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A frog is a tailless amphibian belonging to the order Anura. Used strictly, the term
may be limited to any member of the family Ranidae (true frog), but more broadly the name
frog is often used to distinguish the smooth-skinned, leaping anurans from squat, warty,
hopping ones, which are called toads.
Image showing a Frog
Image showing a Toad
Species: Amphibian
Tobago is home to 15 different frog species, many of which are found inside the Main Ridge
Reserve.
The cartoon-like Tobago Glass Frog
The Tobago Glass Frog is one of the most unusual. This tiny (2cm) frog has a Kermit-like,
cartoon appearance as it is bright green with big eyes. However, if you were to turn it over,
you would see how it got its name: its belly is completely transparent, meaning that its heart,
liver and all other internal organs are plain to see. Remarkable or repulsive, depending on
your perspective!
The other astonishing thing about this species is how it reproduces. First, a male call to attract
multiple females to the underside of a carefully chosen Heliconia leaf by the side of a stream.
A single male may mate with many females, each of which lays their eggs on the leaf before
disappearing. The male then remains for several days to loyally guard them from predators –
such as insects, spiders and crabs. Eventually the bright green tadpoles hatch and simply plop
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into the stream below. Amazingly, the presence of a predator can actually trigger the early
hatching of the tadpoles, as a clever escape mechanism.
The next species we will look at may be less pretty, but is no less interesting. The Tobago
Stream Frog is endemic to Tobago – in other words, it is found nowhere else in the world.
They are widespread within the Main Ridge Forest but you are unlikely to spot them as they
are about the same size as the glass frog and tend to be dull brown in colour from above.
However, on closer inspection, females have a bright yellow throat and – strangely – males
turn black when they are calling to females. They are extremely good at jumping, and almost
impossible to catch, even if you are keen-sighted enough to spot one! Once again, it is the
fathers that are responsible for looking after the babies. After spawn is laid and hatches in
forest leaf litter, the male frog actually carries the young tadpoles on his back to a suitable
pool of water - a very strange sight, and exemplary parenting-behaviour.
The Tobago Stream Frog isn’t the only frog endemic to the island; two other Main Ridge
frogs that are found nowhere else in the world are the Charlotteville Litter Frog and Turpin’s
Litter Frog. ‘Litter’ frogs are so-called for their preference for leaf-litter along the sides of
streams, not because of a preference for garbage, although in some places they are forced to
put up with plastic trash left by those who pass to collect water from the reserve’s clean
supply.
The cryptically-coloured Charlotteville Litter Frog - By
Renoir Auguste
Turpin's Litter Frog is known only from the Northern parts of t
Main Ridge - By Renoir Auguste
These frogs eluded scientists for centuries, perhaps due to their incredible camouflage
abilities, perfectly blending in among dead leaves. The Charlotteville Litter Frog was first
scientifically documented in 1995 and Turpin’s Litter Frog in 2001. The former was
originally discovered in the north-east of the island (hence the name), but has now been
sighted almost everywhere aside from the Scarborough and Crown Point areas. The latter
appears to be restricted to the North Coast Road and parts of the Main Ridge. However, very
little is known about either species in terms of how they breed, what they eat, and their exact
distribution on Tobago. Such knowledge will be essential if we are to effectively conserve
them.
Frog conservation becomes even more important when we consider that the health of the
Main Ridge frog populations can tell us a lot about the health of the whole ecosystem. Frogs
are especially sensitive to environmental change; they need both healthy forests and clean
water to complete their life cycle, so if either is compromised this will be reflected in their
numbers and distribution. Also, their breathable damp skin quickly absorbs toxins from the
environment, so any pollution will affect frogs first, giving us a warning sign. These reasons
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also mean that frogs, and amphibians in general, are in trouble globally, as they are especially
vulnerable to the effects of climate change, disease and human development.
The Tobago Glass Frog in particular has extremely specific habitat needs and tends to be
found in small, isolated populations – which means that the removal of streamside vegetation
for agriculture or development could wipe out a population overnight. For this reason, it is
classified as a ‘vulnerable’ species by the International Union for Conservation of Nature.
We must learn more about our native frogs and ensure their survival – especially those that
we have sole responsibility for as they are found nowhere else on the planet. If we don’t –
who will?
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REASONS WHY THE POPULATION OF FROGS ARE DECREASING.