02. An evaluation of the diet of Cyclura iguanas in the Dominican Republic

W reptiles, iguanas of the subfamily Iguaninae are known for their unique herbivorous feeding strategy (Iverson, 1982). While most reptiles have adopted a more omnivorous strategy, many iguana species are known to specialise on fruits, seeds, and leaves, making them “truly herbivorous” (Alberts, 2004; Iverson, 1982). Indeed these herbivorous lizards have a distinct enlarged colon that is likely related to this ecologically important life strategy (Iverson, 1982). Herbivory plays a key role in plant growth and reproduction, aiding in seed dispersal and germination. Thus, this feeding strategy is essential to maintaining and perpetuating healthy ecosystems (Hartley et al., 2000). Understanding the diet and feeding behaviour of herbivorous lizards, such as iguanas, will not only improve our understanding of their ecological role in a given environment, but can also provide useful information for conservation planning. Given that iguanas are some of the most endangered lizards in the world (ITWG, 2016), dietary information is vital to management efforts focused on the restoration of current and future habitats, as well as translocation strategies, as these data will ensure that the proper food sources can be made available. Restoration and translocation are both common approaches explored in iguana conservation programs (Knapp & Hudson, 2004). To date, detailed information regarding the diet of many iguana species, such as those endemic to Hispaniola, is unavailable. Hispaniola is unique in that it is the only Caribbean island where two native species of Cyclura cooccur: Cyclura cornuta (Bonaterre) (Rhinoceros iguana) and C. ricordii (Duméril & Bibron)(Ricord ́s iguana). The broadly sympatric distribution of C. cornuta and C. ricordii likely arose when Hispaniola was formed through the joining of North and South Paleoislands (Banbury & Ramos, 2005). C. cornuta occurs throughout Hispaniola; however, many populations seem to be dwindling (Powell et al., 2000; SAP pers. obs.). C. ricordii is restricted to four populations: three in southwestern Dominican Republic (Los Olivares, Lago Enriquillo and Isla Cabritos) and one in southeastern Haiti (Alberts, 2000). C. cornuta is categorised as Vulnerable under IUCN Red List criteria and C. ricordii is listed as Critically Endangered (Ottenwalder, 1996 a, b). The introduction of exotic mammals, illegal pet trade, human consumption, and most prominently, habitat alteration and degradation are the main threats to these iguanas (Ottenwalder 1996 a, b). Cyclura spp. are thought to be generally herbivorous; however, precise feeding strategies may differ depending on food availability and preference. Previous studies of Cyclura on Hispaniola have produced limited observations of diet (reviewed by Iverson, 1979). Herein we evaluate the diet of C. cornuta and C. ricordii through an indepth scat analysis, in an effort to characterise the diet and address the aforementioned factors affecting feeding behaviour. Specifically we aimed to: (1) qualitatively and quantitatively describe the diet of Cyclura in the study area and (2) determine if preference for certain plant species occurs by comparing the resources used to those available during the study period.