A Steward’s Circle Note

 One function of county, state, and federal parks is to protect and maintain the native flora and fauna within park boundaries. Another function is to provide access to the general public with opportunities to both experience and learn about native organisms and their ecosystems. This latter function is very important because it also helps build support for the parks within their surrounding community (Moore and Fitchett 2004). However, providing such access may in some ways actually harm the biota the parks are meant to preserve. Park access typically involves visitors driving to the parking area near trails or other recreational facilities. Likewise, placement of sidewalks and paved parking lots often accompany this infrastructure.

In Florida, the northern curlytail lizard (Leiocephalus carinatus armouri Gray) is an invasive lizard that has spread along much of the southeastern coast, Florida Keys, and also into a few inland areas (Meshaka et al. 2004, 2006, Krysko et al. 2005). In its native habitat in the Bahamas, it burrows in sandy soil under rocks and will bask on those rocks. Most areas in peninsular Florida lack natural rock outcrops, but instead concrete and asphalt are readily used as substitutes. Curlytail lizards in South Florida have expanded along developed portions of the southeast (Meshaka et al. 2005), where they especially like curbs, parking lots, and sidewalks (Smith and Engeman 2002, Smith and Engeman 2004a) with shrubbery planted nearby. The addition of shrubbery plantings near these hard substrates is important because shrubs provide shady areas for the lizards, and protected areas to run to when threatened by their many Florida avian and mammalian predators (Smith and Engeman 2004a, 2004b, Smith et al. 2006a, 2006b, 2006c, Meshaka et al. in review).

Curlytails are large lizards, the snout to vent length can be up to 12-13 cm (5-6”) and they have robust bodies (Smith and Engeman 2004a). Despite this size they run very fast, often rushing their prey, and they are voracious predators (Smith and Engeman 2004a). Curlytails are so-called because when threatened or running, they curl their tail up over their body, looking somewhat like a scorpion (Cooper 2001). While largely a terrestrial lizard, curlytails have been observed basking in sabal palm trees up to 1 m above ground (JAM pers. observ.), and basking and foraging as high as 6 m on concrete staircases in apartment complexes (Smith and Engeman 2004a).

If the perimeters of roadways, parking lots, and sidewalks can serve as areas where curlytails will reside, then this leads to an edge effect of curlytails reaching into peripheral portions of natural areas. If those sidewalks penetrate deeper into natural habitat, the influence of curlytail lizards may be more extensive within the park.

And what impacts do curlytail lizards have? When introduced to Bahamian islands where they were previously absent, curlytails quickly devoured some of the brown anole lizards populating those islands and a decline in the population of anoles followed (Schoener et al. 2001). Here in Florida, we have similarly noticed a decline in the number of invasive Cuban brown

Okay, so you think that it might not be bad if curlytails remove an abundant invasive species, such as the Cuban brown anole. But, curlytails are hungry and will eat any animals they can capture in Florida, which frequently means large arthropods (insects, centipedes, spiders, scorpions, see Callahan 1982, Meshaka et al. 2004), but can also include small vertebrates (Smith and Engeman 2004a, Schoener et al. 1982). As terrestrial predators, that means curlytails can also potentially impact small native species in their habitat, such as sixlined racerunners, southern five-lined skinks, scrub lizards, crowned snakes, ringneck snakes, brown snakes, and the young of many other species (Smith and Engeman 2004a, Dean et al. 2005). In experimental populations on several small islands in the Bahamas, curlytail lizards as predators were partially responsible for driving native brown anoles to extinction on four out of six islands (Schoener et al. 2001). Parks sometimes are isolated islands of natural habitat in seas of urban or suburban development. This effect of predators on islands is a serious consideration. In the very least, the threat of predation by curlytails gives this species a competitive edge for food and may be enough to alter the behavior of the other small reptiles in the area, potentially to their detriment (Losos et al. 2004).

...in the Bahamas, curlytail lizards as predators were partially responsible for driving native brown anoles to extinction on four out of six islands.

And what about those brown anoles that become more arboreal? It has been shown that brown anoles selectively eat more young of green anoles than visa versa (Gerber and Echternacht 2000). Green anoles became more arboreal in response to the invasion of brown anoles. If brown anoles are forced to become more arboreal, what happens to the green anoles?

So while infrastructure improvements to the parks, such as sidewalks and paved lots, are necessary and often required by law, habitat conversion plans must also delicately balance the conundrum that such anthropogenic intrusions into natural areas also facilitate the invasion of various exotic plant and wildlife species into these same places. Continued life-history and ecological niche studies of our invasive wildlife species in Florida are critical to this difficult dilemma and likewise an important educational process for our future land stewards (Moore and Fitchett 2004). This will help lessen the future impacts of exotic species on native fauna in Florida’s precious natural areas.

Literature Cited (Removed for space; please contact author for citations.*) 

*Author to whom correspondence should be addressed: Jon Moore [silverroughy@bellsouth.net]

Jon A. Moore - Florida Atlantic University, Wilkes Honors College, 5353 Parkside Drive, Jupiter, FL 33458 USA

Henry T. Smith - Florida Department of Environmental Protection, Florida Park Service, 13798 S.E. Federal Highway, Hobe Sound, FL 33455 USA