Various bins filled with water are placed on the tables in a room located behind the scenes of the Biodôme, which is not accessible to visitors. At the back, there are also terrariums along the wall. These seemingly banal installations play an important role in the survival of a highly publicized and increasingly endangered species: the chorus frog.
“What we see here are several thousand chorus frog tadpoles,” emphasizes Emiko Wong, veterinarian and senior conservation scientist at the Biodôme, showing the room around. Duty. Some tanks also contain freshly laid eggs and others that are about to hatch.
Spring is in fact the reproduction period of this tree frog, which is a little over three centimeters long and weighs around one gram. This is therefore a critical moment for the survival of the species, which must, in just a few weeks, ensure the creation of the next generation of amphibians.
As reproduction in captivity is currently proving too difficult and unpredictable, adult tree frogs are temporarily captured in natural environments and are transported to the Biodôme in order to produce the eggs necessary for the scientific program.
“Once the eggs hatch, the tadpoles grow to reach half a centimeter. At this point, they begin to transform. They will gradually reabsorb their tail and develop legs, and then seek to move more towards terrestrial environments,” explains Emiko Wong. This entire cycle takes place at the Biodôme and lasts around forty days.
Increase survival
Such a program also makes it possible to maximize the number of small frogs, argues the veterinarian. “Our objective is to increase the survival rate, because tree frogs are already sufficiently confronted with anthropogenic threats, such as climate change and the transformation of natural environments. »
You should know that chorus frogs spend most of their year on land and that they only converge in spring on ponds which then form. This is where we can hear their song, which we describe as “choral” when several individuals are in the same area. This is also where they lay their eggs.
This is also what is currently happening on the site of the extension of Béliveau Boulevard, in Longueuil. Tree frogs have gathered in ponds formed along the route of this future street which will destroy a large part of their habitat.
It is in this context that the City is increasing capture operations in order to remove amphibians and be able to restart construction work on the new road section. Some of the tree frogs were sent to the Biodôme. As for the street project already underway, it will permanently destroy “a nerve crossing point” and “breeding habitats” of the species which are “particularly active”, according to a scientific opinion written by experts from the Quebec government in 2021.
Disturbed climate
Climate disruption also makes the years to come more uncertain, particularly due to the probable decline in snow cover, which could harm the formation of vernal pools. The Biodôme program is therefore all the more relevant, according to Emiko Wong. “If the temporary ponds dry up too quickly, there will be a large mortality of tadpoles. It is therefore believed that we offer them environmental protection by keeping them in a captive environment for the first stages of growth. »
Ultimately, the objective is to ensure that this approach, repeated year after year, and supported by the government of Quebec and university researchers, replenishes populations which are declining dangerously due mainly to the destruction of natural environments.
“If the species was doing well, we wouldn’t need to make this kind of effort. But unfortunately, the threats are great,” explains Emiko Wong. According to available data, the species has lost more than 90% of its habitat in Quebec. In recent years, several cases of illegal destruction have also taken place.
Result: according to a report on “threats” dated March 2021 and drawn up by government experts, less than 25% of the populations present in the province will be able to survive, unless the growing threats are curbed.
While it is difficult to measure the survival rate of tree frogs once they find themselves in the wild, the data indicates that assisted reproduction is producing results. More than 4,880 tree frogs have been released since 2016. Some have returned to their original environment, while others are destined to evolve in ponds set up in Mont-Saint-Bruno National Park. Every spring, songs seem to indicate reproduction in this protected natural environment.