The Spectacular Snakes of the Main Ridge Reserve

This week 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). Today, she teams up with herpetologist Renoir Auguste to introduce us to the snakes of the MRR. 
 
Tobago has about 25 species of snake, none of which are venomous. Most of these species can be found in and around the Main Ridge. Among them are the Boa Constrictor - the largest snake on the island; the Brown Vine Snake - a common snake also found in gardens; and the Tobago False Coral  – which can be found nowhere else in the world! Together these three species highlight just some of the different shapes, sizes and habits of snake fauna found in the reserve.

Reaching an intimidating 4 metres long, the Macajuel (Boa constrictor) is the largest snake on the island. Within the Main Ridge it is fairly common, and may be found in the trees or on the ground. Like all snakes, it is a predator and is most active at night when it sets off on a hunt for opossums, rodents, birds and reptiles, which it ambushes, bites and squeezes to death (hence the ‘constrictor’ part of its name). Although this is a terrifying prospect for these small creatures, it is not venomous,  and not aggressive to humans unless provoked.
The Boa Constrictor or Macajuel is the largest snake in Tobago, and an important predator in the MRR. Photo by Renoir Auguste

As Tobago lacks mammalian top predators, such as the ocelot, boa constrictors play an important role within the ecosystem and should be protected both inside and outside of the MRR. Sadly, it is not uncommon to come across boa roadkill, as the snakes commonly use the North Side, Windward and Bloody Bay-Roxborough roads to move between patches of forest in the MRR.

The snake you have the best chance of seeing in Tobago is the Brown Vine Snake (Oxybelis aeneus), thanks to its daytime habits and broad habitat preferences. As well as making its home in the MRR, it is also a frequent visitor to gardens and other open areas where it may be seen posing on fences. It is more commonly known as the ‘Horsewhip’, due to its slender build and distinct pointed snout; indeed it is considerably shorter and slimmer than the Boa, but nonetheless can reach a length of 1.5 metres.
True to its name, this snake spends most of its time in the trees beautifully mimicking a vine to camouflage it from both predators and unsuspecting prey. If a predator sees through its clever disguise, the horsewhip will open its mouth wide, revealing a dark lining which it is believed gives some predators a fright. It too is an important predator in the MRR, favouring lizards but also feasting on frogs and small birds given the opportunity. Being both long and lightweight means it can hunt prey even on the thinnest branches, where it uses a ‘sit and wait’ strategy.
The sleek, well-camouflaged Horsewhip - Photo by Renoir Auguste

Much less is known about the next snake, the Tobago False Coral or ‘Red Snake’ (Erythrolampus ocellatus), aside for the important fact that so far it has been found nowhere else in the world and is thus classified as ‘endemic’ to the island. It is the smallest of the three snakes, reaching just 50 cm long, and is a striking red colour with black and white eye spots along its back. Although it superficially resembles Trinidad’s venomous coral snake, it is in fact harmless to humans.

The Tobago false coral is often found in cocoa plantations as well as inside the MRR; it has been spotted along the Roxborough-Bloody Bay road as well as to the south-west of the reserve, near Castara. It tends to be particularly active early in the morning before it gets too hot, in search of other small snakes and lizards. Undoubtedly we have a lot more to learn about this iconic species, but in the meantime it would be an excellent flagship species for the protection of snakes and other biodiversity within the Main Ridge; not only is it endemic to Tobago, but it already boasts the colours of the national flag!
 Among the snakes endemic to Tobago is this  False Coral sporting the national colours - photo by Renoir Auguste

Some people simply dislike snakes, but there is never a rational reason to kill a snake in Tobago. None of Tobago’s snakes are venomous and they all serve important roles in the ecosystem, not least in regulating the populations of prey species. In fact, snakes can be used as ‘indicators’ of ecosystem health; if there are healthy populations of predators, there must be healthy populations of prey! So, whether you are a snake-lover, or someone who is stricken with fear at the sight of one, when it comes to snakes the right response is always to ‘live and let live’.


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