FACTORS AFFECTING POPULATION FLUCTUATIONS IN LARVAL AND ADULT STAGES OF THE WOOD FROG (RANA-SYLVATICA)

During a 7-yr study, breeding population size fluctuated by a factor of 10 and juvenile production by a factor of 100. Variation in the adult population among years was largely due to variation in juvenile recruitment. Annual net replacement rates varied from 0.009-7.49. Most variation in the proportion of individuals surviving to adulthood was due to variation in larval survival; juvenile and adult survival was relatively constant among years. Because females matured a year later than males, on average 2.3 times as many males as females from a given clutch survived to breed. This difference accounted for the observed male-biased sex ratio in breeding choruses. Premetamorphic survival and size at metamorphosis were negatively correlated with number of eggs deposited. Length of larval period was positively correlated with number of eggs deposited. Survival was higher among juveniles that metamorphosed early and were large at metamorphosis. Mean monthly rainfall positively affected adult survival. -from Author