Nuisance Ecology: Do Scavenging Condors Exact Foraging Costs on Pumas in Patagonia?

Abstract

Predation risk describes the energetic cost an animal suffers when making a trade off between maximizing energy intake and minimizing threats to its survival. We tested whether Andean condors (Vultur gryphus) influenced the foraging behaviors of a top predator in Patagonia, the puma (Puma concolor), in ways comparable to direct risks of predation for prey to address three questions: 1) Do condors exact a foraging cost on pumas?; 2) If so, do pumas exhibit behaviors indicative of these risks?; and 3) Do pumas display predictable behaviors associated with prey species foraging in risky environments? Using GPS location data, we located 433 kill sites of 9 pumas and quantified their kill rates. Based upon time pumas spent at a carcass, we quantified handling time. Pumas abandoned >10% of edible meat at 133 of 266 large carcasses after a single night, and did so most often in open grasslands where their carcasses were easily detected by condors. Our data suggested that condors exacted foraging costs on pumas by significantly decreasing puma handling times at carcasses, and that pumas increased their kill rates by 50% relative to those reported for North America to compensate for these losses. Finally, we determined that the relative risks of detection and associated harassment by condors, rather than prey densities, explained puma “giving up times” (GUTs) across structurally variable risk classes in the study area, and that, like many prey species, pumas disproportionately hunted in high-risk, high-resource reward areas.

Recolonizing wolves influence the realized niche of resident cougars

“…This was likely due to our methods rather than the ecological reality of the system, and a more intensive field effort may have yielded different results (Knopff et al 2010;Elbroch and Wittmer 2013b). Because we employed the night > 1 model to quantify kill rates, we limited our ability to detect small prey or large prey when large competitors displaced cougars from their kills (Elbroch and Wittmer 2013a). This would influence both our comparison of selection for smaller ungulates and the predictive power of our kill rate models.…”

“…We expected summer cougar kill rates to increase because of a shift from larger (elk) to smaller (mule deer) prey (Knopff et al 2010). We expected winter cougar kill rates to increase because of greater wolf presence at cougar kills (Bartnick et al 2013), forcing cougars to abandon their kills more quickly and therefore to hunt more frequently (sensu Elbroch and Wittmer 2013a). Finally, we summarized cause-specific cougar mortality data over the full course of the study.…”

The difference between killing and eating: ecological shortcomings of puma energetic models

“…Perhaps pumas follow rules of optimal foraging theory (MacArthur and Pianka 1966), and abandon carcasses like ''patches'' in v www.esajournals.org marginal value theorem (Charnov 1976), when the benefits of remaining with the carcass diminish to a yet undetermined tipping point (Carbone et al 2005, Vucetich et al 2012. Research from Patagonia revealed that scavenging condors increased puma kill rates by reducing puma handling time at carcasses (Elbroch and Wittmer 2013a), and Murphy (1998) proposed similar effects due to scavenging bears in North America. The influence of kleptoparasitism on other carnivore foraging ecology has also been well documented in wolves and African wild dogs (Gorman et al 1998, Carbone et al 2005, Kaczensky et al 2005.…”

“…Kill rates, defined as the numbers of prey killed per individual predator per unit time (Holling 1959), are possibly the most fundamental component of ecology required for modeling predator-prey dynamics (e.g., Lotka-Volterra equations;Lotka 1925, Volterra 1926. Estimates of kill rates have increased our understanding of dynamic species interactions in complex multispecies communities, including apparent competition affecting rare prey (Holt andLawton 1994, Wittmer et al 2013), predation-mediated Allee effects (McLellan et al 2010), and the effects of kleptoparasitism on the fitness of subordinate competitors (Gorman et al 1998, Elbroch andWittmer 2013a). Accurate estimates of kill rates are also essential for managers charged with setting sustainable harvest quotas for game species coexisting with native predators (e.g., White and Lubow 2002), and developing conservation strategies for species negatively affected by predation, including those in reintroduction programs (e.g., Rominger et al 2004.…”

Top carnivores increase their kill rates on prey as a response to human-induced fear

“…However, because carnivores are constrained by gut capacity, solitary carnivores can only maximize their caloric yield by repeatedly returning to feed on a prey carcass. In developed habitats, carnivores can be particularly vulnerable to risk-foraging trade-offs because disturbance-induced carcass abandonment can result in food loss owing to scavenging [17] or decomposition [18]. Prey consumption time can therefore be limited by external forces that reduce carnivore access to a carcass.…”