The Herpetological Journal

pp. 176-186

Authors: Matthijs P. van den Burg, Hannah Madden & Adolphe O. Debrot

Abstract: Conservation management of natural populations is ideally based on the most accurate data of critical variables including demography, natural history and population size. Although Caribbean iguanids are highly threatened by a range of anthropogenic threats, the native melanistic Iguana iguana populations in the Lesser Antilles have received surprisingly little research attention. Here we assessed population size, distribution and degree of melanism for the melanistic iguanas of Saba, Caribbean Netherlands based on one month of fieldwork. Distance sampling (based on 117 separate surveys along 38 unique transects, totalling 48 survey hrs) estimated the island population size at 8233 ± 2205 (SD) iguanas. Female maximum snout-vent length (39.0 cm) of 56 captured iguanas was less than that of males (43.9 cm). Iguanas mainly occurred on the southern and eastern sides of the island, at mid-altitudes between 180 and 390 m (max 530 m), with highest densities being in residential and certain natural areas. Historically, iguanas have been reported from higher altitudes, where their presence was likely facilitated by former extensive forest clearing for agricultural reasons. Contrary to earlier statements claiming that 20% of adult males were fully melanistic, we found that only 1% of adult iguanas exhibited > 90% melanism, whereas 81% of males were less than 50% melanistic on the body. No relationship was found between the degree of melanism and elevation, which has been suggested by others. Probably, one main threat to the Saba green iguana population is the documented crossbreeding with non-native green iguanas. Beyond non-native iguanas, the long-term stability of the native population appears under pressure given the limited nesting sites and extremely low presence of juvenile and hatchling iguanas (2.4%). In particular, the island’s feral cat and large goat population likely impact nest-site quality, nest success and hatchling survival.

Keywords: ecology, Iguanidae, Lesser Antilles, management, population assessment

pp. 187-197

AUTHORS: Amber H. Mathie, Crinan Jarrett, Kowo Cyril, Tabe T.R. Claire, Diogo F. Ferreira & Luke L. Powell

ABSTRACT: Forests are being converted to agriculture throughout the tropics, driving declines in sensitive rainforest taxa. However, low-intensity agricultural systems, such as cocoa agroforestry, may provide refuges for biodiversity. Little is known about the suitability of these systems for vertebrate fauna in the Afrotropics, especially with regards to amphibians. Here, we contribute novel information on amphibian communities in African cocoa farms by investigating the effects of within-farm characteristics and surrounding habitats on the abundance and richness of amphibians. In August–September 2019, we surveyed amphibians in 15 cocoa farms and four primary forest sites in southern Cameroon, capturing 206 individuals of at least 29 species. Overall, responses of amphibians to within-farm characteristics and surrounding habitat varied between species, but at the community level the main responses were a decrease in number of captures with increasing ground vegetation height, and with increasing open agriculture and villages surrounding farms. Species also showed associations with canopy cover in farms (positive for three species), abundance of husk piles in farms (negative for three species), surrounding forest habitat (positive for two species and negative for one) and surrounding plantation or degraded forest habitat (positive for one species). Our results on the effects of surrounding habitat suggest that the composition of amphibian communities in cocoa farms may be largely influenced by the ability of species to disperse through neighbouring habitats. Additionally, we found that the relative abundance of amphibian species differed significantly between forest and cocoa: this effect appeared to be driven largely by tree frog species (genus Leptopelis), which were more abundant in forest habitats, suggesting that certain tree frog species may serve as an indicator of primary forest-like conditions. Given the current climate of agricultural intensification in Africa, our results contribute to the initial steps towards identifying amphibian-friendly agricultural practices.

Keywords: agroforestry, leaf litter, microhabitat, open agriculture, tropical forest

pp. 187-197

AUTHORS: Amber H. Mathie, Crinan Jarrett, Kowo Cyril, Tabe T.R. Claire, Diogo F. Ferreira & Luke L. Powell