Risk Assessment of Potential Invasiveness of Exotic Reptiles Imported to South Florida
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Biol Invasions DOI 10.1007/s10530-009-9667-1 ORIGINAL PAPER Risk assessment of potential invasiveness of exotic reptiles imported to south Florida Ikuko Fujisaki • Kristen M. Hart • Frank J. Mazzotti • Kenneth G. Rice • Skip Snow • Michael Rochford Received: 5 February 2009 / Accepted: 16 November 2009 Ó Springer Science+Business Media B.V. 2009 Abstract The recent explosion of exotic reptiles in predict establishment success of 33 reptiles that were south Florida requires effective management strate- most frequently imported through Miami and St. gies. The objective of this study is to bring knowledge Petersburg ports from 2000 to 2005 and two additional of ecological correlates and quantitative modeling reptiles of concern in Florida, we identified eight methods into management by providing the foundation lizards and four snakes as potentially successful for a screening procedure that will identify potentially invaders. We further assessed adverse impacts associ- invasive species and assess adverse impacts associated ated with potential invaders, should they become with these species. We considered 17 variables and, established, by identifying species that are (1) danger- based on model selection procedures, we identified the ous to humans, (2) dangerous to the ecosystem (upper following significant predictors of establishment suc- trophic-level predators), and (3) rapidly spreading. cess: taxonomic order, maximum temperature match Controlling exotic reptiles can be expensive and labor between a species’ native range and Florida, animal intensive once they are established. Information on sale price, and manageability (defined as a species’ which species are potential invaders based on screen- maintenance cost, aggressiveness, proneness to ing procedures and what impacts these species might escape, and venomousness). Applying the models to cause will be a valuable contribution to the develop- ment of proactive management strategies. I. Fujisaki (&) Á F. J. Mazzotti Á M. Rochford Ft. Lauderdale Research and Education Center, University Keywords Climate match Á Establishment Á of Florida, 3205 College Ave., Davie, FL 33314, USA Exotic species Á Prediction e-mail: ikuko@ufl.edu K. M. Hart Florida Integrated Science Center Davie Field Office, U.S. Introduction Geological Survey, 3205 College Ave., Davie, FL 33314, USA Global trade of live reptiles has facilitated introduc- tion and establishment of exotic reptiles in many K. G. Rice Florida Integrated Science Center Gainesville, U.S. locations around the world. Located at the southern Geological Survey, 7920 NW 71 Street, Gainesville, FL extent of the continental United States, south Florida 32653-3701, USA (south of Lake Okeechobee) has a history of success- ful establishment of a variety of herpetofauna origi- S. Snow Everglades National Park, 40001 State Road 9336, nating from tropical and temperate zones (Meshaka Homestead, FL 33034, USA et al. 2004). Although early introductions were via 123 I. Fujisaki et al. accidental import from shipping cargo (Butterfield in Australia and has also been used in New Zealand et al. 1997), increased popularity of exotic reptile pets (Pheloung 1995; Pheloung et al. 1999). Daehler et al. has led to a currently booming trade of exotic reptiles, (2004) applied a screening procedure to identify pest and intentional or accidental release by pet owners plants in Hawaii and other Pacific Islands. and dealers became the major cause of recent Despite increasing concern about adverse impacts introductions (Hoover 1998; Kraus 2003). Exotic posed by exotic reptiles, relatively little effort has reptiles can cause adverse impacts in a number of been made to assess the risk of potential invasiveness ways. Some species are dangerous to humans and of exotic reptiles. Bomford et al. (2005) completed an domestic animals due to their large size and venom extensive literature review on ecological correlates, (Bomford et al. 2005; Reed and Rodda 2009). and Bomford et al. (2008) conducted the leading Introductions of exotic reptiles may have ecological quantitative risk assessment of reptiles and found impacts such as alterations to native food webs and climate match, genus, and number of jurisdictions to ecosystem functions through changes in competition be significant predictors of invasiveness. However, a and predation. Socioeconomic impacts are also pos- number of other factors may also be effective sible, such as reduced agricultural productivity, high predictors of successful establishment. Regarding control costs, and elevated consumer concerns (Bom- the adverse impacts potential invaders may have ford et al. 2005). Regulatory rules that consolidate once established (e.g., harm to humans and ecosys- most laws pertaining to non-native species became tems), there is also relatively little empirical infor- effective January 1, 2008 in Florida. These rules mation available. Reed and Rodda (2009) conducted prohibit release of non-native species and the keeping a risk assessment of nine constrictor species in the of certain species as pets. Under the rules, six exotic United States, rating each species (low, medium, reptiles including Python molurus bivittatus, Python high) on probability of establishment and conse- reticulatus, Python sebae, Morelia amethistina, quences of establishment. Their study indicated that Eunectes murinus and Varanus niloticus were iden- the majority of the assessed species had either high tified as ‘‘reptiles of concern’’ (ROC) and a permit is probability of establishment or high risk of estab- now required to possess these species. lishment consequences, or both, and thus are organ- In early 1980s, conservation concerns led a isms with risk potential. Scientific Committee on Problems of the Environ- In this study, we developed optimal quantitative ment (SCOPE) invasion program to identify three models to predict establishment success of exotic questions to guide future studies in invasion biology: reptiles, which can be incorporated into management (1) identifying factors that determine successful strategies. Our goal was to provide a foundation for invasion, (2) characterizing environments that are screening procedures to assess whether newly either vulnerable or resistant to invasions, and (3) imported species are likely to establish in Florida, incorporating knowledge obtained by addressing and if so, what potential adverse impacts may be these questions into effective management strategies associated with these species. The results of this (Davis 2006). Ecological correlates of the invasion study may provide a means to address the current process were identified in various taxa from early explosion of exotic reptiles in south Florida. works in invasion biology (Elton 1958; Baker and Stebbins 1965). Recent studies tend to focus on quantitative models of establishment success or the Methods invasion process (Hayes and Barry 2008). Various modeling methods were applied for this purpose, Data while concerns about inconsistency among different methods were pointed out (Hayes and Barry 2008). We used the Florida Fish and Wildlife Conservation To improve invasive species management in the Commission (FFWCC) website (http://myfwc.com/ United States, the Ecological Society of America nonnatives/) and the U.S. Geological Survey Nonin- recommended the introduction of screening proce- digenous Aquatic Species (USGS NAS) database to dures for imported species (Lodge et al. 2006). A gather information on exotic reptiles in Florida. We similar screening tool was developed for exotic plants also added supplemental information derived from 123 Risk assessment of potential invasiveness of exotic reptiles Bomford et al. (2005), Meshaka et al. (2004), and taxonomic order, that is, Crocodilian (crocodilians), consultations with local herpetologists and USGS Squamata-Lacertilia (lizards), Squamata-Serpentes NAS staff. We used the definition of establishment (snakes), and Testudines (turtles) instead of family success employed by USGS NAS, that the ‘‘popula- and genus. We did not include previous establishment tion is reproducing and over-wintering,’’ because it history, as the majority of recently imported species is inclusive of the definition from the FFWCC. had no record of attempting to establish elsewhere. Although we were initially interested in assessments Propagule pressure (number of arrived/released indi- of exotic reptiles in south Florida, to obtain sufficient viduals) was found to be an important factor for sample sizes for analysis we included all exotic rep- establishment success across different biological tile species that were either established or were groups including reptiles (Bomford et al. 2008; Hayes known to be not yet established (considered ‘‘failed’’) and Barry 2008). Whereas arrival numbers may be in Florida. The majority of species on our list were reflected by import records, release numbers cannot be distinct at the species level except for a few cases for defined (Bomford et al. 2008). Manageability and price which a particular subspecies was known to be are two variables we introduced to reflect release observed in Florida, such as P. molurus bivittatus. likelihood of each species from pet owners based on Also, we included a few species that are native to the assumptions that inexpensive pets and difficult pets United States and were observed in locations in may be more likely to be released. Florida, far from their native range. We excluded For each selected species, we characterized total species with an uncertain establishment