A new record for American Bullfrog (Lithobates catesbeianus) in San Juan, Argentina
Nuevo registro de rana toro americana (Lithobates catesbeianus) en San Juan, Argentina
Eduardo Sanabria1*, Yanina Ripoll1,2, Marcelo Jordan1,2, Lorena Quiroga1, Mariano Ariza2, María Guillemain2, Mauricio Pérez2 and Héctor Chávez2
1 Departamento de Biología, Facultad de Ciencias Exactas Físicas y Naturales, Universidad Nacional de San Juan. Av. Ignacio de la Roza y Meglioli. 5400 San Juan, Argentina.
]]> 2 Subsecretaría de Medio Ambiente, Gobierno de la Provincia de San Juan. Av Ignacio de la Roza y España. 5400 San Juan, Argentina.
*Correspondent:
sanabria.eduardoa@gmail.com
Recibido: 09 marzo 2010
Aceptado: 20 julio 2010
Abstract
We report a new record of Lithobates catesbeianus (American bullfrog) from Argentina. L. catesbeianus was first introduced to San Juan Province 11 years ago in Calingasta Department, where the habitat is pre–cordilleran. The new record is for Zonda Department, San Juan Province, in the Monte desert region. Here, L. catesbeianus uses artificial ponds for reproduction and tadpole development. These ponds receive water from an irrigation system that connects the whole agriculture land in the region. The tadpoles use the irrigation canals to move among ponds. We suggest that legislation should be established to prevent future invasions and to achieve sustainable management of the wild American bullfrog populations in San Juan. Prevention of future invasion and management of established populations of this species requires the cooperation of numerous stake holders.
]]> Key words: Lithobates catesbeianus, invasion, alien species, Monte desert, Argentina.
Resumen
Se presenta un nuevo registro de Lithobates catesbeianus (rana toro americana) en Argentina. L. catesbeianus fue introducida por primera vez a la provincia de San Juan hace 11 años en el Departamento Calingasta, donde el hábitat es pre–cordillerano. El nuevo registro es para el Departamento Zonda en la provincia de San Juan, en el desierto del Monte. En este sitio, L. catesbeianus usa estanques artificiales para la reproducción y desarrollo del renacuajo. Los estanques reciben agua de un sistema de riego que conecta todas las tierras de la agricultura en la región. Los renacuajos utilizan los canales de riego para moverse entre los estanques. Sugerimos que se establezcan leyes para prevenir invasiones futuras y para lograr un manejo integrado de las poblaciones silvestres de rana toro que se encuentran en San Juan. La prevención de futuras invasiones y el manejo de las poblaciones establecidas de esta especie requieren la cooperación de numerosas entidades tanto gubernamentales como privadas.
Palabras clave: Lithobates catesbeianus, invasión, especie exótica, desierto del Monte, Argentina.
The direct and indirect introduction of non–native species by humans is a growing biological concern. The reasons for such introductions are varied and include biological control, human consumption, pet trade, and others (Kraus, 2009). The consequences of these introductions can be destructive to native species and the environment (Begon et al., 2006). Impacts include the extinction or extirpation of natives, biotic homogenization, disruption of food webs, changes in primary productivity of ecosystem, changes in soil formation, and vectors of disease (Kraus, 2009). Lithobates catesbeianus can act as a vector for microorganisms, especially Batrachochytrium dendrobatidis, the pathogen that causes chytridiomycosis in amphibians, which is the principal cause of global amphibian mass mortalities (Berger et al., 1998; Longcore et al., 1999; Ron and Merino, 2000; Daszak et al., 2003).
L. catesbeianus has been widely introduced around the world. In South America, it has been introduced to Brazil (Borges–Martins et al., 2002), Chile (Lever, 2003), Colombia (Rueda Almonacid, 2000), Ecuador (Cisneros–Heredia, 2004), Guayana (Rueda–Almonacid, 1999), Paraguay (Frost, 2009), Perú (Rueda–Almonacid, 1999), Uruguay (Laufer et al., 2008), and Venezuela (Hanselmann et al. 2004). Populations of L. catesbeianus have recently been reported from Argentina in the provinces of San Juan (Sanabria et al., 2005), Misiones (Pereyra et al., 2006), Buenos Aires (Barrasso et al., 2009), Córdoba (Akmentis et al., 2009), and Salta (Akmentis and Cardozo, 2009). Here we report a new population of L. catesbeianus from San Juan Province, Argentina.
We discovered this new population in an agricultural area in Cerro Blanco, Zonda Department, San Juan Province, Argentina (31° 55' S, 68° 70' W; 650 m). The region is part of the phytogeographic province of Monte, which has an arid climate and a mean annual temperature of 17.3 °C (mean annual minimum and maximum: 10.4 and 25.7 °C, respectively) and a mean annual rainfall of 89 mm, which falls mainly in summer (Cabrera, 1994). The dominant native vegetation out of the agricultural region includes Prosopis sp., Larrea sp., Opuntia sp., Trichocereus sp. (Warner, 2004). There are artificial irrigation reservoirs within agricultural lands in this area. Interconnected irrigation canals transfer water from the principal irrigation channel, which is controlled by the provincial Departamento de Hidráulica.
We surveyed the area on 25 March 2009, and searched for reservoirs. At night, we visited 2 artificial ponds, looking for frogs for 2 hours in each one. Tadpoles were collected by hand, euthanized using an overdose of 2% xilocaine, fixed in 10% formalin, and preserved in 70% ethanol.
]]> We captured 12 tadpoles representing various stages of development (6 at stage 25, 5 at stage 40, 1 at stage 42; Gosner, 1960). Five adult males and 7 juveniles were identified but not collected, due to the difficulty in access to the 5 m deep ponds. Males were singing at the time of sighting.These specimens represent the second report of American bullfrogs in San Juan Province. The first record was for Calingasta Department in the pre–cordilleran environment at 1 500 m (Sanabria et al., 2005). The new record is 130 km east of Calingasta and represents an invasion of this species into the more xeric habitat of the Monte desert. In Zonda Department, the system of irrigation channels and artificial ponds connects all agriculture land. We observed tadpoles of L. catesbeianus in the channels and artificial ponds, which provide suitable habitat for the tadpoles to complete their development and for adults to mate. Akmentins and Cardozo (2009) reported the capture of American bullfrogs in ponds and irrigation channels, which the frogs apparently utilize as way of dispersion.
The native range of L. catesbeianus is eastern Canada and the United States to northeastern México (Frost, 2009). Ecologically, the American bullfrog is a highly adaptable species, which has led to its success invading several environments from deserts to tropics (Adams and Pearl, 2007). The ecological impacts of bullfrogs include competition with or even direct consumption of native frogs. Their large size and voracious habits mean that they can decimate often vulnerable populations of myriad aquatic animals (Kraus, 2009). In central Argentina, L. catesbeianus has been reported to feed on amphibians, snakes, mammals, and invertebrates (Akmentins et al., 2009). The reproductive potential, trophic ecology, and prevalence of the parasitic fungus B. dendrobatidis are unknown for introduced populations of bullfrogs. Studies are needed to understand the impacts of this invasive species in San Juan Province and in other regions of Argentina. The American bullfrog was introduced in Argentina for 2 ways. First, by intentional or incidental releases from captive breeding. Second, by home range expansion of a population primarily localized in Rio Grande do Sul, Brazil (Pereyra et al., 2006; Akmentins and Cardozo, 2009). In San Juan, the species was first introduced at least 11 years ago. The lack of government regulation or control over illegal captive–breeding enterprises caused the establishment of numerous wild populations.
This type of finding is important because it provides vital information to determine the distribution of invasive species. Likewise, knowledge about the location of this species allows us to define the territories colonized by American bullfrog and propose control and management of these populations. Also, we suggest that current regulations should be reformed in order to prevent the establishment of additional populations of L. catesbeianus in Argentina. Furthermore, application of control measures and management of previously established populations of L. catesbeianus should employ various control measures while involving local residents and stakeholders as well as academic and governmental institutions.
We thank Robert Espinoza and Rocio Agulilar for your comments and English review. Two anonymous reviewers helped to improve this manuscript.
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