Abstract
Acquisition of resources can be costly and individuals are predicted to optimize foraging strategies to maximize net energy gain. Wolves (Canis lupus) would be expected to scavenge on subsidies from anthropogenic resources when these resources provide an energetic benefit over the capture of wild prey. We examined the effects of subsidies from anthropogenic resources in the form of livestock carcass dumps (LCDs) on wolf space use, activity, tortuosity, and diet in portions of North America’s northern hardwood/boreal ecosystem. We fitted 19 wolves with global positioning system collars during May–August of 2009–2011 and 2013–2015. Wolves with LCDs within their home ranges used areas adjacent to LCDs greater than non-LCD sites and had decreased home ranges and activity as compared to wolves without LCDs in their home ranges. Additionally, cattle comprised at least 22% of wolf diet from scavenging in areas with LCDs present as compared to no cattle in the diet of wolves without access to LCDs. Subsidies from anthropogenic resources in the form of LCDs can serve as attractants for wolves and alter wolf diet, activity, and ranging behavior. Apex predators may alter their behavior where subsidies from anthropogenic resources occur and management of these subsidies should be considered when attempting to reduce the impacts of humans on wolf behavior.
Highlights
An optimal foraging strategy is one that maximizes net gain of energy[1,2] and may be determined by prey distributions[3]
We used collar data collected during May–August for analysis of each study area and excluded three wolves from analysis: one female from each area due to dispersal and one female we considered transient crossing multiple pack territories within the LCDs present (LCDP) area
Resident wolf home ranges in the LCDP area (15.23–46.97 km2) were 1.87 times smaller on average (P = 0.004, t = -3.05, df = 13.8) than home ranges in the LCDA area (20.10–85.09 km[2]; Table 1)
Summary
An optimal foraging strategy is one that maximizes net gain of energy[1,2] and may be determined by prey distributions[3]. Facultative scavenging too may occur when a stable influx of resources such as subsidies from anthropogenic resources (hereafter called food subsidies) becomes available[6]; use of these food subsidies may alter individuals’ diet, space use, and social structure[7] Use of these food subsidies, by apex predators, may result in some level of risk due to human-caused mortality[13]. During the summer period of lesser prey vulnerability and greater nutritional demand during pup rearing, LCDs may be an important resource for wolves and may influence their diet and ranging behavior. We studied indices of wolf diet, activity, and ranging behavior in areas with and without known food subsidies from LCDs. Here, we hypothesized that wolf diet, activity, and ranging behavior follow the expectations from foraging theory within the constraints of a central place forager during early pup rearing and use resources that provide increased calories with decreased energy expenditure. We predicted wolves exposed to food subsidies would exhibit a reduced home and core range, greater use of LCD areas relative to availability, and lesser activity and straighter active trajectories, and include these subsidies in their diet due to increased food availability and reduced energy expenditure searching for and acquiring food
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