Rob Dean, Interpretive Naturalist in Big Bend National Park, alerted us to a new-to-the-park lizard found last month at Rio Grande Village: Sceloporus olivaceus, the Texas rusty lizard (above). The specimen was found and photographed by Dan Leavitt, Ph.D. student at Texas A&M and former Interpretive Naturalist at Big Bend National Park. “This increases the number of lizard species in the park to 23 and the total species of reptiles to 62. While this lizard is common throughout central and east Texas and Mexico…it is unknown whether this represents a range extension, an exotic release, or a research oversight.” wrote Dean.

BBNP Wildlife Biologist and acting Chief of Science and Research Management for the park added Raymond Skiles added a few layers to this news: “Dan worked here in Interpretation, and in Resource Management for several years, got his masters at SRSU, and is now a Ph.D. candidate at Texas A&M. He’s an excellent biologist, and was here pursuing studies and helping a TAMU grad student working to determine the impacts of the exotic green tree frog… when he came upon the new kid on the block. In keeping with our policy on what appears to be an exotic, and to prove the identification, he collected and “vouchered” (bio-speak for pickling in alcohol) the specimen. It will be preserved at the TAMU – Texas Cooperative Wildlife Collection for future reference and study.

A good point to remember is that this species in this location may represent an exotic or non-native. It’s nearest known range is a considerable distance northeast of the park, and despite several reptile surveys and other projects in recent years, it has not been found within or adjacent to the park, between it’s historic known range and Rio Grande Village. Thus, it is debatable whether a natural range expansion might account for the species’ presence at this disjunct location. Nor is this a particularly secretive or cryptic species that would tend to resist detection when present.

Rio Grande Village is our largest, and in cool months, most heavily used, campground. It’s also a busy and popular destination for motorists, picnickers, hikers, and river users. Often these visitors have recently visited other outdoor recreation and natural areas in the state and beyond. RGV is a very diverse habitat that includes desert, wetlands, ponds, woodland, grassland, and river /riparian areas all in close proximity, [making it] very hospitable to a diversity of species, whether native or not.

We have good evidence that now-established exotics inhabiting the Rio Grande Village area – including green tree frogs, elegant sliders, Mediterranean geckos, and possibly others – hitchhiked their way [here] on recreational or other vehicles, or were intentionally released by well-meaning but misguided alternative pet owners.

While it’s always exciting to find a new species in the park, it’s not necessarily a good thing.

It’s the NPS mandate to preserve native species (which includes natives from nearby that are making ‘natural’ range expansions into the area), but to prevent non-native species and their impacts from occurring in the park if possible. It’s sometimes difficult to decipher or determine ‘native-ness,’ and even more difficult to prevent exotic species invasion. We know of 23 other non-native vertebrate species living in the park; this lizard may join an ever-growing list.”