SURVIVAL RATES IN A NONHARVESTED BROWN HARE POPULATION

Survival in the brown hare (Lepus curopacus) is poorly documented beca use only life tables and other nonrobust methods have been used to est imate constant annual survival rates. We used recent developments in m ark-recapture analysis to model survival patterns in a Danish hare pop ulation monitored from 1957 to 1970. Goodness-of-fit tests revealed th at the Cormack-Jolly-Seber (CJS) model was an adequate starting point for adults, and age-dependence was considered in modeling survival of yearlings. We found no differences in annual survival rates (phi) from 1957 to 1967 in adults, but males survived better than females (phi(m ales) = 0.55, 95% CI = 0.50-0.61; phi(females),,,, = 0.50, 95% CI = 0. 44-0.56). Yearling survival rates were time dependent and varied with winter severity, sex, and mass. Indeed, body mass strongly influenced the survival of yearling hares: larger animals (greater than or equal to 3 kg) had higher survival rates than smaller animals, in both males and females (phi = 0.40-0.68 for heavy males and phi = 0.20-0.44 for lighter males; phi = 0.31-0.52 for heavy females and phi = 0.22-0.40 f or lighter females). These variations in survival rates were parallel between body mass classes over time (modeled as a function of winter t emperature) within each sex.