Fox, L.B. 1990. Ecology and population biology of the
bobcat, (Felis rufus) in New York. Ph.D. Dissertation, SUNY-ESF,
Syracuse, 184 pp.
Abstract: Bobcats (Felis rufus) were studied by snow-tracking and radio telemetry on 4 study areas and byexamining 247 carcasses collected in New York during the period 1976 to 1981. Bobcats weredistributed over 35,000 km2 of the Adirondack, Catskill and Taconic regions of the state. Densities of adult bobcats in the late winter to early spring ranged from 2 bobcats per 100 km2 in the central Adirondacks to 6 bobcats per 100 km2 in the western Catskills. An estimated 800-1100 adult bobcats occur in the state. White-tailed deer (Odocoileus virginianus) and lagomorphs were the main diet components, occurring in 32% and 30%, respectively, of the 169 bobcat stomachs that had food items. Deer were eaten more commonly (P < 0.001) in the winter (72%) than during either summer (22.7%) or fall (29.5%). Tracks and examinations of deer carcasses revealed 7 of 17 deer were killed by bobcats. Small mammal populations fluctuated dramatically (P < 0.05) during the study, but no noticeable response occurred in the bobcat population. Home range of Adirondack bobcats was 325.7 -+ 61.1 (X + SE) km2 for 4 males and 86.4 + 28.6 (X + SE) dm2 for 4 females. Home range of 2 males in the Catskills was 36.0 + 28.5 (X + SE) km2, and an adult female had a home range of 31.0 km2. There was considerable individual variability in the use of cover types within an individual's home range. Bobcats used low elevation areas within their home ranges. Stands with a conifer component seemed to be selected in the winter. These areas frequently included deer yards. Males were more numerous than females in the harvest sample from the northern region (66:43) compared to the sample from the southern region (68:65). Juveniles comprised 27.2% of the sample from the northern region and 24.3% of the animals harvested from the southern region. Yearlings comprised a greater (P < 0.05) proportion of the bag in the southern region (42.6%) than the northern region (23.3%). Placental scar counts averaged 1.2, 2.8, and 3.4 for yearlings, 2-year-olds, and bobcats over3 years of age, respectively. Human caused mortality of dispersal age bobcats or recently established family units, particularly around the perimeter of the bobcat distribution, was considered important in limiting bobcats to their present distribution in the state. Discriminant function analysis was useful in classifying occupied range versus unoccupied range. Bobcat habitat quality in New York was positively related to deer densities and negatively elated to road densities. Bobcats in the northern region suffered a greater energy stress (P < 0.0001) during late winter than bobcats in the southern part of the state. An index to condition based on the ratio of dry weight to fresh weight of femur marrow showed that juveniles, adult females and adult males in the northern part of the state had fat indices of 47.1, 38.2 and 62.0 respectively, while juveniles, adult females, and adult males in the southern part of the state had fat indices of 75.5, 77.1 and 73.8 respectively. Take of bobcats steadily declined in the central Adirondacks (Hamilton Co.) from 1955 until 1980 (Y = 7327.5 -3.7X; r =0.82). However, coyotes expanded and constituted an increasing portion of the combined coyote and bobcat harvest (Y = -3618.6 + 1.88x; r = 0.843). bobcats expanded their range northward during a time when deer populations were increasing and few competitors existed. Precise information on location of take should be collected to monitor change sin the distribution of bobcats in the state. Periodic monitoring of the size of bobcat movement patterns in conjunction with information on post-dispersal age structure could be used to estimate changes in bobcat abundance. Critical size and distribution of refugia needs to be determined for future management to ensure that excessive mortality of dispersal age bobcats does not occur.