Prey density affects predator foraging strategy in an Antarctic ecosystem

Abstract

Studying the effects of prey distribution on predator behavior is complex in systems where there are multiple prey species. The role of prey density in predator behavior is rarely studied in closed ecosystems of one predator species and one prey species, despite these being an ideal opportunity to test these hypotheses. In this study, we investigate the effect of prey density on the foraging behavior of a predatory species in an isolated Antarctic ecosystem of effectively a single predatory species and a single prey species. We use resource selection models to compare prey density in areas utilized by predators (obtained from fine‐scale GPS telemetry data) to prey density at randomly generated points (pseudoabsences) throughout the available area. We demonstrate that prey density of breeding Antarctic petrels (Thalassoica antarctica) is negatively associated with the probability of habitat use in its only predator, the south polar skua (Catharacta maccormicki). Skuas are less likely to utilize habitats with higher petrel densities, reducing predation in these areas, but these effects are present during chick rearing only and not during incubation. We suggest that this might be caused by successful group defense strategies employed by petrel chicks, primarily spitting oil at predators.

Influence of reproductive output on divorce rates in polar seabirds

“…With between 100,000 and 250,000 breeding pairs, this colony is one of the largest Antarctic petrel colonies (Descamps et al., 2016 ; Schwaller et al., 2018 ; Van Franeker et al., 1999 ). Svarthamaren also hosts 100–150 skua breeding pairs nesting in the lower flat parts, relying exclusively on petrel eggs and chicks as their food resource during the breeding season (Busdieker et al., 2020 ).…”

“…Svarthamaren also hosts 100-150 skua breeding pairs nesting in the lower flat parts, relying exclusively on petrel eggs and chicks as their food resource during the breeding season (Busdieker et al, 2020). These five species are seabirds, which breed on land and remain at sea during the internuptial period (Coulson, 2011;del Hoyo et al, 1992;Delord et al, 2020;Frederiksen et al, 2012Frederiksen et al, , 2016Gaston & Jones, 1998;Weimerskirch et al, 2015;Weiser & Gilchrist, 2020).…”

Bioaccumulation of Per and Polyfluoroalkyl Substances in Antarctic Breeding South Polar Skuas (Catharacta maccormicki) and Their Prey

“…We quantified PFAS in main prey items and south polar skuas at opposite sides of the Antarctic continent where the skuas breed during the austral summer, preying on eggs and chicks of other seabirds. At the inland colony of Svarthamaren, Dronning Maud Land, the south polar skua feeds almost exclusively on Antarctic petrel (Thalassoica antarctica) eggs and chicks (Brooke et al, 1999;Busdieker et al, 2020), whereas they feed mainly on Adélie penguins but also on other prey such as fish in the coastal colony such as in Dumont d'Urville (Young, 1963;Furness, 2010;Olsen, 2010;Carravieri et al, 2017;Pacoureau et al, 2019). We analysed Antarctic petrel (Thalassoica antarctica) eggs, blood of chicks, adults, and their stomach samples from Svarthamaren, Dronning Maud Land and blood of Adélie penguin chicks (Pygoscelis adeliae) from Dumont d'Urville, Adélie Land.…”

Multi-species mechanistic model of functional response provides new insights into predator-mediated interactions in a vertebrate community

“…We found evidence that changes in predator foraging behavior with respect to main prey density can at least partly explain the positive indirect effects observed in a vertebrate community. Although many empirical studies have demonstrated links between prey availability and predator foraging behavior (e.g., Harding et al 2007; Bertrand et al 2014; Busdieker et al 2019), dependence of predator foraging behavior on prey density is rarely included in predator-prey models (but see Abrams 1982). We recognize that the density-dependent functions used in our study were derived from limited empirical data.…”

“…Both parameters negatively related to prey density Predators adjust the amount of time devoted to foraging, resting, and reproductive behaviors with prey availability (Harding et al, 2007;Busdieker et al, 2019). This behavioral flexibility may result in reduced foraging effort as prey density increases (Harding et al, 2007) or in increased time-consuming behaviors associated with reproduction (e.g., parental care).…”