PWD BK W7000-893 Proceedings.CDR - Mountain Lion Foundation

78
system in 1997 on approximately one third of the
management units. From the early 1970's to 1996
the annual sport take increased approximately
5-fold from 92 to 452 animals, while hunter
numbers increased from approximately 200 to
800. An average of 69 additional cougars (21.4%
of the sport take) was killed annually between
1990 and 1996 due to depredation control,
highway mortality and miscellaneous causes.
Adoption of the quota system resulted in a further
increase of 75% in hunter numbers and an
additional 27.4% increase in the kill. This level of
exploitation occasioned changes in certain
sixth Mountain Lion w o r k s h o p
COUGARS AND DESERT BIGHORN SHEEP
IN THE FRA CRISTOBAL RANGE:
SCALE, GEOGRAPHY, AND SEASONALITY
ANTHONY L. WRIGHT*, Hornocker Wildlife Institute, HC32 Box 191, Truth or Consequences, NM 87901.
KYRAN KUNKEL, Turner Endangered Species Fund, P.O. Box 190, Gallatin Gateway, MT 59730.
MAURICE G. HORNOCKER, Hornocker Wildlife Institute, 2023 Stadium Drive, Suite 1A, Bozeman, MT
59715
HOWARD QUIGLEY, Hornocker Wildlife Institute, 2023 Stadium Drive, Suite 1A, Bozeman, MT 59715
Abstract: Desert bighorn sheep (Ovis canadensis
mexicana) (n = 44) were translocated to the Fra
Cristobal Range of southcentral New Mexico
during 1995 and 1997. This population has grown
(September 2000, n = 57) despite documented
predation by cougars (Puma concolor) on both
naive and non-naive (surviving > 1 year after
translocation) sheep. Of 11 cougar-caused
mortalities of non-naive sheep 10 occurred during
lambing season (January - May). During February
1999 - August 2000 the average number of
observations/month of cougar sign was 31.3 + 8.2
(95% C.I.) during lambing season versus 12.0 + 5.3
(95% C.I.) during other months. This difference
may reflect a pulse of subadult dispersal into the
area during winter as well as reduced movements
by females with litters during summer and fall. The
Rio Grande River and Elephant Butte Lake form
both a barrier to east-west dispersal and a riparian
corridor for north-south movement. Thus, the Fra
Cristobal Range and Caballo Mountains, which lie
parallel to and just east of the river valley, are
spatially ideal as a dispersal corridor for subadult
parameters of demographic importance. These
included an increase in the average proportion of
females in the kill from 35.1% to 47.5%, attenuation
of the age structure of the kill and an 8.9% decrease
in time-specific adult survival rates from 0.67 to
0.61. Population projections revealed that recent
levels of exploitation are not sustainable. We
compare cougar survival rates across ecoregions
within the state and discuss the influence of
environmental variables, including terrain ruggedness,
road density, and weather conditions, on an
index of cougar mortality.
cougars. The composite home ranges of 7 cougars
2
that used the Fra Cristobal Range (66 km of sheep
2
habitat) covered approximately 2,000 km .
Because the cougar population functions at a
geographic scale at least 2 orders of magnitude
greater than the sheep population, non-targeted
removal of cougars probably will not reduce
predation on desert bighorn sheep in the Fra
Cristobals unless cougar numbers are reduced
over a broad portion of southern New Mexico. If
lambing and an influx of dispersing cougars
typically are synchronous, occasional removal of
specific cougars may be necessary to increase the
sheep population to the point where it is regulated
by food supply. Whether targeted predator control
will be needed over the long-term to maintain the
sheep population near this level is still unknown
and may be largely a function of habitat quality. We
warn against generalizing these results to other
bighorn sheep ranges in different geographic
contexts and where mule deer (Odocoileus
hemionus) are not the primary prey of cougars as
they are in the Fra Cristobal Range.