Biology

Permanent URI for this collectionhttps://hdl.handle.net/1807/247

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  • ItemOpen Access
    Predation risk and decision-making of grey squirrels in urban and rural forested parks
    (Springer Science and Business Media LLC, 2025-04-07) Givelas, Mark; Martin, Adam R.; Boonstra, Rudy
    Correlational selection refers to the process by which selection for one trait influences the evolution of others, leading to multivariate trait combinations that enhance fitness. Predation has been shown to drive such changes, and in some instances lead to covariation between species behavioural and morphological traits. The eastern grey squirrel (Sciurus carolinensis) is the prey of several mammalian and avian predators, which has likely contributed to the evolution of multiple coat colors. Morphs with a melanistic (i.e., dark-coloured) coat face an increased predation risk, despite its thermoregulatory benefits. If correlation selection has occurred in this species, we hypothesize that melanistic morphs will show increased antipredator behaviour to offset this greater predation risk. To test this expectation we quantified flight initiation distances (FIDs)—a measure of antipredator behavior based on the distance at which animals flee from an approaching threat—to assess the predator escape responses of grey and black morphs in both urban parks and rural forested environments. We predicted that melanistic squirrels would exhibit greater FIDs in both environments, with a larger difference in morph-specific antipredator behaviour across rural forested park areas. Our findings showed no significant differences in FIDs between grey and black morphs. Increased predator avoidance was more strongly dictated by differences in behaviour associated with urban vs. rural environments. This study extends our understanding of microevolutionary forces on wildlife in human dominated landscapes.
  • ItemOpen Access
    Understanding the Snowshoe Hare Cycle through Large-scale Field Experiments
    (Oxford University Press, 2002) Boutin, Stan; Krebs, Charles J.; Boonstra, Rudy; Sinclair, Anthony R.E.; Hodges, Karen E.
  • ItemOpen Access
    The role of red squirrels and arctic ground squirrels
    (Oxfored University Press, 2001) Boonstra, Rudy; Boutin, Stan; Byrom, Andrea; Karels, Tim J.; Hubbs, Anne H.; Stuart-Smith, K.; Blower, M.; Antpoehler, S
  • ItemOpen Access
    Northern Hawk-Owls in the Nearctic Boreal Forest: Prey Selection and Population Consequences of Multiple Prey Cycles
    (Oxford University Press (OUP), 1995-02) Rohner, Christoph; Stroman, Johan; Joyce, Miranda; Doyle, Frank I.; Boonstra, Rudy
    We studied hawk-owls in the southwestern Yukon, Canada, from 1987-1993. Most information on hawk-owls originates from studies in Europe, and very little is known about the subspecies Surnia ulula caparochi n North America. The boreal forest communities in the two continents differ remarkably in the composition of cyclic herbivore populations. Fennoscandia is dominated by 34 year microtine cycles, whereas northern Canada and Alaska experience a 10-year cycle in snowshoe hare numbers, with voles fluctuating at lower levels. We studied the diets of nine nesting pairs by pellet analysis, and we observed prey deliveries at five nests. The proportion of voles in the diets was lower than reported from Fennoscandia, and snowshoe hares made up 40-50% during the peak of the hare cycle. Estimates of prey densities by live-trapping revealed that hawk-owls strongly prefer voles over snowshoe hares and squirrels. Among voles, Microtus were preferred and Clethrionomys were avoided. Hawk-owls showed, however, a functional response not only to voles but also to juvenile hares, and they may be critically dependent on larger prey during certain nesting stages when vole abundance is moderate or low. Breeding densities and winter observations changed concurrently over years of different prey abundance. Prey selection translated into population consequences hawk-owls did not respond numerically to CIethrionomys outbreaks, but to the combined densities of Microtus and snowshoe hares. We conclude that the Northern Hawk-Owl is less of a vole specialist and more affected by the prey composition in specific systems than commonly assumed, and we discuss this pattern from an evolutionary perspective.
  • ItemOpen Access
    Studying small mammal population dynamics: advice to consider and pitfalls to avoid—a 60-year overview
    (Canadian Science Publishing, 2025-01-01) Boonstra, Rudy; Krebs, Charles J.; Reid, Donald G.
    We consider what we and others have learned and the mistakes that we have made in the last 60 years of research on small mammal population dynamics. We consider all mammals <5 kg as small mammals, covering more than 3200 species including among others, mice, voles, lemmings, gerbils, guinea pigs, muskrats, shrews, squirrels, and hares, but not bats, in ecosystems globally. We start by emphasizing the necessity of posing a good question and what that means scientifically on one or more species or populations of small mammals. We consider the study design, the choice of the study area, the methods of population estimation, the necessity of measuring demographic parameters on births, deaths, and movements, the limitations of enclosure experiments, the problems faced by field experiments to test specific hypotheses, and the need to acquire social licence. By being self-critical we hope to encourage a new round of studies of small mammal populations that will avoid pitfalls, illuminate hypotheses not yet tested properly, and forge new directions.
  • ItemOpen Access
    Cyclic dynamics drive summer movement ecology of snowshoe hares (Lepus americanus)
    (Frontiers Media SA, 2024-07-02) Miller, Hannah A.; Gobin, Jenilee; Boudreau, Melanie R.; Horne, Liam G.; Scholl, Lee E.; Seguin, Jacob L.; Sonnega, Samuel; Krebs, Charles J.; Boonstra, Rudy; Kenney, Alice J.; Jung, Thomas S.; Boutin, Stan; Murray, Dennis L.
    Animals exhibit dynamic movement and activity in response to environmental variation including changes in reproductive opportunities, predation risk, or food availability. Yet, it remains unclear which factors are primary in affecting animal movement, and whether the relative importance of these factors are consistent through time. We tracked snowshoe hares (Lepus americanus) using GPS telemetry during eight summers spanning a hare population cycle (2015–2022) in southwestern Yukon, Canada, to determine associations between environmental variation and hare movement and home range size. Hare density varied 25-fold during the study and home range size increased markedly during low hare density, especially for males. Both sexes retained similar core space use and linearity of movements, but at low densities males had greater and more variable movement rates and time spent travelling. Trail cameras revealed that annual changes in hare movement were also correlated with relative abundance of lynx (Lynx canadensis) and coyotes (Canis latrans). However, hare detection rates within a season were not closely associated with seasonal variation in predator detection. Observed differences between male and female hares in some metrics highlighted that different life histories and reproductive behavior are likely the main drivers of hare movement dynamics. Therefore, fitness rewards associated with successful mate search and reproduction appear to outweigh risks associated with increased movement, even in highly variable environments where costs of prioritizing reproductionrelated activities are notably high and variable.
  • ItemOpen Access
    Long‐term monitoring of cycles in Clethrionomys rutilus in the Yukon boreal forest
    (Wiley, 2023-04-09) Krebs, Charles J.; Kenney, Alice J.; Gilbert, B. Scott; Boonstra, Rudy
    Baseline studies of small rodent populations in undisturbed ecosystems are rare. We report here 50 years of monitoring and experimentation in Yukon of a dominant rodent species in the North American boreal forest, the redbacked vole Clethrionomys rutilus. These voles breed in summer, weigh 20–25 g, and reach a maximum density of 20 to 25 per ha. Their populations have shown consistent 3–4-year cycles for the last 50 years with the only change being that peak densities averaged 8/ha until 2000 and 18/ha since that year. During the last 25 years, we have measured food resources, predator numbers, and winter weather, and for 1-year social interactions, to estimate their contribution to changes in the rate of summer increase and the rate of overwinter decline. All these potential limiting factors could contribute to changes in density, and we measured their relative contributions statistically with multiple regressions. The rate of winter decline in density was related to both food supply and winter severity. The rate of summer increase was related to summer berry crops and white spruce cone production. No measure of predator numbers was related to winter or summer changes in vole abundance. There was a large signal of climate change effects in these populations. There is no density dependence in summer population growth and only a weak one in winter population declines. None of our results provide a clear understanding of what generates 3–4-year cycles in these voles, and the major missing piece may be an understanding of social interactions at high density.
  • ItemOpen Access
    Social, not genetic, programming of development and stress physiology of a colonial seabird
    (The Royal Society, 2024-08) Lemonnier, Camille; Schull, Quentin; Stier, Antoine; Boonstra, Rudy; Delehanty, Brendan; Lefol, Emilie; Durand, Laureline; Pardonnet, Sylvia; Robin, Jean-Patrice; Criscuolo, François; Bize, Pierre; Viblanc, Vincent A.
    Phenotypic differences often stem from genetic/maternal differences and/or early-life adaptations to local environmental conditions. In colonial animals, little is known on how variation in the social environment is embedded into individual phenotypes, nor what the consequences are on individual fitness. We conducted an experimental cross-fostering study on king penguins (Aptenodytes patagonicus), exchanging eggs among 134 pairs breeding in high-density (67 pairs) or low-density (67 pairs) areas of the same breeding colony. We investigated differences in parent and chick phenotypes and survival in relation to the density of their origin and foster environment. Adults breeding in colony areas of high density exhibited decreased resting behaviour and increased aggression and vigilance, increased hypometabolism during incubation fasts, and more moderate corticosterone responses shaped by exposure to chronic stressors (e.g. constant aggression by neighbours). Chick phenotypes were more influenced by the environment in which they were raised than their genetic/maternal origin. Chicks raised in high-density colonial environments showed enhanced weight gain and survival rates regardless of the density of their genetic parents’ breeding areas. Our study experimentally shows advantages to breeding in colonial areas of higher breeder densities in king penguins, and highlights the importance of social settings in shaping phenotype expression in colonial seabirds.
  • ItemOpen Access
    Introduction: Biology of the Canadian Arctic: A Crucible for Change in the 21st Century
    (Oxford University Press (OUP), 2004-04-01) Hik, D. S.; Boonstra, Rudy
  • ItemOpen Access
    Population cycles in microtines: The senescence hypothesis
    (Springer Science and Business Media LLC, 1994-03) Boonstra, R.
    The cause of population cycles in microtines (voles and lemmings) remains an enigma. I propose a new solution to this problem based on a crucial feature of microtine biology, shifts in age structure, that has been ignored until now. Empirical evidence indicates that age structure must shift markedly towards older animals during declines because of three characteristics of the previous peak year: a shortened breeding season, total replacement of the breeding population from peak to decline and density-dependent social inhibition of maturation of young. Declines become inevitable as populations composed of older animals survive and reproduce poorly because of the effects of senescence, possibly interacting with the experiences of peak density and I present both theoretical and empirical evidence for this hypothesis. Although a variety of physiological systems deteriorate with aging, I focus on a crucial one - the inability of older animals to effectively maintain homeostasis in the face of environmental challenges because of a progressive deterioration in the endocrine feedback mechanisms involved in the hippocampal-hypothalamic-pituitaryadrenal axis. Microtine populations will not exhibit cycles where age structure shifts are prevented owing to extrinsic factors such as intense predation. Six testable predictions are made that can falsify this hypothesis.
  • ItemOpen Access
    Common Dynamic Structure of Canada Lynx Populations Within Three Climatic Regions
    (American Association for the Advancement of Science (AAAS), 1999-08-13) Stenseth, Nils Chr.; Chan, Kung-Sik; Tong, Howell; Boonstra, Rudy; Boutin, Stan; Krebs, Charles J.; Post, Eric; O'Donoghue, Mark; Yoccoz, Nigel G.; Forchhammer, Mads C.; Hurrell, James W.
    Across the boreal forest of Canada, lynx populations undergo regular density cycles. Analysis of 21 time series from 1821 onward demonstrated structural similarity in these cycles within large regions of Canada. The observed population dynamics are consistent with a regional structure caused by climatic features, resulting in a grouping of lynx population dynamics into three types (corresponding to three climatic-based geographic regions): Pacific-maritime, Continental, and Atlantic-maritime. A possible link with the North Atlantic Oscillation is suggested.
  • ItemOpen Access
    Energetic constraints drive the decline of a sentinel polar bear population
    (American Association for the Advancement of Science (AAAS), 2025-01-31) Archer, Louise C.; Atkinson, Stephen N.; Lunn, Nicholas J.; Penk, Stephanie R.; Molnár, Péter K.
    Human-driven Arctic warming and resulting sea ice loss have been associated with declines in several polar bear populations. However, quantifying how individual responses to environmental change integrate and scale to influence population dynamics in polar bears has yet to be achieved. We developed an individual-based bioenergetic model and hindcast population dynamics across 42 years of observed sea ice conditions in Western Hudson Bay, a region undergoing rapid environmental change. The model successfully captured trends in individual morphometrics, reproduction, and population abundance observed over four decades of empirical monitoring data. Our study provides evidence for the interplay between individual energetics and environmental constraints in shaping population dynamics and for the fundamental role of a single limiting mechanism—energy—underpinning the decline of an apex Arctic predator.