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Petrullo L, Delaney D, Boutin S, Lane JE, McAdam AG, Dantzer B. A future food boom rescues the negative effects of early-life adversity on adult lifespan in a small mammal. Proc Biol Sci 2024; 291:20232681. [PMID: 38654643 PMCID: PMC11040256 DOI: 10.1098/rspb.2023.2681] [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: 12/04/2023] [Accepted: 03/26/2024] [Indexed: 04/26/2024] Open
Abstract
Early-life adversity, even when transient, can have lasting effects on individual phenotypes and reduce lifespan across species. If these effects can be mitigated by a high-quality later-life environment, then differences in future resources may explain variable resilience to early-life adversity. Using data from over 1000 wild North American red squirrels, we tested the hypothesis that the costs of early-life adversity for adult lifespan could be offset by later-life food abundance. We identified six adversities that reduced juvenile survival in the first year of life, though only one-birth date-had continued independent effects on adult lifespan. We then built a weighted early-life adversity (wELA) index integrating the sum of adversities and their effect sizes. Greater weighted early-life adversity predicted shorter adult lifespans in males and females, but a naturally occurring food boom in the second year of life ameliorated this effect. Experimental food supplementation did not replicate this pattern, despite increasing lifespan, indicating that the buffering effect of a future food boom may hinge on more than an increase in available calories. Our results suggest a non-deterministic role of early-life conditions for later-life phenotype, highlighting the importance of evaluating the consequences of early-life adversity in the context of an animal's entire life course.
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Affiliation(s)
- Lauren Petrullo
- Department of Ecology and Evolutionary Biology, University of Arizona, Tucson, 857192, AZ, USA
| | - David Delaney
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, 803023, CO, USA
- Department of Natural Resource Ecology and Management, Iowa State University, Ames, 500114, IA, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, T6G 2R35, Alberta, Canada
| | - Jeffrey E. Lane
- Department of Biology, University of Saskatchewan, Saskatoon, S7N 5A26, Saskatchewan, Canada
| | - Andrew G. McAdam
- Department of Natural Resource Ecology and Management, Iowa State University, Ames, 500114, IA, USA
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, 481097, MI, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, 481097, MI, USA
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2
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Petrullo L, Boutin S, Lane JE, McAdam AG, Dantzer B. Phenotype-environment mismatch errors enhance lifetime fitness in wild red squirrels. Science 2023; 379:269-272. [PMID: 36656926 DOI: 10.1126/science.abn0665] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
Mismatches between an organism's phenotype and its environment can result in short-term fitness costs. Here, we show that some phenotype-environment mismatch errors can be explained by asymmetrical costs of different types of errors in wild red squirrels. Mothers that mistakenly increased reproductive effort when signals of an upcoming food pulse were absent were more likely to correctly increase effort when a food pulse did occur. However, mothers that failed to increase effort when cues of an upcoming food pulse were present suffered lifetime fitness costs that could only be offset through food supplementation. In fluctuating environments, such phenotype-environment mismatches may therefore reflect a bias to overestimate environmental cues and avoid making the costliest error, ultimately enhancing lifetime fitness.
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Affiliation(s)
- Lauren Petrullo
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, Canada
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, Canada
| | - Andrew G McAdam
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
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3
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Walmsley SF, Boutin S, Dantzer B, Lane JE, Coltman DW, McAdam AG. Benefits of living closer to kin vary by genealogical relationship in a territorial mammal. Proc Biol Sci 2023; 290:20221569. [PMID: 36629099 PMCID: PMC9832554 DOI: 10.1098/rspb.2022.1569] [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: 08/10/2021] [Accepted: 12/05/2022] [Indexed: 01/12/2023] Open
Abstract
While cooperative interactions among kin are a key building block in the societies of group-living species, their importance for species with more variable social environments is unclear. North American red squirrels (Tamiasciurus hudsonicus) defend individual territories in dynamic neighbourhoods and are known to benefit from living among familiar conspecifics, but not relatives. However, kin-directed behaviours may be restricted to specific genealogical relationships or strongly mediated by geographical distance, masking their influence at broader scales. Using distance between territories as a proxy for the ability of individuals to interact, we estimated the influence of primary kin (parents, offspring, siblings) on the annual survival and reproductive success of red squirrels. This approach revealed associations between fitness and access to kin, but only for certain genealogical relationships and fitness components. For example, females had enhanced annual survival when living closer to their daughters, though the reverse was not true. Most surprising was the finding that males had higher annual reproductive success when living closer to their father, suggesting possible recognition and cooperation among fathers and sons. Together, these findings point to unexpected nuance in the fitness consequences of kinship dynamics for a species that is territorial and largely solitary.
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Affiliation(s)
- Sam F. Walmsley
- Department of Ecology and Evolutionary Biology, University of Colorado, 1900 Pleasant Street, Boulder, CO 80309, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, Alberta, Canada T6G 2E9
| | - Ben Dantzer
- Department of Psychology, University of Michigan, 500 South State Street, Ann Arbor, MI 48109, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, 500 South State Street, Ann Arbor, MI 48109, USA
| | - Jeffrey E. Lane
- Department of Biology, University of Saskatchewan, 112 Science Place, Saskatoon, Canada S7N 5E2
| | - David W. Coltman
- Department of Biological Sciences, University of Alberta, 11455 Saskatchewan Drive, Edmonton, Alberta, Canada T6G 2E9
- Biology Department, Western University, 1151 Richmond Street, London, Ontario, Canada N6A 5B7
| | - Andrew G. McAdam
- Department of Ecology and Evolutionary Biology, University of Colorado, 1900 Pleasant Street, Boulder, CO 80309, USA
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Petrullo L, Delaney D, Boutin S, McAdam AG, Lane JE, Boonstra R, Palme R, Dantzer B. The glucocorticoid response to environmental change is not specific to agents of natural selection in wild red squirrels. Horm Behav 2022; 146:105262. [PMID: 36191397 DOI: 10.1016/j.yhbeh.2022.105262] [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: 06/14/2022] [Revised: 08/30/2022] [Accepted: 09/07/2022] [Indexed: 11/04/2022]
Abstract
Evolutionary endocrinology aims to understand how natural selection shapes endocrine systems and the degree to which endocrine systems themselves can induce phenotypic responses to environmental changes. Such responses may be specialized in that they reflect past selection for responsiveness only to those ecological factors that ultimately influence natural selection. Alternatively, endocrine responses may be broad and generalized, allowing organisms to cope with a variety of environmental changes simultaneously. Here, we empirically tested whether the endocrine response of female North American red squirrels (Tamiasciurus hudsonicus) was specialized or generalized. We first quantified the direction and magnitude of natural selection acting on three female life history traits (parturition date, litter size, offspring postnatal growth rate) during 32 years of fluctuations in four potential ecological agents of selection (food availability, conspecific density, predator abundance, and temperature). Only three of the four variables (food, density, and predators) affected patterns of natural selection on female life history traits. We then quantified fecal glucocorticoid metabolites (FGMs) across 7 years and found that all four environmental variables, regardless of their effects on patterns of selection, were associated with glucocorticoid production. Our results provide support for a generalized, rather than specific, glucocorticoid response to environmental change that can integrate across multiple co-occurring environmental stressors.
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Affiliation(s)
- Lauren Petrullo
- Department of Psychology, University of Michigan, Ann Arbor, MI 48108, USA.
| | - David Delaney
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, Alberta T6G 2E9, Canada
| | - Andrew G McAdam
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309, USA
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, Saskatchewan S7N 5E2, Canada
| | - Rudy Boonstra
- Department of Biological Sciences, Centre for the Neurobiology of Stress, University of Toronto Scarborough, Toronto, ON M1C 1A6, Canada
| | - Rupert Palme
- Unit of Physiology, Pathophysiology and Experimental Endocrinology, Department of Biomedical Sciences, University of Veterinary Medicine Vienna, Veterina ̈rplatz 1, Vienna 1210, Austria
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI 48108, USA; Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48108, USA
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5
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Sex-specific effects of capital resources on reproductive timing and success in red squirrels. Behav Ecol Sociobiol 2022. [DOI: 10.1007/s00265-022-03245-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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6
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Gaidica M, Dantzer B. An implantable neurophysiology platform: Broadening research capabilities in free-living and non-traditional animals. Front Neural Circuits 2022; 16:940989. [PMID: 36213207 PMCID: PMC9537467 DOI: 10.3389/fncir.2022.940989] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2022] [Accepted: 09/05/2022] [Indexed: 12/02/2022] Open
Abstract
Animal-borne sensors that can record and transmit data (“biologgers”) are becoming smaller and more capable at a rapid pace. Biologgers have provided enormous insight into the covert lives of many free-ranging animals by characterizing behavioral motifs, estimating energy expenditure, and tracking movement over vast distances, thereby serving both scientific and conservational endpoints. However, given that biologgers are usually attached externally, access to the brain and neurophysiological data has been largely unexplored outside of the laboratory, limiting our understanding of how the brain adapts to, interacts with, or addresses challenges of the natural world. For example, there are only a handful of studies in free-living animals examining the role of sleep, resulting in a wake-centric view of behavior despite the fact that sleep often encompasses a large portion of an animal’s day and plays a vital role in maintaining homeostasis. The growing need to understand sleep from a mechanistic viewpoint and probe its function led us to design an implantable neurophysiology platform that can record brain activity and inertial data, while utilizing a wireless link to enable a suite of forward-looking capabilities. Here, we describe our design approach and demonstrate our device’s capability in a standard laboratory rat as well as a captive fox squirrel. We also discuss the methodological and ethical implications of deploying this new class of device “into the wild” to fill outstanding knowledge gaps.
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Affiliation(s)
- Matt Gaidica
- Department of Psychology, University of Michigan, Ann Arbor, MI, United States
- *Correspondence: Matt Gaidica,
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI, United States
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, United States
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7
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The socioeconomics of food hoarding in wild squirrels. Curr Opin Behav Sci 2022. [DOI: 10.1016/j.cobeha.2022.101139] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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8
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Martinig A, Karst H, Siracusa E, Studd E, McAdam A, Dantzer B, Delaney D, Lane J, Pokharel P, Boutin S. Animal personality: a comparison of standardized assays and focal observations in North American red squirrels. Anim Behav 2022. [DOI: 10.1016/j.anbehav.2022.05.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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9
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Dantzer B, Boutin S, Lane JE, McAdam AG. Integrative Studies of the Effects of Mothers on Offspring: An Example from Wild North American Red Squirrels. ADVANCES IN NEUROBIOLOGY 2022; 27:269-296. [PMID: 36169819 DOI: 10.1007/978-3-030-97762-7_9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/16/2023]
Abstract
Animal species vary in whether they provide parental care or the type of care provided, and this variation in parental care among species has been a common focus of comparative studies. However, the proximate causes and ultimate consequences of within-species variation in parental care have been less studied. Most studies about the impacts of within-species variation in parental care on parental fitness have been in primates, whereas studies in laboratory rodents have been invaluable for understanding what causes inter-individual variation in parental care and its influence on offspring characteristics. We integrated both of these perspectives in our long-term study of North American red squirrels (Tamiasciurus hudsonicus) in the Yukon, Canada, where we have focused on understanding the impacts of mothers on offspring. This includes documenting the impacts that mothers or the maternal environment itself has on their offspring, identifying how changes in maternal physiology impact offspring characteristics, the presence of individual variation in maternal attentiveness toward offspring before weaning and its fitness consequences, and postweaning maternal care and its fitness consequences. We provide an overview of these contributions to understanding the impacts mothers have on their offspring in red squirrels using an integrative framework and contrast them with studies in the laboratory.
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Affiliation(s)
- Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA.
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA.
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Andrew G McAdam
- Department of Ecology and Evolutionary Biology, University of Colorado, Boulder, CO, USA
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10
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Westrick SE, van Kesteren F, Boutin S, Lane JE, McAdam AG, Dantzer B. Maternal glucocorticoids have minimal effects on HPA axis activity and behavior of juvenile wild North American red squirrels. J Exp Biol 2021; 224:jeb.236620. [PMID: 33795416 DOI: 10.1242/jeb.236620] [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: 09/02/2020] [Accepted: 03/29/2021] [Indexed: 12/27/2022]
Abstract
As a response to environmental cues, maternal glucocorticoids (GCs) may trigger adaptive developmental plasticity in the physiology and behavior of offspring. In North American red squirrels (Tamiasciurus hudsonicus), mothers exhibit increased GCs when conspecific density is elevated, and selection favors more aggressive and perhaps more active mothers under these conditions. We tested the hypothesis that elevated maternal GCs cause shifts in offspring behavior that may prepare them for high-density conditions. We experimentally elevated maternal GCs during gestation or early lactation. We measured two behavioral traits (activity and aggression) in weaned offspring using standardized behavioral assays. Because maternal GCs may influence offspring hypothalamic-pituitary-adrenal (HPA) axis dynamics, which may in turn affect behavior, we also measured the impact of our treatments on offspring HPA axis dynamics (adrenal reactivity and negative feedback), and the association between offspring HPA axis dynamics and behavior. Increased maternal GCs during lactation, but not gestation, slightly elevated activity levels in offspring. Offspring aggression and adrenal reactivity did not differ between treatment groups. Male, but not female, offspring from mothers treated with GCs during pregnancy exhibited stronger negative feedback compared with those from control mothers, but there were no differences in negative feedback between lactation treatment groups. Offspring with higher adrenal reactivity from mothers treated during pregnancy (both controls and GC-treated) exhibited lower aggression and activity. These results suggest that maternal GCs during gestation or early lactation alone may not be a sufficient cue to produce substantial changes in behavioral and physiological stress responses in offspring in natural populations.
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Affiliation(s)
- Sarah E Westrick
- Department of Psychology, University of Michigan, Ann Arbor, MI48109-1043, USA
| | - Freya van Kesteren
- Department of Psychology, University of Michigan, Ann Arbor, MI48109-1043, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada, T6G 2E9
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada, S7N 5E2
| | - Andrew G McAdam
- Ecology and Evolutionary Biology, University of Colorado, Boulder, CO 80309-0334, USA
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI48109-1043, USA.,Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI 48109-1085, USA
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11
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Martinig AR, Mathot KJ, Lane JE, Dantzer B, Boutin S. Selective disappearance does not underlie age-related changes in trait repeatability in red squirrels. Behav Ecol 2021. [DOI: 10.1093/beheco/araa136] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Understanding the causes and consequences of repeatable among-individual differences in behavior (i.e., animal personality) is a major area of research in behavioral and evolutionary ecology. Recently, attention has turned to understanding the processes behind changes in repeatability through ontogeny because of their implications for populations. We evaluated the relative importance of selective disappearance (i.e., differential mortality), an among-individual mechanism, in generating age-related changes in the repeatability of aggression and activity in juvenile North American red squirrels (Tamiasciurus hudsonicus). We observed age-related decreases in the repeatability of aggression across ages, arising from lower among-individual variance. Although we found evidence for directional selection on aggressiveness, it was insufficient to erode among-individual variance. Thus, ontogenetic decreases in the repeatability of aggression do not appear to be due to selective disappearance. In contrast, the repeatability of activity was higher across ages due to higher among-individual variance in activity, but there was no support for selective disappearance based on activity. Taken together, our results suggest that age-related changes in trait repeatability in red squirrels are not the result of selective disappearance and instead may be the result of within-individual developmental processes, such as individual differences in developmental trajectories.
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Affiliation(s)
| | - Kimberley J Mathot
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Science Pl, Saskatoon, SK, Canada
| | - Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA
- Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
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12
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Siracusa ER, Boutin S, Dantzer B, Lane JE, Coltman DW, McAdam AG. Familiar Neighbors, but Not Relatives, Enhance Fitness in a Territorial Mammal. Curr Biol 2021; 31:438-445.e3. [DOI: 10.1016/j.cub.2020.10.072] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2020] [Revised: 10/01/2020] [Accepted: 10/23/2020] [Indexed: 01/10/2023]
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13
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Dantzer B, McAdam AG, Humphries MM, Lane JE, Boutin S. Decoupling the effects of food and density on life-history plasticity of wild animals using field experiments: Insights from the steward who sits in the shadow of its tail, the North American red squirrel. J Anim Ecol 2020; 89:2397-2414. [PMID: 32929740 DOI: 10.1111/1365-2656.13341] [Citation(s) in RCA: 18] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2020] [Accepted: 08/07/2020] [Indexed: 01/05/2023]
Abstract
Long-term studies of wild animals provide the opportunity to investigate how phenotypic plasticity is used to cope with environmental fluctuations and how the relationships between phenotypes and fitness can be dependent upon the ecological context. Many previous studies have only investigated life-history plasticity in response to changes in temperature, yet wild animals often experience multiple environmental fluctuations simultaneously. This requires field experiments to decouple which ecological factor induces plasticity in fitness-relevant traits to better understand their population-level responses to those environmental fluctuations. For the past 32 years, we have conducted a long-term integrative study of individually marked North American red squirrels Tamiasciurus hudsonicus Erxleben in the Yukon, Canada. We have used multi-year field experiments to examine the physiological and life-history responses of individual red squirrels to fluctuations in food abundance and conspecific density. Our long-term observational study and field experiments show that squirrels can anticipate increases in food availability and density, thereby decoupling the usual pattern where animals respond to, rather than anticipate, an ecological change. As in many other study systems, ecological factors that can induce plasticity (such as food and density) covary. However, our field experiments that manipulate food availability and social cues of density (frequency of territorial vocalizations) indicate that increases in social (acoustic) cues of density in the absence of additional food can induce similar life-history plasticity, as does experimental food supplementation. Changes in the levels of metabolic hormones (glucocorticoids) in response to variation in food and density are one mechanism that seems to induce this adaptive life-history plasticity. Although we have not yet investigated the energetic response of squirrels to elevated density or its association with life-history plasticity, energetics research in red squirrels has overturned several standard pillars of knowledge in physiological ecology. We show how a tractable model species combined with integrative studies can reveal how animals cope with resource fluctuations through life-history plasticity.
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Affiliation(s)
- Ben Dantzer
- Department of Psychology, University of Michigan, Ann Arbor, MI, USA.,Department of Ecology and Evolutionary Biology, University of Michigan, Ann Arbor, MI, USA
| | - Andrew G McAdam
- Department for Ecology and Evolutionary Biology, University of Colorado Boulder, Boulder, CO, USA
| | - Murray M Humphries
- Natural Resource Sciences Department, McGill University, Ste-Anne-de-Bellevue, QC, Canada
| | - Jeffrey E Lane
- Department of Biology, University of Saskatchewan, Saskatoon, SK, Canada
| | - Stan Boutin
- Department of Biological Sciences, University of Alberta, Edmonton, AB, Canada
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14
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Westrick SE, Taylor RW, Boutin S, Lane JE, McAdam AG, Dantzer B. Attentive red squirrel mothers have faster growing pups and higher lifetime reproductive success. Behav Ecol Sociobiol 2020. [DOI: 10.1007/s00265-020-02856-7] [Citation(s) in RCA: 22] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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