MATE-SELECTION BEHAVIOR AND SAMPLING STRATEGIES IN GEESE

Captive barnacle geese, Branta leucopsis, were allowed to choose mates in large social groups, over 2 years, simulating natural pairing conditions. During the mate-choice process, geese sampled from one to six potential mates in temporary 'trial liaisons', which lasted from a few days to several weeks. The number of trial liaisons did not differ significantly between the sexes, but was greater in heavier and more vigilant females. More vigilant males were sometimes able to acquire more than one long-term partner. Birds that started mate searching earlier in the season sampled more mates and invested more time on individual liaisons. A combination of two mate-sampling strategies was apparently used: (1) the 'one-step-decision strategy', where a bird decides at each encounter whether to accept or reject a mate, before moving onto the next candidate, and (2) the 'partner-hold strategy', where a bird holds onto the previously sampled mate whilst sampling a new one, comparing the relative qualities of both, before making a decision whether to leave the old for the new trial mate. The partner-hold strategy will yield the highest fitness of all mates sampled, yet puts no constraints on a bird of having to remember the qualities of all mates encountered and of re-locating the best mate. Copyright © 1993 The Association for the Study of Animal Behaviour.