the cougar in the santa ana mountain range, california

our best estimate, we observed 4 gestation
periods that averaged 93 days and ranged from
88 to 96 days. To our knowledge, our data are
the first to estimate gestation period for wild
cougars. The mean gestation period for 42
litters born to captive cougars averaged 92 days
and ranged from 84-98 days (Anderson 1983).
We inspected the exact den sites of F3
and F4 within a week of parturition, and
revisited these sites a week after the cubs were
moved. In addition, we knew the den sites of
F 12 and F2 to within 100m and investigated
these sites after the cubs had been moved.
Several traits were common to all 4 sites. Each
site was in a small tributary canyon with very
dense brush on the canyon sides and in the
canyon bottom, lacked a well-developed scour
zone in the canyon bottom, had no detectable
animal trails, and had very few trees (except for
some Rhus or Malosma plants with shrubby
growth form). Each canyon was away from
regular cougar travel routes, and the vegetation
made it very difficult for a person to crawl to
the birth site. The micro-sites were in drainage
bottoms and in the upper Y4 ofthe drainage. No
site was associated with a cave or rock outcrop.
At the 2 den sites where neonates were
observed, there was no physical modification of
the soil or vegetation at the site; the cubs were
simply in a location that looked much like any
other nearby spot in the dense shrubs. Even
after 40 days of use, the only sign of use was
some compression of the leaf litter. In
particular there were no scats, no urine odors,
and no noticeable trampling or breaking of live
I vegetation. Because these sites lacked
distinctive topographic features (e.g., a cave)
and any "nest" or other modification, we use the
term "den site" simply to designate the place
where cubs spend their first few weeks. These
observations suggest that den sites are selected
mainly because they are unlikely to be visited
by other predators, and that mother cougars
avoid enlarging passageways or leaving scents
that might increase the likelihood of such visits.
39
Movement pattems.ofthe adult females suggest
that the den site was used for about 6 weeks.
In addition to the 10 known litters,
tracks indicated that F4 probably had a yearling
at heel when she was initially captured in
January 1988. Tracks of this cub were no
longer evident after May 1988, indicating either
death or dispersal occurred at about that time.
Similarly, tracks suggested that a small-footed
cat may have accompanied F13 just prior to her
initial capture in March 1990. However, the
tracks may also have been F13 doubling back
on her route, and there was no subsequent
evidence ofa cub accompanying her.
In all cases of known parturition, the
adult female greatly constricted her movements
for the next 5-7 weeks. During the first 2
weeks, her daytime locations .were almost
always at the parturition site. About 7 weeks
after birth, cub tracks could often be seen near
their mother's tracks. Thus birth of a litter was
easy to detect at our level of monitoring.
Twelve females were monitored for over 12
months with sufficient intensity to detect
successful cub-rearing if it occurred. To our
surprise, 4 ofthese 12 females never gave birth
during these years of monitoring, or if they did
give birth, their cubs died within days of birth.
We followed 3 of these females with sufficient
intensity that we are quite certain that they had
no litters that survived more than 2 weeks
during the time they were monitored. The 4th
female (F5) ranged widely and used many
remote areas, and was not monitored as
intensively. Although F5 may have had litters
that we did not detect, it is very unlikely that
any such litter survived more than a month.
The non-reproducers were:
• Fl: no successful litter during October
1986-July 1 1989. F1 was bred May 2-4
1989 (copulatory vocalizations heard),
but at her death in early July 1989 she
was not pregnant nor lactating.
• F5: no successful litter during May 1989­
January 1993. F5 was located very close