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Proc Biol Sci. 2013 Jul 24;280(1767):20131210. doi: 10.1098/rspb.2013.1210. Print 2013 Sep 22.

To kill a kangaroo: understanding the decision to pursue high-risk/high-gain resources.

Author information

1
Woods Institute for Environment, Stanford University, Stanford, CA 94305-2034, USA. jhj1@stanford.edu

Abstract

In this paper, we attempt to understand hunter-gatherer foraging decisions about prey that vary in both the mean and variance of energy return using an expected utility framework. We show that for skewed distributions of energetic returns, the standard linear variance discounting (LVD) model for risk-sensitive foraging can produce quite misleading results. In addition to creating difficulties for the LVD model, the skewed distributions characteristic of hunting returns create challenges for estimating probability distribution functions required for expected utility. We present a solution using a two-component finite mixture model for foraging returns. We then use detailed foraging returns data based on focal follows of individual hunters in Western Australia hunting for high-risk/high-gain (hill kangaroo) and relatively low-risk/low-gain (sand monitor) prey. Using probability densities for the two resources estimated from the mixture models, combined with theoretically sensible utility curves characterized by diminishing marginal utility for the highest returns, we find that the expected utility of the sand monitors greatly exceeds that of kangaroos despite the fact that the mean energy return for kangaroos is nearly twice as large as that for sand monitors. We conclude that the decision to hunt hill kangaroos does not arise simply as part of an energetic utility-maximization strategy and that additional social, political or symbolic benefits must accrue to hunters of this highly variable prey.

KEYWORDS:

behavioural ecology; foraging theory; hunter–gatherers; risk; statistical methods

PMID:
23884091
PMCID:
PMC3735252
DOI:
10.1098/rspb.2013.1210
[Indexed for MEDLINE]
Free PMC Article

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