The Mysterious Mammals 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 resumes her series on the biodiversity of the Main Ridge Reserve (MRR). Today, we will visit the mammals of the MRR. The most abundant mammals in the forest by far are the flying ones – the bats - but we will save those amazing creatures for another article. Here we will focus on the wingless mammals that make the Reserve their home. First published in the Tobago Newsday on July 10, 2017

Many will be surprised to learn that Tobago supports 36 native mammals – 16 if you don’t include the bats. I have chosen three of the most interesting of Tobago’s mammals to highlight in today’s column, to convince you that we have lots to learn even about the most charismatic of the Main Ridge’s inhabitants.

The Robinson's Mouse Opossum. This rather cute and compact marsupial spends much of its time up in the trees. Photo courtesy of Renoir Auguste

The Red-rumped Agouti is the mammal you have the best chance of spotting when walking in or around the reserve. This is partly because they are the most abundant but also because, unlike many forest mammals, they tend to be more active during the day time (especially at dawn and dusk). Even so, you are only likely to catch a glimpse as they are, quite sensibly, wary of humans.

Avoiding people is not the only way in which agoutis demonstrate intelligence. Food can be in short supply during the dry season, therefore agoutis have to be good planners. Their clever solution is to bury food in small pits in the ground during the rainy season when it is plentiful, so that when times are hard, they have a back-up plan. This also makes them vital dispersers of seeds for many of the Reserve’s tree species, as some buried treasure inevitably gets left behind to germinate. In this way these large rodents make an important contribution to the health and diversity of the Main Ridge forest.

Although it is illegal to hunt game inside the reserve, humans are still one of the agouti’s main predators, especially once they venture beyond the MRR boundary. Indeed, agouti are the most widely-hunted mammal in T&T as a whole. Other threats come in the form of the large snakes with which they share their habitat – such as the Boa Constrictor (Macajuel). However, on sensing a boa, an agouti will start drumming the ground loudly with its hind foot. This attracts other agouti, and together they drum to discourage the snake from coming closer. They are also capable of making themselves appear larger when in the presence of a predator, by making their hair stand on end.

A much less well-known inhabitant of the reserve is the mysterious Crab-eating Raccoon. Indeed, many people have never even heard of this shy, nocturnal mammal, let alone seen one! This is especially surprising given that they can reach an impressive 90 cm long. With their masked faces and banded tails, these raccoons look similar to their urbanised North American relatives, but are less fluffy and tend not to venture into human settlements as much, although they are found in a variety of habitats in both Trinidad and Tobago.

Unlike the ground-dwelling agouti, crab-eating raccoons split their time between the forest floor and the treetops, and as such they are remarkably agile. They prefer to live near water and possess an incredible sense of touch, allowing them to feel underwater for their prey with their paws– including for their namesake. However, despite their name, they actually enjoy a wide variety of foods from frogs and insects to fruits and seeds, as well as crustaceans.
Crab-eating Raccoon in Tobago. Rarely seen, but captured here using motion-sensor camera technology - Photo courtesy of the MSc Biodiversity Conservation UWI

Equally elusive and undoubtedly one of the Main Ridge’s cutest inhabitants is the Robinson’s Mouse Opossum. These can be found in a wide range of habitats, including lower montane forest, and happily reside throughout the MRR. They feed primarily during the night on fruits and insects up in the canopy, scampering nimbly along branches and using their furry ‘prehensile’ tail to grip on where necessary. As a result of their nocturnal, arboreal habits this tiny marsupial is rarely seen; in the daytime they find or build nest-like homes up in the trees for protection.

If you are lucky enough to see one, you will easily tell it apart from a regular opossum (Manicou) both by its much smaller size (adults don’t get any larger than 20cm), and distinctive black face mask.
Unusually, despite being a marsupial (thus related to kangaroos and the other Australian mammals) mouse opossums do not have a pouch. Nonetheless, their tiny 6-14 babies are born just 1cm long and must cling on to their mother’s teats for five weeks. Without the security of a protective pouch they have to hold on extremely tight, especially as their mother continues to climb acrobatically though the canopy in search of food!

For all three of these species, the Main Ridge Reserve provides vital refuge – in the case of the agouti from hunters, and for the others in the form of protecting their forest home from development and agriculture. We still have much to learn about the MRR’s mammals and it is hoped that recent and continuing surveys using motion-sensor cameras will greatly improve our understanding of their habits and distribution, helping us to do an even better job of protecting them.
Agouti captured on a motion-sensor camera. Such cameras allow us to learn more about the habits and distribution of the MRR's often elusive mammals- Photo courtesy of the MSc Biodiversity Conservation UWI

Comments

  1. Comment from Ian Lambie: Hurricane Flora hit Tobago in 1963 which destroyed a large part of the Main Ridge forest cover; with the loss of much of their food supply, forest mammals and other wildlife,in search of food, moved into the human habitated areas.
    Most of the mammals, especially tattoo, ended up in the pot but the cocrico, which was fed by many sympathetic persons including Mrs Eleanor Alefounder of Grafton Estate, have remained and have increased in number.
    The cocrico is an agricultural pest, a fact known to Tobago farmers long before it was selected as one of our National birds at Independence in 1962. The question may be asked: why two National birds for one country?
    Politics again.
    It is thought that the last known "Tobago deer" was killed in 1972 when the Mt.Irvine Golf Course was being constructed. The "Tobago Deer" was the name given to White-tailed deer which had been introduced into Tobago by Sir George Huggins, then a major landowner in Tobago. Should my information be correct, White-tailed deer were also introduced into the Huggins Estate at Macqueripe in Trinidad.

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