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Providing evidence to improve practice

Action: Remove or control invasive bullfrogs Amphibian Conservation

Key messages

Read our guidance on Key messages before continuing

  • One replicated, before-and-after study in the USA found that removing American bullfrogs significantly increased a population of California red-legged frogs.
  • One before-and-after study in the USA and Mexico found that eradicating bullfrogs from the area increased the range of leopard frogs. One replicated, before-and-after study in the USA found that once bullfrogs had been removed, California red-legged frogs were found out in the open twice as frequently.


Supporting evidence from individual studies


A replicated, before-and-after study in 2004–2007 of 12 ponds in California, USA (D’Amore, Kirby & McNicholas 2009) found that there was a significant increase in adult California red-legged frogs Rana draytonii in ponds in the two years after American bullfrog Rana catesbeiana removal. Counts increased from eight to 11 frogs in removal ponds. Numbers did not change in control ponds. Adult frogs were less visible when bullfrogs were present. Frogs used willows significantly less as cover, and were found on bare shores twice as much when adult bullfrogs were absent. Invasive American bullfrogs were removed from 12 ponds in 2004–2007. They were captured by hand, Hawaiian slings (spears) and seine netting (for tadpoles). Six ponds without bullfrogs in an adjacent field were monitored for comparison. Amphibians were monitored three times each week until October 2007.



A before-and-after study in 2008–2011 of leopard frogs in Arizona, USA and Mexico (Sredl et al. 2011) found that eradication of bullfrogs Rana catesbeiana resulted in an increase in range of chiricahua leopard frogs Lithobates chiricahuensis and lowland leopard frogs Lithobates yavapaiensis. Surveys in 2010–2011 showed that chiricahua leopard frogs had dispersed into eight and lowland leopard frogs into three sites that had previously been unsuitable due to presence of bullfrogs. Chiricahua leopard frogs dispersed over 8 km to a site further north than it had recently been documented in the region. Bullfrogs were eradicated between 2008 and 2010.


Referenced papers

Please cite as:

Smith, R.K., Meredith, H. & Sutherland, W.J. (2019) Amphibian Conservation. Pages 9-65 in: W.J. Sutherland, L.V. Dicks, N. Ockendon, S.O. Petrovan & R.K. Smith (eds) What Works in Conservation 2019. Open Book Publishers, Cambridge, UK.