Androgen levels in breeding Utah tiger salamanders

Many recent papers have investigated the relationship between plasma levels of testosterone (T) and male behavior during the breeding season. One question of interest is whether male reproductive behavior is associated or dissociated with maximal levels of circulating T. Data concerning patterns of association are scarce for amphibians, particularly for salamanders studied in the field. We measured sex steroid levels (T, DHT, E) for 6 adult male tiger salamanders (Ambystoma tigrinum nebulosum) collected during their spring breeding season from ponds in the Wasatch Mountains near Ogden, UT (elev. 8000 n 8500 ft.) Blood samples were taken within 5 minutes of capture. Mean hormone values (range) were: T = 2.25 (0.3 - 6.22) ng/ml, DHT = 481 (114 - 1785) pg/ml, and E = 17 (7 - 28) pg/ml. These values are comparable to plasma levels measured for spring-breeding Colorado A. tigrinum that are neotenic (aquatic adults breed despite retaining larval morphology.) The dissociated pattern described for these two A. triginum populations is in contrast with maximal T and DHT levels recorded for a fall breeding congener, A. opacum. These data suggest that elevated levels of plasma androgens are not required for concurrent breeding behavior in spring-breeding ambystomatid salamanders.