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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 squirrelsTamiasciurus hudsonicusErxleben 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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This content will become publicly available on November 1, 2026
Harbingers of change: Towards a mechanistic understanding of anticipatory plasticity in animal systems
Abstract Phenotypic plasticity is a strategy by which animals alter behaviour, morphology and/or physiology in response to cues of current conditions to cope with environmental heterogeneity.If environmental change is impending and cues reliably predict future conditions, animals can also respond in anticipation of these changes (i.e. anticipatory plasticity) if they possess the mechanistic architecture necessary to do so. This phenomenon has been documented across the tree of life, but how animals integrate cues of future conditions and mount anticipatory responses remains largely ambiguous.Here, we synthesize theoretical principles from sensory biology and animal communication with recent advances in physiological ecology to identify candidate physiological mechanisms underpinning anticipatory plasticity in animal systems.We discuss how socio‐ecological rhythms, cue perception and interactions between the epigenome, neuroendocrine system and gut microbiota can contribute to the maintenance and evolution of anticipatory plasticity, including anticipatory reproduction.We shed light on the proximate and ultimate mechanisms that facilitate the evolution and maintenance of anticipatory plasticity in the face of environmental heterogeneity, contributing to a broader understanding of how animals may respond to rapid global change as environmental cues become unreliable and conditions unpredictable. Read the freePlain Language Summaryfor this article on the Journal blog.
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- PAR ID:
- 10655910
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- Functional Ecology
- Volume:
- 39
- Issue:
- 11
- ISSN:
- 0269-8463
- Page Range / eLocation ID:
- 2999 to 3020
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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