Masters Thesis

Orientation during Post-Metamorphic Migration in an Endangered Population of the California Tiger Salamander, Ambystoma californiense

Purpose of the Study: The endangered Sonoma County population of the California tiger salamander, Ambystoma californiense, undergoes migrations between breeding pools and upland dry-season refugia. Orientation in this species during breeding migrations has been addressed minimally in previous studies, and literature is particularly sparse concerning newly metamorphosed juveniles. Previous works have not addressed the ability of metamorphs to orient or the way in which they search for upland refugia. The purpose of this study is to evaluate if California tiger salamander metamorphs can re-orient during initial migration and if search movements constitute a Correlated Random Walk. Procedure: We evaluated fine scale movements of newly metamorphosed California tiger salamanders as they moved away from breeding pools, by capturing salamanders with a drift fence. Metamorphs received different orientation treatments, and subsequent movement was tracked with fluorescent powder. We measured turning angles and step lengths at each segment of the tracks, and compared the effect of different treatments. Findings: Here we show that newly metamorphosed juveniles can re-orient to their upland migration path after being interrupted and disoriented. Further, we demonstrate that while searching for burrow refugia, metamorph movement is a correlated random walk. Conclusions: The initial migration from natal pools to uplands following metamorphosis has been identified as a crucial life history juncture for the persistence of this species. Our findings show that these migrations are directed by some orientation, and that these movements are not random. The presence of a Correlated Random Walk is consistent with search patterns in many vertebrates.

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