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Economics, Adult Feeding and Larval Growth of Rana catesbeiana on a Fish Hatchery
Abstract
Bullfrogs, Rana catesbeiana, cause considerable economic damage on the fish hatchery studied. Hatchery fish form a major part of the adult diet throughout the nonhibernating season. Each frog eats several dollars worth of fish per year varying with the value of the fish. Food appears to be more important than temperature in both tadpole growth and transformation; tadpoles in a hatchery pond ate the commercial food provided for the fish and grew and transformed at a rate faster than any previously reported. Tadpoles in a stock pond grew at normally expected rates.
... Sin embargo, los alevines encontrados en los estómagos de los jóvenes del presente estudio pueden haber sido aportados por los cuerpos de agua (artificiales) que circulan cercanos a los ranarios, que son desviaciones desde los ríos para producir tilapias, en estanques principalmente. Este comportamiento es corroborado por otros autores que afirman que L. catesbeiana come vorazmente, incluso pequeños vertebrados como los peces (Korschgen y Moyle, 1976;Corse y Metter, 1980), ranas (McKamie y Heidt, 1947;Hays, 1985), tortugas (Corse y Metter, 1980;Graham, 1984), serpientes (Minton, 1949;Smith, 1977), aves (Gollop, 1978), murciélagos (Lee, 1969;Kirkpatric; y comadrejas (Beringery Johnson, 1995), que pueden afectar a mediano plazo a las poblaciones de los animales que consumen. Además del canibalismo, propio de esta especie (Campbell, 1993;Dickerson, 1906;Storer, 1922;Viosca, 1931;Brooks, 1964;Fulk y Whitaker, 1969;Bruneau y Magnin, 1980) las ranas toro no presentaron otras especies de anuros en sus contenidos estomacales, lo que contradice los resultados encontrados por otros autores (Werner et al. 1995;Hayes y Jennings, 1986;McAlpine y Dirworth, 1989;Cross y Gerstenberg, 2002;Carpenteret al., 2002;y Wu et al. 2005), quienes reportan otras especies de anuros en los tractos digestivos de L. catesbeiana. ...
... Sin embargo, los alevines encontrados en los estómagos de los jóvenes del presente estudio pueden haber sido aportados por los cuerpos de agua (artificiales) que circulan cercanos a los ranarios, que son desviaciones desde los ríos para producir tilapias, en estanques principalmente. Este comportamiento es corroborado por otros autores que afirman que L. catesbeiana come vorazmente, incluso pequeños vertebrados como los peces (Korschgen y Moyle, 1976;Corse y Metter, 1980), ranas (McKamie y Heidt, 1947;Hays, 1985), tortugas (Corse y Metter, 1980;Graham, 1984), serpientes (Minton, 1949;Smith, 1977), aves (Gollop, 1978), murciélagos (Lee, 1969;Kirkpatric; y comadrejas (Beringery Johnson, 1995), que pueden afectar a mediano plazo a las poblaciones de los animales que consumen. Además del canibalismo, propio de esta especie (Campbell, 1993;Dickerson, 1906;Storer, 1922;Viosca, 1931;Brooks, 1964;Fulk y Whitaker, 1969;Bruneau y Magnin, 1980) las ranas toro no presentaron otras especies de anuros en sus contenidos estomacales, lo que contradice los resultados encontrados por otros autores (Werner et al. 1995;Hayes y Jennings, 1986;McAlpine y Dirworth, 1989;Cross y Gerstenberg, 2002;Carpenteret al., 2002;y Wu et al. 2005), quienes reportan otras especies de anuros en los tractos digestivos de L. catesbeiana. ...
... Esta puede ser la razón que incide para que no exista una superposición en sus hábitos alimenticios. Existen muchos trabajos sobre hábitos alimenticios donde se menciona la dominancia de presas acuáticas en la dieta de L. catesbeiana (por ej Howard, 1950;Hewitt, 1950;Perez, 1951;Corse y Metter, 1980), pero no son abundantes los estudios sobre dieta en R. marina. ...
Lithobates catesbeiana (rana toro), catalogada entre las peores especies invasoras a nivel mundial, fue introducida en Ecuador en 1988 con fines económicos y desde entonces se han observado numerosas poblaciones ferales; sin embargo, no se ha realizado ningún estudio sobre su impacto hacia las especies nativas. En base a lo reportado en otros países, el presente trabajo investiga la dieta y la superposición de nicho trófico entre Lithobates catesbeiana y Rhinella marina. Se muestrearon 16 ranarios legalmente establecidos donde se abarcó el contorno y fuentes de agua cercanas de cada ranario desde las 19h00 a 22h00. Se caracterizó el contenido estomacal y se midio: talla, peso y estadio de 215 individuos, de los cuales 170 correspondieron a Lithobates catesbeiana y 45 a Rhinella marina; 99 fueron machos, 47 hembras y 67 jóvenes. La fase de campo se realizó entre agosto y noviembre del 2010. Se registraron 1156 presas dentro de 50 categorías dietéticas. El 19,05 % de los adultos presentaron estómagos llenos mientras el 37,78 % de jóvenes tenían estómagos vacíos. Las hormigas fueron las presas más importantes numéricamente de las dos especies de anuros, seguidas por las larvas de dípteros (18,69 %) e isópodos (5,71 %). Volumétricamente, la presa más importante fueron los renacuajos de Lithobates catesbeiana con el 58,44 %, seguida por gasterópoda Pomacea sp. (con 6,29 %) y larva de lepidóptera (5,31 %). No existió superposición de nicho trófico entre Lithobates catesbiana y Rhinella marina.
... it is mostly aquatic and is a generalist predator, reflecting prey availability , including cannibalism (Bury and whelan, 1984). the feeding habits of L. catesbeianus have been studied several times and many of these studies described the occurrence of uncommon prey types for an anuran, such as moles, mice, bats, birds, snakes, lizards, turtles, small alligators, salamanders and fish (Korschgen and Moyle, 1955 ; Cohen and howard , 1958; Korschgen and Baskett, 1963; Brooks Jr., 1964; Corse and Metter, 1980; Bury and whelan, 1984; silva et al., 2007; Camargo filho et al., 2008). the Bullfrog was chosen for commercial exploitation because of its high fecundity, which results in greater performance in captivity than other frog species (vizotto, 1984; fontanelo, 1994). in Brazil, the first individuals of L. catesbeianus arrived in 1935 (fontanello, 1994 ), and since then tadpoles and mature frogs were freely given to producers in order to stimulate the cultivation of this species. ...
... their diets often reflect the availability of prey in their habitats, and they ingest any prey of appropriate size (Korschgen and Baskett, 1963 ; Duellman and trueb, 1994; stebbins and Cohen, 1995). Compared to other frogs, L. catesbeianus seems to be an extremely opportunistic predator (Korschgen and Moyle, 1955; Cohen and howard, 1958; Korschgen and Baskett, 1963; Brooks Jr., 1964; Corse and Metter, 1980; Bury and whelan, 1984; silva et al., 2007; Camargo filho et al., 2008) and the results herein on the diet of invasive populations corroborate this suggestion. insects were the most diverse and abundant prey group in the diet of L. catesbeianus, as observed by Korschgen and Moyle (1955) , Korschgen and Baskett (1963) and Corse and Metter (1980), probably because of their high availability, although this was not evaluated in this study. ...
... Compared to other frogs, L. catesbeianus seems to be an extremely opportunistic predator (Korschgen and Moyle, 1955; Cohen and howard, 1958; Korschgen and Baskett, 1963; Brooks Jr., 1964; Corse and Metter, 1980; Bury and whelan, 1984; silva et al., 2007; Camargo filho et al., 2008) and the results herein on the diet of invasive populations corroborate this suggestion. insects were the most diverse and abundant prey group in the diet of L. catesbeianus, as observed by Korschgen and Moyle (1955) , Korschgen and Baskett (1963) and Corse and Metter (1980), probably because of their high availability, although this was not evaluated in this study. amphibia and Diplopoda also represented a considerable portion of total prey volume (53.9% and 19.9%, respectively). ...
Based on the stomach content analysis of 113 individuals, the diet of the invasive amphibian Lithobates catesbeianus (American Bullfrog) was examined in four sites located within the municipality of Viçosa (20°45′S and 42°51′W), state of Minas Gerais, Brazil, from August 2005 to March 2007. The effects of frog size and sexual maturity on stomach contents were determined. Prey items were grouped according to their primary habitat, being classified as aquatic, terrestrial and amphibious. In general, the most frequent prey categories were post-metamorphic Anura, Diplopoda, Hemiptera, Hymenoptera Formicidae and Araneae. The diet of adults of both sexes was similar, but differed from the diet of young frogs. Terrestrial prey were most abundant both in number and occurrence. For adult Bullfrogs, amphibious prey were most significant in volume. There was a significant correlation between prey and predator sizes, as well as a greater consumption of native anurans by larger Bullfrogs. The results confirmed that Bullfrogs have a generalist feeding habit that can have important negative effects on native amphibian communities in environments occupied by this invasive species.
... Lithobates catesbeianus has a generalised diet (Werner et al. 1995;Hirai 2004;Boelter and Cechin 2007;Texeira Da Silva et al. 2009) consisting primarily of insects and crustaceans, often overlapping with the diet of native frogs (Kupferberg 1997;Kiesecker and Blaustein 1998;Lawler et al. 1999;Kiesecker et al. 2001;Boone et al. 2004). Also, bullfrogs consume small vertebrates such as fish (Korschgen and Moyle 1955;Corse and Metter 1980), frogs (Mckamie and Heidt 1974;Hays 1985;Sanabria and Quiroga 2010), turtles (Corse and Metter 1980;Graham 1984), snakes (Minton 1949), birds (Gollop 1978), bats (Lee 1969) and weasels (Beringer and Johnson 1995). ...
... Lithobates catesbeianus has a generalised diet (Werner et al. 1995;Hirai 2004;Boelter and Cechin 2007;Texeira Da Silva et al. 2009) consisting primarily of insects and crustaceans, often overlapping with the diet of native frogs (Kupferberg 1997;Kiesecker and Blaustein 1998;Lawler et al. 1999;Kiesecker et al. 2001;Boone et al. 2004). Also, bullfrogs consume small vertebrates such as fish (Korschgen and Moyle 1955;Corse and Metter 1980), frogs (Mckamie and Heidt 1974;Hays 1985;Sanabria and Quiroga 2010), turtles (Corse and Metter 1980;Graham 1984), snakes (Minton 1949), birds (Gollop 1978), bats (Lee 1969) and weasels (Beringer and Johnson 1995). ...
The competitive effects among tadpoles make the bullfrog a possible agent of native amphibian population declines at its introduction sites. Our aim was to analyze the dietary composition of an invasive population of Lithobates catesbeianus tadpoles and to evaluate the degree of dietary changes among activity months. We hypothesized that bullfrog tadpoles would exhibit temporal changes in diet, consistent with the variation of tadpole size and availability of resources. We collected 94 bullfrog tadpoles and identified 50 taxa in their digestive tracts. The items most frequently consumed were microalgae of the genera Navicula (frequency of occurrence [Fo] = 19) and Cymbella (Fo = 17). The trophic niche breadth was 8.13, which is considered moderate-high. The trophic habits of L. catesbeianus larvae changed seasonally, with the diets during October and December being numerically similar (Morisita's quantitative index = 0.86). The composition of the diet had a similarity of 63% (Jaccard's qualitative index) between August and October. The larvae of L. catesbeianus collected during the different months showed significant differences in their stages of development and body mass. On average, individuals were larger and more developed in the month of December, which was to be expected given that the abundance of prey items is greatest during the summer season. Our results show that L. catesbeianus tadpoles have a wide trophic niche with a diet that is not strongly selective; thus, the aquatic life-history stages play an important role in the structuring of invaded anuran larval communities.
... Dense populations of tadpoles in commercial ponds can be detrimental in several ways. Tadpoles consume feed intended for fish (Corse and Metter, 1980;Kane et al., 1992). Tadpoles can also interfere with postharvest sorting and grading, resulting in additional labor costs to manually remove them. ...
... Adult bullfrogs cause economic losses to farmers by consuming fish (Corse and Metter, 1980). A study on a Missouri fish farm found that the average fish based meal for a bullfrog consisted of two goldfish or three bait minnows, with each bullfrog consuming approximately 60 meals during its eightmonth active season. ...
... Lithobates catesbeianus has a generalised diet (Werner et al. 1995;Hirai 2004;Boelter and Cechin 2007;Texeira Da Silva et al. 2009) consisting primarily of insects and crustaceans, often overlapping with the diet of native frogs (Kupferberg 1997;Kiesecker and Blaustein 1998;Lawler et al. 1999;Kiesecker et al. 2001;Boone et al. 2004). Also, bullfrogs consume small vertebrates such as fish (Korschgen and Moyle 1955;Corse and Metter 1980), frogs (Mckamie and Heidt 1974;Hays 1985;Sanabria and Quiroga 2010), turtles (Corse and Metter 1980;Graham 1984), snakes (Minton 1949), birds (Gollop 1978), bats (Lee 1969) and weasels (Beringer and Johnson 1995). ...
... Lithobates catesbeianus has a generalised diet (Werner et al. 1995;Hirai 2004;Boelter and Cechin 2007;Texeira Da Silva et al. 2009) consisting primarily of insects and crustaceans, often overlapping with the diet of native frogs (Kupferberg 1997;Kiesecker and Blaustein 1998;Lawler et al. 1999;Kiesecker et al. 2001;Boone et al. 2004). Also, bullfrogs consume small vertebrates such as fish (Korschgen and Moyle 1955;Corse and Metter 1980), frogs (Mckamie and Heidt 1974;Hays 1985;Sanabria and Quiroga 2010), turtles (Corse and Metter 1980;Graham 1984), snakes (Minton 1949), birds (Gollop 1978), bats (Lee 1969) and weasels (Beringer and Johnson 1995). ...
The American bullfrog Lithobates catesbeianus has been introduced around the world, with invasive populations reported from almost all South American countries. A population of this species was introduced in the Calingasta department of San Juan province, which is an arid environment in western Argentina. This work provides information on the dietary composition of an invasive population of L. catesbeianus, and compares the degree of dietary overlap between adults and juveniles. Stomach contents of 169 bullfrogs (82 adults and 87 juveniles) were analysed. Adults consumed 40 prey taxa and Hymenoptera (Insecta) was the most numerous prey item (41.8%), followed by Araneae (13.6%) and Aeglidae (13.4%). Juveniles consumed 29 prey taxa and Hymenoptera constituted the highest percentage in prey number (77.2%). The trophic overlap niche index at the same level shows a value of 0.64 overlap in dietary community between adults and juveniles of this bullfrog. Aeglidae was volumetrically the most important trophic item (25.4%), followed by Anura (25.02%). Our results showed that cannibalism in bullfrogs is more common than the consumption of native anurans, coinciding with that reported in other populations of introduced bullfrogs. The high similarity in the diets of both size classes and the association between the size of the predator and prey suggest that the impact caused by bullfrogs throughout their ontogeny is high and probably has an impact on their prey. Freshwater crabs are the main items in the diet of Lithobates catesbeianus in other introduced populations and are usually the most conspicuous at our study site. The crabs in freshwater ecosystems are part of the lowest trophic level in the food chain. The major threats to the southern region’s freshwater crabs include deforestation, farming and exotic species. Lithobates catesbeianus has a generalist diet and high overlap between adults and juveniles.
... Young and subadult individuals mainly feed on invertebrate prey, often macro-invertebrate tadpole predators such as dragonfly and beetle larvae. Adult bullfrogs are gape-limited generalist predators and eat anything they can manage from invertebrates and amphibians to fish, small rodents, reptiles and birds (Corse & Metter, 1980; Jancowski & Orchard, 2013). Da Silva et al. (2009) found, in an invasive south American population, that for adult bullfrogs, terrestrial prey were most abundant in the diet, with amphibious prey being most significant in volume. ...
... American bullfrog caused considerable damage to a fish hatchery in Missouri used for raising goldfish Carassius auratus for aquarium trade and golden shiners Notemigonus chrysoleucus as fish bait. Both direct predation by adult bullfrogs on fish and eating of commercial food provided for the fish by tadpoles caused an economic loss calculated at $US 42.000 per year (Corse & Metter, 1980). In theory, bullfrogs could inflict similar damage to aquaculture facilities in Belgium. ...
Executive summary
PROBABILITY OF ESTABLISHMENT AND SPREAD (EXPOSURE)
Entry in Belgium The pathways of introduction in Belgium remain largely undocumented. The risk
of escaping American bullfrogs from captivity is currently considered low as
compared to other introduction pathways such as deliberate introductions for
ornamental purposes and accidental introduction through contaminated fish
lots. Natural colonisation from neighbouring countries is considered unlikely.
Establishment capacity American bullfrog has flexible life-history strategies in favour of successful
establishment from only a very limited number of founders. It is a generalist
species that can occupy a broad range wetland habitat types and profits from
human interference in the landscape. The species has a high reproductive
capacity and few natural enemies in Belgium. Belgian climatic variables are well
within it physiological requirements and climatic conditions are not limiting
successful establishment. Meanwhile, it is well established in Belgium for more
than a decade and has invaded areas of conservation concern.
Dispersion capacity Natural dispersal in American bullfrog can be considerable (> 1km/year).
Translocation by humans often complements natural spread.
EFFECT OF ESTABLISHMENT
Environmental impacts There is substantial evidence that American bullfrog may negatively affect
native amphibians through competition for resources and through direct and
indirect predation effects. The effects will be enhanced when species are under
pressure from other factors, such as habitat loss, fragmentation, habitat
degradation or the presence of invasive fish. Moreover, the bullfrog is a vector
of a number of important amphibian diseases that have been implicated in
amphibian declines in Europe and throughout the world.
RISK MANAGEMENT
The relative importance of accidental importation (e.g. through fish stocking) versus natural dispersal or
secondary translocations is unknown. Accidental importation of bullfrog larvae hitchhiking in fish stocking
lots for angling, is also a pathway to consider. The extent of this phenomenon is however unknown. As
there are no reports on farming facilities in Belgium, these pathways are likely to be more important than
escapes from rearing facilities. Data on trade of American bullfrog (e.g. in pet shops, on internet) are
lacking. In light of these uncertainties, the precautionary principle seems an appropriate way to reduce
the risk of both deliberate and accidental importations of American bullfrog in Belgium. The species can
easily be overlooked at early stages of invasion. Small, isolated populations can be removed but large
interconnected metapopulations are extremely hard to tackle and eradication or control is probably only
feasible at very high cost here. Therefore, prevention of further spread, a targeted action plan for existing
populations and a dedicated early warning are crucial in tackling this invasive alien in Belgium.
... The general trophic spectrum reported for Lithobates catesbeianus diets (Werner et al., 1995;Daza-Vaca and Castro-Herrera, 1999;Hirai, 2004) is consistent with results of the present study (Table 1). However, as reported in other studies, L. catesbeianus can also prey on larger animals such as birds (Gollop, 1978;Wu et al., 2005), turtles (Corse and Metter, 1980;Graham, 1984), snakes (Minton, 1949), bats (Lee, 1969;Kirkpatric, 1982), and weasels (Beringer and Johnson, 1995). Several studies demonstrate that aquatic prey and frogs constitute a substantial portion of the bullfrog diet (Korschgen and Moyle, 1976;Corse and Metter, 1980;Werner et al., 1995;Hirai, 2004;Wu et al., 2005). ...
... However, as reported in other studies, L. catesbeianus can also prey on larger animals such as birds (Gollop, 1978;Wu et al., 2005), turtles (Corse and Metter, 1980;Graham, 1984), snakes (Minton, 1949), bats (Lee, 1969;Kirkpatric, 1982), and weasels (Beringer and Johnson, 1995). Several studies demonstrate that aquatic prey and frogs constitute a substantial portion of the bullfrog diet (Korschgen and Moyle, 1976;Corse and Metter, 1980;Werner et al., 1995;Hirai, 2004;Wu et al., 2005). We observed similar diet characteristics in adult bullfrogs from 9 de Julio district. ...
Several previous studies have established that the introduction of the American bullfrog, Lithobates catesbeianus, produces negative effects on native communities. Herein, the American bullfrog is reported for the first time in the province of Buenos Aires, Argentina in the locality of 9 de Julio. The stomach contents of the collected specimens were examined and the reproduction of the species was also confirmed at the study area. A total of 85.7% (n = 30) of the analyzed stomachs contained prey items, and eleven of these were identified. The prey items belonged mostly to coleopterans (50%) and vertebrates (11%). The pathogen Batrachochytrium dendrobatidis was not found on skin samples examined. The installation of Lithobates catesbeianus breeding facilities contributes to the incidental release of this species. A tightening of rules in the regulation of aquaculture activities and the use of control programs for naturalized populations are necessary to address the increasing dispersion of the species in Argentina and potential ecological problems.
... Rana catesbeiana is native to the eastern United States, occurring naturally as far west as the great plains (Nussbaum et al. 1983; Stebbins 1985 ). Bullfrogs, however , have been extensively introduced throughout much of the western United States, including much of Oregon west of the Cascade mountains (Nussbaum et al. 1983; Hayes & Jennings 1986; Stebbins & Cohen 1995). Adult bullfrogs feed on a variety of aquatic prey, including other amphibians (Corse & Metter 1980; Bury & Whelan 1986; Beringer & Johnson 1995; Werner et al. 1995). Both tadpoles and adults of R. catesbeiana prey on tadpoles of other species (Ehrlich 1979; Bury & Whelan 1986; Werner et al. 1995; Kiesecker & Blaustein 1997 b ). ...
... Larvae likely shifted position to avoid predation by adult R. catesbeiana. Adult R. catesbeiana are aquatic predators consuming a broad diversity of prey, including other amphibians (Corse & Metter 1980; Bury & Whelan 1986; Clarkson & DeVos 1986; Schwalbe & Rosen 1988; Beringer & Johnson 1995; Werner et al. 1995 ). The use of deep water by R. aurora in the presence of adult R. catesbeiana may be an effective way for tadpoles to avoid predation. ...
We examined the direct and indirect effects of two introduced species, the bullfrog ( Rana catesbeiana ) and smallmouth bass ( Micropterus dolomieui ), on the microhabitat use, growth, development, and survival of larval and metamorphic red‐legged frogs ( Rana aurora ). In field enclosure experiments, tadpoles of R. aurora altered their microhabitat use in the presence of both species. The shift in microhabitat use by R. aurora corresponded to increased activity in adult R. catesbeiana . Time to metamorphosis increased and mass at metamorphosis decreased when R. aurora tadpoles were exposed to either larval or adult R. catesbeiana . In contrast, smallmouth bass alone had little effect on the growth and development of R. aurora . In all experiments, survivorship of R. aurora was significantly affected only when R. aurora were exposed to the combined effects of bullfrog larvae and adults or bullfrog larvae and smallmouth bass. Thus, the interaction between stages (larval‐adult) or species (bullfrog–smallmouth bass) produced indirect effects that were greater than when each factor was considered separately.
Efectos de la Introducción de la Rana toro Rana catesbeiana y el Pez Micropterus dolomieui en el Uso del Microhabitat, Crecimiento y Supervivencia de la Rana patiroja Rana aurora
Examinamos los efectos directos e indirectos de dos especies introducidas; la rana toro Rana catesbeiana y el pez Micropterus dolomieui en el uso del microhabitat, crecimiento, desarrollo y supervivencia de la Rana patiroja Rana aurora en estados larvales y metamórficos. En encierros experimentales de campo, los renacuajos de R. aurora alteraron el uso de su microhábitat en presencia de ambas especies. El cambio en uso de microhábitat por R. aurora correspondió con un incremento en la actividad de adultos de R. catesbeiana . El tiempo de metamorfósis incrementó y la masa durante metamorfósis disminuyó cuando los renacuajos de R. aurora fueron expuestos tanto a larvas como adultos de R. catesbeiana . En contraste, la presencia de solo Micropterus dolomieui tuvo poco efecto en el crecimiento y desarrollo de R. aurora . En todos los experimentos la supervivencia de R. aurora fue significativamente afectada solo cuando R. aurora estuvo expuesta a los efectos combinados de larvas y adultos de la rana toro y el pez. Por lo tanto, la interacción entre estados (larval/adulto) o especies ( rana toro /Micropterus) produjo efectos indirectos que fueron mayores que cuando cada factor se consideró por separado.
... 200 mm) and wide food habits (Bury and Whelan, 1984), the adults can nearly eat anything smaller than their mouths (Dickerson, 1931;Bury and Whelan, 1984). Previous studies have shown that their diets are mainly composed of invertebrates such as insects and crayfishes (Procambarus clarkii) (Frost, 1935;Penn, 1950;Korschgen and Moyle, 1955;Cohen and Howard, 1958;Hirai, 2004) as well as small vertebrates such as fishes (Korschgen and Moyle, 1955;Corse and Metter, 1980), frogs (Cohen and Howard, 1958;McAlpine and Dilworth, 1989;Werner et al., 1995), turtles (Corse and Metter, 1980;Clarkson and Devos, 1986), snakes (Minton, 1949;Korschgen and Moyle, 1955;McAlpine and Dilworth, 1989), birds (Howard, 1950;Hewitt, 1950;Ló pez-Flores et al., 2003) and small mammals (McAlpine and Dilworth, 1989;Werner et al., 1995). Therefore, the bullfrogs have a potential to exert a serious impact on biodiversity and ecosystems. ...
... 200 mm) and wide food habits (Bury and Whelan, 1984), the adults can nearly eat anything smaller than their mouths (Dickerson, 1931;Bury and Whelan, 1984). Previous studies have shown that their diets are mainly composed of invertebrates such as insects and crayfishes (Procambarus clarkii) (Frost, 1935;Penn, 1950;Korschgen and Moyle, 1955;Cohen and Howard, 1958;Hirai, 2004) as well as small vertebrates such as fishes (Korschgen and Moyle, 1955;Corse and Metter, 1980), frogs (Cohen and Howard, 1958;McAlpine and Dilworth, 1989;Werner et al., 1995), turtles (Corse and Metter, 1980;Clarkson and Devos, 1986), snakes (Minton, 1949;Korschgen and Moyle, 1955;McAlpine and Dilworth, 1989), birds (Howard, 1950;Hewitt, 1950;Ló pez-Flores et al., 2003) and small mammals (McAlpine and Dilworth, 1989;Werner et al., 1995). Therefore, the bullfrogs have a potential to exert a serious impact on biodiversity and ecosystems. ...
Bullfrogs (Rana catesbeiana) are listed as one of the 100 worst invasive alien species in the world. They are generalist predators and thus may affect
native species through predation. In previous studies, the food contents of bullfrogs were mostly examined at a single site.
In the present study, the diet composition of post-metamorphic bullfrogs on eight islands (Daishan, Liuheng, Xiushan, Fodu,
Taohua, Xiashi, Cezi, and Putuoshan) in the Zhoushan Archipelago, Zhejiang Province of China, were examined by using the stomach
flushing method from June 30 to August 11 in 2005. A total of 391 individual frogs were measured, including 113 adults and
278 juveniles. The analysis of the stomach contents shows that, for adult bullfrogs, the most important prey (by diet volume)
overall were Decapoda, Coleoptera, Odonata, Mesogastropoda, Raniformes, and Cypriniformes. For juvenile bullfrogs, these were
Decapoda, Coleoptera, Cypriniformes, Odonata, Orthoptera, Hymenoptera, Lepidoptera larvae, Mesogastropoda, and Raniformes.
Moreover, the prey size and diet volume increased with the body size of both adult and juvenile bullfrogs. The diet composition
of primary preys of bullfrogs was significantly different among the islands. The results indicate that bullfrogs exert different
predatory influences on native fauna at different sites and that bullfrogs are generalist predators with extensive ecological
impacts on native fauna.
... American bullfrogs also typically remain around the breeding sites during and outside their breeding season (end of May to mid-June in South Korea) (Sung et al., 2006). Third, adult American bullfrogs are generalist predators that consume most prey that will fit in their mouths, including amphibians and reptiles (Tyler and Hoestenbach, 1979;Corse and Metter, 1980;Kang and Youn, 1994). Smaller gold-spotted pond frogs are more likely to be preyed on by the American bullfrog (Wang et al., 2007). ...
... The possible impacts of terrestrial bullfrogs as predators and competitors are considerable, but difficult to quantify. Adult bullfrogs are generalist consumers with a broad taxonomic spectrum of prey (Korschgen and Moyle 1955, Korschgen and Baskett 1963, Corse and Metter 1980, Clarkson and DeVos 1986, notably including other amphibians (Cohen and Howard 1958, Stewart and Sandison 1972, Smith 1977, Hayes and Warner 1985. Bullfrogs could eat native tadpoles and metamorphs, as they are known to cannibalize their own (Schwalbe and Rosen 1988). ...
... Lithobates catesbeianus is considered an opportunistic generalist predator (Bury & Whelan, 1984), although the present results only partially confirm this suggestion. The high trophic position occupied by adults at the study site confirmed the capability of the species to feed on different kinds of prey, such as frogs (Sanabria & Quiroga, 2010;Silva et al., 2009;Silva et al., 2011), fish (Corse & Metter, 1980;Korschgen & Moyle, 1955;McAuliffe, 1978), crayfish (Hirai, 2004;Liu et al., 2015;Wu, Li, Wang, & Adams, 2005), and insects (Bury & Whelan, 1984;Govindarajulu, Price, & Anholt, 2006;Stewart & Sandison, 1972). Although adults are able to consume a broad range of prey taxa, a few prey types dominated their diet Werner et al., 1995). ...
... On fish farms, the economic damage depends in part on the unit value of the fish produced. Corse and Metter (1980) provided data suggesting that a 350-pond farm that produced goldfish might sustain $42,000 in annual losses to bullfrogs, whereas the same facility might sustain only $12,600 in losses if it produced golden shiners, a less valuable species. It follows that losses might be still higher on farms specializing in valuable aquarium fishes. ...
Frogs and toads are amphibians with four legs and no tail. At least 85 species of frogs are native to the United States, and there are three well-established exotic species. Frogs occur in almost all nonmarine habitats. Most frogs have a two-phased life cycle, including an aquatic larval form (tadpole) and a terrestrial or semiaquatic adult form. Although some species spend most of their adult lives away from water, most frogs native to North America must return to water to lay eggs. The greatest potential for economic damage is at fish farms and hatcheries. Laws pertaining to frogs vary from state to state.
... La rana toro es la especie más grande de Norteamérica y es nativa de la parte oriental de Canadá y los Estados Unidos de América (Stebbins 2003, Frost 2009); es una especie voraz, un depredador oportunista y competidor allá donde ha invadido o ha sido introducida (Casper y Hendricks 2005). Los individuos jóvenes y subadultos pueden alimentarse de invertebrados, pero los adultos se alimentan de distintos ítems, que incluyen diversos tipos de invertebrados, anfibios, peces, pequeños roedores, reptiles y aves (Corse y Metter 1980, Albertini y Lanza 1987, Beringer y Johnson 1995. También se ha documentado la ocurrencia de canibalismo en esta especie (Bury y Whelan 1984, Stuart y Painter 1993. ...
La rana toro Lithobates catesbeianus es considerada una de las 100 especies exóticas invasoras más importantes a nivel mundial. No se conocen aspectos de su ecología alimentaria, particularmente en el noroeste de Chihuahua, por ello se realizó el estudio en Ojo Caliente y Rancho San Pedro, Janos. Entre
julio y octubre de 2009, se capturaron 96 individuos en colectas nocturnas (288 hrs/ hombre). El 76% (n=73) de los individuos presentaron partículas alimentarias para los cuales se calcularon los valores porcentuales. Los valores mayores calculados fueron para coleópteros: 18.89% N, 32.74% FO y 26.06% V, seguido por Orthoptera (13.89% N, 24.22% FO y un 12.72% V), además se encontraron vertebrados como presas (Bufo debilis y Thamnophis sp.), los cuales se encuentran en alguna categoría de riesgo de acuerdo con la NOM-
059-Semarnat-2010, destacando el impacto de la rana toro sobre las especies nativas. Se calculó la amplitud de nicho trófico, el cual arrojó un valor de 0.26 para el total de los ejemplares, para machos un valor del 0.26, las hembras 0.47 y juveniles 0.42, con ello, podemos concluir que los machos tienden
a ser generalistas, mientras las hembras y los juveniles son especialistas en el área de estudio. Estos resultados son de utilidad para justificar la creación e implementación de un programa de erradicación de la rana toro en los sistemas acuáticos.
... La rana toro es la especie más grande de Norteamérica y es nativa de la parte oriental de Canadá y los Estados Unidos de América (Stebbins 2003, Frost 2009); es una especie voraz, un depredador oportunista y competidor allá donde ha invadido o ha sido introducida (Casper y Hendricks 2005). Los individuos jóvenes y subadultos pueden alimentarse de invertebrados, pero los adultos se alimentan de distintos ítems, que incluyen diversos tipos de invertebrados , anfibios, peces, pequeños roedores, reptiles y aves (Corse y Metter 1980, Albertini y Lanza 1987, Beringer y Johnson 1995). También se ha documentado la ocurrencia de canibalismo en esta especie (Bury y Whelan 1984, Stuart y Painter 1993). ...
La rana toro Lithobates catesbeianus es considerada una de las 100 especies
exóticas invasoras más importantes a nivel mundial. No se conocen aspectos
de su ecología alimentaria, particularmente en el noroeste de Chihuahua,
por ello se realizó el estudio en Ojo Caliente y Rancho San Pedro, Janos. Entre
julio y octubre de 2009, se capturaron 96 individuos en colectas nocturnas
(288 hrs/ hombre). El 76% (n=73) de los individuos presentaron partículas
alimentarias para los cuales se calcularon los valores porcentuales. Los valores
mayores calculados fueron para coleópteros: 18.89% N, 32.74% FO y 26.06%
V, seguido por Orthoptera (13.89% N, 24.22% FO y un 12.72% V), además
se encontraron vertebrados como presas (Bufo debilis y Thamnophis sp.), los
cuales se encuentran en alguna categoría de riesgo de acuerdo con la NOM-
059-Semarnat-2010, destacando el impacto de la rana toro sobre las especies
nativas. Se calculó la amplitud de nicho trófico, el cual arrojó un valor de
0.26 para el total de los ejemplares, para machos un valor del 0.26, las hembras
0.47 y juveniles 0.42, con ello, podemos concluir que los machos tienden
a ser generalistas, mientras las hembras y los juveniles son especialistas en el
área de estudio. Estos resultados son de utilidad para justificar la creación e
implementación de un programa de erradicación de la rana toro en los sistemas
acuáticos.
Palabra clave: rana toro, Lithobates catesbeianus, dieta, Chihuahua, Janos.
... Los peces presentaron el segundo índice más alto (1= 14.98). En Missouri (USA) se estimó que una rana adulta alcanza a consumir en un período de ocho meses en promedio 120 peces dorados (Carassius auratus), para el año de 1980 el costo de estos peces era de US $12.00, ésta es la pérdida por cada rana toro que resida en los estanques, Corse & Metter (1980). Este comportamiento ictiófago podría afectar la piscicultura del Valle del Cauca, debido a que esta actividad es común en la zona de muestreo. ...
... )、龟类(Corse & Metter, 1980; Clarkson & Devos, 1986)、蛇类(Minton, 1949; Korschgen & Moyle, 1955; McAlpine & Dilworth, 1989) 、 鸟 类 (Howard, 1950; Hewitt, 1950; López-Flores et al., 2003)、小型兽类(McAlpine & Dilworth, 1989; Werner et al., 1995)等多种脊椎动 ...
... Los peces presentaron el segundo índice más alto (1= 14.98). En Missouri (USA) se estimó que una rana adulta alcanza a consumir en un período de ocho meses en promedio 120 peces dorados (Carassius auratus), para el año de 1980 el costo de estos peces era de US $12.00, ésta es la pérdida por cada rana toro que resida en los estanques, Corse & Metter (1980). Este comportamiento ictiófago podría afectar la piscicultura del Valle del Cauca, debido a que esta actividad es común en la zona de muestreo. ...
Daza, J. D y F. Castro. Hábitos alimenticios de la rana toro (Rana catesbeiana) Anura: Ranidae en el Valle del Cauca, Colombia. Rev. Acad Colomb. Cienc. Vol XXIII (suplemento especial):265-274. 1999 RESUMEN Los hábitos alimenticios de Rana catesbeiana fueron determinados por medio del análisis del contenido estomacal de 544 ranas, procedentes de 18 localidades en el Valle del Cauca. Se
... Adult bullfrogs are established predators of tadpoles (e.g., Whelan 1986, Werner et al. 1995). However, most anuran larvae, including R. catesbeiana, are thought to be primarily herbivorous filter feeders or grazers on algae or detritus (Wright and Wright 1949, Dickman 1968, Thrall 1972, Corse and Metter 1980, Wassersug 1980, Duellman and Trueb 1986. Except for the specialized larvae of some cannibalistic species (e.g., Bragg 1964, Pomeroy 1981, Crump 1983, predation by tadpoles on other species has rarely been reported (e.g., Heyer et al. 1975, Kluge 1981, Duellman and Trueb 1986. ...
We studied eight populations of the red-legged frog, Rana aurora, to examine responses of allotopic and syntopic tadpoles to the bullfrog, Rana catesbeiana, an introduced predator of R. aurora. We also assessed predation rates by R. catesbeiana on syntopic and allotopic populations of R. aurora. Syntopic R. aurora tadpoles significantly reduced their activity and increased their refuge use when presented with the chemical cues of both tadpoles and adult R. catesbeiana. In contrast, allotopic tadpoles did not significantly alter their behavior in the presence of either R. catesbeiana adults or larvae. Predation by R. catesbeiana was lower in syntopic than in allotopic populations of R. aurora tadpoles. Our results show differential responses of syntopic and allotopic R. aurora tadpoles to larval and adult R. catesbeiana. Syntopic tadpoles avoid predation by R. catesbeiana more efficiently than do tadpoles from allotopic populations. Apparently, individuals that are unfamiliar with novel, introduced organisms may not possess adaptations that would prevent a negative encounter.
... The possible impacts of terrestrial bullfrogs as predators and competitors are considerable, but difficult to quantify. Adult bullfrogs are generalist consumers with a broad taxonomic spectrum of prey (Korschgen and Moyle 1955, Korschgen and Baskett 1963, Corse and Metter 1980, Clarkson and DeVos 1986, notably including other amphibians (Cohen and Howard 1958, Stewart and Sandison 1972, Smith 1977, Hayes and Warner 1985. Bullfrogs could eat native tadpoles and metamorphs, as they are known to cannibalize their own (Schwalbe and Rosen 1988). ...
I studied the invasion of Rana catesbeiana (the bullfrog) into a northern California river system where bullfrogs are not native. Native yellow-legged frogs, Rana boylii, a species of special concern, were almost an order of magnitude less abundant in reaches where bullfrogs were well established. I assessed the potential role of larval competition in contributing to this displacement in a series of field manipulations of tadpole density and species composition. The impact of R. catesbeiana on native tadpoles in the natural community agreed with the outcome of more artificial experiments testing pairwise and three-way interactions. In 2-m2 enclosures with ambient densities of tadpoles and natural river biota, bullfrog tadpoles caused a 48% reduction in survivorship of R. boylii, and a 24% decline in mass at metamorphosis. Bullfrog larvae had smaller impacts on Pacific treefrogs, Hyla regilla, causing 16% reduction in metamorph size, and no significant effect on survivorship. Bullfrog tadpoles significantly affected benthic algae, although effects varied across sites. Responses to bullfrogs in field settings were similar qualitatively to results seen in smaller-scale experiments designed to study size-structured competition among disparate age/size classes of species pairs and trios. Competition from large over-wintering bullfrog larvae significantly decreased survivorship and growth of native tadpoles. Competition from recently hatched bullfrog larvae also decreased survivorship of R. boylii and H. regilla. Native species competed weakly, both interspecifically and intraspecifically. The only suggestion of a negative impact of a native species on bullfrogs was a weak effect of H. regilla on recent hatchlings. Competition appeared to be mediated by algal resources, and there was no evidence for behavioral or chemical interference. These results indicate that, through larval interactions, bullfrogs can exert differential effects on native frogs and perturb aquatic community structure.
... The impact of predatory adult frogs in fish pond production should not be overlooked. Bullfrogs were responsible for an estimated loss of $43,800 of goldfish and minnows at a fish hatchery in Missouri in one year (Corse and Metter 1980). Data from this survey and other reports indicate that tadpole infestations cause economic damage and production hindrance in warmwater fish pond culture. ...
A survey was conducted to evaluate the effect of tadpole infestations on warmwater fish pond culture. The survey was sent to 174 pond culturists in Florida and 30 in Arkansas with a 21% overall response rate. Most respondents believed: (1) tadpole infestation was a serious problem, primarily due to competition between tadpoles and fish for food; (2) tadpoles caused harvest problems and impaired post-harvest sorting and grading; and (3) their tadpole control efforts were ≤30% effective. It was estimated that an average of 117 worker-hours of labor per surveyed facility were expended annually to contend with tadpole-related problems. Financial losses due to tadpoles were 10,000–30,000 per year for others (36%). Annual losses of revenue from ornamental fish production in Florida (based on survey) and baitfish production in Arkansas (U.S. Fish and Wildlife Service) due to tadpole infestations were estimated at 6.2 million, respectively.
... In addition, some older literature describes tadpoles generically, without reference to a particular stage, or only in terms of body size or length (e.g., Larsell 1934;Paterson 1949/50;Sedra and Michael 1959;van Bergeijk 1959). Because body size is influenced by diet, temperature, and rearing condition (Corse and Metter 1980;Nieuwkoop and Faber 1994;McDiarmid and Altig 1999), it can vary widely among individuals even at the same stage of development, making classification based on this parameter unreliable. McDiarmid and Altig (1999) propose that the Gosner (1960) classification, first described for Rana, be used as a standard staging system, and they provide a table of approximation between Gosner stages and other staging systems often used. ...
... American bullfrogs also typically remain around the breeding sites during and outside their breeding season (end of May to mid-June in South Korea) (Sung et al., 2006). Third, adult American bullfrogs are generalist predators that consume most prey that will fit in their mouths, including amphibians and reptiles (Tyler and Hoestenbach, 1979;Corse and Metter, 1980;Kang and Youn, 1994). Smaller gold-spotted pond frogs are more likely to be preyed on by the American bullfrog (Wang et al., 2007). ...
We used field surveys and statistical models to investigate habitat associations of the endangered gold-spotted pond frog (Rana chosenica). The characteristics of its habitat are of great importance for effective conservation for this declining species in western South Korea. We evaluated a priori models that incorporated biotic and abiotic variables at the pond and landscape scales. The best-ranked model predicts that gold-spotted pond frogs will be more abundant at sites with fewer introduced American bullfrogs (Rana [= Lithobates] catesbeianus) and greater coverage of shallow, vegetated water. Our study leads us to conclude that limiting the spread and abundance of bullfrogs has the potential to aid conservation of the gold-spotted pond frog in our region.
... These correlations were also significant for the subset of frogs used for physiological analyses (see below). SVL can vary at completion of metamorphosis and during postmetamorphic development due to variations in diet and temperature (Corse and Metter 1980). This implies that SVL alone may not be a good indicator of absolute age. ...
During metamorphosis, the lateral line system of ranid frogs (Rana catesbeiana) degenerates and an auditory system sensitive to airborne sounds develops. We examined the onset of function and developmental changes in the central auditory system by recording multi-unit activity from the principal nucleus of the torus semicircularis (TSp) of bullfrogs at different postmetamorphic stages in response to tympanically-presented auditory stimuli. No responses were recorded to stimuli of up to 95 dB SPL from late-metamorphic tadpoles, but auditory responses were recorded within 24 hours of completion of metamorphosis. Audiograms from froglets (SVL < 5.5 cm) were relatively flat in shape with high thresholds, and showed a decrease in most sensitive frequency (MSF) from about 2500 Hz to about 1500 Hz throughout the first 7-10 days after completion of metamorphosis. Audiograms from frogs larger than 5.5 cm showed continuous downward shifts in MSF and thresholds, and increases in sharpness around MSF until reaching adult-like values. Spontaneous activity in the TSp increased throughout postmetamorphic development. The torus increased in volume by approximately 50% throughout development and displayed changes in cell density and nuclear organization. These observations suggest that the onset of sensitivity to tympanically presented airborne sounds is limited by peripheral, rather than central, auditory maturation.
... Species such as Hyla, Bufo and Scaphiopus tend to undergo metamorphic development very rapidly in shallow, temporary bodies of water (Crump, 1989;Newman, 1989 ;Beck, 1997). Bullfrog tadpoles, on the other hand, often live in ponds of several meters depth, and can remain in their larval form from about 3 months to up to 2 years (Corse and Metter, 1980;unpublished observations). Evolutionary pressures leading to extended larval life in a complex, semi-permanent aquatic environment would impose a need for the animal to be able to move through the water without inducing profound variability in the function of the inner ear. ...
Histological and immunohistochemical analyses of head and respiratory structures in bullfrog (Rana catesbeiana) tadpoles were undertaken to address the hypothesis that the bronchial columella (BC) is the primary sound conduction pathway in these larval anurans. In postembryonic tadpoles, the BC is composed of fibroblasts surrounded by a Type I collagen matrix, with Type II collagen located in basement membranes at the distal ends. It provides a highly flexible tendon-like attachment between the round window and the membranous sac of the primary bronchus of the ipsilateral lung. As the animals approach metamorphic climax stages, the fibroblasts decrease in number and the BC becomes almost exclusively collagenous. During metamorphic climax, the BC degenerates and is completely resorbed by the time the animal becomes a postmetamorphic froglet. At all larval stages examined, the BC is structurally and immunohistochemically different from both the opercularis muscle of tadpoles and the tympanic columella (stapes homolog) of postmetamorphic animals. These observations suggest that the BC may not be rigid enough to provide an effective coupling between the lungs and the round window. An alternative hypothesis for the function of the BC, based on its structure, is presented.
... For this reason, we included at least one, and often two, images per stage group to identify any within-stage group changes (because of limitations of file size for uploading the morph videos, more images could not be included). Use of external stages rather than temporal measures such as embryonic day is a necessity with ranids due to their highly variable and environmentally dependent development rates (Corse and Metter, 1980). Images are derived from the following specimens: medulla, 8 animals [1 hatchling (stage 22), 2 early larval (stages 25, 33), 2 late larval (stages 36, 37), 1 deaf period (stage 40), 1 climax (stage 43), 1 froglet]; midbrain, 7 animals [1 hatchling (stage 22), 2 early larval (stages 25, 30), 1 late larval (stage 37), 1 deaf period (stage 40), 1 climax (stage 43), 1 froglet]; thalamus, 7 animals (1 hatchling (stage 22), 1 early larval (stage 30), 1 late larval (stage 35), 1 deaf period (stage 40), 2 climax (stage 43, 45) 1 froglet]. ...
Anuran amphibians undergo a rapid and dramatic process of metamorphosis featuring widespread structural reorganization of the central nervous system. Although morphological changes during embryonic stages of anuran development have been well documented, much less information is available describing structural changes in the brain during larval (tadpole) stages. Using still images from cresyl-violet-stained material, we present an adaptation of the digital image and video manipulation technique of morphing that allows these images to be compiled in such a manner as to highlight key periods in tadpole brain development in a dynamic fashion. We present three morphed video data sets from ranid tadpoles that facilitate the identification of developmental changes in nuclear boundaries at different levels of the neuraxis. The use of animation allows dynamic examination of anatomical changes across long developmental spans without requiring additional anatomical preparations or specialized expensive equipment.
The study investigated predation risk to pond-reared Nile Tilapia Oreochromis niloticus and African Catfish Clarias gariepinus by amphibians, whether this is driven by height of pond-side grass or pond proximity to surface-water source and how this varies with fish stocking options. Based on small-scale freshwater aquaculture farms in western Kenya, field surveys were conducted during three sampling seasons spread across 6 months. These involved the following: (1) a sociological survey of 29 fish farming households; (2) sampling of amphibians for density, species richness and encounter rates and (3) measuring grass height, pond dimensions and water-source proximity across 24 ponds. Overall, 131 individual frogs from three families were recorded in 78 encounters. Amphibian density increased with pond-side grass height, presumably increasing predation risk, but decreased with water-source proximity. Amphibian encounter rate also decreased with water-source proximity, but was unaffected by grass height, while species richness responded positively to pond-side grass height, but not to water-source proximity. Amphibian encounter likelihood was higher in tilapia-only than in catfish-only or tilapia and catfish ponds irrespective of habitat variables. We demonstrate here that management practices for mitigating fish loss to predatory amphibians should include trimming pond-side vegetation, siting ponds close-to-moderate distances from water-sources and including catfish in pond polycultures.
This study was conducted to clarify diet items and predatory behavior of American bullfrog (Lithobates catesbeianus) according to the sex, maturity and season from April to September 2014 at Gahang wetland of Changnyeong-gun, Gyeongsangnamdo province, Korea. We examined the stomach contents of L. catesbeianus using a gastrectomy technique and identified the contents to a genus or species. The examination showed that
large and heavy individual of L. catesbeianus fed on larger amounts of food. However, there were no statistically significant differences in predation amount according to the sex and maturity of L. catesbeianus. The main diet item of during the study period was mostly Insecta (average population rate of 65.5%), followed by Crustacea (13.5%) and Gastropoda (7.9%). The most preferred diet item of L. catesbeianus was Muljarus japonicus. Surprisingly, L. catesbeianus also foraged Parus major, Apodemus agrarius, and Crocidura lasiura. This findings showed that L. catesbeianus directly disturbed the wetland ecosystem. We expect the results will be the important reference data for checking the impact of L. catesbeianus, which is designated as invasive species by the Ministry of Environment, on wetland ecosystem.
The Sacramento-San Joaquin Delta (Delta) is a heterogeneous, highly modified aquatic system. I reviewed relevant predator-prey theory, and described extant data on predator-prey relationships of Delta fishes. I ranked predator consumption rates as occasional, moderate, and common, based on frequency-of-occurrence data, and evaluated the frequency, and hypothesized the effects of predation on native and invasive species. I identified 32 different predator categories and 41 different prey categories. Most predators were occasional consumers of individual prey species, although I also observed moderate and common consumption of some prey types. My analysis yielded few generalizations regarding predator-prey interactions for Delta fishes; most predators consumed a variety of both native and invasive fishes. The only evidence for predator specialization on either native or invasive fishes occurred in Prickly Sculpin which, when it consumed fishes, ate mostly native species. Both Striped and Largemouth Bass exhibited wide dietary breadth, preying upon 32 and 28 categories of fish prey respectively. Sacramento Pikeminnow, a native predator, also displayed wide dietary breadth of piscine prey, with 14 different prey categories consumed. Data for reptilian, avian, and mammalian predators were sparse; however, these predators may be significant fish predators in altered habitats or when hatchery salmonids are released. The database for predators and their fish prey was not strong, and I recommend long-term dietary studies combined with prey availability and behavioral and experimental studies to establish predator preferences and antipredator behaviors, rather than just consumption. The behavioral effects of contaminants on prey species also warrant further examination. Although it has been suggested that a reduction in the Striped Bass population be implemented to reduce predation mortality of Chinook Salmon, the large number of salmon predators in the Delta make it unlikely that this effort will significantly affect salmon mortality.
The bullfrog (Lithobates-catesbeianus) has been introduced oft several continents, causing impacts on native species. In an area in southern Brazil with high bullfrog density, we studied this species predation on native fauna by analyzing'the diet of 291 specimens collected between May 2002 and June. 2003. The Pinks index was used to verify the importance of items found in the stomach content, which were then classified according to their relative importance (RI). The bullfrog diet in natural environments revealed that the most consumed items in order of relative importance Were adul anura, Araneae, Coleoptera,Hemiptera, Odonata, Hymenoptera, Orthoptera, larvae and tadpoles. The RI also showed there are differences in young and adult diets. These results indicate strong predation pressure on native fauna. These results reveal the urgency needed to develop a management and control program in for this exotic species in natural environments.
I studied the invasion of Rana catesbeiana (the bullfrog) into a northern California river system where bullfrogs are not native. Native yellow-legged frogs, Rana boylii, a species of special concern, were almost an order of magnitude less abundant in reaches where bullfrogs were well established. I assessed the potential role of larval competition in contributing to this displacement in a series of field manipulations of tadpole density and species composition. The impact of R. catesbeiana on native tadpoles in the natural community agreed with the outcome of more artificial experiments testing pairwise and three-way interactions. In 2-m2 enclosures with ambient densities of tadpoles and natural river biota, bullfrog tadpoles caused a 48% reduction in survivorship of R. boylii, and a 24% decline in mass at metamorphosis. Bullfrog larvae had smaller impacts on Pacific treefrogs, Hyla regilla, causing 16% reduction in metamorph size, and no significant effect on survivorship. Bullfrog tadpoles significantly affected benthic algae, although effects varied across sites. Responses to bullfrogs in field settings were similar qualitatively to results seen in smaller-scale experiments designed to study size-structured competition among disparate age/size classes of species pairs and trios. Competition from large overwintering bullfrog larvae significantly decreased survivorship and growth of native tadpoles. Competition from recently hatched bullfrog larvae also decreased survivorship of R. boylii and H. regilla. Native species competed weakly, both interspecifically and intraspecifically. The only suggestion of a negative impact of a native species on bullfrogs was a weak effect of H. regilla on recent hatchlings. Competition appeared to be mediated by algal resources, and there was no evidence for behavioral or chemical interference. These results indicate that, through larval interactions, bullfrogs can exert differential effects on native frogs and perturb aquatic community structure.
To evaluate predation by bullfrogs, Rana catesbeiana, on giant garter snakes, Thamnophis gigas, at Colusa National Wildlife Refuge (NWR) we collected 99 bullfrogs during three field seasons from 2000-2002. Crayfish, Procambarus clarkii, were in 90% of the bullfrogs and were usually the only food item. We found four neonate giant garter snakes in three bullfrogs. We estimated the total annual predation of bullfrogs to be about 22% of neonate production, a value similar to the 20% tail loss we documented for giant garter snakes on the Refuge as another index of bullfrog predation pressure. Even with mortality from bullfrogs and other predators, snake size classes indicate sustainable recruitment into the Colusa NWR giant garter snake population. Smaller bullfrogs and bullfrog tadpoles are also food for giant garter snakes, so further studies are needed to determine the net effect of bullfrog removal for local giant garter snake populations.
This benchmark volume documents in comprehensive detail a major environmental crisis: rapidly declining amphibian populations and the disturbing developmental problems that are increasingly prevalent within many amphibian species. Horror stories on this topic have been featured in the scientific and popular press over the past fifteen years, invariably asking what amphibian declines are telling us about the state of the environment. Are declines harbingers of devastated ecosystems or simply weird reflections of a peculiar amphibian world? This compendium-presenting new data, reviews of current literature, and comprehensive species accounts-reinforces what scientists have begun to suspect, that amphibians are a lens through which the state of the environment can be viewed more clearly. And, that the view is alarming and presages serious concerns for all life, including that of our own species. The first part of this work consists of more than fifty essays covering topics from the causes of declines to conservation, surveys and monitoring, and education. The second part consists of species accounts describing the life history and natural history of every known amphibian species in the United States.
During 1993-94, we observed predators and surveyed managers at Intermountain West fish hatcheries to quantify the extent and species responsible for depredation losses. Our field study confirmed hatchery managers' impressions that great blue herons (Ardea herodias), black-crowned night herons (Nycticorax nycticorax), ospreys (Pandion haliaetus), and California gulls (Larus californicus) were the most important predators. At 2 intensively monitored hatcheries, we calculated losses to avian predation to be 7.0 and 0.6% of annual production, in contrast to the managers' estimates of 15% at each hatchery. Feeding mostly on dead or moribund fish, feral cats (Felis catus), raccoons (Procyon lotor), and striped skunks (Mephitis mephitis) had little effect on fish production. Private hatchery managers estimated higher (13%) total depredation losses than did managers of state owned hatcheries (5%). Hatchery managers viewed netting to be the only effective nonlethal control measure.
This study examines direct and indirect interactions that influence the distribution of larvae of the bullfrog (Rana catesbeiana) and green frog (R. clamitans) along the environmental gradient of permanent to temporary ponds. The bullfrog is found in permanent ponds that typically contain fish, whereas the green frog is widely distributed along the gradient and is most successful in ponds where the bullfrog is absent. In a set of experimental ponds, bullfrogs were most abundant in ponds containing fish (bluegill, Lepomis macrochirus) and were rare in permanent ponds that lacked fish. In contrast, green frogs were most abundant in ponds that had been drained the previous fall, second most abundant in those that lacked fish, and sparse in ponds containing bluegill. When presence and absence of bluegill were experimentally manipulated in divided ponds, bullfrogs survived well in the presence of bluegill, whereas no individuals survived in the absence of bluegill. Green frogs survived in low numbers under both treatments with a tendency to better survivorship in the absence of bluegill. A series of laboratory choice experiments was conducted with three major predator types: the dragonfly larva Anax junius, the salamander Ambystoma tigrinum, and L. macrochirus. Bullfrog larvae were more vulnerable to Anax and Ambystoma than were green frogs (because of higher activity levels), and green frogs were more vulnerable to bluegill than were bullfrogs (because tadpoles were less noxious). We argue that the high densities of bullfrogs found in the presence of bluegill reflect an indirect facilitation through two pathways: bluegill had strong negative effects on invertebrate and salamander predators of bullfrogs and on the green frog, which is a bullfrog competitor. The direct and indirect effects of these suites of predators appear to explain the differences in species abundances along the environmental gradient. Finally, we discuss the trade-offs at the individual level contributing to these differences in species performance along the gradient.
The decline of ranid frog species native to western North America is a pattern alluded to by many workers. We review the factors cited as having caused these declines, using, as primary examples, some of the ranid species native to California. We present explicit statements of four major alternative hypotheses: 1) bullfrog introduction, 2) habitat alteration, 3) predation by introduced fishes, and 4) commercial exploitation. Additionally, we review data relating to four other factors suggested as having caused declines: 1) toxicants, 2) pathogens and parasites, 3) acid rain, and 4) catastrophic mortality. Notably, data do not exist that suggest that the often-invoked bullfrog hypothesis is most compelling. Some factors, like commercial exploitation, are untestable because the putative causal conditions no longer exist, whereas others, like catastrophic mortality, are difficult to test because of their unpredictability. Perhaps the most neglected but potentially important alternative is predation by introduced fishes. Existing data cannot distinguish adequately among three major testable alternatives: bullfrogs, habitat alteration, and introduced fish predation. In the absence of satisfactory data, the chronological priority of fish introductions over those of bullfrogs and the greater access fish may have to earlier ranid life stages make the fish predation hypothesis more compelling. Several alternative hypotheses are confounded because existing correlative data support at least two alternatives equally well. Manipulations of testable alternatives are imperative to distinguish causal factors.
Serial blood samples were collected from the adult American bullfrog (Rana catesbeiana) via a non-occlusive cannula chronically placed in the systemic subdivision (aortic) of the right truncus arteriosus. Plasma glucose, alanine, lactate, and β-hydroxybutyrate levels were estimated by standard enzymatic procedures. The metabolites remained relatively stable in the control animals during the 8-day experiments. A single infusion of mammalian insulin (5, 15, or 45 IU/kg body weight) via the cannula depressed plasma glucose and alanine to near or below detectable levels that required a minimum of 3 days to return to approximately the time-zero levels. Plasma lactate also fell severely after the infusion, but subsequently displayed precipitous surges followed by sharp declines on days 1 and 3, and also in some animals on day 5. In contrast, plasma β-hydroxybutyrate levels were not significantly altered by insulin. Despite the severe depressions of plasma glucose, alanine, and initially lactate, no symptoms were observed in the bullfrogs infused with 5 or 15 IU of insulin. The carnivorous adult bullfrog consumes abundant protein and lipid, but little carbohydrate, and is adapted to periods of food scarcity. The results are consistent with the hypothesis that the bullfrog may rely on non-esterified fatty acids and ketone bodies as primary energy sources. Glucose, most of which must be synthesized, probably serves to maintain muscle glycogen reserves that are used for anaerobic glycolysis when the animal is engaged in predation, escape, or other vigorous activity. If other tissues and organs require glucose as a fuel, the amounts must be exceptionally small.
I analyzed stomach contents of the American bullfrog, Rana catesbeiana, in the Mizorogaike Pond of Kyoto, Japan. As a result, adult bullfrogs were found to feed predominantly on crayfish, and juveniles eat diverse arthropods. A wide variety of aquatic organisms occurred in the diet of both adult and juvenile bullfrogs.
Toads of the genus Bufo co-occur with true frogs (family Ranidae) throughout their North American ranges. Yet, Bufo are rarely reported as prey for ranid frogs, perhaps due to dermal toxins that afford them protection from some predators. We report field observations from four different localities demonstrating that Oregon spotted frogs (Rana pretiosa) readily consume juvenile western toads (Bufo boreas) at breeding sites in Oregon. Unpalatability thought to deter predators of selected taxa and feeding mode may not protect juvenile stages of western toads from adult Oregon spotted frogs. Activity of juvenile western toads can elicit ambush behavior by Oregon spotted frog adults. Our review of published literature suggests that regular consumption of toadlets sets Oregon spotted frogs apart from most North American ranid frogs. Importance of the trophic context of juvenile western toads as a seasonally important resource to Oregon spotted frogs needs critical investigation.
We studied diets of an Asian ranid, Rana rugosa, inhabiting three different environments (reservoir, river shoreline, and paddy fields) in Kyoto, Japan. In all the three habitats, ants were the most frequently consumed prey, representing surprisingly similar proportions in both the frequency of occurrence (81.9-85.7%) and the number of total prey items (56.8-59.4%). These values are exceptionally large for Rana, and equivalent to those reported for ant specialists in other families of frogs such as dendrobatids or bufonids. However, R. rugosa consumed ants lower in proportions than those found in the environment, and could not be regarded as purely ant specialists. Instead, we conclude that this species tends to avoid ants more weakly than other species of Rana. Other than ants, larger prey were more and smaller ones less frequently taken in proportion to frog body size, indicating that the frog consumes ants because of its weak avoidance of these abundant potential prey.
The effects of a single infusion of mammalian ACTH on plasma glucose, alanine, urea, and lactate were determined in the American bullfrog (Rana catesbeiana). The ACTH (10 U/250 g body wt) was administered, and serial blood samples were collected via a nonocclusive cannula chronically placed in the right truncus arteriosus. Plasma metabolite levels were estimated by standard enzymatic techniques. The plasma metabolites declined following the surgery to levels that were relatively stable by postoperative Day 2. The levels did not vary significantly for the remainder of the 3- or 4-day pretreatment period and in the control bullfrogs during the 48-hr experiments. Plasma glucose levels were essentially unchanged from the time-zero levels at 6 hr following ACTH infusion. Plasma glucose levels subsequently increased to levels that were approximately 24% greater than the control levels by 24 hr and then declined to near control levels by 48 hr. Plasma alanine increased to levels that were approximately 60% greater than the control levels by 12 hr after ACTH treatment and returned to essentially the time-zero levels by 24 hr. Plasma urea rose to levels that were approximately 110% greater than the control levels by 45 min after ACTH infusion, but urea returned to essentially the time-zero levels by 1.5 through 3 hr. Plasma urea increased again to levels that were approximately 90% greater than the control levels by 6 hr and returned to essentially the initial levels by 24 hr. Plasma lactate levels were not significantly influenced by ACTH treatment. The results suggest that a function of the bullfrog hypothalamic-pituitary-adrenocortical axis is to regulate gluconeogenesis from alanine, and probably other glucogenic amino acids.
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