|SREL Reprint #1051|
Diel Activity Patterns in the Breeding Migrations of Winter Breeding Anurans
H. K. Pechmann and Raymond D. Semlitsch
Diel activity patterns in the breeding migrations of
four winter-breeding anurans (Hyla crucifer, Pseudacris nigrita,
Pseudacris ornata, and Rana utricularia) were
examined at a breeding pond in South Carolina, U.S.A., using a terrestrial drift
fence with pitfall traps. Traps
were censused at 0600, 1200, 1800, and 2400 during six 24-h periods from 1982
through 1984. Census dates were
selected during which the weather was expected to remain uniformly warm and
rainy throughout all four time intervals. This
allowed us to separate the effect of time of day on migratory activity from the
effects of temperature and rainfall. There
were significant differences in migratory activity among time intervals, but no
significant differences among time intervals in either mean air temperature or
rainfall. Males and females of all
four species migrated to and from the pond primarily during the two night
intervals. The absence of daylight
appears to be a necessary trigger for migratory behavior in these anurans.
Temperature and moisture conditions often limit their breeding
migrations, and the failure to utilize suitable diurnal weather conditions
represents an additional constraint. We
suggest that the observed diel pattern of migratory activity may be an
adaptation to avoid visual predators.
SREL Reprint #1051
Pechmann, J.H.K. and R.D. Semlitsch. 1986. Diel activity
patterns in the breeding migrations of winter breeding anurans.
Canadian Journal of Zoology 64:1116-1120.