Population differences in response to an invasive predator in the Pacific treefrog.
- Lee Kats, Associate Dean for Research , Pepperdine University
- Rodney Honeycutt, Professor of Biology , Pepperdine University
The Pacific tree frog, Pseudacris regilla, is a native species in the Santa Monica mountain range and can be found in many of the local streams throughout the region. These streams are also commonly inhabited by the invasive swamp crayfish, Procambarus clarkii who prey upon many amphibian species including P. regilla. Initial observations led us to hypothesize that individual tadpoles from naïve populations, those occurring in streams without crayfish, should be less responsive to P. clarkii than individuals from populations that coexist with crayfish. In order to test this, tadpoles were collected from streams with and without P. clarkii and their responses were examined and compared. A total of 40 tadpoles were individually placed into separate experimental tubs with a mesh cage at one end; half of these mesh enclosures housed an invasive crayfish while the other half were empty and served as controls. Tadpole movement was measured over the span of 30 minutes. Our findings showed that tadpoles from a stream with invasive crayfish moved significantly less frequently then the control tadpoles (p<.0005); these tadpoles also moved shorter distances than the tadpoles in the control group (p<.001). Tadpoles from a stream without invasive crayfish, however, showed no significant response to the presence of a predator in either the number of times they moved (p=.1807) or in the total distance moved (p=.6780). This preliminary data suggests that P. regilla is capable of developing a response to invasive predators when they coexist with them in local streams.