Predation risk and food quantity in the selection of habitat by black-tailed jackrabbit (Lepus californicus): an optimal foraging approach

摘要

Optimal foraging theory predicts animals should balance foraging benefits (energy gain) with foraging cost (predation risk). It has been widely shown that food or resource levels are important in the selection of habitats. Other studies have shown the importance of cover as safe areas to decrease predation risk indicating the role of cover in habitat selection. With regards to lagomorphs, no studies have characterized vegetation cover and resource levels simultaneously. This study tested whether black-tailed jackrabbits (Lepus californicus), as predicted by optimal foraging theory, consider resource and predation risk levels in their habitat selection. We conducted our study in grassland and shrubland habitats in the Chihuahuan desert to test the following predictions: (1) in habitats with equal levels of predation risk, areas used more by jackrabbits will have higher resource levels; (2) between habitats with different levels of predation risk, the higher used low risk area will have lower resource levels. To test these predictions, we measured and compared the quantity of grass/ forb species between a high use, low risk grassland and a low use, high risk shrubland and in areas of high and low jackrabbit use within these two habitats. We found less forbs and grasses in the high use grassland (linear density index (LDI) = 48.1 +- 12.4ind., grassland vs. 63.3 +- 9.9 ind., shrubland, F_(1,27) = 19.1, p≤0.005)). Inside habitats we found more forbs and grasses in the high use than the low use areas (LDI = 83.1 +- 11.4ind., high use vs. 30.4 +- 5.2 ind., low use, F_(1,27) = 177.7, p≤0.001). These results supported our predictions and we concluded that optimal foraging theory helps explain habitat use by black-tailed jackrabbits in the Chihuahuan desert.