Meeting Abstract
20.2 Jan. 5 Seasonal variation in the endocrine regulation of aggressive behavior in a sedentary tropical bird HAU, M*; BEEBE, K; CANOINE, V; SCHLINGER, BA; Princeton University hau@princeton.edu
Evidence is accumulating from studies in temperate-zone male vertebrates that the endocrine regulation of aggressive territorial behavior differs seasonally. During the breeding season a combination of androgenic and estrogenic mechanisms appear to regulate male aggressive behavior, while during the non-breeding season either only estrogenic or non-sex steroidal mechanisms control male aggression. Research on sedentary neotropical spotted antbirds (Hylophylax n. naevioides) that defend a multi-purpose territory together with a long-term partner had suggested that testosterone is involved in regulating territorial aggression at all times of year. Here we experimentally test this notion in both male and female spotted antbirds. Free-living males and females responded to simulated territorial intrusion (STIs) with a live male decoy by displaying aggressive behavior of similar quality and quantity in the non-breeding season, the early and the middle of the breeding season. Circulating concentrations of testosterone after STIs in both sexes were low and seasonally invariant, but both sexes had increased plasma dehydroepiandrosterone (DHEA) concentrations during the non-breeding season. The combined administration of an androgen receptor antagonist (Flutamide) and an aromatase inhibitor (ATD) during the non-breeding season did not reduce aggressive behavior in captive spotted antbirds, while in a previous study a similar treatment during the breeding season did reduce aggressive behavior. These data confirm that aggressive behavior can be regulated by divergent endocrine mechanisms in different seasons, even in sedentary species that remain on the same territory with the same partner for many years. The specific endocrine mechanisms that regulate aggressive territorial behavior in spotted antbirds during the non-breeding season remain to be determined, but may include low concentrations of estrogens.
