Gobush K S, Booth R K, Wasser S K
Pacific Islands Fisheries Science Center, National Marine Fisheries Service, National Oceanic and Atmospheric Administration, 1601 Kapiolani Blvd. Suite 1000, Honolulu, HI 96814, USA; Save the Elephants, P.O. Box 54667, Nairobi 00200, Kenya.
The Center for Conservation Biology, University of Washington, Seattle, WA 98195, USA.
Gen Comp Endocrinol. 2014 Jan 1;195:174-82. doi: 10.1016/j.ygcen.2013.10.020. Epub 2013 Nov 13.
We validate fecal glucocorticoid (GC) and thyroid (T3) hormone metabolite measures in the Critically Endangered Hawaiian monk seal for the first time, and examine variation in the concentrations of these hormones in individuals across the species' range. We test hypotheses that monk seals from declining subpopulations have relatively high GCs and low T3 on average suggesting impacts of food limitation, and that this hormone pattern is more apparent in immature animals compared to adults, as food limitation is specifically indicated as a principal cause of poor body condition and survival of juvenile monk seals. We opportunistically sampled scat from 84 individually identifiable monk seals during the 2010 breeding season from two geographic regions, the main Hawaiian Islands (MHI) and the Northwestern Hawaiian Islands (NWHI). The MHI subpopulation of monk seals is growing, whereas subpopulations at many sites in the NWHI are in decline. Best fit general linear models predicting variation in GCs and T3 (examined separately) were similar (after accounting for significantly elevated hormone concentrations associated with molt and possibly lactation); both included sample date, region, and monk seal age as predictors. GC concentrations were significantly lower in MHI versus NWHI monk seals and decreased as the breeding season progressed. T3 concentrations were significantly lower in immature monk seals compared to adults. GC and T3 concentrations were positively correlated at 4 NWHI sites; prey may be adequate for physiological growth or maintenance at these sites but relatively stressful to acquire. GCs were highest at French Frigate Shoals, (a NWHI site) while T3 was relatively low here, indicating a possible signal of food limitation. GCs were lowest in the MHI. Disturbance associated with living near a high human population in the MHI appears to impact monk seal physiology less than other stressors encountered in the remote and highly protected NWHI where human presence is extremely low.
我们首次验证了极度濒危的夏威夷僧海豹粪便中糖皮质激素（GC）和甲状腺激素（T3）代谢物的测量方法，并研究了这些激素在该物种分布范围内个体中的浓度变化。我们检验了以下假设：来自数量下降亚种群的僧海豹平均具有相对较高的GC和较低的T3，这表明食物限制的影响；与成年动物相比，这种激素模式在未成年动物中更为明显，因为食物限制被明确指出是幼年僧海豹身体状况不佳和生存困难的主要原因。在2010年繁殖季节，我们从两个地理区域，即夏威夷主岛（MHI）和夏威夷西北群岛（NWHI），对84只个体可识别的僧海豹的粪便进行了机会性采样。MHI的僧海豹亚种群数量在增加，而NWHI许多地点的亚种群数量在下降。预测GC和T3变化（分别进行检验）的最佳拟合一般线性模型相似（在考虑到与换毛和可能的哺乳期相关的激素浓度显著升高之后）；两者都将采样日期、区域和僧海豹年龄作为预测变量。MHI僧海豹的GC浓度显著低于NWHI僧海豹，并且随着繁殖季节的推进而降低。未成年僧海豹的T3浓度显著低于成年僧海豹。在NWHI的4个地点，GC和T3浓度呈正相关；在这些地点，猎物可能足以满足生理生长或维持需求，但获取过程相对压力较大。在法属护卫舰浅滩（一个NWHI地点），GC最高，而T3相对较低，这表明可能存在食物限制的信号。GC在MHI最低。与MHI人口密集地区附近生活相关的干扰对僧海豹生理的影响似乎小于在偏远且受到高度保护的NWHI遇到的其他压力源，在NWHI人类活动极少。
