Spatial ecology of refuge selection by an herbivore under risk of predation

Abstract

Abstract. Prey species use structures such as burrows to minimize predation risk. The spatial arrangement of these resources can have important implications for individual and population fitness. For example, there is evidence that clustered resources can benefit individuals by reducing predation risk and increasing foraging opportunity concurrently, which leads to higher population density. However, the scale of clustering that is important in these processes has been ignored during theoretical and empirical development of resource models. Ecological understanding of refuge exploitation by prey can be improved by spatial analysis of refuge use and availability that incorporates the effect of scale. We measured the spatial distribution of pygmy rabbit (Brachylagus idahoensis) refugia (burrows) through censuses in four 6-ha sites. Point pattern analyses were used to evaluate burrow selection by comparing the spatial distribution of used and available burrows. The presence of food resources and additional overstory cover resources was further examined using logistic regression. Burrows were spatially clustered at scales up to approximately 25 m, and then regularly spaced at distances beyond ;40 m. Pygmy rabbit exploitation of burrows did not match availability. Burrows used by pygmy rabbits were likely to be located in areas with high overall burrow density (resource clusters) and high overstory cover, which together minimized predation risk. However, in some cases we observed an interaction between either overstory cover (safety) or understory cover (forage) and burrow density. The interactions show that pygmy rabbits will use burrows in areas with low relative burrow density (high relative predation risk) if understory food resources are high. This points to a potential trade-off whereby rabbits must sacrifice some safety afforded by additional nearby burrows to obtain ample forage resources. Observed patterns of clustered burrows and non-random burrow use improve understanding of the importance of spatial distribution of refugia for burrowing herbivores. The analyses used allowed for the estimation of the spatial scale where subtle trade-offs between predation avoidance and foraging opportunity are likely to occur in a natural system.

A “death trap” in the landscape of fear

“…Although evidences exist that prey animals are often trading the risk of being killed with better food quality (e.g. Cooper 2000; Kittle et al 2008;Wilson et al 2012), our example turns attention to specific circumstances where foraging under high predation risk is the best choice for prey animals. Whereas in heterogeneous landscapes prey may find habitats with varying levels of forage quality and quantity and refuges even within the areas highly used by wolves (Fortin et al 2005), such behavioural responses may not be possible in more homogenous environments, such as a closed forest ecosystem with limited and small food-abundant patches and no refuge areas.…”

Foraging ecology of black bears in urban environments: guidance for human‐bear conflict mitigation

“…Resource selection, defined as the disproportionate use of a resource in comparison to its availability (Johnson 1980), is commonly studied to gain insights on wildlife foraging ecology (e.g., Bakian et al 2012, Wilson et al 2012, Marshall et al 2013. Selection is hierarchical in nature and can vary by spatial and temporal scales (Johnson 1980, Thomas and Taylor 1990, Boyce 2006.…”

Selection of food patches by sympatric herbivores in response to concealment and distance from a refuge

“…; Sanchez and Rachlow ; Wilson et al. ), switched among burrow refuges more often and had larger home ranges at sites where greater shrub cover was present across the landscape (Sanchez and Rachlow ). In addition, pygmy rabbits exhibited different movement patterns and burrow switching behaviors based on the dispersion of habitat resources (Sanchez and Rachlow ).…”

“…; Wilson et al. ). In contrast, mountain cottontails are more than twice as large (~1100 g), and are considered habitat generalists because they inhabit a range of habitats from woody, brushy areas, to rocky sagebrush areas, to grassy hills, canyons, and agricultural areas (Chapman ).…”

“…for food and cover year-round (Thines et al 2004;Shipley et al 2006;Camp et al 2012). They are also obligate burrowers that require deep soils where they dig natal (Rachlow et al 2005) and residential burrows as refuges from predators and thermal stress (Green and Flinders 1980;Katzner et al 1997;Camp et al 2012;Wilson et al 2012). In contrast, mountain cottontails are more than twice as large (~1100 g), and are considered habitat generalists because they inhabit a range of habitats from woody, brushy areas, to rocky sagebrush areas, to grassy hills, canyons, and agricultural areas (Chapman 1975).…”