Territory revisits reduce intrusion during spawning trips by female yellowtail damselfish, Microspathodon chrysurus

Abstract

When territory owners temporarily leave their territories, intrusion often increases. Periodic returns (revisits) may reduce intrusion, but not necessarily, because this tactic might increase total time away from the territory. The effectiveness of revisits also depends on a subsequent delay in the return of intruders. Adult female yellowtail damselfish briefly leave their territories in the early morning every 3 days to spawn. Some females make a single trip; others return to their territory several times before they finish spawning. To determine how much time females spent on revisits and whether it reduced intrusion, we observed revisits by multiple-trip females and compared intrusion on the territories of spawning and experimentally caged single-trip and multiple-trip females. If revisits reduce intrusions, multiple-trip females should have higher intrusions when caged than when spawning. If revisits show adaptive plasticity, caged single-trip females should have lower intrusion rates than caged multiple-trip females. Not counting the first trip to the male's nest and the final return trip, we estimated that spawning multiple-trip females averaged 86% of their time at the male's nest, 11% back in the territory and 3% travelling. When owners were spawning, territories of both single- and multiple-trip fish received about 5–7 min of intrusion. When owners were caged, intrusion increased significantly only on territories of multiple-trip females. We consider this the first direct evidence that revisits during temporary absences reduce intrusion on territories, suggesting that revisiting is a plastic trait that females may vary in response to intruder pressure.