| Summary: | Juvenile snowshoe hares (Lepus americanus) in southwestern Yukon were monitored
using radio telemetry to determine the effects of litter group on natal dispersal and postweaning
survival. A total of 84 juveniles representing the four litter groups bom in 1995 were
monitored from June 1995 to April 1996 on control areas and areas in which supplemental
food was provided. Natal dispersal distance, age and date of emigration, survival rate, and
proximate cause of death were examined.
Natal dispersal distances (distance from nest site to site of first breeding) of hares
ranged from 23 m to over 16 km. Fifty percent (9/18) of juveniles whose nest sites were
known and survived until their first breeding season were classified as emigrants (dispersed a
distance further than two adult home range diameters). Emigrants did not suffer significantly
higher mortality than those individuals which did not emigrate. Neither dispersal distance nor
the proportion of hares which emigrated differed between food addition and control areas. On
the control areas, there was no evidence of sex-biased natal dispersal. However, on the food
addition areas, a higher proportion of males than females emigrated and males dispersed
significantly farther than females. This pattern possibly resulted from the increased population
density on the food addition areas.
Age at emigration varied from 31 days to 140 days, but was not related to the sex of
the individuals. Food addition had no observable effect on emigration age, however there was
a significant effect of litter group. Third litter juveniles emigrated at an older mean age (84
days) than first (48 days) and second (42 days) litter juveniles.
Twenty-eight day survival did not differ between food addition and control areas for
any litter group. Over the study period, 28-day survival of juveniles (all litters combined) did
not differ significantly from adults (juveniles: 0.91, adults: 0.93). However, when examined
by litter group, third litter survival was significantly lower than adult and second litter survival,
while fourth litter survival was significantly lower than adult, first, and second litter survival.
These differences were the result of differential survival among the litter groups during a three month period in the fall (September-November). Predation was the primary proximate cause
of death for weaned juvenile hares, accounting for 86% (37/43) of deaths. Although the
dominant predators of juvenile snowshoe hares were annual residents, avian predation was
low after November while mammalian predation was constant from mid-August through
April. No collared weaned juveniles died before mid-August. === Science, Faculty of === Zoology, Department of === Graduate
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