Tracking Trinidad's Treefrogs

Leaf nesting frog (Phyllomedusa trinitatis) from Trinidad. Photo by Renoir Auguste

One of the fundamental aspects of assessing the ecology of an animal, is to track its movement. Often, this is difficult as animals cannot be observed continuously. One way to off set this disadvantage, is with the use of tracking devices. However, tracking methods can have both advantages and disadvantages.

The leaf nesting frog (Phyllomedusa trinitatis) is a frog found in Trinidad and Venezuela (Murphy et al. 2018). An evaluation study on tracking the movement of this species was undertaken at Simla, in the Arima Valley in Trinidad (Gourevitch and Downie 2018). Tracking devices consisted of (1) harness made of cotton with bobbins, and (2) radio-tags. Observations on the frogs were conducted in lab and in the field.

Twenty-six frogs were assessed, with 16 of these successfully tracked. Both methods presented challenges. However, the locations of where the 16 frogs (1 female and 15 males) rest during the day were revealed and gives greater insight to the habitat use of these frogs. Further, the female that was tracked appeared to move further away from the breeding pool than the males. Though both tracking methods appear to not work perfectly for Phyllomedusa trinitatis, the study emphasizes the need to test out tracking methods on different species in their respective habitats.


Citations:

Gourevitch, E.H.Z., and Downie, .J.R. 2018. An evaluation of of tree frog tracking methods using Phyllomedusa trinitatis (Anura: Phyllomedusidae). Phyllomedusa: Journal of Herpetology 17: 233-246.

Murphy, J.C., Downie, J.R., Smith, J.M., Livingstone, S.R., Mohammed, R.S., Auguste, R.J., Lehtinen, R.M., Eyre, M., Sewlal, J.N., Noriega, N., Casper, G.S., Anton, T., Thomas, R.A., Rutherford, M.G., Braswell, A.L., and Jowers, M.J. 2018. A field guide to the amphibians and reptiles of Trinidad and Tobago.  Trinidad and Tobago Field Naturalists’ Club. 336 pp.

The elusive and important freshwater turtles of Trinidad

One of three native freshwater turtles on Trinidad: Gibba turtle (Mesoclemmys gibba) Photo by Renoir Auguste.

Trinidad and Tobago are well known for the nesting marine turtles along the coasts. There have been numerous conservation efforts to highlight their importance thanks to local community groups, and international bodies. Typically, when a local person thinks of 'turtle' the Leatherback (Dermochelys coriacea) might usually come to mind more often than any other. However, Trinidad has three native freshwater species of turtles. Surprisingly, not many people are aware of these three turtles’ existence on Trinidad. 

The first of the three native species is perhaps currently the most commonly encountered: The Galap or painted wood turtle (Rhinoclemmys punctularia) from the family Geomyididae. This family is the most species rich family of turtles globally with about 75 species recorded. They are represented with species across Europe, Asia, Africa and Central and South America. The Galap is the sole species from the family here. Individuals grow to an average size of about 20 cm. They can be identified by having red blotches on the crown of their head, yellow reticulations near the ear, and yellow or red spotted scales on the forelimbs. The Galap appears to be mainly found in south Trinidad with populations north centrally as well. Their habitat mainly consists of ponds or streams in forests, and can also be found at road side ditches. They are omnivores, and are known to act as seed disperses as they feed on fruits thus contributing to plant growth which benefits plants, other animals, and humans. 

Galap (Rhinoclemmys punctularia) feeding on fruit in south Trinidad. Photo by Renoir Auguste

The second of the three native freshwater turtles is the scorpion mud turtle (Kinosternon scorpioides) from the family Kinosternidae. This family has 25 species and are restricted to the western hemisphere. The scorpion mud turtle is the sole species on Trinidad currently, although subfossil remains hints at another species once being here. They grow to about 27 cm. The turtle can be identified by their domed carapace (shell) which varies from light brown to olive, with a brown-yellow head. They appear to be distributed across the south and northern basins of Trinidad; similar to the Galap. They may be found in temporary or permanent freshwater habitats, roadside ditches, and stream impoundments surrounded by forests. Although it may be relatively common, they are not always commonly seen and this may be because they bury themselves in the bottom of the pond or stream where they reside when it dries up, or are almost always under water when wet. Like the other two species they are nocturnal but may be active during the day. They are predominantly carnivores feeding on insects, molluscs, crustaceans, fish, frogs, worms, and mammals, but will consume algae and plant matter, including fruits thus also making them potential seed disperses.

Scorpion mud turtle (Kinosternon scorpioides) from central Trinidad. Photo by Rainer Deo

The third native freshwater turtle species is perhaps the rarest on the island and rarely encountered: the Gibba turtle or side neck turtle (Mesoclemmys gibba) from the family Chelidae. There are about 53 species restricted to Central and South America. They are able to move their necks sideways into the shell (hence the common name). All are highly aquatic with the capacity to stay submerged for long periods of time. The Gibba turtle grows to about 30 cm. They can be identified by having a wide and flattened head with two barbles on the chin, dark brown or black carapace or shell and extensive webbing in the feet. Very little is known about this species locally. Previous literature suggests it is an uncommon lowland species. A survey published in 2010 found that they were restricted to the South Oropouche catchment based on anecdotal evidence from locals. However, as of 2018, individuals have been spotted by myself not far from the Aripo Savannas Scientific Reserve which is designated an Environmentally Sensitive Area in Trinidad. Like the other two species, they prefer areas with stagnant waters in forests, however with closed canopy. This suggests they would be susceptible and sensitive to habitat alteration. They are also nocturnal and are omnivores: also feeding on fruits like the other two species.

Gibba turtle (Mesoclemmys gibba) from northern Trinidad. Photo by Renoir Auguste

Given the high precedent to marine turtle conservation, these three freshwater turtles should also be considered for priority conservation in Trinidad. They are an important component of the local fauna and ecosystems because of their seed dispersing capabilities and varied diet. They also comprise an important component of freshwater ecosystems. Greater effort towards learning more about their ecology is needed, which would not only benefit the local population of turtles but the freshwater ecosystems where they reside, other wildlife, and people.

Murphy, J.C., Downie, J.R., Smith, J.M., Livingstone, S.R., Mohammed, R.S., Auguste, R.J., Lehtinen, R.M., Eyre, M., Sewlal, J.N., Noriega, N., Casper, G.S., Anton, T., Thomas, R.A., Rutherford, M.G., Braswell, A.L., and Jowers, M.J. 2018. A field guide to the amphibians and reptiles of Trinidad and Tobago.  Trinidad and Tobago Field Naturalists’ Club. 336 pp.

The frog Leptodactylus nesiotus is no longer endemic to Trinidad

Leptodactylus nesiotus from Trinidad. Photo by Renoir Auguste.

As of 2014, the island of Trinidad was known to have four species of endemic frogs: Trinidad stream frog Mannophryne trinitatis, Urich's litter frog Pristimantis urichi, Golden tree frog Phytotriades auratus and Trinidad thin-toed frog Leptodactylus nesiotus. 

In 2015, there were now three endemic species after the discovery of the Golden tree frog (Phytotriades auratus) in Venezuela (Rivas and de Freitas 2015). Now, at the end of 2018, the number of endemic frog species is down to two after Leptodactylus nesiotus were discovered in the Guianas (Guyana, Suriname and French Guiana), South America.

The Trinidad thin-toed frog (Leptodactylus nesiotus) is a member of the Leptodactylus melanotus group. They are known from swampy areas in south west Trinidad and also from the Nariva Swamp. Jairam and Fouquet (2018) reported on specimens occurring along coastal savannas and swamps on mainland South America, along the Guianas. Given the very wide distribution and continuity of habitat, the authors suggest that specimens of L. nesiotus may have been mistaken for L. validus or other species of the L. melanotus group. They also suggest that specimens are also likely to occur in Venezuela and may even occur in Colombia and Brazil. 

Little is known about the biology of the species from Trinidad and prior to its discovery in South America, it was given the IUCN Red List Status of Vulnerable. With an extension of greater than 1000 km, perhaps the status of Vulnerable now needs to be reassessed to Least Concern. 

It is unsurprising that L. nesiotus is not an island endemic to Trinidad, especially given its main population in south western Trinidad is less than 20 km from Venezuela. Also, in Trinidad, the species has been observed to live alongside L. validus. Perhaps further investigations of other endemics may reveal a much wider distribution, which further highlights the biogeographical link to the Trinidad and South America fauna.

Literature Cited

Rivas, G. and de Freitas,M. 2015. Discovery of the critically endangered Golden tree frog Phytotriades auratus (Boulenger, 1917), in eastern Venezuela, with comments on its distribution, conservation, and biogeography. Herpetological Review 46: 153-157.

Jairam, R. and Fouquet, A. 2018. First records of Leptodactylus nesiotus (Anura: Leptodactylidae) for Guyana, Suriname and French Guiana. Herpetology Notes 11: 997-999.

Reviews for the Trinidad and Tobago Herpetofauna Field Guide

In 1997, John Murphy's book covered an account of the amphibians and reptiles of Trinidad and Tobago; the only one at the time covering both amphibians and reptiles of the country. Two decades later, this first field guide edition to the herpetofauna of the country was published which provides an update on its predecessor. It features updated information on species, along with name changes and some new species. The book was published by the Trinidad and Tobago Field Naturalists' Club (Founded 1891) and can be bought locally in most leading bookstores as well as internationally from the club's website, see link here.  To date, international orders for the field guide have come from the US, UK, Germany, France, Israel, Sweden, and Guadeloupe.

Two international reviews have come out for the book this year. One in The Herpetological Bulletin, and one in Herpetological Review. The following are some direct comments from the reviews:

Suzanne Simpson, Hadlow College, Hadlow, Tonbridge, Kent, TN11 0AL, UK.

Herpetological Bulletin 144, 2018: 34-35.

"This field guide is a user-friendly, detailed, step-by-step guide to the herpetofauna of Trinidad and Tobago. It breaks down into multiple sections with an easy to use index at the back for readers who want to just look at a few species. Anyone interested in amphibians and reptiles could pick up this book and enjoy the pictures and information. At the price it is excellent value for money."

Robert Powell, Department of Biology, Avila University, Kansas City, Missouri 64145, USA

Herpetological Review 2018, 49(3) 561-563.

"This is an outstanding, educational, and entertaining overview of a complex insular herpetofauna. Sufficiently detailed and documented to meet the needs of professionals but adequately straight-forward and not too technical to serve readers using it solely as a means to identify species they encounter during a visit to the islands. This excellent guide is a must for the libraries of herpetologists with an interest in insular herpetofauna and for the backpacks of any naturalist fortunate enough to experience Trinidad and Tobago."

Cost to order online is $42. USD ($290. TTD) which includes the cost of postage. For further information on how you can order a copy, please email admin@ttfnc.org. For local purchases, contact the club for additional information.

Citation for the Field guide:

Murphy, J.C., Downie, J.R., Smith, J.M., Livingstone, S.R., Mohammed, R.S., Auguste, R.J., Lehtinen, R.M., Eyre, M., Sewlal, J.N., Noriega, N., Casper, G.S., Anton, T., Thomas, R.A., Rutherford, M.G., Braswell, A.L., and Jowers, M.J. 2018. A field guide to the amphibians and reptiles of Trinidad and Tobago.  Trinidad and Tobago Field Naturalists’ Club. 336 pp.

Herpetofauna results from the Toco Bioblitz

Bioblitz results. Photo by Renoir Auguste

The seventh annual Bioblitz of Trinidad and Tobago came and went. The amphibian and reptile group which consisted of two main groups; one from the Trinidad and Tobago Field Naturalists' Club and the other by Serpentarium observed 37 species over the weekend. These 37 species consisted of 13 species of amphibians, 11 lizards, 11 snakes, one crocodilian and one sea turtle.

Although we wished that all 37 observations were of herpetofauna living in the wild, this was not the case. The one sea turtle observed was a green sea turtle carcass with shell on nearby beach. With some parts of the turtle still in the shell, it was uncertain as to what may have caused its demise. It would be a shame if this was an act of poaching by people in the area. Sea turtles are still poached in Trinidad and Tobago despite year-long legal protection. The Serpentarium also observed a roadkill snake (Leptophis  coeruleodorsus).

Perhaps the most notable amphibian sighting was that of the narrow-mouth frog Elachistocleis sp. These explosive breeders are difficult to spot unless they are out calling in abundance, but we managed to spot one not too far from the coastline in secondary forest type vegetation.

Elachistocleis sp. Photo by Rainer Deo

Although we did not spot any rare or elusive reptiles, seeing four Bothrops along a single trail at Cumana on the same night was very notable. One local in the area did mention to us that there are many "Mapepire Balsains" (the local common name for Bothrops) along the trail, and he did not exaggerate. The four individuals were all observed along the side of the trail and were all estimated to be about two to four feet (60 to 120 cm) long. Considering we saw four, there is a great likelihood that there are more individuals in the area nearby.

Special thanks to all the volunteers that came out and especially Rainer Deo for the photos. The full list of species observed at the Bioblitz will be made available in the final report and will be shared here when it is compiled and completed.

Bothrops sp. Photo by Rainer Deo

Trinidad and Tobago's 7th annual Bioblitz goes to Toco in 2018

Bioblitz is a 24 hour event where scientists, naturalists and members of the public all come together to collect, identify and record as many species of fungi, plant and animal in a certain area. It is an opportunity for the public to see scientists at work and allows scientists to share their knowledge with others. It can also promote an area and showcase the biodiversity to be found there. 

This year will be the seventh edition and the chosen location is Toco to take place on 17-18 November. Toco is located in north east Trinidad and represents a portion of the island that has not been covered yet for the 24 hour event. It represents an area that covers a portion of the Northern Range forest as well as coastal ecosystems. The base camp will be the Toco Regional Complex. The main organizers for the Bioblitz are once again the Trinidad and Tobago Field Naturalists' Club in collaboration with The University of the West Indies Zoology Museum (UWIZM). This year as in past editions, it is sponsored by First Citizens. 

Given that there are proposed works to build a port in the area, these surveys offer a baseline of the biodiversity that are likely to be impacted by the work. What species of reptiles and amphibians are likely to be found in the area and how many? Perhaps something rare or new? Stay tuned to find out next week!

Simla's Reptiles and Amphibians

Photo by Renoir Auguste

The William Beebe Research Station, also known as Simla is known by many scientists that have visited Trinidad. It is located in the Arima Valley and surrounded by tropical forests: ideal for researchers wanting to get a feel of the environment. However, over recent years the nearby quarry has altered the habitat. One wonders what kind of effect this may have on the wildlife, including the local herpetofauna?

Tantilla melanocephala. Photo by Rainer Deo

In October 2018 the Trinidad and Tobago Field Naturalists' Club's Herpetology Group, lead by current president undertook a trip to see what amphibian and reptile species they can find. Searches took place in the afternoon from 2:30 pm to 3:30 pm and then again at night from 6 pm to 9 pm. Within those 4 hours, the group collectively observed 17 herpetofauna species, including 3 snake species (Bothrops sp, Tantilla melanocephala, and Corallus ruschenbergerii), 6 lizard species (Hemidactylus mabouia, Thecadactylus rapicauda, Gonatodes vittatus, G. ceciliae, Anolis planiceps, and Plica caribeana), and 8 amphibian species (Mannophryne trinitatis, Rhinella marina, Pristimantis urichi, Flectonotus fitzgeraldi, Boana xerophylla, Leptodactylus validus, Engystomops pustulosus, Phyllomedusa trinitatis).

Thecadactylus rapicauda. Photo by Rainer Deo

It was a bit surprising given the warm afternoon and relatively dry conditions at night to see that many species. Although most of these may be considered generalist type species, the habitat specialists (Pristimantis urichi and Flectonotus fitzgeraldi) were visually and audibly observed. This may suggest that the forest at and around Simla does offer suitable habitat for these species, for now. It would be interesting to regularly keep track of the diversity of herpetofauna at Simla.

Rhinella marina (background) and Pristimantis urichi (foreground) at Simla. Photo by Rainer Deo

Lack of chytrid disease in Tobago's frogs

Chytridiomycosis has caused declines in multiple amphibian species across the world. The fungal infection has been detected in frogs in Tobago, specifically the endemic Aromobatidae stream frog Mannophryne olmonae (Alemu et al. 2008). However, there were no signs of clinical mortality.

A follow up study was conducted on six species of frogs (Leptodactylus validus, Engystomops pustulosus, Boana xerophylla, Pristimantis charlottevillensis, Hyalinobatrachium orientale tobagoense, and Mannophryne olmonae) from northeast Tobago in 2016 by Thomson et al. 2018 to assess the presence of the chytrid fungus. Based on their data of 176 samples, no chytrid was detected. According to the authors, their findings appear to indicate that the infection may have died out or is at very low levels. At least, for the species sampled and those in the northeast of the island.

Boana xerophylla from Tobago (Photo by: Renoir Auguste)

Alemu,J.B., Cazabon, M.N.E, Dempewolf, L., Hailey, A., Lehtinen, R.M., Mannette, R.P., Naranjit, K.T. and Roach, A.C.J. 2008. Presence of the chytrid fungus Batrachochytrium dendrobatidis in populations of the Critically Endangered frog Mannophryne olmonae in Tobago, West Indies. Ecohealth, 5:34-39.

Thomson, R., Hoskisson, P.A., Brozio, S., Downie, J.R. 2018. Apparent lack of chytrid infection in northeast Tobago's frogs. Living World, Journal of the Trinidad and Tobago Field Naturalists' Club, 2018: 82-86.

Another Anolis lizard introduced to Trinidad

Anolis cristatellus (Photo by Kester Dass)

As of 2018, there have been eight species of Anolis lizards reported for Trinidad and Tobago (Murphy et al. 2018). Most of these (6/8) have been introduced from other Caribbean islands. It is uncertain as to exactly how these non-native Anolis lizards came into the country. A recent report by Auguste et al. 2018 now adds a ninth Anolis lizard to the country: Anolis cristatellus, the Puerto Rican Crested Anole. Given the recent spread of other introduced Anolis lizards across Trinidad and Tobago, it will be important to keep track of the distribution of the Puerto Rican Crested Anole as it has the potential to compete with and displace native Anolis species.

Auguste, RJ, Dass K, Baldeo, D. 2018. Discovery of the Puerto Rican Crested Anole, Anolis cristatellus Dumeril and Bibron, on Trinidad. Caribbean Herpetology 63: 1-2. DOI: 10.311611/ch63

Murphy, J.C., Downie, J.R., Smith, J.M., Livingstone, S.R., Mohammed, R.S., Auguste, R.J., Lehtinen, R.M., Eyre, M., Sewlal, J.N., Noriega, N., Casper, G.S., Anton, T., Thomas, R.A., Rutherford, M.G., Braswell, A.L., and Jowers, M.J. 2018. A field guide to the amphibians and reptiles of Trinidad and Tobago.  Trinidad and Tobago Field Naturalists’ Club. 336 pp.

Additional evidence for Phyllomedusa trinitatus being distinct from P. tarsius

Phyllomedusa trinitatis. JCM

The Tarsier Leaf Frog (family Phyllomedusidae), was described as Pithecopus tarsius by Cope in 1868. It is found in Brazil, Colombia, Ecuador, Peru, and Venezuela, and possibly Bolivia and Guyana. Its natural habitats are subtropical or tropical moist lowland forests, subtropical or tropical swamps, intermittent freshwater marshes, and heavily degraded former forest.

Mertens (1926) described Phyllomedusa trinitatis from Port of Spain, Trinidad and Phyllomedusa venusta was described by Duellman and Trueb (1967) from Darién Province, Panamá.

Barrio-Amorós (2009) doubted the distinctiveness of Phyllomedusa venusta from P. trinitatis, and also reidentified specimens identified as Phyllomedusa tarsius from along the Guyana border as P. trinitatis. This suggests  Phyllomedusa trinitatis likely extends into Guyana, and the records of Phyllomedusa tarsius from Guyana need re-examination.

A forthcoming paper by Mechkarska et al. (2018) examined peptidomic analysis of norepinephrine-stimulated skin secretions from the Trinidadian Leaf Frog and found 26 host-defense peptides. The primary structures of the peptides support the claim that P. trinitatis and P. tarsius are very closely related phylogenetically but are probably not conspecific as suggested by Duellman (1974).

Left: Phyllomedusa tarsius by Jean-Marc Hero. Right Phyllomeusa venusta
by Mauricio Rivera Correa

References

Barrio-Amorós CL. 2009. Distribución y aspectos de la historia natural de las ranas lémur (Hylidae: Phyllomedusinae) en Venezuela. Memoria de la Fundación La Salle de Ciencias Naturales. Caracas 171: 19–46.

Cope ED. 1868. An examination of the Reptilia and Batrachia obtained by the Orton Expedition to Equador and the Upper Amazon, with notes on other species. Proceedings of the Academy of Natural Sciences of Philadelphia 20:96–140.

Duellman WE. 1974. Taxonomic notes on Phyllomedusa (Anura: Hylidae) from the upper Amazon basin. Herpetologica  1:105-12.

Duellman WE, Trueb L. 1967. Two new species of tree frogs (genus Phyllomedusa) from Panamá. Copeia 1967:125–131.

Mechkarska M, Coquet L, Leprince J, Auguste RJ, Jouenne T, Mangoni ML, Conlon JM. 2018. Peptidomic analysis of the host-defense peptides in skin secretions of the Trinidadian leaf frog Phyllomedusa trinitatis (Phyllomedusidae). Comparative Biochemistry and Physiology Part D: Genomics and Proteomics. 2018 Dec 1;28:72-9.

Mertens R. 1926. Herpetologischen Mitteilungen VIII–XV. Senckenbergiana Biologica 8: 137–155.

Tadpoles of the Tobago Glass Frog

A metamorph of the Tobago Glass Frog.

The Tobago glass frog, Hyalinobatrachium orientale tobagoense is endemic to the island of Tobago. They reproduce by laying a clutch of gelatinous eggs on the underside of broad leaves overhanging streams, a mode of reproduction which is characteristic of all Hyalinobatrachium. The embryos develop on the leaf until hatching when they drop into the stream below where they develop further, eventually emerging as metamorphs.

Previous authors have reported on embryonic development, hatching, and tadpole growth and morphology in this frog. The tads initially lacking pigmentation, but with age develop pigment over much of the body, darker on the dorsal side, but lacking on the tail fins and ventral body. The tadpoles’ eyes are small and dorsally oriented.  They have very long tails, 64% of total length. In the lab, growth, is very slow. After six weeks, tadpoles had tripled in mass, increased in length by a little under 40%, but were still at Gosner stage 25, with no sign of limb buds. Previous authors have reported very slow growth and development in two glass frog species which took more than  200 days to reach metamorphosis.

Tadpoles hide in sediment and among rocks, gravel, and fallen leaves, and escape with bursts of fast swimming when disturbed. Given their secretive nature, it is not surprising that the behavior of these tadpoles is poorly known.

In a recent paper, Byrne et al. (2018) collected egg clutches of the Tobago Glass Frog and allowed them to hatch into tanks of native stream water.  Observations were made through a series of tests for substrate preference (gravel, rocks or leaves), shelter or open water preference, and surfacing behavior under different depths and turbulence levels. Tests found that tadpoles showed a preference for stream substrates over plastic tank floor, with the highest percentage of tadpoles found in gravel. Tadpoles preferred sheltered areas of the tank and surfaced significantly less when water was turbulent, with depth having no significant effect on surfacing behavior.

Byrne I, Judge C, Downie JR. 2018. The behaviour of recently hatched Tobago glass frog tadpoles. Herpetological Bulletin. 2018 Jun 1(144).

Brazilian Bent-toed Gecko, Gymnodactylus geckoides Spix

Bent-toed Gecko, Gymnodactylus geckoides is listed here on the basis of a single museum specimen. It is not likely part of the current fauna. If this genus is present on Trinidad, it can be identified by the presence of free fingers that are not expanded; the fingers have wide, undivided sub-digital lamellae; the distal phalanges are elevated above the basal ones; the nail or claw is placed between two scales with the ventral scale indented; straight, vertical pupils and dorsal scales are a mixture of granules and tubercles. This lizard is otherwise known from Brazil; its presence on Trinidad is problematic.

The only known specimen (FMNH 177679) of Gymnodactylus gekkoides supposedly collected in Trinidad's Arima Valley in 1962 by Edward Taylor.