Hau Michaela, Stoddard Steven T, Soma Kiran K
Department of Ecology and Evolutionary Biology, Princeton University, Princeton, NJ 08544, USA.
Horm Behav. 2004 Jan;45(1):40-9. doi: 10.1016/j.yhbeh.2003.08.002.
The hormonal control of territorial aggression in male and female vertebrates outside the breeding season is still unresolved. Most vertebrates have regressed gonads when not breeding and do not secrete high levels of sex steroids. However, recent studies implicate estrogens in the regulation of non-breeding territoriality in some bird species. One possible source of steroids during the non-breeding season could be the adrenal glands that are known to produce sex steroid precursors such as dehydroepiandrosterone (DHEA). We studied tropical, year-round territorial spotted antbirds (Hylophylax n. naevioides) and asked (1). whether both males and females are aggressive in the non-breeding season and (2). whether DHEA is detectable in the plasma at that time. We conducted simulated territorial intrusions (STIs) with live decoys to male and female free-living spotted antbirds in central Panama. Non-breeding males and females displayed robust aggressive responses to STIs, and responded more intensely to decoys of their own sex. In both sexes, plasma DHEA concentrations were detectable and higher than levels of testosterone (T) and 17beta-estradiol (E(2)). In males, plasma DHEA concentrations were positively correlated with STI duration. Next, we conducted STIs in captive non-breeding birds. Captive males and females displayed robust aggressive behavior. Plasma DHEA concentrations were detectable in both sexes, whereas T was non-detectable (E(2) was not measured). Plasma DHEA concentrations of males were positively correlated with aggressive vocalizations and appeared to increase with longer STI durations. We conclude that male and female spotted antbirds can produce DHEA during the non-breeding season and DHEA may serve as a precursor of sex steroids for the regulation of year-round territorial behavior in both sexes.
在繁殖季节之外，雄性和雌性脊椎动物的领地攻击性的激素控制问题仍未解决。大多数脊椎动物在非繁殖期性腺会退化，不会分泌高水平的性类固醇。然而，最近的研究表明，雌激素在某些鸟类非繁殖期领地行为的调节中起作用。非繁殖季节类固醇的一个可能来源是肾上腺，已知肾上腺会产生脱氢表雄酮（DHEA）等性类固醇前体。我们研究了终年具有领地性的热带斑蚁鸟（Hylophylax n. naevioides），并提出了两个问题：（1）雄性和雌性在非繁殖季节是否具有攻击性；（2）此时血浆中是否可检测到DHEA。我们在巴拿马中部对自由生活的雄性和雌性斑蚁鸟使用活诱饵进行了模拟领地入侵（STI）实验。非繁殖期的雄性和雌性对STI都表现出强烈的攻击性反应，并且对同性诱饵的反应更强烈。在两性中，血浆DHEA浓度均可检测到，且高于睾酮（T）和17β-雌二醇（E₂）的水平。在雄性中，血浆DHEA浓度与STI持续时间呈正相关。接下来，我们对圈养的非繁殖期鸟类进行了STI实验。圈养的雄性和雌性表现出强烈的攻击行为。两性血浆中均可检测到DHEA浓度，而T检测不到（未测量E₂）。雄性的血浆DHEA浓度与攻击性鸣叫呈正相关，并且似乎随着STI持续时间的延长而增加。我们得出结论，雄性和雌性斑蚁鸟在非繁殖季节能够产生DHEA，并且DHEA可能作为性类固醇的前体来调节两性终年的领地行为。
