180 PROCEEDINGS OF THE NATIONAL MUSEUM vol. no 



75.2° F. but did not fly agily until a temperature of 82° to 86° F. was 

 reached. 



Pearson, et al. (1952, p. 276) found most P. townsendii lethargic at 

 air temperatures below 62° F. and recorded temperature as low as 

 28.5° F. near hibernating individuals. Twente (1955b, p. 715) ob- 

 served an air temperature range of 37.4° to 69.8° F. where lethargic 

 big-eared bats were resting. When Dalquest (1947, p. 29) placed 

 active specimens of P. townsendii in a refrigerator at a temperature of 

 40° F. all became lethargic within 20 minutes. 



Pearson, et al. (1952, p. 277) observed in their studies of P. town- 

 sendii in California that the bats began to arrive in their hibernating 

 quarters in late October, reached peak numbers in January, and de- 

 parted by April. Females arrived earlier and stayed later than males. 

 Females were usually lethargic both day and night during the coldest 

 periods, whereas males tended to awaken at night the year around, 

 even in midwinter. During spring, summer, and fall both sexes were 

 usually alert day and night and lethargic individuals were uncommon, 

 especially in September when the males were coming into breeding 

 condition. 



In central California, Pearson, et al. (1952, p. 280) found that some 

 male P. townsendii apparently did not hibernate. Individuals came 

 to night roosting places throughout the winter in outside air tempera- 

 tures ranging from 37° to 57° F. Winter records of females at night 

 roosts were more UTegular but indicated activity on nights when the 

 outside air temperature ranged between 47° and 57° F. Pearson, 

 et al., did not determine what food sustained this winter activity. 

 Although flying insects were probably scarce at this season, these 

 authors captured adult male bats that lacked stored fat. Elsewhere, 

 males that they weighed averaged 8.36 grams on 3 February and had 

 dropped 0.64 grams to 7.72 grams by 2 April. This loss probably rep- 

 resented the amount of stored fat required to sustain the bats for this 

 period (temperatures 37° to 50° F.) without intake of additional food. 



For further data on roosts, sociability, and movement during hiber- 

 nation, see pp. 168, 170, and 176. 



Reproduction: Unless otherwise noted, all of the following infor- 

 mation on reproduction in P. townsendii is taken from Pearson, et al. 

 (1952, pp. 281-314). 



Insemination. — The mating season extends from early October to 

 late February. Copulatory activity is greatest in the winter roosts, 

 but some, perhaps most, females have mated at least once before they 

 arrive at the wintering places. Unmated females may be found 

 throughout September, but spermatozoa are to be found in all after 

 about the third week of October. Young females (as little as 3 or 4 

 months old) mate as early as do adult females, but because they pro- 



