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Data from: Exploration profiles drive activity patterns and temporal niche specialization in a wild rodent
Gharnit, Elouana; Bergeron, Patrick; Garant, Dany; Réale, Denis — 2020-03-02 <p>Individual niche specialization can have important consequences for competition, fitness, and ultimately population dynamics and ecological speciation. The temporal window and the level of daily activity are niche components that may vary with sex, breeding season, food supply, population density, and predator’s circadian rhythm. More recently, ecologists emphasized that traits such as dispersal and space use could depend on personality differences. Boldness and exploration have been shown to correlate with variation in foraging patterns, habitat use, and home range. Here we assessed the link between exploration, measured from repeated novel environment tests, activity patterns, and temporal niche specialization in wild eastern chipmunks (<i>Tamias striatus</i>). Intrinsic differences in exploration should drive daily activity patterns through differences in energy requirements, space use, or the speed to access resources. We used collar-mounted accelerometers to assess whether individual exploration profiles predicted: (1) daily overall dynamic body acceleration, reflecting overall activity levels; (2) mean activity duration and the rate of activity sequences, reflecting the structure of daily activity; and (3) patterns of dawn and dusk activity, reflecting temporal niche differentiation. Exploration and overall activity levels were weakly related. However, both dawn activity and rate of activity sequences increased with the speed of exploration. Overall, activity patterns varied according to temporal variability in food conditions. This study emphasizes the role of intrinsic behavioral differences in activity patterns in a wild animal population. Future studies will help us understand how yearly seasonality in reproduction, food abundance, and population density modulate personality-dependent foraging patterns and temporal niche specialization.</p>
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Chipmunk body mass variations and life-histories in a pulsed resource ecosystem
Bergeron, Patrick — 2022-04-27 <p><span lang="EN-US">Phenotypic plasticity is the most immediate mechanism of adaptative response to environmental change. Studying plastic changes in response to fluctuating environments provides insights into how such adjustments may impact life-history traits. Here, we used a 14-year dataset of repeated body mass measurements in male eastern chipmunks (<em>Tamias striatus</em>) to assess the extent of plastic changes for this trait in a resource pulse ecosystem. We first determined the magnitude of variation in body mass at the population level in response to the drastic change in food resource availability from American beech tree seeds (<em>Fagus grandifolia</em>). Males that emerged in the spring from winter torpor following a non-mast year had a lower body mass than males emerging after a mast year, but they tended to recover this loss by mid-June. We found significant among-individual variation in spring body mass plasticity (i.e., individual by environment interaction, I x E). We then investigated the relationships between individual spring body mass plasticity, longevity and lifetime reproductive success. Interestingly, heavier males lived longer than lighter males, but more plastic males had a lower longevity and lower lifetime reproductive success than less plastic males. The report of such plastic response in a stochastic resource system provides valuable insights into the interplay between the costs and benefits of phenotypic plasticity as an adaptation to environmental fluctuations.</span></p>
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Data from: Environmental conditions affect spatial genetic structures and dispersal patterns in a solitary rodent
Dubuc Messier, Gabrielle; Garant, Dany; Bergeron, Patrick; Réale, Denis — 2012-08-17 The study of the spatial distribution of relatives in a population under contrasted environmental conditions provides critical insights into the flexibility of dispersal behaviour and the role of environmental conditions in shaping population relatedness and social structure. Yet few studies have evaluated the effects of fluctuating environmental conditions on relatedness structure of solitary species in the wild. The aim of this study was to determine the impact of interannual variations in environmental conditions on the spatial distribution of relatives [spatial genetic structure (SGS)] and dispersal patterns of a wild population of eastern chipmunks (Tamias striatus), a solitary rodent of North America. Eastern chipmunks depend on the seed of masting trees for reproduction and survival. Here, we combined the analysis of the SGS of adults with direct estimates of juvenile dispersal distance during six contrasted years with different dispersal seasons, population sizes and seed production. We found that environmental conditions influences the dispersal distances of juveniles and that male juveniles dispersed farther than females. The extent of the SGS of adult females varied between years and matched the variation in environmental conditions. In contrast, the SGS of males did not vary between years. We also found a difference in SGS between males and females that was consistent with male-biased dispersal. This study suggests that both the dispersal behaviour and the relatedness structure in a population of a solitary species can be relatively labile and change according to environmental conditions.
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Data from: Social selection acts on behavior and body mass but does not contribute to the total selection differential in Eastern chipmunks
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Santostefano, Francesca; Garant, Dany; Bergeron, Patrick; Montiglio, Pierre-Olivier; Réale, Denis — 2019-11-04 <p>Through social interactions, phenotypes of conspecifics can affect an individual’s fitness, resulting in social selection. Social selection is assumed to represent a strong and dynamic evolutionary force that can act with or in opposition to natural selection. Few studies, however, have estimated social selection and its contribution to total selection in the wild. We estimated natural and social selection gradients on exploration, docility, and body mass, and their contribution to selection differentials, in a wild Eastern chipmunk population (<i>Tamias striatus</i>). We applied trait-based multiple regression models derived from classical phenotypic selection analyses, which allowed us to include several social partners (i.e., neighbors). We detected social selection gradients on female docility and male body mass, indicating that female with docile neighbors and males with large neighbors had lower fitness. In both sexes, social selection gradients varied with the season. However, we found no phenotypic assortment or disassortment for the studied traits. Social selection gradients, therefore, did not contribute to total selection differentials, and natural selection alone could drive phenotypic changes. Evaluating the factors that drive the evolution of the covariance between interacting phenotypes is necessary to understand the role of social selection as an evolutionary force. </p>
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Exploration and social environment affect inbreeding avoidance in a small mammal
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Vandal, Katherine; Garant, Dany; Bergeron, Patrick; Réale, Denis — 2023-11-27 <p><span lang="EN-CA">Individual exploration types are based on the cognitive speed-accuracy trade-off, which suggests that higher speed of information acquisition is done by sacrificing information quality</span><span lang="EN-CA">. In a mating context, fast exploration could thus increase the probability of finding mates at the cost of mating with kin or suboptimal partners. We tested this hypothesis by studying male mate choice patterns in a species with a scramble competition mating system. We used genotyping, localisation by radio-collar, trapping, and repeated exploration measures from a long-term study on wild Eastern chipmunks (<em>Tamias</em> <em>striatus</em>). We predicted that, according to the speed-accuracy trade-off hypothesis, slower-thorough explorers should be choosier than faster-superficial ones, and thus avoid inbreeding. We found that slower males reproduced more often with less related females, but only on one site where variance in relatedness and female density were high. Males showed no preference for their mates’ exploration type. Our results suggest that superficial exploration decreases male choosiness and increases the risk of inbreeding, but only under decreased mate search costs due to high variance in relatedness among mates (at high density). Our findings reveal exploration-related, among-individual variance in inbreeding, highlighting the complexity of mate choice, and showing that many aspects of an individual’s life contribute to animal decision-making.</span></p>
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Consumption of red maple in anticipation of beech mast-seeding drives reproduction in Eastern chipmunks
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Tissier, Mathilde; Réale, Denis; Garant, Dany; Bergeron, Patrick — 2020-01-10 1. Understanding the determinants of reproduction is a central question in evolutionary ecology. In pulsed resources environments, the reproduction and population dynamics of seed consumers is driven by pulsed production of seeds by trees, or mast-seeding. In Southern Québec, eastern chipmunks (Tamias striatus) exclusively reproduce during the summer before and the spring after a mast-seeding event of American beech. They thus seem to anticipate beech mast by reproducing during early summer, so that juveniles can emerge at the time of maximum beechnut abundance during late summer. 2. However, the cues allowing chipmunks to anticipate beech mast remain unknown, and the existence of the anticipation process itself has been questioned. To tackle those issues, we investigated the links between the nutritional ecology and reproduction of adult chipmunks and compared their spring diet in mast- vs post-mast years. 3. We monitored female’s reproductive status (N=446), analyzed cheek pouch contents at capture (n=3761 captures), and recorded seed production by deciduous trees on three different sites in Mont-Sutton from 2006 to 2018. 4. Results revealed a systematic shift in chipmunk diet towards red maple seeds in springs preceding a beech mast, with red maple seeds composing more than 77% of chipmunk diet. However, red maple consumption was unrelated to red maple production, but was related to beech seed production in the upcoming fall. We also found that red maple consumption best predicted the proportion of females in summer estrus. 5. Our results confirm that chipmunks anticipate beech mast-seeding and suggest a key role of red maple consumption in that anticipation. Results also suggest that red maple seeds may contain nutrients or secondary-plant components essential to sustain or trigger the summer reproduction in chipmunks, which allow them to remain synchronized with pulsed productions of both red maple and beech and improve their fitness. 08-Jan-2020

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(Author: Bergeron, Patrick)

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