Temporal breeding patterns and mating strategy of the Foothill yellow-legged frog (Rana boylii)

Thesis (M.S.)--Humboldt State University, Natural Resources: Wildlife, 2007This study investigated the temporal breeding patterns, mating strategy, and associated behaviors of the Foothill Yellow-legged Frog, Rana boylii, in order to identify the type of mating system utilized. It was conducted on a naturally dynamic, primarily rain-driven and un-regulated stream, in an area with high frog densities relative to many other populations within the range of the species. Data was collected from spring of 2002 to fall of 2003 at Hurdygurdy Creek, in Del Norte County, California. A 20m2 breeding site that consisted of shallow glide and riffle habitat was monitored for temporal patterns in frog breeding activity. Mark-recapture was used to track individuals over space and time and strategic behavioral observations were recorded to investigate aspects of the mating strategy.\ud \ud The duration of breeding activity varied, lasting six weeks in 2002 and three weeks in 2003. Breeding activity was influenced by the day of the breeding season (e.g., early, mid, late), stream flow, and year. Male frogs aggregated at the breeding site during the reproductive season (April-May), but female arrival was asynchronous. Male frogs had attachment to and vocally and/or physically maintained individual sites (< 1m2 on average) within the breeding area. The daily operational sex ratio of adults attending the breeding site was male-biased, while the overall breeding season operational sex ratio was female-biased. Males in amplexus were larger than males never observed in amplexus, providing evidence of female mate selection. \ud \ud Results indicated that these frogs were facultative in regards to duration of breeding activity and were not exclusively prolonged or explosive breeders. However, frog behaviors at the breeding site were more typical of prolonged breeding anurans.California Department of Fish and Gam