REPRODUCTIVE ECOLOGY OF A POPULATION OF THE CALIFORNIA TIGER SALAMANDER

We studied breeding migrations and variation in reproductive traits of the California tiger salamander, Ambystoma californiense, in Contra C osta County, California over two winter breeding seasons and three sum mer metamorphosis seasons (1992-1994). Initiation of adult breeding mi grations followed major storm systems; in both 1993 and 1994, males ar rived at the breeding pond first and stayed longer than females. Breed ing population sizes of males and females varied annually and appeared to be determined by different mechanisms. Within a season, variation in weekly numbers of migrating adults was attributable only to rainfal l; variation in numbers of emigrating juveniles could not be attribute d to any measured environmental parameters. Sexual dimorphism in adult s is expressed through longer tails in males. Annual numbers of juveni les produced varied substantially, ranging from over 1000 metamorphs i n 1992 to only three in 1994. Timing and mean size at metamorphosis sh owed substantial annual variation.