DOI: 10.5061/dryad.c866t1g4g
title: Multi-event capture-recapture analysis in Alpine chamois reveals contrasting responses to interspecific competition, within and between populations

description: 1. Understanding components of interspecific competition has long been a
 major goal in ecological studies. Classical models of competition
 typically consider equal responses of all individuals to the density of
 competitors, however responses may differ both among individuals from the
 same population, and between populations. 2. Based on individual long-term
 monitoring of two chamois populations in sympatry with red deer, we built
 a multi-event capture-recapture model to assess how vital rates of the
 smaller chamois are affected by competition from the larger red deer. 3.
 In both populations, mortality and breeding probabilities of female
 chamois depend on age and in most cases, of breeding status the preceding
 year. Successful breeders always performed better the next year,
 indicating that some females are of high quality. In one population where
 there was high spatial overlap between the two species, the survival of
 old female chamois that were successful breeders the preceding year
 (high-quality) was negatively related to an index of red deer population
 size suggesting that they tend to skip reproduction instead of
 jeopardizing their own survival when the number of competitors increases.
 The breeding probability of young breeders (ages 2 and 3) was similarly
 affected by red deer population size. In contrast, in the second site with
 low spatial overlap between the two species, the vital rates of female
 chamois were not related to red deer population size. 4. We provide
 evidence for population-specific responses to interspecific competition
 and more generally, for context-, age- and state-dependent effects of
 interspecific competition. 5. Our results also suggest that the classical
 assumption of equal responses of all individuals to interspecific
 competition should be relaxed, and emphasize the need to move towards more
 mechanistic approaches to better understand how natural populations
 respond to changes in their environment.
description: Counts of red deer and chamois were performed annually at maximum
 seasonal densities, i.e. during July-August by experienced park rangers.
 Counts were performed in the same area within each study site for both
 species. Il Fuorn was divided into seven blocks and Val Trupchun into five
 blocks. Censuses were then conducted from the exact same points each year,
 selected for their optimal viewshed. Counts were performed for two weeks,
 chosen for their optimal viewing conditions (for further details, see
 Haller 2006). Double counting of individuals at adjacent blocks was
 avoided by noting the time of the sightings, the exact location and the
 group composition and by sharing this information between rangers thanks
 to radio contact (Sæther <i>et al.</i> 2002). Thus, the
 invested effort in avoiding double counts and the open landscape suggest
 that counts are precise compared to most other ungulate population counts
 (Sæther <i>et al.</i> 2002). The same protocol was applied
 twice during the two weeks counting period and the higher number of
 counted individuals was kept as a proxy of the minimum red deer (and
 chamois) population size index (Anderwald <i>et al.</i> 2015
 for a similar approach; see also Anderwald, Haller & Filli 2016;
 Herfindal <i>et al.</i> 2019).