Thunder, the result of electricity’s vibrations bouncing off of clouds and the ground, is an ominous sound to most, but music to the ears of small amphibians which inhabit most of the island. That being said, whistling frogs, both of which species are only about an inch long, are only concentrating on the calls of their own kind. For me, the calls of the whistling frog stir the naturalist inside me. It reminds me that I am a Bermudian, and that this sound will happily put locals to sleep at night, but will keep most tourists awake. This weather is also good news for other fauna which depend on the moisture of Bermuda to survive, such as garden snails, slugs and cane toads.
Storms are the key to survival of whistling frogs in Bermuda. Bermudian amphibians are not like much of the rest of the world’s frogs or toads in that whistlers are not pond dwellers. They don’t require fresh water to breed, since their young are hatched from eggs. The larval stage takes place in watery egg sacs which are laid in damp notches in trees and hatch into small frogs and not into tadpoles. You can probably find many whistling frogs in the weeds alongside a riverbank, since it’s so moist there, and there are plenty of tasty insects waiting to be eaten. However, whistling frogs cannot swim. Their toes are not webbed, and rather have small suction cups on their tips with which to climb. Since they cannot moisten their skin by swimming, they rely on dewy nights and wet days to keep them alive.
A stormy night such as tonight is a magical time. It is a beautiful twilight, with grey clouds overhead and green tendrils of plants dripping with precipitation. The sighs are decadent, but the real experience is the cacophony of sound. The sky will light up for a moment as delicate drops of rain splatter down to earth, the illumination is followed by a brilliant crack of thunder. Living here for so long, one gets used to the symphony of whistles. They become almost a background noise that is momentarily overcome by thunder.
Bermuda has two species of tree frog which are both introduced and both called whistling frogs. The first species is much more abundant, hence the name common whistling frog. They are very similar in many ways, such as their colouring, size and behavior. Both were thought to be introduced sometime in the 1800’s, and the only real way to tell them apart for sure is the sound of their calls.
The whistles, the small weep-weep-weep or less common pit-up-up tew-tew-tew sound is actually only produced by males as a mating call. They create the sound all year round, but are intensified in fall and spring, the mating season, and after rain. Now imagine for every small peep of sound, that there is twice the number of small frogs out there. A staggering number, but it wasn’t always this way. About 30 years ago there were even more tree frogs than today, along with cane toads that are very scarce now. Back then, the population was at such a point you would get tree frogs in the house and be able to observe them on your doors, and toads were so abundant that it would be a miracle if you didn’t run over at least one on the roads.
Whistling frogs are two of the three amphibians, both of which were introduced, which inhabit Bermuda. About 20 years ago, both amphibian’s number’s seemed to be decreasing; less and less seemed to be seen and more and more toads were turning up as road kill. In addition, more toads seemed to be growing deformities, extra eyes or legs that were never fully functional and only slowed down the toad and made it more vulnerable.
Great news for herons, who made easy prey of the deformed toads, but not so much for the toad or the environment.
Frogs and toads are considered environmental monitors, since their permeable skin allows moisture through, enabling them to breathe, but also forcing them to soak up any harmful toxins in the water. Their unique skin makes them the ultimate environment indicator. In other words, when the amphibian population decreases, its bad news for our environments as well. When tissue samples of amphibians were examined, it was found that they were absorbing worryingly high levels of metals, pesticides and petroleum hydrocarbons. This research told us that there were, in turn, many harmful chemicals in ponds and all around our island, which were probably also seeping into the surrounding ocean. Conservation efforts have been made, but the toad population is still on the decline. Tree frogs seem to be making a comeback, but it is unknown whether they will ever be restored to their full number.
For now, all we can do is listen.