Risk Assessments at Carterville FWCO Reveal Important
Information and Interesting Species
BY ALLISON LENAERTS AND LUCAS SHEA, CARTERVILLE FWCO
As technicians at the Carterville Fish and Wildlife Conservation Office (FWCO), most of our office work consists of the dreaded Risk Assessment. Risk Assessments are kind of self-explanatory; we use current information to assess the risk of a species becoming invasive in the United States. Although the work is important and can yield valuable species information, we all still prefer to sample in the field or do anything to not be chained to a desk. As daunting as the work is, we have encountered some interesting species, for example the African clawed frog (Xenopus laevis).
The African clawed frog is native to most of Africa, except for East Africa, but has multiple occurrences in the United States. They can reach sizes of five inches and live up to 12 years but have been recorded to live as long as 30 years. This species is highly adaptable and has the ability to tolerate sewage and saline waterways. In addition, the African clawed frog has a high tolerance for fairly cold temperatures and can easily take advantage of new man made habitats. Unlike native frog species, the African clawed frog lacks a tongue, doesn’t hold its hind legs underneath itself and lacks a visible tympanum. Mature adults also have three black claws on the toes of their hind feet.
African clawed frogs have been introduced into the United States through their use in laboratory research. This species has been extensively used in laboratories from genetics to human pregnancy diagnosis in the 1950s and 1960s. Human pregnancy was tested by injecting urine from a woman into the frog then observing if the frog had produced eggs, meaning the woman was pregnant. African clawed frogs were used in other experimentation because of their close evolutionary relationship to humans. Their establishment in the wild is correlated to the termination of their use in diagnosing human pregnancy, but they are also a popular aquarium pet which can lead to further introductions. Currently, the African clawed frog is considered a nuisance in its native and introduced range. The main impact it has on native areas is consumption of fish, amphibians and benthic species. It is also a known carrier of the chytrid fungus. Due to its high adaptability, this species continues to expand its global distribution. Although the African clawed frog is already present in the United States, this information is beneficial in understanding pathway vectors and introduction impacts, which may be applied to numerous other species of concern.
As we begin sampling in the field this spring, we are reminded by the invasive species present that preventative measures like Risk Assessments are crucial to stopping the spread of other invaders.