-tolerant method to correct for sea ice drift in tracking data. Next, we used hidden Markov models with movement and orientation relative to wind to study three behaviors (stationary, area-restricted search, and olfactory search) and examine effects of 11 covariates on behavior. RESULTS Polar bears spent approximately 47% of their time in the stationary drift state, 29% in olfactory search, and 24% in area-restricted search. High energy behaviors occurred later in the day (around 20:00) compared to other populations. Second, olfactory search increased as the season progressed, which may reflect a shift in foraging strategy from still-hunting to active search linked to a shift in seal availability (i.e., increase in haul-outs from winter to the spring pupping and molting seasons). Last, we found spatial patterns of distribution linked to season, ice concentration, and bear age that may be tied to habitat quality and competitive exclusion. CONCLUSIONS Our observations were generally consistent with predictions of the marginal value theorem, and differences between our findings and other populations could be explained by regional or temporal variation in resource availability. Our novel movement analyses and finding can help identify periods, regions, and conditions of critical habitat.
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Affiliation(s)
- Ron R. Togunov
- Institute for the Oceans and Fisheries, The University of British Columbia, V6T 1Z4 Vancouver, Canada
- Department of Zoology, The University of British Columbia, Vancouver, V6T 1Z4 Canada
| | - Andrew E. Derocher
- Department of Biological Sciences, University of Alberta, Edmonton, T6G 2E9 Canada
| | - Nicholas J. Lunn
- Wildlife Research Division, Science and Technology Branch, Environment and Climate Change Canada, Edmonton, T6G 2E9 Canada
| | - Marie Auger-Méthé
- Institute for the Oceans and Fisheries, The University of British Columbia, V6T 1Z4 Vancouver, Canada
- Department of Statistics, The University of British Columbia, Vancouver, V6T 1Z4 Canada
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Patil VP, Durner GM, Douglas DC, Atwood TC. Modeling the spatial and temporal dynamics of land‐based polar bear denning in Alaska. J Wildl Manage 2022. [DOI: 10.1002/jwmg.22302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Affiliation(s)
- Vijay P. Patil
- Alaska Science Center U.S. Geological Survey 4210 University Drive Anchorage AK 99508 USA
| | - George M. Durner
- Alaska Science Center U.S. Geological Survey 4210 University Drive Anchorage AK 99508 USA
| | - David C. Douglas
- Alaska Science Center U.S. Geological Survey 250 Egan Drive Juneau AK 99801 USA
| | - Todd C. Atwood
- Alaska Science Center U.S. Geological Survey 4210 University Drive Anchorage AK 99508 USA
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Wilson RR, Martin MS, Regehr EV, Rode KD. Intrapopulation differences in polar bear movement and step selection patterns. MOVEMENT ECOLOGY 2022; 10:25. [PMID: 35606849 PMCID: PMC9128121 DOI: 10.1186/s40462-022-00326-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 05/14/2022] [Indexed: 06/15/2023]
Abstract
BACKGROUND The spatial ecology of individuals often varies within a population or species. Identifying how individuals in different classes interact with their environment can lead to a better understanding of population responses to human activities and environmental change and improve population estimates. Most inferences about polar bear (Ursus maritimus) spatial ecology are based on data from adult females due to morphological constraints on applying satellite radio collars to other classes of bears. Recent studies, however, have provided limited movement data for adult males and sub-adults of both sexes using ear-mounted and glue-on tags. We evaluated class-specific movements and step selection patterns for polar bears in the Chukchi Sea subpopulation during spring. METHODS We developed hierarchical Bayesian models to evaluate polar bear movement (i.e., step length and directional persistence) and step selection at the scale of 4-day step lengths. We assessed differences in movement and step selection parameters among the three classes of polar bears (i.e., adult males, sub-adults, and adult females without cubs-of-the-year). RESULTS Adult males had larger step lengths and less directed movements than adult females. Sub-adult movement parameters did not differ from the other classes but point estimates were most similar to adult females. We did not detect differences among polar bear classes in step selection parameters and parameter estimates were consistent with previous studies. CONCLUSIONS Our findings support the use of estimated step selection patterns from adult females as a proxy for other classes of polar bears during spring. Conversely, movement analyses indicated that using data from adult females as a proxy for the movements of adult males is likely inappropriate. We recommend that researchers consider whether it is valid to extend inference derived from adult female movements to other classes, based on the questions being asked and the spatial and temporal scope of the data. Because our data were specific to spring, these findings highlight the need to evaluate differences in movement and step selection during other periods of the year, for which data from ear-mounted and glue-on tags are currently lacking.
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Affiliation(s)
- Ryan R Wilson
- U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA.
| | - Michelle St Martin
- U.S. Fish and Wildlife Service, Marine Mammals Management, Anchorage, AK, USA
- U.S. Fish and Wildlife Service, Portland, OR, 97266, USA
| | - Eric V Regehr
- Polar Science Center, University of Washington, Seattle, WA, USA
| | - Karyn D Rode
- U.S. Geological Survey, Alaska Science Center, Anchorage, AK, USA
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Atwood TC, Rode KD, Douglas DC, Simac K, Pagano AM, Bromaghin JF. Long-term variation in polar bear body condition and maternal investment relative to a changing environment. Glob Ecol Conserv 2021. [DOI: 10.1016/j.gecco.2021.e01925] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Pagano AM, Durner GM, Atwood TC, Douglas DC. Effects of sea ice decline and summer land use on polar bear home range size in the Beaufort Sea. Ecosphere 2021. [DOI: 10.1002/ecs2.3768] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Affiliation(s)
- Anthony M. Pagano
- U.S. Geological Survey Alaska Science Center Anchorage Alaska 99508 USA
| | - George M. Durner
- U.S. Geological Survey Alaska Science Center Anchorage Alaska 99508 USA
| | - Todd C. Atwood
- U.S. Geological Survey Alaska Science Center Anchorage Alaska 99508 USA
| | - David C. Douglas
- U.S. Geological Survey Alaska Science Center Juneau Alaska 99801 USA
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Bromaghin JF, Douglas DC, Durner GM, Simac KS, Atwood TC. Survival and abundance of polar bears in Alaska's Beaufort Sea, 2001-2016. Ecol Evol 2021; 11:14250-14267. [PMID: 34707852 PMCID: PMC8525099 DOI: 10.1002/ece3.8139] [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: 04/07/2021] [Revised: 08/02/2021] [Accepted: 09/06/2021] [Indexed: 12/20/2022] Open
Abstract
The Arctic Ocean is undergoing rapid transformation toward a seasonally ice-free ecosystem. As ice-adapted apex predators, polar bears (Ursus maritimus) are challenged to cope with ongoing habitat degradation and changes in their prey base driven by food-web response to climate warming. Knowledge of polar bear response to environmental change is necessary to understand ecosystem dynamics and inform conservation decisions. In the southern Beaufort Sea (SBS) of Alaska and western Canada, sea ice extent has declined since satellite observations began in 1979 and available evidence suggests that the carrying capacity of the SBS for polar bears has trended lower for nearly two decades. In this study, we investigated the population dynamics of polar bears in Alaska's SBS from 2001 to 2016 using a multistate Cormack-Jolly-Seber mark-recapture model. States were defined as geographic regions, and we used location data from mark-recapture observations and satellite-telemetered bears to model transitions between states and thereby explain heterogeneity in recapture probabilities. Our results corroborate prior findings that the SBS subpopulation experienced low survival from 2003 to 2006. Survival improved modestly from 2006 to 2008 and afterward rebounded to comparatively high levels for the remainder of the study, except in 2012. Abundance moved in concert with survival throughout the study period, declining substantially from 2003 and 2006 and afterward fluctuating with lower variation around an average of 565 bears (95% Bayesian credible interval [340, 920]) through 2015. Even though abundance was comparatively stable and without sustained trend from 2006 to 2015, polar bears in the Alaska SBS were less abundant over that period than at any time since passage of the U.S. Marine Mammal Protection Act. The potential for recovery is likely limited by the degree of habitat degradation the subpopulation has experienced, and future reductions in carrying capacity are expected given current projections for continued climate warming.
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Affiliation(s)
| | | | | | | | - Todd C. Atwood
- U.S. Geological SurveyAlaska Science CenterAnchorageAKUSA
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Van der Walt M, Neuman-Lee LA, Terletzky PA, Atwood TC, Gese EM, French SS. Measuring adrenal and reproductive hormones in hair from Southern Beaufort Sea polar bears (Ursus maritimus). Gen Comp Endocrinol 2021; 310:113807. [PMID: 33964286 DOI: 10.1016/j.ygcen.2021.113807] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/02/2020] [Revised: 04/29/2021] [Accepted: 05/03/2021] [Indexed: 11/23/2022]
Abstract
Polar bears (Ursus maritimus) use sea ice to access marine mammal prey. In Alaska's Southern Beaufort Sea, the declining availability of sea ice habitat in summer and fall has reduced opportunities for polar bears to routinely hunt on the ice for seals, their primary prey. This reduced access to prey may result in physiological stress with subsequent potential consequences to reproductive function (physiological changes that accompany reproduction), which can be measured via reproductive hormones. Hormone concentrations in hair can be used as a minimally invasive alternative to serum concentrations, which must come from animal captures. Hair samples also provide a long-term average measurement of hormone concentrations that is not influenced by short-term fluctuations like that of serum. The aim of this study was (1) to determine if a radioimmunoassay could be used to measure adrenal and reproductive hormones in polar bear hair, and (2) to determine what the relationship is between these hormones and other reproductive, condition, and demographic parameters of polar bears. We successfully validated this method for cortisol, progesterone, estradiol, and testosterone through the analysis of hair and serum of 141 free-ranging polar bears. We found that while hair cannot be used to estimate serum hormone concentrations during the breeding season, hormone concentrations in hair can be used to measure reproductive function in polar bears. Further, our findings support trends in previous studies measuring hormone concentrations in serum. We found that adrenal and some reproductive hormones were positively correlated in hair samples of females. Associations between hormone concentrations in hair and serum did not vary relative to reproductive status of adult females. Serum testosterone increased throughout the breeding season for adult males and was significantly associated with body mass index (BMI). Our research supports the use of hair as a measure of reproductive function in polar bears and allows us to monitor the future effects of climate change on polar bear physiology.
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Affiliation(s)
- Marilize Van der Walt
- Department of Biology and the Ecology Center, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA.
| | - Lorin A Neuman-Lee
- Department of Biology and the Ecology Center, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA.
| | - Patricia A Terletzky
- Department of Wildland Resources, Utah State University, 5230 Old Main Hill, Logan, UT 84322, USA.
| | - Todd C Atwood
- U.S. Geological Survey, Alaska Science Center, 4210 University Drive, Anchorage, AK 99508, USA.
| | - Eric M Gese
- U.S. Department of Agriculture, Wildlife Services, National Wildlife Research Center, Department of Wildland Resources, Utah State University, Logan, UT 84322, USA.
| | - Susannah S French
- Department of Biology and the Ecology Center, Utah State University, 5305 Old Main Hill, Logan, UT 84322, USA
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Pagano AM, Atwood TC, Durner GM, Williams TM. The seasonal energetic landscape of an apex marine carnivore, the polar bear. Ecology 2020; 101:e02959. [DOI: 10.1002/ecy.2959] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/20/2019] [Revised: 10/22/2019] [Accepted: 11/12/2019] [Indexed: 12/12/2022]
Affiliation(s)
- Anthony M. Pagano
- U.S. Geological SurveyAlaska Science Center4210 University Drive Anchorage Alaska99508USA
- Department of Ecology & Evolutionary Biology University of California Santa Cruz 130 McAllister Way Santa Cruz California95060USA
| | - Todd C. Atwood
- U.S. Geological SurveyAlaska Science Center4210 University Drive Anchorage Alaska99508USA
| | - George M. Durner
- U.S. Geological SurveyAlaska Science Center4210 University Drive Anchorage Alaska99508USA
| | - Terrie M. Williams
- Department of Ecology & Evolutionary Biology University of California Santa Cruz 130 McAllister Way Santa Cruz California95060USA
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