Rainy evenings can be very loud in the Virgin Islands, as male
frogs call out in the night to declare their availability for mating, or to assert
their territorial rights.
Despite their lusty roaring, the native tree frogs are quite
small and hard for most people to see. However, when I went out hunting one night
with frog expert Pearl Cales and her team of researchers, she was able to locate
several of them within just a few minutes.
We were particularly looking for a type of native tree frog,
Eleutherodactylus
lentus, found only in Virgin Islands
woodland areas. It is a yellow mottled coqui, commonly known as a mute frog. While
it is not really mute, it does have a call that is much softer than the other
local frogs.
Cales was excited to find a few of
the mute frogs last year along a gut behind Cruz Bay. It was the first recorded
sighting of these frogs on St. John since 2004, when they were seen near The
Westin.
(Photo by William Stelzer)
Cales was hoping the mute frogs
were still around.
Wearing our headlamps, we walked
carefully along the trail until Cales quickly spotted one of the frogs sitting
on a log, very close to where she saw them last year. I was happy that the frog
didn’t seem scared, and sat still for a while so I could get a close look and a
photo.
There are more mute
frogs on St. Thomas and St. Croix, but they have all suffered from habitat loss,
particularly where land has been cleared for roads, houses, tourism and agricultural
use.
In 2004 these Virgin
Islands mute frogs were listed as endangered by the International Union for the
Conservation of Nature.
Eleutherodactylus
frogs evolved to survive in forest habitats, rather than ponds. During the
rainy season, they lay their eggs in ditches or bromeliad plants, or on wet
leaves on the ground (which is what the mute frogs do). The developing frogs go
through their tadpole phase inside the tiny egg, and hatch as miniature grown frogs.
Cales received a grant this year from the Friends of the
Virgin Islands National Park to support her research. She will gather more
information about how many mute frogs are living in St. John’s Cruz Bay area,
and what sorts of habitat they prefer. She will also follow up on her earlier
data collection studies. For six years she has been conducting ‘roadside
listening’ surveys to document the calls and population numbers of native frogs
on St. John, including: the red-eyed coqui (Eleutherodactylus
antillensis), the whistling coqui (Eleutherodactylus cochranae), and the Caribbean
white-lipped frog (Leptodactylus
albilabris).
A whistling coqui frog on a bromeliad (Photo by William Stelzer)
Cales’s goal is to provide a baseline for protecting the endangered
mute frogs, as well as the other types of native frogs.
“Data gathered from this project, and our prior work over
the past years, will help support future preservation efforts in the Virgin
Islands”, said Cales. “Conservation is the ultimate duty we, as scientists, owe
to species around the world. Public outreach and education is critical for that
work.”
One particular threat comes in the form of large, non-native
cane toads. They are voracious eaters, consuming anything they can fit into
their mouths, including smaller frogs. A couple of years ago some of these
toads were found very close to the gut where the mute frogs live in Cruz Bay,
and nearby residents have been alerted to watch out for them.
Cales first came to the Virgin Islands in January 2014 for an undergraduate
course in Tropical Ecology taught by Richard Veit, a professor at the City
University of New York in Staten Island. She is expecting to receive a master’s degree in Environmental Science in June 2020, and is currently working at the Staten
Island Zoo, which is also supporting her Virgin Islands frog research.
Pearl Cales with her colleagues on a recent evening of frog research. From left to right: Jessica Abalos, Educator/ Lead Farmer at Snug Harbor Cultural Center and Botanical Garden; Pearl Cales, Adjunct Professor at the College of Staten Island and Urban Advantage Coordinator at the Staten Island Zoo; and Danielle Fibikar, Wildlife Field Biologist/ Adjunct Professor at the College of Staten Island, and Educator at Snug Harbor Cultural Center and Botanical Garden
