Predator foraging response to a resurgent dangerous prey

Abstract

Summary Prey switching occurs when a generalist predator kills disproportionately more of an abundant prey species and correspondingly spares a rarer species. Although this behaviour is a classic stabilizing mechanism in food web models, little is known about its operation in free‐living systems which often include dangerous prey species that resist predation. We used long‐term (1995–2015) data from a large mammal system in northern Yellowstone National Park, USA, to understand how prey preference of a wild, generalist predator (Canis lupus) responds to a shift in prey species evenness involving rising numbers of dangerous prey (Bison bison) and dropping numbers of relatively safer prey (Cervus elaphus). Contrary to the prey switching hypothesis, wolves attacked and killed disproportionately more of the rarer, but safer, species. Wolves maintained a strong preference against bison even when this species was nearly twice as abundant as elk. [Correction added after online publication on 26 April 2017: ‘more than’ changed to ‘nearly’]. There was also evidence that wolves were increasingly averse to hunting bison as relative bison abundance increased. Wolves seldom hunted bison because capture success was limited to a narrow set of conditions: larger packs (>11 wolves) chasing smaller herds (10–20 bison) with calves. Wolves scavenged bison carrion instead and did so more frequently as bison abundance increased. Our study demonstrates the overarching importance of prey vulnerability to understanding the prey preferences of generalist predators in ecological communities with dangerous prey. The formidable defences of such prey diminish the potential for switching and its stabilizing influence on population dynamics. In these communities, shifts from hunting to scavenging are perhaps more likely than shifts in prey preference. The assumption of switching may therefore overestimate the stability of multi‐prey systems that include dangerous prey species. A http://onlinelibrary.wiley.com/doi/10.1111/1365-2435.12866/suppinfo is available for this article.

Climatically driven changes in primary production propagate through trophic levels

“…Although density varied with climatically driven changes in POS NDVI, the prey to predator ratio remained constant, further suggesting that food availability, and not social dominance, was the ultimate factor regulating individual spatial requirements and female population density (Logan & Sweanor, ; Pierce et al, ). Corroborating other recent efforts (Bårdsen & Tveraa, ; Duncan et al, ; Pettorelli, Bro‐Jørgensen, Durant, Blackburn, & Carbone, ), our results suggest that although top‐down effects remain important at local scales (Tallian et al, ), demographic processes operate within—or are even governed by—climatic constraints.…”

“…Corroborating other recent efforts (Bårdsen & Tveraa, 2012;Duncan et al, 2012;Pettorelli, Bro-Jørgensen, Durant, Blackburn, & Carbone, 2009), our results suggest that although top-down effects remain important at local scales (Tallian et al, 2017), demographic processes operate within-or are even governed by-climatic constraints.…”

Complex tactics in a dynamic large herbivore–carnivore spatiotemporal game

“…From the point of view of prey, studies have shown underuse of resource patches to avoid predators preferentially targeting these same patches, such as anuran tadpoles subject to dragonfly predation in an experimental setting (Hammond et al 2007), and woodland caribou subject to wolf predation in the boreal forest (Courbin et al 2014). In the case of bison, wolves do represent a threat even in multi-prey systems (Larter et al 1994, Tallian et al 2017. Even a single wolf can harass bison and trigger a behavioural response (Carbyn and Trottier 1987).…”

“…Even large and dangerous prey should have to adjust their use of space to perceived predation risk on a regular basis, even if mortality risk is ultimately relatively low. First, large prey such as bison Bison bison or buffalo Syncerus caffer can succumb to predators (Tambling et al 2012, Tallian et al 2017. Second, for every successful kill, a predator experiences a large number of failed attempts, especially when hunting large and relatively dangerous prey (Mech and Peterson 2003).…”

“…Second, for every successful kill, a predator experiences a large number of failed attempts, especially when hunting large and relatively dangerous prey (Mech and Peterson 2003). Of 187 encounters between bison and wolves in Yellowstone National Park, 173 resulted in an attack but only 24 resulted in capture and only eight led to a kill (Tallian et al 2017). Even for prey populations under bottom-up control, there should be a fitness advantage in engaging in anti-predator tactics (Creel and Christianson 2008).…”