. Bulletin. Science; Natural history; Natural history. Figure 4. Seasonal changes in body weights of five individual adult male Spermophiliis beldingi beldingi at Tioga Pass. were smaller than adult males but their v^'eight gain due to fattening, proportionately, was the same, percent (Table 4). Females had fluctuations in body weight as- sociated with parturition early in the season and, later, abrupt weight increases due to fattening (Fig. 5). According to body weight changes, fe- males fattened proportionately less than males; percent in 18 adults and percent in 14 yearlings
. Bulletin. Science; Natural history; Natural history. Figure 4. Seasonal changes in body weights of five individual adult male Spermophiliis beldingi beldingi at Tioga Pass. were smaller than adult males but their v^'eight gain due to fattening, proportionately, was the same, percent (Table 4). Females had fluctuations in body weight as- sociated with parturition early in the season and, later, abrupt weight increases due to fattening (Fig. 5). According to body weight changes, fe- males fattened proportionately less than males; percent in 18 adults and percent in 14 yearlings (Table 4). The fattening response took less time in females, however, and their rate of fattening was higher (Table 4). Using the body weight records of 20 frequently retrapped females, 8 adults and 12 Figure 5. Seasonal changes in body weights of five individual adult female Spenuophilus beldingi beldingi at Tioga Pass. I calculated that prehibernatory fattening began days ( = days) after parturition in adults and days ( = days) in year- lings. According to a f-test, these means are sig- nificantly different (P < ). Because trapping was conducted throughout the season of activity at Tioga Pass, some quantitative statements can be made concerning the duration of hibernation and its effect on body weight in adult and yearling S. b. beldingi. Data from in- dividuals judged to be captured very near the on- set and subsequent termination of their whole hibernation period are shown in Table 5. When squirrels of the same group are compared, males tend to lose more weight than females during hibernation. In adult males this would seem to be a consequence of a longer hibernation period Table 4. Magnitude, duration and rate of fattening in Spermophiliis beldingi beldingi frequently retrapped at Tioga Pass, 1969-1972. Adults Yearlings Males Females (N = 20) (N = 18) Mean body weight at onset of fattening (g) Mean body weight at end
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