My investigation of sexual selection in American toads concentrates on acoustic communication. Analyses of male mating calls that I recorded under field conditions revealed that males often lower the dominant frequency of their call when vocally interacting with neighboring males. I have conducted acoustic play back experiments on males under field conditions using synthesized mating calls to determine how males respond to particular spectral and temporal characteristics of a neighbor's call. I am also performing acoustic play back experiments on females in the laboratory to determine their call preferences. My study on sexual dimorphism concerns the ontogeny of the tail dimorphism in tiger salamanders.
Adult males have higher and longer tails than do adult females.
I hand-reared salamanders from the zygote stage through adulthood to determine when tail height and length became dimorphic between the sexes. I also wanted to determine if one or both sexes differ from the original growth trajectory to produce this dimorphism. My study on the fate of transgenic organisms involves the fish, Japanese medaka. A colleague and I have created several strains of transgenic medaka produced by the insertion of either a human growth hormone or a salmon growth hormone gene construct. This study combines applied aspects of risk assessment with my interests in sexual selection and life history.