Invasive Species Spotlight: Cuban Treefrog

Photo Credit: Denise Gregoire/U.S. Geological Survey

The tropical location and peninsular isolation of southern Florida make it an ideal habitat for invasive species including a variety of reptiles and amphibians. Florida currently has over 50 different invasive reptile and amphibian species considered established, or able to sustain a persistent population year after year. One of the oldest established non-natives is the Cuban treefrog (Osteopilus septentrionalis) which has been documented since the 1930’s but may date back even further, perhaps as far as the mid 17th century. Its native home range included the Bahamas, Cayman Islands and of course Cuba. The Introduction of this large treefrog to Florida probably occurred as trade connections with the Caribbean grew and the shipping of cargo from diverse islands to the US mainland increased. Cuban treefrogs are robust and are adapted to tolerate long periods of drought, which further enabled their spread from the Caribbean to Florida, and now up through the Carolinas and even to the islands of Hawaii.

The Cuban treefrog is the largest tree frog in North America. It is nocturnal and an excellent climber, commonly found near artificial lighting feeding on prey attracted to the light. They are such excellent climbers that they sometimes cause power outages by climbing up power poles and shorting out the line. Although they are endearing, as most treefrogs are, these large invaders cause ecological havoc through an appetite which matches their size. These Atlas amphibians can attain lengths approaching half a foot (versus the 2.5” maximum size of our native green treefrogs) and besides feeding on insects, will also consume lizards, bird hatchlings, snails, and other tree frogs—including smaller members of their own species. This voracity and the longevity of their invasion has allowed scientists to document the impact of Cuban treefrogs on native treefrog populations.  As expected, there are detrimental effects on green and squirrel treefrog populations though predation and competition. Because Cuban treefrogs are so well established, eradication is considered impossible, and management of populations is problematic.

Cuban treefrogs are also resistant to predation. They secrete a toxic mucus through their skin, making them unpalatable to many predaceous birds and snakes, such as the American crow and black racer. However, yellow rat snakes, ribbon snakes, and barred owls have been recorded preying on Cuban treefrogs, and scientists believe that alligators, raccoons, opossums and birds of prey may all occasionally snack on them as well. However, the best control mechanism to prevent their further spread is temperature, and die-offs are common for Northern populations during periods of cold. Because Cuban treefrogs reproduce rapidly, even following a die-off populations may quickly rebound. Cuban treefrogs are able to reproduce throughout the year (although reproduction is more common in the wetter months between May and October). Females will lay a partial clutch of eggs numbering between 100-1,000. A full clutch can number above 3,000 eggs! Furthermore, eggs can hatch within 30 hours of being laid. The newly hatched tadpoles, like their parents, eat copiously and grow rapidly, switching from an algae diet to one of insect larvae to other tadpoles and even newly metamorphosised juvenile frogs.  

Florida native frogs are definitely on the menu for Cuban treefrogs, but they are far from the only threat to our native populations. Of Florida’s 27 native frog species, 14 are found in South Florida, and in recent years their populations have declined as a result of predation by invasive species, habitat loss, pollution, and disease. The International Union for the Conservation of Nature (IUCN) maintains a “Red List” of Threatened Species, and their scientists have identified amphibians as being the most threatened group of vertebrates globally, with about 41% of all studied amphibian species at risk of extinction. Everyone can play a part in helping amphibians survive—from building a place for them to shelter (more on that later) to making amphibian friendly choices—for example, the production of disposable wood chopsticks is a driver of deforestation and habitat loss for salamanders. Making a difference doesn’t have to be hard: you can contribute just by purchasing and using reusable chopsticks (http://www.chopsticksforsalamanders.org). Small actions made by many people can have a big impact!

  Although the south Florida Cuban treefrog population is established, people are also encouraged to help control the spread of this amphibian from new areas. The University of Florida recommends catching in a plastic bag to minimize exposure to the noxious skin mucus and the application of benzocaine containing products (ie: sunburn relief) to the animal, rendering it unconsciousness. The animal can then be placed in a sealed bag into a freezer for euthanasia. We hope it goes without saying, but: do not euthanize a frog unless you are absolutely certain you have correctly identified it as a Cuban treefrog. If you are uncertain about your identification, or would like to report the sighting without euthanizing the frog, you can e-mail Dr. Steve A. Johnson (tadpole@ufl.edu) of the University of Florida. In your email, please report the county and street address of the sighting (for mapping purposes) and provide a digital photograph of the frog if possible. If you would like to help native tree frog populations recover and remove Cuban treefrogs from your yard, instructions for building a frog-friendly “frog treehouse” are available here: http://edis.ifas.ufl.edu/uw308. For help identifying the frogs you are likely to sight in your treehouse, the University of Florida maintains a helpful database of native and non-native frogs and toads here: http://ufwildlife.ifas.ufl.edu/frogs/south.shtml.

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