Abstract
The interaction between predators and their prey is a key factor driving population dynamics and shaping wildlife communities. Most predators will scavenge in addition to killing their own prey, which alters predation effects and implies that one cannot treat these as independent processes. However, the relative importance of predation vs. scavenging and the mechanisms driving variation of such are relatively unstudied in ecological research on predator-prey relationships. Foraging decisions in facultative predators are likely to respond to environmental conditions (e.g., seasonality) and inter- or intraspecific interactions (e.g., prey availability, presence of top predators, scavenging competition). Using data on 41 GPS-collared wolverines (Gulo gulo) during 2401 monitoring days, in four study sites in Scandinavia, we studied variation in diet and feeding strategies (predation vs. scavenging), along a gradient of environmental productivity, seasonality, density, and body mass of their main prey, semidomestic reindeer (Rangifer tarandus). The most important factor affecting the relative extent of predation and scavenging was mean prey body mass. Predation was more pronounced in summer, when vulnerable reindeer calves are abundant, and individual kill rates were negatively related to local reindeer body mass. This relationship was absent in winter. The probability of scavenging was higher in winter and increased with decreasing local reindeer body mass, likely as a response to increased carrion supply. Wolverine feeding strategy was further influenced by predictable anthropogenic food resources (e.g., slaughter remains from hunted ungulates) and the presence of a top predator, Eurasian lynx (Lynx lynx), which provided a continuous carrion supply promoting scavenging. Our results suggest that wolverine feeding strategies are flexible and strongly influenced by seasonally dependent responses to prey body condition in combination with carrion supply. This study demonstrates that large-scale environmental variation can result in contrasting predator feeding strategies, strongly affecting trophic interactions and potentially shaping the dynamics of ecological communities.
Highlights
The interaction between predators and their prey is a key factor driving population dynamics and shaping wildlife communities (Sinclair et al 2003)
The relative importance of predation vs. scavenging has so far been underrepresented in the ecological research on predator–prey relations (DeVault et al 2003, Wilson and Wolkovich 2011, Moleón et al 2014, Pereira et al 2014)
The composition of food items differed between the study areas where the highest proportion of moose and anthropogenic food items were found in the southernmost area (Fig. 1, Appendix S3: Tables S2 and S3)
Summary
The interaction between predators and their prey is a key factor driving population dynamics and shaping wildlife communities (Sinclair et al 2003). Hunting is both energetically costly and risky for carnivores (Carbone et al 2007) and as a result many carnivores will scavenge when the opportunity arises, in addition to killing their own prey, affecting predator–prey v www.esajournals.org. Where a carnivore is situated on this range between scavenging and predation will have consequences for the effects of predators on prey populations and the predator’s response to prey abundance (i.e., functional response), but eventually for the flux of biomass and nutrients through the ecosystem (Wilson and Wolkovich 2011). The relative importance of predation vs. scavenging has so far been underrepresented in the ecological research on predator–prey relations (DeVault et al 2003, Wilson and Wolkovich 2011, Moleón et al 2014, Pereira et al 2014)
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