A Morphometric Comparison of Island and Mainland Boas (Boa Constrictor) in Belize
Relative to mainland Boa constrictor , boas from islands off the coast of Belize aredescribed as being smaller, having longer tails, more elongate snouts, andproportionately larger eyes. However, no systematic confirmation of these patternshas been made. A morphometric study was initiated to investigate the body size andhead shape variation between island and mainland boas in Belize. One hundred twenty-nine boas from five islands and the mainland were caught and measured. Univariateand multivariate analyses indicated that, in general, previous descriptions are accurate.Island boas are about half the length and one-fifth the mass of mainland boas. Incontrast to mainland boas, no sexual size dimorphism is evident in island boas. Thehead shape of island boas differs from that of mainland boas but this divergence is not consistent among populations. Some island boas have more attenuate snouts comparedto mainland boas whereas other island boas have larger eyes and narrower heads. Maleisland boas have longer tails compared to males from the mainland, but sucha difference is not found in females from the two localities. The morphology of islandboas is consistent with an arboreal habit and reduced prey size. Because these changeshave occurred over an extremely short time interval, this may be another example of the speed and magnitude of adaptation that is possible in squamates.
Boback, Scott M. "A Morphometric Comparison of Island and Mainland Boas (Boa Constrictor) in Belize." Copeia 2006, no. 2 (2006): 261-267.