Sexual differences in head form and diet in a population of Mexican Lance-headed Rattlesnakes, Crotalus polystictus

Sexual dimorphism of phenotypic traits associated with resource use is common in animals, and may result from niche divergence between sexes. Snakes have become widely used in studies of the ecological basis of sexual dimorphism because they are gape-limited predators and their head morphology is likely to be a direct indicator of the size and shape of prey consumed. We examined sexual dimorphism of body size and head morphology, and sexual differences in diet in a population of Mexican lance-headed rattlesnakes, Crotalus polystictus, from the State of México, Mexico. Maximum snout–vent length of males was greater than that of females by 21%. Males had relatively larger heads, and differed from females in head shape after removing effects of head size. In addition, male rattlesnakes showed positive allometry in head shape: head width was amplified while snout length was truncated with increased head size. In contrast, our data did not provide clear evidence of allometry in head shape of...与资源利用相关的表型性状的性二态性在动物类群中普遍存在，其成因可能为两性间的生态位分化。蛇类因属于受颌间距限制的捕食者，且头部形态可直接反映其捕食猎物的大小与形状，已被广泛应用于性二态性生态基础的相关研究。本研究针对来自墨西哥墨西哥州的墨西哥矛头响尾蛇（Crotalus polystictus）种群，考察了其体型与头部形态的性二态性，以及饮食的性别差异。研究结果显示，雄性个体的最大吻肛长较雌性高出21%；雄性头部相对更大，且在剔除头部尺寸的影响后，其头部形状与雌性存在显著差异。此外，雄性响尾蛇的头部形态呈现正异速生长特征：随着头部尺寸增大，头部宽度显著增加，而吻部长度则相对缩短。与之相反，本研究数据并未为……的头部形态异速生长提供明确证据。