- June 21, 2023 - Biodôme : Environmental news, Behind the scenes at the Biodôme, Animal portrait
The sweet melodies of frogs
The songs of birds cheerfully announce the arrival of spring, but it is the song of frogs that I most listen out for! In Québec, species like the wood frog (Lithobates sylvaticus), spring peeper (Pseudacris crucifer) and chorus frog (Pseudacris triseriata) call as the last crystals of winter snow melt away. These hardy species can tolerate below-freezing temperatures thanks to physiological mechanisms they’ve evolved to prevent ice from forming within their cells. The frenzied choirs of these frogs may only last a few days, but their offspring get a head start at life.
Male American toads wait until the weather warms a bit more before filling the air with their long-lasting trills in late April or May. They hit different notes, like a well-harmonized ensemble, such that each individual’s voice can be made out distinctly by females. Others, like the gray treefrog (Hyla versicolor), postpone their music festivals until May, while the green frog (Lithobates clamitans) and bullfrog (Lithobates catesbeianus) can better be said to announce the arrival of summer.
In July, the intensity of the last frogs’ mating rituals greatly dwindles, and for me, the best time of the year is already over. By September, apart from the occasional chirp of a treefrog that has climbed into the trees, or the odd twang of a green frog that appears to be confused, the amphibians go silent.
To me, all eleven of Québec’s anuran species are special. To learn who they are and what they sound like, you can visit the webpage of the Atlas des Amphibiens et Reptiles du Québec (AARQ). Familiar with them and their biology, I love looking at any natural habitat and trying to guess which species I could find there. Each species has its own call, so the easiest way to conduct a species inventory at any location is to listen for them at the right time. In fact, you can help the AARQ monitor the health of amphibian populations by participating in their call census! It’s a fun activity that you can do with your family and friends.
Our resident toads
While caring for two American toads that live behind the scenes at the Montréal Biodôme, I photographed them and was struck by their beauty. Yes, I realize that beauty is in the eye of the beholder, but I felt compelled to share my photos in this blog so that you can judge for yourself.
We maintain these toads – one male and one female – in a vivarium filled with soft sphagnum moss, live plants, and wood to hide under or bask on top of. In the summertime we transfer their care to children that attend our nature camp in order to teach them about the particular needs of amphibians and foster in them a desire to protect these important animals and the ecosystems they live in. While it is reported that 48 percent of animal species on our planet are currently undergoing declines due to stressors like habitat destruction and climate change, amphibians are feeling a larger part of the brunt for a number of reasons (63 percent of their species are declining). By protecting their habitats, we invariably protect the other species that inhabit them, so it is a very worthwhile cause.
Animal welfare is of the utmost importance at the Biodôme. To keep our toads active and stimulated, we occasionally change up their scenery by either placing them in a stagnant water–filled basin, where they can soak in deeper water or bask under a UV-light releasing heat lamp, or by placing them in a larger basin with circulating water, where they can swim in the gentle current or stay put on a rock. We feed them a variety of insects, including crickets and moth larvae that we dust with calcium and vitamin powder, and we offer them earthworms too. Our veterinarian ensures that they maintain a good body weight and remain healthy.
American toads, according to Desroches and Rodrigue (2004)
American toads are common in Québec, throughout Canada and in the eastern United States. They breed in a variety of habitats, including shallow ponds, river edges, bays, streams and ditches. In the summer and fall, they are frequently encountered in forests, fields, quarries and bogs, as well as in urban gardens. In the winter, they move underground, below the frost line.
At maturity, females are bigger than males, while the latter develop black thumb pads that help them grip onto the backs of females. Once in position, males wait for a female’s eggs to be laid in water, so that they can be fertilized externally. Toad tadpoles are dark black, with big round heads relative to their skinny tails. About 50 to 65 days after hatching, tadpoles metamorphose into miniature toads that are smaller than a thumbnail.
The skin of American toads is rough, but contrary to popular myth, the bumps are not warts. The thickness of their skin helps them avoid water loss, enabling them to inhabit dryer environments than other amphibians. American toads do not jump far or fast, so they’ve evolved other methods to avoid being eaten. Firstly, the various shades and tones of their skin offer great camouflage in most environments. Secondly, they can take in a lot of air to look too big to mess with or swallow. Otherwise, poison (parotid) glands located behind each eye quite effectively deter predators that still try to eat them. Humans frequently become disenchanted with toads when the animals “pee” in their hands. The “pee” is a release of water that toads opportunistically absorb through a thin layer of skin surrounding the cloaca (cloacal patch) when they encounter water. But perhaps their best strategy for maintaining healthy populations is the number of eggs they lay, given that each female can lay 2,000 to 20,000 of them in two long strands. Such a large number ensures that at least a few individuals will survive to reach sexual maturity!
Perhaps what impresses me most about toads, and many amphibians for that matter, is the metallic color of their eyes. I haven’t found out why their eyes are this way yet, but to me they’re finer than gold!
References:
- Desroches, J.-F., Rodrigue, D., 2004. Amphibiens et reptiles du Québec et des Maritimes. Éditions Michel Quintin, Waterloo, Québec, 288 pp.
- Finn, C., Grattarolla, F., Pincheira-Donoso, D., 2023. More losers than winners: investigating Anthropocene defaunation through the diversity of population trends. Biological Reviews. doi.org/10.1111/brv.12974.
