BREEDING HABITS.

Observations on breeding habits have consisted mainly in taking records
from the females trapped at all seasons of the year throughout the
course of the investigation, and from examinations made during poisoning
operations, and yet from this source the number of pregnant females
taken or of young discovered is disappointingly small. The records
indicate a breeding period of considerable length, extending from
January to August, inclusive. It is possible that the length of the
period may be increased by a second litter from the earliest breeding
females in summer, but the large percentage of nonpregnant or
nonbreeding animals which occurs throughout the season would indicate a
wide variation in the time of breeding of different individuals.

Trapping in February and March for the purpose of securing greater
numbers of female specimens, begun with the idea that these months were
most likely to be the breeding months, has invariably yielded an
unsatisfactory number of nonbreeding specimens and males. Unfortunately,
the numbers of females secured in some months were not sufficient to be
significant if worked out in percentages of breeding and nonbreeding
individuals, and this, coupled with the fact that the importance of
recording carefully all nonbreeders was not at first recognized, makes
it impossible to tabulate such information reliably. The total of
females taken in April, for example, is only 3, of which 1 was breeding;
while in June, during the course of poisoning operations, 45 females
were examined, of which 21 were breeding.

Five breeding females were taken in January, all during the last three
days of the month. One of these was a suckling female, the young of