Meet the Lizards of Tobago's Main Ridge

Amy Deacon, Lecturer in the Department of Life Sciences at The University of the West Indies, St Augustine and Secretary of the Trinidad and Tobago Field Naturalists’ Club continues her series on the biodiversity of the Main Ridge Reserve (MRR). She teams up with herpetologist Renoir Auguste once again; this time to introduce us to the lizards of the MRR. 

 The beautifully patterned Ocellated Gecko is endemic to Tobago. Photo by Renoir Auguste

There are at least 17 different species of lizard on Tobago. The majority of this diversity lies within the Main Ridge Reserve. Here, we will meet three of the species most associated with the Main Ridge: the stunningly beautiful ocellated gecko which is found nowhere else in the world; the elusive hex-scaled bachia, a species you probably never knew existed until now; and finally the prehistoric-looking green iguana.

We’ll start by introducing the endemic ocellated gecko. Geckos are a type of lizard, known for their climbing abilities; six species of gecko are found in Tobago but the ocellated gecko is the only one that is unique to Tobago. It is a small species (reaching around 7cm) and undoubtedly wins the title of ‘most colourful lizard on the island’. Males are especially vibrant, sporting a beautiful yellow head, patterned with black and orange spots reminiscent of the markings of a jaguar or ocelot, and bordered by a bright yellow neck ring. The ‘ocellated’ part of their name derives from the pairs of dazzling pale blue eye-spots along the side of their body, which ends in a rusty orange tail. This showy outfit is most likely an attempt to impress females, which have a much more subtle patterning to prevent them from being seen by predators, such as birds. After mating with a suitably attractive male, females will lay a single egg under a layer of bark, although it is common for several different females to lay their eggs in the same place for added protection.

In the MRR, the ocellated gecko is most often seen on stream-side tree trunks, but it may also be spotted in less pristine settings outside the reserve, for example it is frequently seen scuttling around deserted buildings. If you sit and watch one for a few minutes, it becomes clear that males are very territorial, and tend to inhabit and defend a particular area with one or more females nearby. It is diurnal (active in the daytime) and is considered an ambush predator, pouncing upon unsuspecting insects and land snails that come a little too close.

This strange looking lizard is the Hex-Scaled Bachia, which makes its home in the leaf litter of the Main Ridge Forest. Photo by Renoir Auguste

It is unlikely that many readers will have heard of the strangely-named hex-scaled bachia lizard, let alone seen one. Even if you are lucky enough to catch a glimpse of this bizarre-looking creature, at first glance it could be confused with a worm or small snake. It has a slender body with surprisingly short limbs relative to its body length (reaching about 16cm long). It is named after the distinctive hexagonal shaped scales on its back; yet another lizard named after its morphological features. Like the ocellated gecko, the hex-scaled bachia lizard is diurnal and feeds on a variety of small leaf-litter invertebrates, although its favourite food is termites. As a result, this species makes its home in the leaf litter and soil of the forest floor, where it can find plentiful food and a safe place to nest. Given that bachia lizards appear to spend the majority of their life hidden under the leaves, is not surprising that they are rarely seen!

A lizard that everyone will be familiar with is the green iguana – although not everyone realises that it is officially the largest lizard in the western hemisphere! This lizard can reach up to 2 metres long at maturity and has a wide distribution in the region, from Mexico to Brazil. Juveniles and females are an incredible bright green colour, while adult males may be silvery grey, and can turn red-orange during breeding season. Females construct nesting burrows to lay their eggs in. Here, they are sometimes predated on by another lizard – the tegu, also known as the matte. It is not just their eggs that are vulnerable to predation; juveniles and adults may be preyed upon by snakes, raptors, cats, and especially humans. Indeed, iguanas are perhaps the most hunted reptile in the country. Of course, it is illegal to hunt iguana (or any animal) inside the MRR at any time of year. However, with a permit, iguanas can be legally hunted outside of the MRR during open season (October –February).

Green iguanas can be found almost anywhere on Tobago, from the primary evergreen forest of the MRR, to mangrove swamps and urban parks and gardens. As they are active during the day they are often seen wandering around or basking in the sun. Unlike most of Tobago’s lizards, which prey upon insects and other small creatures, iguanas are strict vegetarians. In fact, they have a specialized digestive system for processing difficult-to-digest plant material. They are also surprisingly good swimmers and are known to dive into water to avoid potential predation when disturbed.

The majestic Green Iguana. Photo by Renoir Auguste

Despite being closely related to snakes (both snakes and lizards are reptiles of the order Squamata), for some reason lizards seem to provoke less fear in people, and have an easier time being liked – apparently we are less suspicious of creatures with legs! Legs or no legs, our reptilian neighbours play an important role in the ecosystem by acting as predator and prey to a variety of animals – not to mention the role that iguanas play in dispersing seeds that they do not digest. We should also be grateful for the lizards that share our gardens and homes, providing a natural pest-control service for mosquitoes and cockroaches. In return, we should take care with the chemicals we use in the house and garden so as to encourage this mutually beneficial arrangement, and ensure that their forest home in the MRR continues to be preserved for many years to come.