Masters Thesis

Breeding pool selection and larval mortality of three California ampibians; Ambystoma tigrinum californiense Gray Hyla regilla Baird and Girard and Scaphiopus hammondi hammondi Girard

Amphibians "that: breed in temporary bodies of water are confronted with problems of pool availability and larval mortality due to dessication of the breeding pools. Due to the low normal rainfall during the spring of the year, the mortality to the larvae is great because many pools dry before the larvae are able to complete development. In the area studied there are three species of amphibians which use vernal, pools and other temporary bodies of water for breeding. These are the California Tigar Salamander, Ambystoma tigrinum californiense Gray, the Pacific Tree Frog, Hyla regilla Baird and Girard, and the Western Spadefoot Toad, Scaphiopus hammondi hammondi Baird. The California Tiger Salamander (Ambystoma) and the Western Spadefoot Toad (Scaphiopus) breed only in temporary bodies of water, usually vernal pools. The Pacific Tree Frog (Hyla) breeds both in vernal pools and in permanent bodies of water. The purpose of this study was to try to determine the factors influencing breeding pool selection by Amby stoma, Hyla and Scaphiopus and to observe the development and survival of their larvae in pools selected for breeding. The factors examined in this study were pool size, pool location, the amount of vegetation and zooplankton in the pools, and the effect of mixed larval populations in the pools. The particular area of study was selected because of the number and variety of vernal pools and because all three species of amphibians breed in the pools in the area. The study was carried out from March 14 to May 7, 1.970, although information on the migration and breeding of the amphibians was noted before the initiation of the study.

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