University of Nebraska - Lincoln DigitalCommons@University of Nebraska - Lincoln USDA National Wildlife Research Center - Staff U.S. Department of Agriculture: Animal and Publications Plant Health Inspection Service 2011 A field ve aluation of a trap for invasive American bullfrogs Nathan P. Snow USDA/APHIS/WS National Wildlife Research Center, [email protected] Gary W. Witmer USDA-APHIS-Wildlife Services, [email protected] Follow this and additional works at: https://digitalcommons.unl.edu/icwdm_usdanwrc Snow, Nathan P. and Witmer, Gary W., "A field ve aluation of a trap for invasive American bullfrogs" (2011). USDA National Wildlife Research Center - Staff Publications. 1369. https://digitalcommons.unl.edu/icwdm_usdanwrc/1369 This Article is brought to you for free and open access by the U.S. Department of Agriculture: Animal and Plant Health Inspection Service at DigitalCommons@University of Nebraska - Lincoln. It has been accepted for inclusion in USDA National Wildlife Research Center - Staff Publications by an authorized administrator of DigitalCommons@University of Nebraska - Lincoln. A field evaluation of a trap for invasive American bullfrogs NATHAN P. SNOW1,2 and GARY W. WITMER1* Native to the eastern United States, American bullfrogs (Rana catesbeiana [Lithobates catesbeianus]) have been introduced in many countries throughout the world. There have been relatively few effective and efficient control methods developed to manage bullfrogs. Particularly in the Hawaiian Islands, Pacific coast of North America, and Japan, finding effective methods for controlling invasive bullfrogs is needed with special emphasis on low impacts for sensitive native species. We conducted a field study to examine the efficacy of a newly designed live trap for capturing invasive bullfrogs. We found that our trap was successful at capturing bullfrogs because we captured up to seven in a single trap overnight. Fishing lures, live crickets, and lights were used as attractants and all capture bullfrogs, however more research is needed for finding effective attractants. We captured one known non-target frog that was released. Our findings suggest that the multiple capture traps could effectively be used as part of an integrated pest management strategy for controlling invasive bullfrog populations. Key words: American bullfrog, attractants, integrated pest management, invasive species, multiple capture trap, Rana catesbeiana INTRODUCTION and Sandison 1972). However, in their introduced range, invasive bullfrogs may RIGINALLY native to eastern North O displace native amphibians from their preferred America, American bullfrogs (Rana catesbeiana habitats (e.g., Moyle 1973; Hammerson 1982; [Lithobates catesbeianus]), hereafter referred to as Kats and Ferrer 2003), which can indirectly bullfrogs, have been introduced throughout increase the native species’ susceptibility to other western North America, Oceania (Pacific Ocean predators (Kiesecker and Blaustein 1998). islands), Asia, Europe, the Caribbean, and South America (Staples and Cowie 2001; Witmer and The relatively large body size of bullfrogs gives Lewis 2001; Lever 2003; Govindarajulu 2004; them a competitive advantage over many native Palen 2006). Most introductions occurred species (Bury and Whelan 1984; Kraus 2009). from1900 to 1940, primarily because bullfrogs Invasive bullfrogs out-compete and depredate served as a food source for humans, but also as native species (Hecnar and M’Closky 1997; Díaz released pets or biological control agents De Pascual and Guerrero 2008). Many studies (Witmer and Lewis 2001; Lever 2003; Boersma have implicated invasive bullfrogs as being et al. 2006; Kraus 2009). The ecological impacts directly responsible for declines in native of invasive bullfrogs are known to cause herpetofauna (Moyle 1973; Hammerson 1982; significant impairment to native species (Hayes Schwalbe and Rosen 1988; Kupferberg 1997). and Jennings 1986; Kiesecker and Blaustein Some examples of the native species that are 1997; Kiesecker et al. 2001; Doubledee et al. consumed by bullfrogs include: Pacific treefrogs 2003; Lever 2003). In places like the Hawaiian (Hyla regilla), red-legged frogs (R. aurora), Islands, control of bullfrogs is becoming leopard frogs (R. pipiens), yellow-legged frogs increasingly essential to assist the recovery of (R.muscosa), alligator lizards (Elgaria native species (Staples and Cowie 2001). multicarinatus), western fence lizards (Sceloporus However, in other locations, (e.g., Japanese occidentalis), and Oregon garter snakes Islands), little information is known about the (Thamnophis atratus hydrophilus) among many impacts from bullfrogs, even though they have others (Hammerson 1982; Crayon 1998; Adams been established for over 50 years (Lever 2003). 1999; Doubledee et al. 2003; Kats and Ferrer 2003; Govindarajulu 2004). Typically, bullfrogs Bullfrogs can inhabit most permanent water will consume any fish, wildlife, or insects smaller sources including canals, reservoirs, marshes, than it is (Staples and Cowie 2001). ponds, and lakes (Bury and Whelan 1984). There have been reports of bullfrogs travelling Bullfrogs may also impact native amphibian distances of 1–2.8 km, over land, to colonize populations through other, less obvious means; new water sources (Willis et al. 1956; Miera such as carrying pathogens which adversely 1999). In their native range, bullfrogs and other affect native frogs. Recent research has Rana species coexist through selective habitat implicated invasive bullfrogs as reservoir hosts preferences, where the bullfrogs primarily select of the chytrid fungus, Batrachochytrium the water margins and other species select dendrobatidis, which if transmitted to some deeper water or more inland locations (Stewart indigenous amphibians can be severely 1USDA/APHIS Wildlife Services, National Wildlife Research Center, 4101 Laporte Avenue, Fort Collins, CO 80521-2154, USA 2Current address: Department of Fisheries and Wildlife, Michigan State University, 13 Natural Resource Bldg., East Lansing, MI 48824, USA *Corresponding author email: [email protected] PACIFIC CONSERVATION BIOLOGY Vol. 17: 285–291. Surrey Beatty & Sons, Sydney. 2011. 286 PACIFIC CONSERVATION BIOLOGY pathogenic (Hanselmann et al. 2004; Pearl and (2007) predicted that highly effective trapping Green 2005; Garner et al. 2006). Additionally, (i.e., removing 25–40% of the population juvenile and subadult bullfrogs have been [McCallum 2006]) could provide a valuable observed initiating interspecific amplexus with means of controlling toads. native frogs, possibly resulting in reproductive There are currently no multiple capture traps interference with negative demographic that are commercially available for bullfrogs; consequences for native ranid populations (Pearl and, to our knowledge, none have been tested et al. 2005). for bullfrogs. Therefore, the goal of this study An immediate solution is needed to reduce or was to test the effectiveness of a multiple capture eradicate localized populations of invasive trap for capturing bullfrogs. We modified a bullfrogs, especially those populations that serve multiple capture trap, originally designed for as reservoirs for new infestations or expanding cane toads (FrogWatch, Darwin, Australia), to be populations. However, bullfrogs are challenging used for bullfrogs. We tested these traps in to control because of their high mobility, ponds along the Rocky Mountain Front Range generalized eating habits, and high reproductive of Colorado, USA that contained bullfrogs capacity (Moyle 1973; Adams and Pearl 2007). resulting from introductions after the 1940s Bullfrogs can live at extremely high densities, (Bury and Whelan 1984). Bullfrogs are and when densities are reduced (e.g., after an considered non-native and invasive throughout unsuccessful eradication), their survival and the state of Colorado by the Colorado Division successful reproductive rates increase (Altwegg of Wildlife (CDOW 2010). Because there is little 2002; Govindarajulu 2004). Hand-capturing, information available on trapping of bullfrogs, netting, spearing (gigging), shooting (Bury and we used various types of attractants within the Whelan 1984; Moler 1994), and electro-shocking traps, and various placements of the traps along (S. A. Orchard, BullfrogControl.com Inc., ponds. We also attempted to identify any non- personal communication) are some of the methods target effects to native species. that have been used to remove bullfrogs. In some cases, habitat manipulation has also been METHODS used (Adams and Pearly 2007). Many of these methods are labour and time intensive, and We conducted trials during September 2008 in often do not reduce bullfrogs to desired levels small ponds near the cities of Windsor and (Miera 1999). Eggs and tadpoles typically are Longmont, Colorado, and again during August destroyed by draining ponds or chemical 2009 in a small pond near the city of Pueblo, treatment (Moler 1994), however these methods Colorado. We placed the traps completely or can have undesired effects on native species, partially in ponds where invasive bullfrogs which are not well understood (e.g., Maret et al. occurred. In all of the ponds, we tested two 2006). Effective traps may provide a more non- identical 69 cm × 69 cm × 25 cm traps intrusive way to reduce bullfrog populations, constructed with 1.3cm × 1.3 cm wire mesh. especially when compared to logistically Three sides of each trap had a one-way door challenging techniques such as hand-capture,