The average number is increased consider- 
ably by the litter of 10 observed in 1972. 
Curiously, the animals in this litter were only 
approximately one-fourth grown in late July, 
while all other litters observed were nearly three- 
fourths grown. It is not known whether the 
animals were small because they had been born 
abnormally late in the season, or because the 
adults were not supplying them with enough 
food. However, their behavior appeared normal, 
and the three individuals that were trapped and 
examined seemed to have normal alertness, ‘‘fat- 
ness,’’ and quality and thickness of pelage. 
Behavioral Observations. Adult foxes were 
encountered relatively infrequently—only four 
times during approximately 50 visits or observa- 
tion sessions at active dens. The earliest of these 
encounters occurred on 12 June 1972. Upon 
initial examination, no foxes were in evidence, 
although fresh diggings and patches of molted 
fur were associated with several of the den 
entrances. After several minutes, an adult fox 
exited one of the entrances and quickly left the 
den area. Approximately 10 minutes later, the 
fox returned and attacked the observer as he 
tried to retrieve an object deep in one of the 
dens. The attack consisted of grabbing and 
jerking the observer’s hair. Thereafter, the fox 
approached from the rear to within a meter of 
the observer several times, and was noticeably 
aggressive (i.e., threat displays, vocalizations and 
snapping). As the observer left the den site, the 
fox reentered the den. No pups were seen or 
heard, but six weeks later a litter of three pups 
which were more than half-grown were ob- 
served. 
The second adult fox was encountered on 20 
July 1972. Carrying two brown lemming car- 
casses, it approached two observers sitting quiet- 
ly on a den site. At a distance of approximately 
9m, the adult became aware of the 
observers, dropped the lemmings, barked, picked 
up the prey, ran behind a small hummock, and 
buried the prey under a light coat of moss and 
lichen. The fox then approached the den aggres- 
sively, but with less intensity than in the en- 
counter described above (i.e., the second adult 
approached the observers less frequently and 
never closer than 4m). The fox seemed more 
defensive of the prey than the den site. 
The third encounter occurred on 21 July 
147 
1972. An adult fox observed the approach of 
two observers, barked once, and left the den site 
when they were within 45m of it. The adult 
moved off for approximately % km, hid behind 
some relatively high tundra grass, and observed 
the den. The fox soon became distracted by a 
golden plover, which he unsuccessfully tried to 
capture. 
The fourth encounter occurred on 3 August 
1972 at den site DH6, when an adult was 
observed for 4% hours. Behavior consisted almost 
entirely of resting approximately 15m _ from 
the den site. During this period, a person who is 
not associated with the project approached the 
den to take photographs. The adult fox sat up 
and watched the person, but was not aggressive, 
and returned to a resting position as soon as the 
individual left. One of the pups that was 
playing actively in the area approached the adult 
fox only once. The adult snapped and growled, 
and the pup moved off. 
It appears from these limited data that the 
adults become less attached to the den as the 
litter matures. Reaction of adults to the pres- 
ence of humans in the den areas seems to 
progress from strongly defensive and aggressive 
in early June to nearly indifferent in early 
August. Casual human activity in the den area 
does not appear to seriously inhibit litter raising. 
On the other hand, frequent human activity may 
cause the adults to move the litters to new 
locations. 
Pup behavior was observed for a total of 33 
hr, 44 min, during approximately half of which 
time the pups were inside the den. When out of 
the den, the pups rested half of the time (sleep- 
ing, lying, sitting, standing, and often staring out 
across the tundra), and were active for the other 
half (walking, running, playing moderately or 
intensely). During active periods, the pups 
explored the den site and surrounding area. Solo 
play consisted of pouncing on grass clumps and 
other objects in the den site area and occasional- 
ly tossing objects into the air. Group play, which 
rarely involved more than two interacting indi- 
viduals, often consisted of chases and wrestling. 
Wrestling matches were usually preceded by a 
“tail display’’ (upright tail, arched back, side- 
ways walk), followed by a quick pounce by the 
displaying individual onto the more passive one. 
Wrestling consisted of rolling and biting in the 
