Proceedings of the fifth mountain lion workshop: 27

88 PROCEEDINGS OF THE FIFTH MOUNTAIN LION WORKSHOP
EFFECTS OF COUGAR (Puma concolor) PREDATION ON DESERT
BIGHORN SHEEP (Ovis canadensis mexicana) IN THE SAN ANDRES
MOUNTAINS, NEW MEXICO
Kenneth A. Logan. Hornocker Wildlife Institute Field Station, 7315 Aloe Court, Las Cruces, MN 88012 USA
L.L. Sweanor. Hornocker Wildlife Institute Field Station, 7315 Aloe Court, Las Cruces, MN 88012 USA
M.G. Hornocker. Hornocker Wildlife Institute, P.O. Box 3246, University Station, Moscow, ID 83843 USA
We quantified the effects of cougar production on a remnant population (range=30-37) of desert bighorn sheep on the
San Andres Mountains in southern New Mexico from 1985-1994. At the same time, we intensively studied cougar population
dynamics. The finite rate of survival (FRS) for 48 lambs was 0.771. The FRS for 9 radiocollared yearlings was 0.777. Program
MICROMORT was used to estimate annual survival rates for 36 radiocollared bighorns (21 ewes, 15 rams) that occupied a 703
km 2 treatment area where we experimentally removed 760.6% of the independent cougars in 1991. Annual survival rates for
ewes and rams combined averaged 0.814 (range=0.639-1.0). Of 21 radiocollared sheep deaths, 8 (0.38) were due to cougar
predation and 13 (0.62) were due to other causes. Other causes included falls (4), disease (4), old age (2), unknown (2), and
breached birth (1). The mean age of radiocollared sheep killed by cougars was 6.13 years (SD=5.33, range=1-16). Five of 8
sheep killed by cougars had clinical scabies (Psoroptes ovis) and 1 was in poor physical condition. The mean age of sheep that
died from other causes was 6.46 years (SD=3.57, range=3-14). Nine of 13 sheep that died of other causes had clinical scabies.
Two apparently died from scabies. There was no correlation between cougar predation rates on radiocollared sheep and cougar
density on the treatment area (r 2 =0.022). On the San Andres Mountains, a reduction in cougar density did not cause a
corresponding increase in the desert bighorn sheep population.
SURVIVAL AND MORTALITY OF COUGARS (Puma concolor)
IN THE SAN ANDRES MOUNTAINS, NEW MEXICO
Kenneth A. Logan. Hornocker Wildlife Institute Field Station, 7315 Aloe Court, Las Cruces, MN 88012 USA
L.L. Sweanor. Hornocker Wildlife Institute Field Station, 7315 Aloe Court, Las Cruces, MN 88012 USA
M.G. Hornocker. Hornocker Wildlife Institute, P.O. Box 3246, University Station, Moscow, ID 83843 USA
We quantified survival and natural mortality in an unhunted cougar population that we studied for 10 years (1985-1995)
on the San Andres Mountains (2060 km 2 ) in southern New Mexico. Survival rates of cubs were estimated using the finite rate
of survival (FRS) for 211 cubs and the change in the mean number of cubs per litter (CN) in 74 litters. Estimated cub survival
rates using the FRS and the CN methods were ).706 and 0.725, respectively. The sex ratio of cubs that died was 1:1, identical
to the observed sex ratio at birth. Natural causes of mortality were from cannibalism (0.44), starvation (0.37), disease (0.11),
accidental fall (0.04), and coyote predation (0.04). Twenty-six radiocollared subadults (16 F, 10 M, 7.6-27 months old) had a
FRS of 0.88 for females and 0.60 for males. Survival rates of subadult females and males were not significantly different
(X 2 =2.62, 1 df, P=0.11). All 6 of the subadult cougar deaths were due to intraspecific killing. Annual and span survival rates
were estimated for 85 radiocollared adult cougars (51 F, 34 M, 18-152 months old) by using program MICROMORT. Adult
female annual survival rates averaged 0.811 (range = 0.523-1.0). Adult male annual survival rates averaged 0.905 (range =
0.790-1.0). The 8-year span survival rate for adult males (0.450) was significantly greater (Z=1.724, P=0.04) than the span
survival rate for females (0.188). Intraspecific killing was the greatest mortality factor, causing 50% of the deaths in adult
females and adult males. Intraspecific killing of adults was not related to cougar density (Z=0.300, P=0.76). Other natural causes
of mortality included accidents (0.22 of female deaths, 0 male deaths), disease (0.11 of female and 0.30 of male deaths), old age
(0.06 of female and 0.20 of male deaths) and unknown causes (0.11 of female deaths). Sport-hunting may cause additive
mortality in cougar populations.