Behavioral Ecology Advance Access originally published online on July 21, 2004
Behavioral Ecology 2005 16(1):8-14; doi:10.1093/beheco/arh127
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Risky decisions: a test of risk sensitivity in socially foraging flocks of Lonchura punctulata
a Department of Biology, Concordia University, b Département des sciences biologiques, Université du Québec à Montréal, CP 8888, succursale Centre-Ville, Montréal, Quebec H3C 3P8, Canada
Address correspondence to L-A. Giraldeau. E-mail: giraldeau.luc-alain{at}uqam.ca.
Group foraging allows for individuals to exploit the food discoveries of other group members. If searching for food and searching for exploitation opportunities within a group are mutually exclusive alternatives, the decision to use one or the other is modeled as a producer-scrounger game because the value of each alternative is frequency dependent. Stochastic producer-scrounger models generally assume that producer provides a more variable and uncertain reward than does the scrounger and hence is a riskier foraging alternative. Socially foraging animals that are attempting to reduce their risk of starvation should therefore alter their use of producer and scrounger alternatives in response to changes in energy budget. We observed flocks of nutmeg mannikins (L. punctulata) foraging in an indoor aviary to determine whether their use of producer and scrounger alternatives were risk sensitive. Analyses of the foraging rewards of three flocks of seven birds confirm that producer is a riskier foraging strategy than is scrounger, although the difference in risk is rather small. We then submitted two other flocks to two different energy budgets and observed the foraging decision of four focal birds in each flock. All but one bird increased their relative use of the riskier producer strategy in the low food reserve treatment, but the overall use of producer did not differ significantly between treatments, providing evidence for a small but consistent effect.
Key words: energy budget, producer-scrounger game, risk-sensitive foraging, social foraging.