The release of livestock on Anegada in 1968 has not only caused a decline in population numbers, but has also had a profound affect on the Anegada ground iguana’s social organisation and diet (2). Estimates in the late 1960s showed the average home range size for iguanas on Anegada to be small, at less than 0.1 hectares, and non-overlapping (2) (4). Additionally, there were roughly equal numbers of males and females, each individual was found to occupy one principle burrow, and habits indicated monogamy, with pairs inhabiting separate but proximate burrows in a joint home range isolated from other pairs. However, by 1991, the sex ratio had changed to two males to every female. Now, home ranges are quite large and overlap, at 6.6 hectares for males and 4.2 hectares for females; with these changes thought to be a result of male competition for far more limited females (4). Males suspected of having a mate have noticeably smaller home ranges, presumed to be due to their greater need to guard the female against wandering bachelors. Females typically lay one clutch of around 12 to 16 eggs per year between May and June, and clutches hatch in August and September at the beginning of the rainy season, when there is greater availability of lush vegetation (2).
Although predominantly herbivorous, the Anegada ground iguana is also an opportunistic carnivore, feeding on invertebrates such as beetles, caterpillars, centipedes and roaches supplementing a diet of leaves and fruit (4). Where the iguana’s range overlaps with feral livestock, the bulk of the diet consists of plants that are rejected by the livestock. These are usually plants containing high levels of secondary compounds that are poorly digested and therefore of poor nutritional value (2).