A comparative ecology of Rana aurora Baird and Girard and Rana catesbeiana Shaw at Freshwater Lagoon, Humboldt County, California

Brian Twedt

Graduation Date

1993

Document Type

Thesis

Program

Other

Program

Thesis (M.A.)--Humboldt State University, Biology, 1993

Committee Chair Name

James F. Waters

Committee Chair Affiliation

HSU Faculty or Staff

Keywords

Bullfrogs, Red-legged frog, Humboldt State University -- Theses -- Biology, Freshwater Lagoon, Ecology

Abstract

Populations of Rana aurora Baird and Girard (red-legged frog) and Rana catesbeiana Shaw (Bullfrog) were studied at Freshwater Lagoon from December 1990 through January 1991. Significant differences in habitat-use between species were confirmed using log-linear analysis. I found red-legged frogs most often on land, while bullfrogs were found most frequently in the water. An analysis of the stomach contents of bullfrogs provides proof that bullfrogs prey on red-legged frogs at Freshwater Lagoon. Bullfrogs were shown to also feed on the highly toxic Taricha granulosa (Skilton) (rough-skinned newt). I examined the seasonal activities of both species, and I found that adult male and sub-adult red-legged frogs are absent from the lagoon after bullfrogs emerge from hibernation. Interspecific amplexus between male red-legged frogs and sub-adult and juvenile bullfrogs was observed on 31 separate occasions. Estimates of the population structure of bullfrogs confirm that it is well established at Freshwater Lagoon. Although the differences in habitat use between red-legged frogs and bullfrogs at Freshwater Lagoon appear to be great enough to alleviate the effects of predation and interspecific amplexus on the population of red-legged frogs, the two populations should be monitored through time to see if they are increasing or decreasing relative to one another.

https://scholarworks.calstate.edu/concern/theses/z890rw645

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