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Ecology and Vulnerability American Bullfrog
Ecology and Vulnerability
The bullfrog ranges throughout North America, though it was introduced in the western portion of the continent. In the east, it ranges from Canada to Florida.... Read More
The bullfrog ranges throughout North America, though it was introduced in the western portion of the continent. In the east, it ranges from Canada to Florida. Abroad, the bullfrog has significant adverse impacts on local animal species. It breeds primarily in permanent water sources with dense vegetation, such as lakes, rivers, ponds, irrigation areas, and occasionally in ephemeral pools near permanent water sources 3. Metamorphosis can take 1-2 years and bullfrogs can live from 8-10 years 2. Bullfrogs are not tolerant of freezing conditions 2, so they hibernate deeply under water in mud and leaves from mid-October to late March in New England 3. Adult bullfrogs are primarily nocturnal. They are aggressive predators that consume invertebrates (species without a backbone such as insects), snakes, fish, rodents, frogs, and salamanders 2. This species can move well over a kilometer during periods of warm rain 7.
The most significant climate related threat to bullfrogs is likely due to their dependence on permanent water bodies that may be affected through hydrological changes, temperature increases, or drought 4. Tadpole development is limited above 31°C 2, so the reproductive period for bullfrogs may decrease during summer months in regions with large temperature increases. However, moderate increases in water temperature may benefit bullfrogs through accelerated tadpole development, which subsequently reduces their exposure to predators 1. Since this species tends to occupy relatively permanent water sources, it may be more resilient to the lethal effects of drought compared to other amphibians, and is likely to outlive drought conditions, given its lifespan 2.
Changes in temperature are likely to influence many amphibians 1. However, the bullfrog may be more resilient than most amphibians because it is tolerant of a broad range of water temperatures and can consume a wide variety of food resources 4. Indeed, its ability to invade, survive, and outcompete native amphibians in regions where it is newly introduced indicates that its climate limitations are not as severe as for many amphibians. A number of amphibian species seem to initiate breeding activities earlier in response to warmer spring temperature or milder winters, including the common toad (Bufo bufo) 1,8. However, the bullfrog has a prolonged reproductive period that does not appear to rely as strongly on temperature or precipitation cues as other amphibians 2,4.
There is some evidence that increased drought, changes in temperature regimes, and amplified ultraviolet exposure associated with climate change might make amphibians more susceptible to infectious diseases 1,6,8. Bullfrogs may be less vulnerable than other amphibians to the fungal pathogen (Batrachochytrium dendrobatidis - Bd) that is causing widespread declines in amphibians 4, as experiments indicated that bullfrogs were resistant to some strains of Bd 5.
1. Carey, C., and M.A. Alexander. 2003. Climate change and amphibian declines : is there a link ? Diversity and Distributions 9: 111–121.
2. Degenhardt, G., C. Painter, and A. Price. 1996. Amphibians and Reptiles of New Mexico. UNM Press, Albuquerque, NM.
3. DeGraaf, R.M., and D.D. Rudis. 1986. New England Wildlife: Habitat, Natural History, and Distribution. Forest Service Northeast Forest Experiment Station General Technical Report NE - 108.
4. Friggens, M.M., D.M. Finch, K.E. Bagne, S.J. Coe, D.L. Hawksworth, M. Megan, et al. 2013. Vulnerability of Species to Climate Change in the Southwest : Terrestrial Species of the Middle Rio Grande. Forest Service Rocky Mountain Research Station General Technical Report RMRS-GTR-306.
5. Gervasi, S.S., J. Urbina, J. Hua, T. Chestnut, R.A. Relyea, and A.R. Blaustein. 2013. Experimental Evidence for American Bullfrog ( Lithobates catesbeianus ) Susceptibility to Chytrid Fungus ( Batrachochytrium dendrobatidis ). Ecohealth DOI: 10.10.
6. Rohr, J.R., and T.R. Raffel. 2010. Linking global climate and temperature variability to widespread amphibian declines putatively caused by disease. PNAS 107: 8269–8274.
7. Smith, M.A., and D.M. Green. 2005. Dispersal and metapopulation paradigm in amphibian ecology and conservation: are all amphibian populations metapopulations? Ecography 28: 110–128.
8. Yiming, L., J.M. Cohen, and J.R. Rohr. 2013. Review and synthesis of the effects of climate change on amphibians. Integrative Zoology 8: 145–161.
Related Adaptation Strategies and Actions
Related Habitats (detailed)
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