Red-eared slider turtles slip into SA, another invasive species

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Cormac Price recently received a call from the Durban Botanic Gardens asking whether he could remove two adult red-eared sliders found on the property. 

Red-eared sliders are freshwater terrapins or turtles from North America and are the most globally traded turtles in the pet industry. They are listed by the International Union for Conservation of Nature’s Invasive Species Specialist Group as one of “Top 100” worst invasive species in the world.

Price, a herpetology postdoctoral fellow at North West University with Che Weldon’s HerpHealth Lab, told of how he kept the reptiles overnight in separate aquariums before they were to be humanely euthanised. 

But what worried him was that when he went to inspect them the next morning, the female had laid two eggs. “It was probably stress-induced laying, which happens sometimes. I didn’t investigate further whether these eggs were fertilised but the fact that there’s adult females laying eggs is a big concern. 

Then the SPCA told him that a woman had dropped off a hatchling red-eared slider that she had found.

Price said there was no way of proving that hatchling was incubated and raised artificially in captivity. “It was such a young animal; there was a very strong possibility this came from a clutch of eggs that was laid naturally wild in that suburb in Durban and that hatchling was a record of success in the wild. There was no way of proving that but it’s still a big sign of concern.”

The turtles are a concern because they pose a threat to local terrapins by spreading diseases and parasites and they compete for resources,according to Invasives South Africa. There is also a concern for the harm they can cause to native frog species. 

The popularity of red-eared sliders as pets have seen them be released or escape into the wild in many parts of the world. It is estimated that more than 52 million individuals were produced in the US on turtle farms and sold to foreign markets from 1989 to 1997. 

Individual red-eared sliders have been found in Johannesburg, Pretoria, Hartbeespoort Dam, Durban, Scottburgh and Cape Town, according to Invasives South Africa. 

All turtles and sliders native to the Americas are listed as category 2 species in South Africa according to the Alien and Invasive Species Regulation and Species Lists of 2020. These are species that require a permit to carry out any restricted activity. The two restricted activities that are permitted include “having in possession or exercising physical control over any specimen” as well as “conveying, moving or otherwise translocating a specimen of the species”.

“They spread across wetland ecosystems and can migrate up rivers and across land to new water bodies. These exotic reptiles pose a threat to our indigenous terrapins through disease and parasite transmission as well as competition for similar resources. They also threaten biodiversity in wetland ecosystems,” said Invasives South Africa.

Price said red-eared sliders present in South Africa are borderline established. 

“They cause a lot of havoc and grief to local habitats and ecosystems already, particularly in countries like France, Spain and Italy. They’re also causing big issues in Australia, South America and Japan,” he said.

“My opinion from the little data I’ve collected and experience I’ve found is that they are present in South Africa. Adults are not just surviving, but thriving in certain climates of ours, particularly in KwaZulu-Natal because it’s very similar to Florida — it’s subtropical. They also seem to be getting on well in city parks in Cape Town and Johannesburg so even on the Highveld and the high plateau, they seem to be coping with our winters.” 

But finding juveniles and records of successful breeding in the country is almost impossible, which Price said is a good sign. 

“From the little data I’ve been shown they seem to be getting on very well in towns, cities particularly city parks and botanic gardens, but whether their population grows and actually spreads out into the natural environment is another question.”  

He added that he had received a single report of an adult female red-eared slider being picked up in a non-urban environment in the Underberg, which is rural and isolated, but this was his only record outside urban areas.

One of the major concerns about the potential invasion of alien turtles is their effect on native frog species, macroinvertebrates and smaller fish in pristine wetlands in KwaZulu-Natal where there are anything from eight to 14 different species of frogs. 

“If you introduce red-eared sliders, you could find that maybe only two or will be left. They will wipe out the more sensitive species of frogs and less prolific breeding frogs,” Price said. “So they will really wreak havoc on native wetland biodiversity … if we keep ignoring it and if people keep selling them illegally without being persecuted or prosecuted.”

Price said that when the Teenage Mutant Ninja Turtles cartoon came out, “everyone wanted a pet red-eared slider. They were so popular in the pet trade thanks to Hollywood and the media. Another example was the Rocky movies where Sylvester Stallone had pet red-eared sliders.” 

The reptiles are sold when they’re about the size of a R5 coin but can grow to be the size of a dinner plate and are not suitable for home aquariums. “Unscrupulous pet shops that are solely obsessed with profit, not obsessed with animal welfare or educating potential buyers, will deceive the public or will not inform the public,” he said. 

Red-eared sliders can live for about 30 years and can be quite prolific breeders, laying up to 30 eggs. 

Price said there’s still time to nip any potential invasion in the bud. “We have a chance now to stop it before it becomes a problem.”

The red-eared slider is not the only turtle popular in the pet trade. “The red-eared slider was probably exported in the largest numbers but you’ve also got painted turtles and mud turtles. The other two big dangers, which are popular, are the common snapping turtle and the alligator snapping turtle, so there were many species of freshwater turtle being exported from the US.” 

He said any of those turtle species may become invasive in South Africa.

Then there are the snakes. “Ball pythons are very popular in the pet trade, as are corn snakes. There’s an unfortunate trend, it seems to be mostly happening in Johannesburg, where other very venomous species are becoming very popular in the trade such as rattlesnakes and king cobras. Most hospitals will not supply anti-venom that could work on those exotic species.”

South Africa’s snakes are more “street smart”, compared with some North American snakes in the country as pets. “We’re very fortunate to have snake-feeding snakes in our native natural environments. So, with the ball pythons and the corn snakes in the trade, if any of those get out and they encounter a Cape cobra or a Mozambique spitting cobra, they don’t really stand a chance. Our own native wildlife in a way is sort of protecting us from our own mistakes, which is great. Our native wildlife is protecting us from an invasion.”

For his master’s dissertation in 2021, Asekho Mantintsilili, of the School of Life Sciences College of Agriculture, Engineering and Science at the University of KwaZulu-Natal, assessed the trade of reptile species in the South African pet trade industry.

It described how the trade in pet reptiles in South Africa is large and one of the major pathways through which invasive species are introduced into the country.

The research found that reptile species with high availability in the pet trade and extensive occurrence records would have wider climatic suitability distribution than rare species with relatively small occurrence records.

“In our study, the corn snake (high availability in the trade), red-eared slider, and western diamondback rattlesnake with extensive occurrence records had larger climatic suitability distribution ranges. These species represent the most serious threat to South African wildlife as they showed a wider potential distribution in South Africa.”

The present geographical distribution of the invasive red-eared slider and western diamondback rattlesnake will “increase significantly in the future, covering most parts of South Africa”, it noted.

“The invasive red-eared slider and red-tailed boa present high risks of colonising many parts of South Africa in the future. These species have colonised many parts of the world, including the US (Florida), China (Beijing) and three localities in southwestern Spain and have caused significant impacts in those areas after they have successfully colonised them.”

The latter species have a history of invasion elsewhere and are causing significant environmental and socio-economic damage in invaded environments. 

“This further suggests that these reptile species have a relatively high potential of establishing, becoming invasive and causing environmental and socio-economic impacts in South Africa should they be released or escape into the wild,” the research said, recommending that the trade in pet reptiles should be constantly monitored to avoid new introductions and the implications that the pet trade may have on the country.

Albi Modise, spokesperson for the department of forestry, fisheries and the environment, said it has taken measures to manage alien and invasive species through the National Environmental Management Biodiversity Act and the Alien and Invasive Species Regulations and Species Lists 2020. This lists four categories of invasive species and their respective management interventions.

All turtles or sliders native to the Americas, “that is all Trachemys species are listed as category 2 species in South Africa, according to the Alien and Invasive Species regulations and Species Lists of 2020,” he said.

Any species listed under category 2 requires a permit issued by the department.

Modise said that in the 2022-23 financial year, more than 1 000 compliance inspections were carried out at pet shops, aquaria and reptile centres and other facilities. 

“Where non-compliance is detected, the matter is referred to the department’s enforcement unit to take further actions, which may include administrative penalties or criminal prosecution,” he said.

Contact Cormac Price if you have information or records of red-eared sliders or any species of non-native reptiles in the wild at [email protected] or 076 873 8110