Interspecific prey neighborhoods shape risk of predation in a savanna ecosystem

Abstract

The vulnerability of an individual to predation depends on the availability of other prey items in the surrounding environment. Interspecific prey aggregations or “neighborhoods” may therefore affect an individual's vulnerability to predation. We examined the influence of prey neighborhood structure (i.e., the densities and identities of prey neighborhoods) on spatial variation in predation in a multi‐prey system with a primary apex predator. We combined GPS locations of lions (Panthera leo), kill‐site surveys, and spatially explicit density estimates of five species of ungulates for which a significant level of predation was attributable to lions. In addition to the dual influence of predator activity and vegetation, predation risk was attributable to the structure of prey neighborhoods for at least two of the five species of prey. Along with traditionally recognized components of predation (the rate of predator–prey encounters and prey catchability), we encourage ecologists to consider how prey neighborhood structure influences spatial variation in predation risk.

Experimental evidence that effects of megaherbivores on mesoherbivore space use are influenced by species' traits

“…Zebras were the only species that responded positively to megaherbivores, consistent with previous research in this system (Goheen et al, 2013;Kimuyu et al, 2017). This may in part be because megaherbivores increase visibility by reducing stalking cover for large carnivores such as lions Panthera leo (Ng'weno et al, 2019;Riginos & Grace, 2008). Additionally, megaherbivores could increase zebra occurrence and use intensity by enhancing grass cover (zebras in this system eat ≥95% grass, more than any other species; .…”

Apparent Competition, Lion Predation, and Managed Livestock Grazing: Can Conservation Value Be Enhanced?

“…Instances where apparent competition has been implicated in limiting ungulate populations are becoming numerous, including bighorn sheep (Ovis canadensis), mountain caribou (Rangifer tarandus), huemul (Hippocamelus bisulcus), and roan antelope (Hippotragus equinus; Harrington et al, 1999;DeCesare et al, 2010;McLellan et al, 2010;Wittmer et al, 2013;but see O'Brien et al, 2018 for an example contrary to the hypothesis of apparent competition involving Grevy's zebra [E. grevyi] in Laikipia). In our study system, spatial separation between zebra and hartebeest improved survival rates of hartebeest, probably by reducing encounters with lions hunting in areas with high zebra densities (Ng'weno et al;Ng'weno, 2017 in revision; see also Palmer et al, 2003;Forrester and Steele, 2004). Strategic placement of glades therefore offers a promising approach to creating refuges for hartebeest and perhaps other species of secondary prey.…”

“…These lions belonged to 5 different prides, which collectively accounted for ca. 80% of lions on Ol Pejeta (Ng'weno et al;Ng'weno, 2017 in revision). Overlap between home ranges of prides was minimal (1-12%) throughout the course of our study (Ng'weno et al in revision).…”

“…From March 2014 to December 2015, we located lion kills from clustered locations of lions with GPS collars using an algorithm adapted from Knopff et al (2009). Between August 2014 and December 2015, there were 246 instances in which prey carcasses were found to have been killed by lions (Ng'weno et al;Ng'weno, 2017 in revision). We then used Jacobs' index (Jacobs, 1974;Hayward and Kerley, 2005) to quantify seasonal selectivity for each of 11 species of lion prey,…”

Optimal prey switching: Predator foraging costs provide a mechanism for functional responses in multi‐prey systems

“…The effect of alternative prey density is included in the concept of “neighborhood effects” in predator–prey interactions. In a savanna system, lion predation depended upon both the composition and abundance of other prey species in the local area (i.e., the prey neighborhood; Ng'weno et al, 2019). Similarly, a neighborhood effect occurred between streams: The amount of salmon killed by bears in a stream decreased with prey abundance in surrounding streams (Quinn et al, 2017).…”