200 JOURNAL OF MAMMALOGY Vol. 46, No.2 REPRODUCTIVE HABITS OF ROUND-TAILED AND HARRIS ANTELOPE GROUND SQUIRRELS

ABSTRACT: Harris antelope squirrels breed earlier and for longer periods than do the round-tailed ground squirrels in southern Arizona. Apparently, hibernation in the latter species limits its reproductive season. The mean number of young in the Harris antelope squirrel based on 34 records is 6.5; the mean number of young for the round-tailed ground squirrel based on 71 records is 6.5. 'The reproductive habits of the round-tailed ground squirrel (Citellus tereti-caudus) and the Harris antelope squirrel (Citellus hamsii) are compared in the present study. 'The two squirrels are sympatric over most of their ranges and are found only a few feet apart in some areas. Within the range common to the two species, C. tereticaudus prefers flat sandy areas, and C. harrisr,'i prefers rocky hills or rocky soils. Brief references on reproductive habits of C. tereticaudus and C. hanisi