PERFITO, N.*; ZANN, R.A.; BENTLEY, G.E.; HAU, M.; Princeton Univ., New Jersey; LaTrobe Univ., Victoria, Australia; Univ. of Washington, Seattle; Princeton Univ., New Jersey: Endocrine mechanisms mediating reproduction in an unpredictable environment

Opportunistically breeding species respond to short-term, local cues in their environment to time reproduction appropriately. However, the neuroendocrine and endocrine control of this highly flexible breeding strategy are not well understood. Previous work has suggested that zebra finches (Taeniopygia guttata castanotis) breeding in arid and semi-arid habitats of Australia maintain reproductive systems in a state of readiness to breed year round. This allows them to respond quickly to favorable breeding conditions (i.e., sufficient rainfall to produce grass seed) when they occur. We tested the extent to which wild zebra finches regulate reproductive physiology according to environmental conditions by measuring reproductive development and circulating luteinizing hormone (LH) and testosterone (T) in free-living zebra finches during short, cool days in winter (9h 42min L: 14h 18min D) and long, warmer days during spring (12h 57 min L: 11h 03min D). Further, to test sensitivity to water cues specifically, we primed individual males by slowly restricting water availability over 11 weeks (to 1 ml water/bird/week) in order to increase sensitivity to stimulatory cues. We then measured rapid responses to two weeks of renewed ad libitum access to water and green grass by measuring gonad size, LH and T. Findings from these studies allow us to test both the sensitivity of the reproductive axis to changing environmental conditions in opportunistic breeders and potential hormonal mechanisms mediating opportunistic breeding strategies.