CORTICOSTERONE AND ANDROGEN PLASMA-LEVELS IN MALE TOADS BUFO-BUFO DURING THE REPRODUCTIVE PERIOD

In the toad Bufo bufo reproductive activity took place within a few we eks in early spring: males were sexually active when entering and stay ing in the breeding pond and did not exibit any sexual behaviour when leaving. We analyzed changes in the plasma levels of corticosterone an d androgens in the toad Bufo bufo during two consecutive breeding seas ons under natural conditions. Males were trapped and blood collected a t their arrival and departure from the pond where reproductive behavio ur occurred. Androgens decreased in animals leaving the pond in both y ears and the final levers were negatively correlated with the length o f stay in the water. The final levels of corticosterone were also nega tively correlated to the time spent in the water. A significant cortic osterone decrease in animals leaving the pond was observed only in the first year, and it is probably due to sampling technique.