Individual study: Invasive species shifts ontogenetic resource partitioning and microhabitat use of a threatened native amphibian
D’Amore A., Kirby E. & McNicholas M. (2009) Invasive species shifts ontogenetic resource partitioning and microhabitat use of a threatened native amphibian. Aquatic Conservation: Marine and Freshwater Ecosystems, 19, 534–541
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Remove or control invasive bullfrogs
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.