| Summary: | I used movements of 74 radio-collared black-tailed deer to investigate
whether an hierarchically-structured decision process constrains habitat
choices. Constraints on habitat can lead to rejection of the ideal-free
distribution hypothesis for black-tailed deer where their habitats are prone
to large and rapid disturbances. I recorded 11,150 deer locations at 2 time
scales (2-hourly and weekly) at 4 study areas on Vancouver Island, British
Columbia from 1982-1991. I assessed the temporal and spatial independence
of these observations before examining the distance, frequency, timing, and
direction of movements.
Deer that migrated every year (n = 12) occupied natal ranges at high
elevations and used alternate ranges for >6 mo/yr. Migration route
directions varied and were used in the absence of snow. Alternate ranges
were established at mid-slope elevations on southern aspects and always
enclosed some old forest, the only forest type preferred more in winter than
summer. Areas of intense use on alternate ranges included old forests.
Deer that migrated less consistently (n = 16) occupied natal ranges at midto
low-slope positions and used alternate ranges for <4 mo/yr. All but 2 of
these deer migrated in response to snow accumulation or ablation and along
routes consistent with valley direction. They established alternate ranges
at similar topographic positions as other migratory deer but did not
necessarily have access to old forests. Non-migratory deer (n = 44)
occupied natal ranges at mid- to low-elevations and used whatever forests
were available. Areas of intense use tended not to include old forest. I
was unable to trap migratory deer in young forests and the survival rate I
estimated for resident deer indicated a declining population. Decisions concerning home- and seasonal-range establishment
constrained more spatially specific decisions about habitat use. Further,
these decisions were themselves likely to be limited by rigid tactics such
as philopatry and site fidelity.
These conclusions were tested by logging old forest winter habitat in
2 separate study areas. Fidelity, rather than habitat choice, dominated the
initial responses. Deer accepted remaining habitats rather than finding old
forest winter habitat elsewhere. Lack of freedom in choosing habitats has
implications for habitat management, for deer response to habitat change,
and for factors that affect population dynamics. === Forestry, Faculty of === Graduate
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