Context-dependent acquisition of territories by male collared lizards: the role of mortality

Abstract

We recorded the behavior of free-ranging collared lizards for 11 consecutive seasons to test the hypotheses that natural mortality of territorial males that were 2 years and older (2yp) allows first-year males to switch to territorial tactics and that such events increase opportunities for courtship. Because neighboring 2yp males sometimes expanded and sometimes did not expand into the areas made vacant by mortality, we also compared first-year male behavior under these 2 conditions. In response to 2yp male mortality, first-year males increased rates of travel, distant display, courtship frequency, and number of different females courted. Newly territorial first-year males did not significantly increase aggression with rival males. Travel and both courtship frequency and number of females courted were higher when neighboring males did not expand. First-year males that acquired territories during the breeding season had lower values for all variables than 2yp males, whereas first-year males acquiring territories after over-winter mortality courted less frequently than 2yp males. First-year males acquiring territories after over-winter mortality traveled at higher rates and were more aggressive with rivals than those that gained territories after mortality during the breeding season and established 2yp males. Our results indicate that mortality of territorial males both during the reproductive season and over winter prompts first-year males to adopt territorial tactics that promote increased opportunities to court females. Acquisition of territories during the first-year as a consequence of territory owner mortality potentially increases the lifetime mating success of these males markedly. Copyright 2010, Oxford University Press.