Socially mediated effects of climate change decrease survival of hibernating Alpine marmots

Abstract

In the context of global change, an increasing challenge is to understand the interaction between weather variables and life histories. Species-specific life histories should condition the way climate influences population dynamics, particularly those that are associated with environmental constraints, such as lifestyles like hibernation and sociality. However, the influence of lifestyle in the response of organisms to climate change remains poorly understood. Based on a 23-year longitudinal study on Alpine marmots, we investigated how their lifestyle, characterized by a long hibernation and a high degree of sociality, interacts with the ongoing climate change to shape temporal variation in age-specific survival. As generally reported in other hibernating species, we expected survival of Alpine marmots to be affected by the continuous lengthening of the growing season of plants more than by changes in winter conditions. We found, however, that Alpine marmots displayed lower juvenile survival over time. Colder winters associated with a thinner snow layer lowered juvenile survival, which in turn was associated with a decrease in the relative number of helpers in groups the following years, and therefore lowered the chances of over-winter survival of juveniles born in the most recent years. Our results provide evidence that constraints on life-history traits associated with hibernation and sociality caused juvenile survival to decrease over time, which might prevent Alpine marmots coping successfully with climate change.

Extrinsic and intrinsic constraints interact to drive extra‐pair paternities in the Alpine marmot

“…Earlier spring snowmelt is expected to relax energetic, movement and time constraints linked to mate searching. Snowier winters result in a higher proportion of families with sexually mature male subordinates (Bichet et al ., ; Rézouki et al ., ), and further create a social context within which extra‐pair paternity is favoured (Bichet et al ., ). Indeed, the presence of sexually mature males increases the cost of reproductive monopolization for dominant males and facilitates that dominant females escape mate guarding (Cohas et al ., ; Lardy et al ., ).…”

Differential plasticity of size and mass to environmental change in a hibernating mammal

“…Concerning subadults, the positive trend observed in Δmass might result from more delayed dispersal in recent years. Indeed, subadult apparent survival increased over the studied period while all other age classes’ survival decreased or remained constant (Rézouki et al ., in press). Although body mass had no impact on the decision to disperse in another Alpine population (Arnold, , ), in our population, body mass was influential on dispersal (Magnolon, ).…”

“…The phenotypic plasticity observed in Alpine marmots does not appear adaptive despite their wide ranged reaction norms ( i.e., phenotype as a function of an environmental variable) showing their ability to withstand extreme environmental conditions. Indeed, recent studies on this population showed a decline of individual performances over the past decades with observed decreasing litter size, juvenile survival, and family group size (Tafani et al ., ; Rézouki et al ., in press). These results contrast with the abrupt increase in population size of yellow‐bellied marmots triggered by their mass shift (Ozgul et al ., ).…”

“…In mammals, structural size and mass are key phenotypic traits influencing survival and reproductive success. Thus, we focused on environmental variables known to affect survival (Farand et al ., ; Rézouki et al ., in press) and reproductive output (Tafani et al ., ) in this species.…”

Faithful or not: direct and indirect effects of climate on extra-pair paternities in a population of Alpine marmots

“…A high snow depth ensures burrow insulation during hibernation, leading to larger litters [27] and favouring pup survival [28]. In turn, it results in more families with mature male subordinates 2 years later.…”