Date

1999

Document Type

Capstone Project

Degree Name

Bachelor of Science (B.S.)

Department

Science & Environmental Policy

Abstract

mphibians are declining worldwide due to a variety of factors, including habitat loss and alteration, global climate change and predation and competition by non-native species. At the former Fort Ord in Monterey County, California the Bureau of Land Management (BLM) is attempting to document changes in amphibian populations by surveying each year. One of the concerns of the BLM is that the bullfrog (Rana catesbeiana), a non-native species, will negatively impact native amphibians living on the former Ft. Ord. Several sensitive species such as the California tiger salamander (Ambystoma tigrinum californiese), and the California red legged frog (Rana aurora draytonii) could be impacted. The 1999 survey include 3 vernal pools and 2 stock ponds and was completed between March 15 and May 2, 1999. This survey focused on the tadpole or larval stage of the amphibian life cycle. The results of the presence survey were analyzed using Sorensen's coefficient or quotient of similarity. The vernal pools compared were very similar, as were the stock ponds, although the difference in the numbers of tadpoles collected in ponds versus pools was drastically different. Pacific tree frog tadpoles were the only tadpoles collected during the actual survey, although adult bullfrogs were observed at several sites. In order to obtain more comprehensive information in the future a more statistically rigorous sampling method should be employed. This would include sampling in each of the different vegetation zones in the vernal pools and ponds, counting numbers of samples taken, and numbers of each kind of tadpoles captured. In addition, surveys for adults, visual surveys by boat, funnel trapping and call surveys should be conducted during the breeding season to provide a more complete picture of which amphibians are utilizing different habitats. Only by following these more rigorous methods will we be able to gauge the effect, if any, the bullfrog is having on local native amphibians. If bullfrogs are having a negative impact on local populations, then measures for controlling their population can be proposed.

Comments

Capstone Project (B.S.) Earth Systems Science & Policy Institute

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