Stable isotopes to detect food‐conditioned bears and to evaluate human‐bear management

Abstract

We used genetic and stable isotope analysis of hair from free‐ranging black bears (Ursus americanus) in Yosemite National Park, California, USA to: 1) identify bears that consume human food, 2) estimate the diets of these bears, and 3) evaluate the Yosemite human–bear management program. Specifically, we analyzed the isotopic composition of hair from bears known a priori to be food‐conditioned or non‐food‐conditioned and used these data to predict whether bears with an unknown management status were food‐conditioned (FC) or non‐food‐conditioned (NFC). We used a stable isotope mixing model to estimate the proportional contribution of natural foods (plants and animals) versus human food in the diets of FC bears. We then used results from both analyses to evaluate proactive (population‐level) and reactive (individual‐level) human–bear management, and discussed new metrics to evaluate the overall human–bear management program in Yosemite. Our results indicated that 19 out of 145 (13%) unknown bears sampled from 2005 to 2007 were food‐conditioned. The proportion of human food in the diets of known FC bears likely declined from 2001–2003 to 2005–2007, suggesting proactive management was successful in reducing the amount of human food available to bears. In contrast, reactive management was not successful in changing the management status of known FC bears to NFC bears, or in reducing the contribution of human food to the diets of FC bears. Nine known FC bears were recaptured on 14 occasions from 2001 to 2007; all bears were classified as FC during subsequent recaptures, and human–bear management did not reduce the amount of human food in the diets of FC bears. Based on our results, we suggest Yosemite continue implementing proactive human–bear management, reevaluate reactive management, and consider removing problem bears (those involved in repeated bear incidents) from the population. © 2012 The Wildlife Society.

Measuring the realized niches of animals using stable isotopes: from rats to bears

“…For a previous investigation, we sampled black bears throughout Yosemite National Park via hair snare (2006 and 2007) and predicted the foraging behaviour of each bear in 2005–2007 (Hopkins et al . ). In this study, we used δ 13 C and δ 15 N values derived from the hair of bears that were predicted to forage for plants and animals exclusively (hereafter, NFC bears or bears not conditioned to forage for human foods) in 2005 and 2006 (Hopkins et al .…”

“…In this study, we used δ 13 C and δ 15 N values derived from the hair of bears that were predicted to forage for plants and animals exclusively (hereafter, NFC bears or bears not conditioned to forage for human foods) in 2005 and 2006 (Hopkins et al . ). We did not include bears in this study if they were sampled in the late summer and fall of 2006 and 2007 because isotopes in their hair do not represent bear diets for a full year.…”

“…; Kurle, Croll & Tershy ), whereas black bears that forage for anthropogenically derived foods (hereafter, human foods) in Yosemite are often in conflict with people and their property (Hopkins et al . , ). Although the main purpose of our study is to demonstrate the use of stable isotopes in measuring the realized niches of consumers, we also aim to inform wildlife management in the Aleutian Islands and Yosemite National Park by estimating the resource use of omnivorous Norway rats and American black bears.…”

Caching behaviour by red squirrels may contribute to food conditioning of grizzly bears

“…Bears (Ursus spp.) are particularly prone to food conditioning (Hopkins et al 2012), which also makes them more likely to exhibit conflict behaviour (Hopkins et al 2014a). Experience-based knowledge of this association by wildlife managers is the reason that preventing food conditioning has become a mainstay of wildlife management in protected areas (Herrero 1970, McCullough 1982.…”

Selecting the best stable isotope mixing model to estimate grizzly bear diets in the Greater Yellowstone Ecosystem

“…Before sending the hair, we sub-selected 333 samples to reduce the probability of identifying the same individual multiple times each survey [21]. WGI extracted DNA from the roots of hairs using QIAGEN’s DNeasy Blood and Tissue kits (Qiagen, Mississiauga, Ontario, Canada), following the manufacturer’s instructions.…”