Figure - available from: Ecology
This content is subject to copyright. Terms and conditions apply.
Monthly (30‐day time step) survival probability (±95% CI) of northern Idaho ground squirrels (NIDGS; n = 1689) was influenced by Columbian ground squirrel (COGS) density, and the relationship varied with active‐season precipitation (1 April–31 July). The figure depicts only the survival probability estimates for adult females for simplicity; the interactive effect of Columbian ground squirrel density and active‐season precipitation on northern Idaho ground squirrel survival probability was the same across age‐sex classes, and the effects of age and sex were additive. High and low precipitation levels correspond to range extremes in annual site‐level active‐season precipitation documented during the study. Survival estimates are predictions from the top Cormack–Jolly–Seber model designed to explain variation in survival probability that included a significant effect (α = 0.05) of the two‐way interaction between Columbian ground squirrel density and active‐season precipitation.
Source publication
Ecologists have studied the role of interspecific competition in structuring ecological communities for decades. Differential weather effects on animal competitors may be a particularly important factor contributing to the outcome of competitive interactions, though few studies have tested this hypothesis in free‐ranging animals. Specifically, weat...
Citations
... It is therefore possible that larger groups may be actually more conspicuous for predators or that more eyes and ears cannot defend against certain types of predators that hunt by immediate attacks or ambush 83 . Large group size may affect survival also indirectly because individuals experience greater feeding competition that may translate into greater variance in body condition 84 . ...
The costs and benefits of group living are also reflected in intraspecific variation in group size. Yet, little is known about general patterns of fitness consequences of this variation. We use demographic records collected over 25 years to determine how survival and reproductive success vary with group size in a Malagasy primate. We show that female reproductive rates of Verreaux’s sifakas (Propithecus verreauxi) are not affected by total group size, but that they are supressed by the number of co-resident females, whereas mortality rates are significantly higher in larger groups. Neither annual rainfall nor the adult sex ratio have significant effects on birth and death rates. Hence, these sifakas enjoy the greatest net fitness benefits at small, and not the predicted intermediate group sizes. Thus, independent fitness proxies can vary independently as a function of group size as well as other factors, leading to deviations from optimal intermediate group sizes.
... Reentry into torpor for as few as 2 d specifically implies that the fitness costs of terminating hibernation too early or too late are substantial and further supports the idea that torpor reentry does not necessarily defer reproduction to the following year. The costs of terminating hibernation and emerging too early likely include increased predation risk during aboveground activity (reducing the probability of surviving to reproduce; Allison et al. 2023Allison et al. , 2024, increased thermoregulatory costs, and decreased body condition resulting from low forage availability (Allison and Conway 2022), whereas the costs of terminating hibernation and emerging too late presumably involve diminished reproductive success (Sherman 1989;Viblanc et al. 2022;Thompson et al. 2023). This novel facultative reentry into torpor contradicts the assumption that endogenous circannual rhythms (e.g., in testosterone production and establishment of spermatogenesis) entirely constrain plasticity in hibernation termination phenology in reproductive male ground squirrels (Williams et al. 2014(Williams et al. , 2017aRichter et al. 2017;Kucheravy et al. 2021). ...
