Context dependent fitness costs of reproduction despite stable body mass costs in an Arctic herbivore

1. The cost of reproduction on demographic rates is often assumed to operate through changing body condition. Several studies have found that reproduction depresses body mass more if the current conditions are severe, such as high population densities or adverse weather, than under benign environmental conditions. However, few studies have investigated the association between the fitness and body mass costs of reproduction.

2. Using 25 years of individual-based capture-recapture data from Svalbard reindeer (Rangifer tarandus platyrhynchus), we built a novel Bayesian state-space model that jointly estimated inter-annual change in mass, annual reproductive success, and survival, while accounting for incomplete observations. The model allowed us to partition the differential effects of intrinsic and extrinsic factors on both non-reproductive mass change and the body mass cost of reproduction and to quantify their consequences on demographic rates.

3. Contrary to our expectation, the ...