Hidden Enemies For Turtles:
WHEN INVASIVE SPECIES BECOME A THREAT:
THE HIDDEN DANGER FOR TURTLES
What is an invasive species?
An invasive species is a non-native organism that has been introduced, usually through human activity, into a new environment where it causes economic, environmental, or human health harm. Because invasive species often lack natural predators in their new range, their populations can grow rapidly. This can lead to displacement of native species, habitat degradation, and disruption of entire ecosystems. Invasive species are a top driver of biodiversity loss.
Invasive species threaten turtles by competing for food and nesting sites, preying on eggs and hatchlings, spreading disease, and disrupting the fragile ecosystems they rely on for survival. Below, we take a closer look at some invasive species and the trouble they’re causing for turtle populations.
Invasive Turtle Species
Red-eared Sliders
Red-eared Sliders (Trachemys scripta elegans) are one of the most common species of pet turtles. When many people picture a “pet turtle,” this is the species they imagine. What few people realize is that they are listed among the world’s 100 worst invasive species and are considered the most invasive turtle globally.
Native to the Mississippi River basin in the United States, this species has spread worldwide due to the pet trade. Hatchlings are sold small and inexpensive, but they grow into large adults with complex care requirements and can live up to 40 years. When owners are unprepared for this long-term commitment, Red-eared Sliders are often released into local ponds, lakes, or wetlands.
Once established, Red-eared Sliders:
- Compete aggressively with native turtles for food
- Displace native species from basking sites
- Compete for nesting habitat
- Potentially introduce parasites and pathogens
Red-eared Sliders are highly effective at outcompeting native turtles due to several biological advantages. They grow quickly, reproduce in large numbers, and can thrive in polluted or human-altered habitats where native species may struggle. Their broad diet allows them to exploit a wide range of food sources, and their aggressive basking behavior helps them dominate limited basking sites that are essential for turtle health and survival.
Across Europe and the United Kingdom, the sale, import, transport, and breeding of pond sliders (Trachemys scripta and all three of its subspecies, including Red-eared Sliders) is restricted or prohibited due to their invasive status. Releasing them into the wild is illegal.
Ironically, although this invasive species is itself a turtle, it can have devastating impacts on native turtle populations. Other invasive turtle species, such as the Common Snapping Turtle (Chelydra serpentina), have also established non-native populations that wreak havoc on ecosystems around the world.
Thinking of Buying a Pet Turtle? Read This First
- Understand that turtles are a long-term commitment. Many species have a lifespan of 30–40+ years and require specialized care.
- Adopt, don’t shop. Many surrendered turtles are in need of homes through rescues.
- If you can no longer care for your turtle, contact a rescue or reptile organization for alternatives.
- Never release unwanted pets into the environment.
Responsible pet ownership is one of the most powerful tools we have to prevent biological invasions. Many invasive turtle populations began with a single release event that multiplied over decades.
If you’re looking for tortoise care tips, please check out our guide.
Meet More Invasive Species Putting Turtles at Risk
Invasive mammals, reptiles, and insects also significantly impact turtle populations through predation, habitat destruction, and ecosystem disruption.
Wild Boar
The Wild Boar (also called feral swine or wild pigs) is one of the most destructive invasive mammals worldwide, with populations established across North and South America, Australia, and many island nations. In the USA, populations are estimated in the millions across more than 30 states. Boars cause significant damage that have detrimental effects on the environment and economy. Specifically, boars cause damage to wildlife habitat, are predators to native populations, and transmit diseases to plants and animals, many of which are endangered already.
Wild boar:
+ Destroy turtle nests and consume eggs, including those of endangered sea turtles
+ Damage wetlands and riparian habitats
+ Uproot aquatic vegetation critical for freshwater turtle survival
+ Transmit diseases to wildlife
Boars turn over large areas of ground during their characteristic “rooting” behavior, digging into soil in search of roots, fungi, and invertebrates. This alters soil structure, nutrient cycling, and hydrology, often degrading sensitive wetland ecosystems that turtles depend on.
Feral or Pet Cats
Cats are a significant predator of wildlife worldwide.
Cats:
+ Prey on hatchling turtles and small tortoises
+ Are particularly devastating on islands
+ Contribute to the decline of already vulnerable populations
+ Keeping pet cats indoors reduces predation on native wildlife.
Burmese Pythons
The Burmese Python is invasive in southern Florida, particularly within Everglades National Park, which holds a large diversity and volume of turtles.
These large constrictors:
+ Consume native turtles and juvenile tortoises
+ Prey on species such as the threatened Gopher Tortoise (Gopherus polyphemus)
+ Contribute to large-scale ecological disruption
Interestingly, some research suggests that pythons may reduce populations of egg-eating mammals such as raccoons and opossums, which could increase turtle nesting success in certain localized areas. However, this is part of a complex and unpredictable ecological cascade involving population collapse of small mammals. Overall, Burmese Pythons have widespread negative impacts on native wildlife communities (Willson et al. 2017).
Red imported Fire Ants
The Red imported Fire Ant, native to South America, is considered one of the world’s most destructive invasive insects in the United States, causing over 5 billion in annual US damages to agriculture, wildlife, and infrastructure.
Fire ants:
+ Attack and swarm turtle hatchlings as they emerge from nests
+ Can injure or kill young turtles with venom
+ Invade sea turtle and freshwater turtle nests
+ A study in Georgia found fire ants present in 42% of sampled Gopher Tortoise nests (Dziadzio et al. 2016)
Fire ants are particularly dangerous because they attack in large numbers, injecting venom that can blind, disorient, or kill hatchlings before they reach water.
How Invasive Species Affect Our Field Projects
The Vallarta Mud Turtle
One of the species we have devoted significant conservation efforts to is the Vallarta Mud Turtle (Kinosternon vogti), the world’s smallest turtle species. Endemic to Puerto Vallarta, Mexico, this Critically Endangered species faces numerous threats, including habitat destruction, road mortality, illegal collection for the pet trade, and increasing pressure from invasive species.
In western Mexico, the Jalisco Mud Turtle (Kinosternon chimalhuaca) has been documented in the Puerto Vallarta region outside its known native range, suggesting it may have been introduced. There is growing concern that it may already be hybridizing with the endemic Vallarta Mud Turtle, potentially threatening the genetic integrity of this localized population.
Another concern in the region is the Mexican Giant Musk Turtle (Staurotypus triporcatus), which has been introduced beyond its native distribution. This large, highly predatory species is known to consume other turtles, and smaller endemic species such as the Vallarta Mud Turtle may be particularly vulnerable.
To learn more about the Vallarta Mud Turtle and our conservation work, visit the Vallarta Mud Turtle Project page.
European Pond Turtle
Another species we have dedicated significant research and conservation efforts to is the European Pond Turtle (Emys orbicularis). Across parts of its range, this native freshwater turtle faces increasing pressure from invasive species, particularly the Red-eared Slider.
During field surveys in Slovenia focused on monitoring native European Pond Turtles, invasive Red-eared Sliders were increasingly encountered. In our initial survey, native European Pond Turtles were successfully documented. However, during a subsequent survey at the same site, the only turtle captured was a Red-eared Slider. This shift illustrates how invasive turtle species can rapidly establish and dominate habitats once occupied by native populations.
Additional studies have confirmed that Red-eared Sliders are now reproducing in parts of Slovenia, raising serious concerns about long-term competition, displacement, and potential population decline of native European Pond Turtles.
To learn more about the subspecies we work with, visit our Eiselt’s Pond Turtle conservation project page.
How You Can Help Protect Turtles from Invasive Species
Invasive species are a major driver of turtle decline, but they are also one of the most preventable threats. Individual actions can make a measurable difference.
You can help by:
- Never releasing pet turtles or other animals into the wild
- Researching long-term care requirements before purchasing a pet reptile
- Adopting surrendered turtles instead of buying from pet stores
- Keeping pet cats indoors and dogs leashed to reduce predation on wildlife
- Reporting invasive species sightings to local wildlife authorities
- Supporting conservation programs that protect native turtle nesting sites
- Many invasive turtle populations began with a single pet release. Responsible pet ownership is one of the most effective tools in preventing new invasions.
Why This Matters
Invasive species are a major but preventable driver of turtle and tortoise decline worldwide. Through responsible pet ownership, habitat protection, invasive species management, and public education, we can reduce these threats.
Protecting turtles means protecting the ecosystems they depend on and preventing the next invasion before it begins.
If you would like to help protect endangered turtles and tortoises from threats like invasive species, habitat loss, and illegal trade, please consider making a donation to support our conservation efforts.