The increasing population of an invasive species of turtle, the red-eared terrapin in the Diyawanna system as well as other areas of the Western Province poses a threat to native species of terrapins and can result in possible ecological imbalance, says environmentalist and Attorney at Law, Jagath Gunawardana. According to Gunawardana, the spread of this species can be observed in the water systems of the Diyasaru Park, Kimbulawala and Nawala/ Nugegoda areas connecting the Diyawanna system.
The red eared terrapin is an exotic species of turtle which is exported alongside fish, to be reared in ponds. However, Gunawardana notes that red-eared terrapins display an invasive and predatory behaviour in most countries. In fact, it has gained much notoriety as an invasive species outside its home range in Southern United States and Northern Mexico. The International Union for Conservation of Nature
(IUCN) lists the red eared terrapin as one of the 100 worst invasive alien species in the world. The Global Invasive Species Database notes red-eared terrapin to be an environmental pest outside its home range as they effectively compete for food, nesting sites and basking areas with native species. Also, the European Union has banned the import of this species.
Beautiful creature
Due to the attractive red markings on either side of its head, surrounded by green colouring, the red-eared terrapin juvenile is in high demand as pets. However, it tends to grow as large as one foot long, generally too big for its tank, a characteristic which does not endear them to their owners at this juncture. This, coupled with the gradual loss of its attractive colouring and its tendency to prey on other exotic fish, compels the owner to throw them out, says Gunawardana. “At times, this terrapin also has a tendency to escape from its tank. Either way, they end up in natural water systems in the country,”Gunawardana says, adding that red-eared terrapin has been populating in Sri Lanka for approximately 20 years.
He says that upto now, populations of red-eared terrapin have mainly been found in Colombo, Gampaha and Kalutara areas. He further says circumstantial evidence of its breeding is found only from the Diyawanna system. “However, Kalu and Kelani rivers connect to the Diyawanna system. Also, Diyawanna is home to the two indigenous species of terrapins in the country, Parker’s terrapin and soft-shelled terrapin,” he says.Therefore, there is a possibility of red-eared terrapins becoming a threat to these two indigenous species, due to its invasive and predatory behaviour, Gunawardana says. “The red-eared terrapin displays highly carnivorous behaviour, where, at times it preys on its own young. There is a possibility of this behaviour affecting the indigenous populations in the Diyawanna system adversely,” he says.
It takes 90 days to hatch one clutch of red-eared terrapin eggs, but provided optimal conditions, the female can lay eggs up to six times per year, which would lead to rapid increase in their populations, Gunawardana says. “Red-eared terrapin is highly elusive. Therefore, it is difficult to spot and to capture while it is swimming. If it is spotted while on land, it tends to jump into the water. Also, it bites people when attempting to capture it,” he says. Hence, one of the only ways to spot red-eared terrapin remains when at 10 am in the morning, it basks in the sun. At the same time, the red-eared terrapin is adapted in such a way that if the water body it inhabits dries up, it can walk to another. “ Therefore, this species can populate not only the interconnected waterways, but any other water bodies that are not connected to each other,” he says.
An exotic invasion
Gunawardana adds that the red-eared terrapin displays invasive and predatory behaviour in most countries. Indeed, Richard Aaron Gibbs states in his study,
An Assesment of Environmental Impacts of Red-eared Slider Introduction (2017) that half of the Australian continent is at risk due to expansion of red-eared terrapin populations, with Queensland, Australia establishing red-eared terrapin eradication programmes.
Further, a recent research paper published by Oliver Stringham and Julie Lockwood in the Journal of Applied Ecology states exotic pets serve as the main source of invasive species in the world. The study further notes that these invasive species of amphibians and reptiles have the potential to drive native species towards extinction, a hefty ecological cost to bear.
Nevertheless, Gunawardana argues that the populations of red-eared terrapins in Sri Lanka are still at a level that can be controlled with vigilance and immediate action, since it is not yet being found in large populations or areas.
Gunawardana says that section 37 of Flora and Fauna Protection Ordinance, banned the import of red-eared terrapin to the country without permission. The Department of Wildlife Conservation confirms that they have not issued permits to import the species. The Director of Biodiversity Secretariat, Padma Abeykoon asserts that red-eared terrapin is included in the Invasive Alien Species list, as a species that threatens the local species due to its competitive behaviour. “However, red-eared terrapins are still brought into the country. Also, nobody knows the exact, present situation of their populations in the country, as no recent study on red-eared terrapins exists” Gunawardana notes.
Recently, a consignment of red-eared terrapins that reached India from Sri Lanka, was seized by the Indian authorities. In 2017, a similar incident took place, where Indian authorities seized another consignment of 3000 red-eared terrapins from a Sri Lankan passenger.
Reports say that Indians believe these exotic turtles bring good luck and thus they are being smuggled and sold there with a large profit margin. “The fact that these large consignments are being smuggled from Sri Lanka indicates possible breeding of the species for commercial purposes, which in the absence of legal instruments, remains perfectly legal,” Gunawardana says. The new act to control invasive alien species has been drafted but is yet to be presented to the Parliament, he says. At the same time, Gunawardana says experts have made multiple requests to ban the import of the red eared terrapin by issuing an order under the Section 30 of the Fisheries and Aquatic Resources Act, to no avail.
Thus, immediate action is needed on the part of the authorities to ban and control this invasive alien species, to minimise the damage on native species and the local ecosystem.
A study on the distribution and impacts of the red-eared slider is a dire need, along with legislative support to take necessary action to ensure the situation does not grow out of proportion and the country needs programmes to eradicate this exotic invader.
