be traced to the habit of still nursing juveniles, 
who trail their mother from the home burrow. 
This situation has previously been discussed in 
more detail with reference to the socialization of 
juveniles. A second behavior is the one involved 
in recognition, in which approaching rats touch 
noses. This is frequently followed by genital 
inspection. As the rats begin to pass each other 
after nose touching, one or both extend their 
heads under the other’s belly just in front of the 
hindleg. This inspection may also take the form 
of extending the head under the other rats tail 
until the nose apparently is in contact with the 
anal region. A third behavior is that of the for- 
mation of signposts associated with urination and 
defecation. Urination and defecation normally 
occur at those points where forward locomotion is 
temporarily halted. Passages through barrier 
fences, intersections of trails, and proximity to a 
vertical structure are the most frequent locations. 
Rats also urinated on sticks and over rocks. Geni- 
tal inspection and signpost formation normally 
elicit no further behaviors of sexual implication. 
There is only momentary inspection of a signpost 
or of another rat, before the rat continues with 
nonsexual behaviors. 
On or near the date when females are capable of 
conception, the behavior of both sexes becomes 
altered. There is a precopulatory phase. This 
lasts for at least part of 1 night, and in some 
instances apparently for the entire night before 
copulation occurs. The female wanders more than 
normal beyond the limits of her customary home 
range. She actively seeks males; they touch noses, 
exchange genital inspections; and as the female 
moves away the male may follow her for a few 
feet, before returning to his prior activities. There 
then develops a change in the attractiveness of the 
female to males. Involved in this change is an 
alteration of the scent of the female and her 
behavior in dispersing it. As she wanders about 
she rubs her sides and anal region against the tiles 
through fences, or into harborage boxes, or the 
sides of entries into burrows, at the entries of the 
activity recorders, or against trees or posts. At 
these times she frequently drags her genital-anal 
region over the soil at these points. The ventral 
part of the body is kept flat against the ground as 
the rat wriggles back and forth and pulls itself 
along. Within seconds or a few minutes after the 
female has left such a point a male frequently 
arrives. He repeats her performance, and trails 
her from point to point until he locates her in a 
burrow or harborage box. Rarely did the male 
enter, although he frequently extended the forepart 
of his body down into the entry, while at the same 
time rubbing his genital region against the arc of 
earth surrounding the entry. After a few minutes 
the male usually desisted in these activities and 
went away. When the female left she continued 
in her signpost activity. During this phase she 
might also actively seek a male. When a male was 
located she sometimes chased him for a short way, 
as if in a mock aggression; then she would turn 
around and he would pursue and closely trail after 
her for quite some distance before she again entered 
a burrow or harborage box, where he would repeat 
his rubbing and rolling. 
Other sexually oriented behaviors accompany 
this precopulatory phase. Upon approach and 
nose touching the female may back up. The male 
follows keeping his nose close to hers. Then he 
rolls over, gets up, turns around with his anal 
region toward her, and she inspects it. While they 
are close together he may throw his hips against 
her. This same behavior is utilized as an aggres- 
sive threat between males (p. 180). The female 
may also lick the nape of the male’s neck as he 
extends his head under her belly. There is also 
a dancing, pebble-rolling routine. This was noted 
twice on the night of October 7-8 1948, but by two 
different rats. This was on a night during which 
at least one female was leaving scent attractive to 
males. At 5:45 p.m. there were two unidentified 
rats in the Food Pen. Their sex was not deter- 
mined. The larger rat was probably over a year 
old, and the smaller one 4 to 6 months of age. The 
larger of the two kept rubbing against one of the 
posts supporting the food hopper. The smaller rat 
kept approaching the larger one with a stamping 
gait, but would retreat as the larger turned toward 
it. This stamping gait is one in which the back is 
slightly arched. The legs are maintained some- 
what extended and rigid as rapid steps are taken. 
Three times the smaller rat included in this routine 
the rolling of a pebble or ball of mud. Just before 
dawn male 30, who was over a year old, was seen 
rubbing and throwing his hips against the inside 
entry to one of the activity recorders. He then 
went 2 feet toward the food hopper before turning 
around. In the return toward the recorder tunnel 
he exhibited the stamping gait and the rolling of a 
pebble with his forefeet. I suspect that a female, 
capable of conception, was in the recorder tunnel. 
676-768 0—63 
11 
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