The Enigmatic Rhinoceros Iguana: A Glimpse into a Remarkable Reptile

Kingdom: Animalia

Phylum: Chordata

Subphylum: Vertebrata

Class: Reptile

Order: Squamata

Family: Iguanidae

Genus: Cyclura

Species: Cyclura Cornuta

The rhinoceros iguana (Cyclura cornuta) is an endangered species of iguana that is native to the Caribbean island of Hispaniola and its surrounding islands. These islands are shared by Haiti and the Dominican Republic meaning that this iguana species lives in a tropical climate zone and within the neotropical biogeographical realm.

These unusual looking reptiles prefer to live within a scrub woodland, scrubland, or moist forest environment, where they are typically most active during the day. However, they can also be found inhabiting dry forests rocky habitats of eroded limestone in coastal terraces, lowlands of the mainland, and several offshore islands and small cays. During the night this species will often be found in hollow trunks or caves where they can sleep with some form of protection.

This species is a large lizard, varying in length from 60 to 136 centimetres (24 to 54 in), making them the largest in their genus. Males tend to be larger than the females, and have more prominent dorsal crests and horns; with males also featuring large femoral pores on their thighs, which are used to release pheromones. The skin colours of the rhinoceros iguana range from a steely/stone grey to a dark green and even can even be a brown colour. The name ‘rhinoceros iguana’ derives from the bony-plated pseudo-horn or outgrowth typically on the iguana’s snout which resembles that of the horn of a rhinoceros.

The rhinoceros iguana is primarily a herbivore species consuming leaves, flowers, berries, seeds, and fruits from different plant species. However, they will also eat small lizards, snakes, insects, and even carrion. This species typically attacks aggressively; biting and repeatedly striking their tail, especially if threatened although typically quick to flee.

They are a polygynous species meaning that a single male will have multiple female mates, with their breeding season typically being between the months of May and June (lasting 2-3 weeks). During these 2-3 weeks males tend to become the most territorial and the most aggressive. Females have a pregnancy duration of 4 to 5 months and the eggs within a clutch have an incubation period of approximately 85 days. After the female has laid her clutch they will guard and protect their nests for several days. The size of a clutch can typically vary between 2 to 34 eggs with an average of 17, with these being some off the largest lizard eggs to be produced in the world. Once the young have hatched they are very active, do not require any parental care, and are able to fend for themselves from the very first moment. Male rhinoceros iguanas reach reproductive maturity at 4 to 5 years of age, while females reach reproductive maturity when they are around 2 to 3 years old.

The International Iguana Foundation (IIF) estimate there to be between 10,000-17,000 individual rhinoceros iguanas within the wild. Their IUCN status currently is endangered (EN) on the IUCN red list, with their numbers decreasing. Rhinoceros iguanas are threatened by illegal poaching for food and medicinal use, non-native species such as feral cats, dogs, mongoose and pigs pose a predation risk, and competitors for food sources like herbivores such as cows and goats. Habitat is often destroyed due to charcoal production, as well as development for tourism, land conversion for agriculture, and bauxite mining. A local non-governmental organisation, Grupo Jaragua, manages conservation efforts for Rhinoceros iguanas in the Dominican Republic. These include habitat monitoring and restoration, outreach and education, and land acquisition. Recommended conservation measures are better law enforcement and the development of an island-wide conservation management plan. Rhinoceros iguanas play an important role in distributing seeds to new areas (particularly when females migrate to nesting sites) and, as the largest native herbivores of their island's ecosystem, they are essential for maintaining the balance of vegetation.