Forests buffer the climate-induced decline of body mass in a mountain herbivore

Abstract

Climate change is known to affect key life-history traits, such as body mass, reproduction, and survival in many species. Animal populations inhabiting mountain habitats are adapted to extreme seasonal environmental conditions but are also expected to be especially vulnerable to climate change. Studies on mountain ungulates typically focus on populations or sections of populations living above the tree line, whereas populations inhabiting forested habitats are largely understudied. Here, we investigate whether forested areas can mitigate the impact of climatic change on life-history traits by evaluating the interactive effects of temperature and habitat characteristics on body mass variation in the Alpine chamois Rupicapra rupicapra rupicapra. We examined data of 20,573 yearling chamois collected from 1993 to 2019 in 28 mountain ranges in the Austrian Eastern Alps, characterized by different proportion of forest cover. Our results show that the temporal decline of chamois body mass is less pronounced in areas with greater proportion of forest cover. For chamois living in forest habitats only, no significant temporal change in body mass was detected. Variation in body mass was affected by the interaction between density and snow cover, as well as by the interaction between spring temperatures and forest cover, supporting the role of forests as thermal buffer against the effects of increasing temperatures on life-history traits in a mountain ungulate. In turn, this study suggests a buffering effect of forests against climate change impacts. Assessments of the consequences of climate change on the life-history traits and population dynamics of mountain-dwelling species should thus consider the plasticity of the species with respect to the use and availability of different habitat types.

Keywords: Rupicapra rupicapra; body mass; chamois; climate change; forest; temperature; ungulate.

FIGURE 1

The study area in the provinces of Carinthia, Salzburg, and Styria, Austria. Numbers and black lines correspond to the geographic subdivision of the Eastern Alps. Mountain range IDs between 9 and 21 belong to the Northern Limestone Zone, 35–47 to the Central Alps, ≥56 to the Southern Limestone Zone. Colored areas show suitable habitat for chamois within hunting areas, which are defined as the sum of all open Alpine areas (i.e., Alpine meadows, sparsely vegetated areas, and bare rocks) and all forested areas (i.e., broad leaved, coniferous, and mixed forests) for hunting areas with chamois harvest during the study period

FIGURE 2

Mean spring (April–May) temperature (a), mean summer (June–August) temperature (b), and mean snow depth (c) in mountain ranges in the study area, between 1993 and 2019. The red horizontal lines indicate the average value of the corresponding climate variable. Bars indicate standard deviations across mountain ranges

FIGURE 3

Eviscerated body mass of yearling chamois males (light gray, dashed line) and females (dark gray, solid line) harvested in the provinces of Carinthia, Salzburg, and Styria, Austria, between 1993 and 2019 as a function of year (a) and of the interaction between year and forest cover for both sexes (b) (all other terms of the model are kept at their mean values). The levels of forest cover correspond to the 5th (32% forest cover; red dotted line), 50th (83% forest cover; yellow solid line), and 95th (95% forest cover; green dashed line) quantiles. Shaded areas indicate 95% confidence intervals

FIGURE 4

Marginal effects of the interaction between spring temperature at year [t] and forest cover, fitted to explain variation in yearling chamois body mass in Austria, between 1993 and 2019. The levels of forest cover correspond to the 5th (32% forest cover; red dotted line), 50th (83% forest cover; yellow solid line), and 95th (95% forest cover; green dashed line) quantiles. Shaded areas indicate 95% confidence intervals (all other terms of the model are kept at their mean values). The x‐axis indicates the annual deviation (in °C) from the mean spring temperature for the entire study period