Biology
Reproductive Season (W):
Breeding peak late winter (Feb-Mar), birth peak early spring (Apr-May), but in the south of
their range litters have been recorded from every month of the year (Anderson 1987,
Rolley 1987)
Estrus (C,W): 5-10 days
Estrus Cycle (C,W):
Approx. 44 days (Crowe 1975a, Mehrer 1975). Bobcats may ovulate spontaneously
rather than by induction (Duke 1949, Crowe 1975a, Fritts and Sealander 1978b)
Gestation (C,W):
Mode 62, range 50-70 days (McCord and Cardoza 1982)
Litter Size (C,W):
Average 2.6-2.8, range 1-8. Younger females produce consistently smaller litter sizes than
older adults (review by Anderson 1987)
Pregnancy Rates (W):
As with litter size, probably density-dependent, and generally decline at times of low
prey density (Rolley 1983) or high bobcat population density (Lembeck and
Gould 1979). Yearling pregnancy rates have ranged from 26-46% (Bailey 1979,
Parker and Smith 1983, Rolley 1985), while adult (>3 years) pregnancy rates are much
higher at 73-100% (Bailey 1979, Lembeck and Gould 1979, Miller 1980, Parker and
Smith 1983)
Interbirth Interval (W):
Generally one year (McCord and Cardoza 1982, Anderson 1987, Rolley 1987)
Age at Sexual Maturity (W):
Females are physiologically mature at 9-12 months (Crowe 1975a, Fritts and Sealander
1978b), but probably do not breed until their second year (Pollack 1950, Fritts 1973,
Crowe 1975a, Sweeney 1978). The onset of breeding activity may be delayed during prey
shortages (Rolley 1985) or in high density bobcat populations (Zezulak and Schwab
1979, Miller 1980). Onset of spermatogenesis in males at 1.5 years (Fritts and Sealander
1978a)
Age at Independence (W):
About one year, dispersal occurs during peak of adult breeding activity (Crowe 1975b, Bailey
1981, Griffith and Fendley 1986, Kitchings and Story 1984)
Mortality (W):
From life history tables, Crowe (1975b) estimated annual average juvenile mortality at
26% in Wyoming from 1948-1973 (range 18-71%). Mortality is strongly correlated with prey
availability (Bailey 1974, Knick 1990). In protected populations with an abundant prey
base, natural adult mortality is low, estimated at 3% in Idaho (Crowe 1975b based on Bailey
1972), and may be slightly higher in high density populations (Lembeck and Gould
1979). In exploited populations, annual adult survival is reduced; estimates of the annual
proportion of surviving adults range from 49-67% (Crowe 1975b, Fredrickson and Rice 1979,
Hamilton 1982, Parker and Smith 1983, Fuller et al. 1985, Rolley 1985, Knick 1990). The
highest mortality rate -- 81% -- was found for a legally harvested Minnesota population where
illegal hunting was believed to be high (Fuller et al. 1985). In general, harvest mortality
is greatest among the yearling and 1-2 year-old young adult age classes (Govt. of US 1983a,
Litvaitis et al. 1987, Knick 1990)
Longevity:
W: 12-13 years (Bailey 1974, Crowe 1975a, Blankenship and Swank 1979)
C: up to 25-33 years (Carter 1955, Jones 1977)
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