Trinidad & Tobago Herpetofauna, a sample
The Islands
The Trinidad and Tobago climate is tropical with two major seasons. The dry season for the first six months of the year, and the rainy season for the rest of the year. Winds are predominantly from the northeast, dominated by the northeast trade winds. Unlike most of the other Caribbean islands, Trinidad and Tobago lie south of the hurricane belt. In Trinidad’s Northern Range, the climate is significantly different from that of the lowlands. Cloud cover, mist, and almost daily rains in the higher elevations create a cooler, moister climate than the lowland climate. Record temperatures for urban Trinidad (Port of Spain) are 39°C (102°F) for the high and a low of 12°C (54°F).
Trinidad Bromeliad Frog, Phytotriades auratus
Known from the type locality (the summit of Mt. Aripo 940 m asl), and the summit of Mt. Tucuche (936 m asl) in the Northern Range. It has also been suggested as present on Morne Bleu Ridge in Trinidad’s Northern Range, but this seems unlikely. The species has also been found at a third locality on Trinidad – Mt. Chaguaramal. And, the species was recently discovered on Cerro Humo in Venezuela’s Peninsula de Paria (1150 – 1250 m ASL). The total range of the species on Trinidad is estimated to be less than 10 km²; in Venezuela it is known from more than the originally reported two hectares. In Venezuela, it was found sharing the bromeliads with the lizard Euspondylus monsfumus. A species not yet reported from Trinidad.
Phytotriades is found in montane rainforest and elfin woodland where it uses a specialized microhabitat, the water tanks of the giant epiphytic bromeliad, Glomeropitcairnia erectiflora. The high-altitude habitat receives rainfall in excess of 3000 mm per year. The rainwater as well as condensation from fog is collected by the strap-like leaves of the plant and drains into the center formed by a whorl of leaves. The bromeliads are often 3-35 m above the ground.
Biology: The depressed head and body allow the frog to slide between the overlapping leaves of the bromeliad. The frogs reproduce in the bromeliads and the tadpoles undergo development in the bromeliad tanks. The males may call, but it needs confirmation. Speculation that males defend their territory from other males using combat behaviour that involves biting is based upon behaviour reported in members of the genus Phyllodytes. The tadpoles are almost transparent and have thin, almost fin-less tails and are probably not strong swimmers. They are often attached to leaves where they may feed on algae and detritus growing in the bromeliad tank, but they may also feed on their siblings. Plants containing tadpoles also had an adult frog, thus this species may have some form of parental care.
Conservation status: The International Union for Conservation of Nature (IUCN) categorized Phytotriades auratus as being Critically Endangered in part due to the collection of the bromeliads and the frog’s small distribution. The species is also considered an Environmentally Sensitive Species by the Environmental Management Authority in Trinidad. While these threats may be a problem, the larger issue is likely to be climate change which includes higher temperatures and reduced moisture. This would place the frog’s habitat at risk during a drought that may result in a fire in the elfin woodland.
Giant Treefrog, Boana boans
Boana boans is a widespread species across Southern and Central America, with distribution records from Panama to Brazil, Bolivia, and Guyana. In Trinidad and Tobago, it is found on Trinidad only, with these frogs representing the most easterly population of B. boans. It is commonly described from undisturbed primary forest elsewhere in its range, but in Trinidad is found in bamboo stands in disturbed rainforest habitat as well as in more completely forested areas.
Reports from mainland populations suggest that their diet chiefly consists of insects such as grasshoppers and beetles, but also includes larger prey such as caterpillars, crabs, and even bats.
Boana boans occur in riparian habitats throughout the year, calling to maintain territories from positions high in the trees. Breeding season for these frogs in Trinidad is the dry season (December to April) though fresh spawn can sometimes be found as late as June and July. Reproductively active males construct ‘nests’ on the river edge consisting of shallow basins of around 6 cm depth and 30-40 cm diameter. Nest construction is highly variable between populations, according to both substrate availability and predation risk with nests ranging from water collecting in roots, to shallow unmodified scrapes to constructed mud nests with slight raised walls.
On Trinidad nests were monitored in a tributary of the Caura River, north Trinidad, during the wet season (July 2013) and during the following dry season (March 2014) by Downie and Greener (2014). Most nests were found at the stream edge, in contact withBoana boans is a widespread species across Southern and Central America, with distribution records from Panama to Brazil, Bolivia, and Guyana. In Trinidad and Tobago, it is found on Trinidad only, with these frogs representing the most easterly population of B. boans. It is commonly described from undisturbed primary forest elsewhere in its range, but in Trinidad is found in bamboo stands in disturbed rainforest habitat as well as in more completely forested areas.
Reports from mainland populations suggest that their diet chiefly consists of insects such as grasshoppers and beetles, but also includes larger prey such as caterpillars, crabs, and even bats.
Boana boans occur in riparian habitats throughout the year, calling to maintain territories from positions high in the trees. Breeding season for these frogs in Trinidad is the dry season (December to April) though fresh spawn can sometimes be found as late as June and July. Reproductively active males construct ‘nests’ on the river edge consisting of shallow basins of around 6 cm depth and 30-40 cm diameter. Nest construction is highly variable between populations, according to both substrate availability and predation risk with nests ranging from water collecting in roots, to shallow unmodified scrapes to constructed mud nests with slight raised walls.
On Trinidad nests were monitored in a tributary of the Caura River, north Trinidad, during the wet season (July 2013) and during the following dry season (March 2014) by Downie and Greener (2014). Most nests were found at the stream edge, in contact with
Scinax rubra
A widespread species found east of the Andes from Panama, southward to Peru and Ecuador, across the Amazon Basin of Brazil; and it is present in Venezuela, and Guyana. It occurs on both Trinidad and Tobago in open habitats, including ones that have been greatly disturbed. It is a savanna species. Some authors consider its distribution influenced by the actions of lumber companies (Krause, 2009). It has been introduced into Puerto Rico (Rivero 1989), St Lucia (Schwartz and Henderson 1991), and Martinique (Breuil 2009).
In Trinidad and Venezuela, this species is a commensal with humans; commonly entering houses, outhouses and other buildings where they appear to be attracted by lights, or perhaps drawn by congregating insects. Frogs are extremely fast-moving and difficult to catch and have a characteristic scurrying locomotion when moving over logs and other large diameter surfaces. In Venezuela, frogs have been recorded sheltering during the day in terrestrial bromeliads and rolled up leaves. The Lesser Brown Treefrog is categorized as ‘explosive breeders’ with intense periods of reproductive activity triggered by heavy rains. In Trinidad, breeding behaviour is typically seen from May through to September, although there have been records from as late as January. Calling behaviour is nocturnal, with calling times typically peaking between 1900 and 01.00 hours. Males call from bushes and vegetation in clearings and from margins of ponds.
The Glass Frog, Hyalinobatrachium orientale
It occurs on Tobago and in northern Venezuela. Its distribution is focused on streams that drain the Main Ridge. Populations do occur to the west in the area around Castara.
This species inhabits stream margins that have Heliconia, or other plants overhanging the forest streams. It has been found along streams in both primary and secondary forest but not in non-forested areas.
Males call starting at dusk from streamside vegetation (a high pitched ‘peep’). Females are occasionally seen in amplexus with males and these couples deposit eggs above the water on the underside of Heliconia, cacao or other leaves. Males have been heard to give a different type of vocalization as females approach closely but females do not themselves call. Males care for the eggs after they are laid, often until the embryos hatch and drop into the stream below. It is not uncommon to see males with more than one clutch; one male in the Tobago Forest Reserve was observed attending seven clutches. Advanced embryos can spontaneously hatch from their egg capsules when threatened. Predators of embryos include wasps, ants and crickets; adults have been witnessed being eaten by bats. Recently metamorphosed individuals have been found in January, July, and August; mating probably occurs year-round, as rainfall allows.
Lehtinen and Georgiadis (2014) observed three different males calling from leaves above an unnamed stream in the Tobago Forest Reserve. The males were found adjacent to egg masses. and in one case, a male was attending six different egg masses simultaneously. Because the developmental stages of the eggs differed (ranging from Gosner Stages ~14–22, Gosner 1960), it is likely that these clutches were from different females.
A seventh egg mass already had fully hatched. Each of two other males were attending a single egg mass. These males were commonly seen on top of, or otherwise in direct contact with, the egg masses. The observations suggest males were attending the eggs and were not coincidentally found in their proximity. However, removal experiments would be necessary to ascertain the functional significance of these behaviors. In all cases, the males continued to call as they attended the eggs. The height above the stream at the oviposition site varied from approximately 1–3 m.
