Geographic variations in underwater male Weddell seal Trills suggest breeding area fidelity

Adult Weddell seals (Leptonychotes weddellii) exhibit site fidelity to where they first breed but juveniles, and perhaps transient adult males, may disperse from their natal location. If there is mixing between adjacent breeding groups, we would expect that common vocalisations would exhibit clinal patterns. Underwater Trill vocalisations of male Weddell seals at Mawson, Davis, Casey, McMurdo Sound, Neumayer and Drescher Inlet separated by ca. 500 to greater than 9,000 km, were examined for evidence of clinal variation. Trills are only emitted by males and have a known territorial defence function. Trills from Davis and Mawson, ca. 630 km apart, were distinct from each other and exhibited the greatest number of unique frequency contour patterns.The acoustic features (duration, waveform, frequency contour) of Trills from Neumayer and Drescher Inlet, ca. 500 km apart, were more distinct from each other than they were from the other four locations. General Discriminant Analysis and Classification Tree Analysis correctly classified 65.8 and 76.9% of the Trills to the correct location. The classification errors assigned more locations to sites greater than 630 km away than to nearest neighbours. Weddell seal Trills exhibit geographic variation but there is no evidence of a clinal pattern. This suggests that males remain close to single breeding areas throughout their lifetime.This work was completed as part of ASAC project 1132 and 2122 (ASAC_1132, ASAC_2122).

成年威德尔海豹（Leptonychotes weddellii）对其首次繁殖的栖息位点具有忠实性，但幼体乃至暂居的成年雄性可能会从出生地扩散开来。若相邻繁殖群体间存在基因交流，我们预期其常见发声会呈现渐变群模式。本研究对分别位于莫森、戴维斯、凯西、麦克默多湾、诺伊迈尔和德雷舍尔湾的雄性威德尔海豹的水下颤音发声进行了分析，各采样点间距约500千米至9000千米以上，以探究其是否存在渐变变异的相关证据。颤音仅由雄性海豹发出，已知其功能为领地防御。戴维斯与莫森两地的颤音（间距约630千米）彼此差异显著，且拥有最多的独特频率轮廓模式。诺伊迈尔与德雷舍尔湾的颤音声学特征（时长、波形、频率轮廓）间距仅约500千米，二者间的差异程度高于它们与其余四个采样点间的差异。广义判别分析（General Discriminant Analysis）与分类树分析（Classification Tree Analysis）可分别将65.8%与76.9%的颤音样本正确归类至其来源采样点。分类误差更多地将样本划归至距离超过630千米的采样点，而非其最近邻采样点。威德尔海豹的颤音存在地理变异，但未呈现渐变群模式，这表明雄性威德尔海豹在其一生中会坚守单一繁殖区域。本研究作为ASAC项目1132与2122（ASAC_1132、ASAC_2122）的一部分完成。