Morphological and demographic analyses of Ctenosaura melanosterna across its range: Implications for population level management

Abstract

The Black-chested Spiny-tailed Iguana, Ctenosaura melanosterna, is listed as Endangered by the IUCN Redlist Assessment and under Appendix II of CITES. The species has two evolutionarily significant units (ESUs), found in the Valle de Aguán and the Cayos Cochinos Archipelago, Honduras. Each ESU has been shown to be genetically distinct and each is listed, for differing reasons, as Critically Endangered by the IUCN. Habitat destruction and overharvesting for consumption and the pet trade are among the top threats facing the mainland, Valle de Aguán, population. The Cayos Cochinos population faces similar threats to a lesser degree; however, its restricted range (2.2 km2 ) heightens the potential severity of these threats, and makes this population highly susceptible to the impact of hurricanes. We examined body size, demography, and body condition in both populations. Our results show that the average adult size is smaller on the mainland, and there are more than expected small individuals in that population. Additionally the sex ratio is significantly male biased on the mainland relative to the islands. These results demonstrate evidence of a more severe poaching pressure on the mainland that is biased towards larger individuals and females. Body condition index did not differ between the more disturbed mainland area and the more pristine island area, suggesting that habitat alteration does not pose as serious a threat to the mainland population as poaching. Potential negative effects of a restricted range on the morphology and demography of the island ESU were observed. Conservation measures should acknowledge the differences between the ESUs when defining management initiatives for this species.