To investigate constraints on males associated with maintenance of har
ems, we used a time-energy approach to explore the relationship betwee
n temporal occupancy of roosts and nightly foraging activity in male a
nd female greater spear-nosed bats, Phyllostomus hastatus. Harem males
and females differed significantly in frequency and duration of night
ly foraging bouts. Harem males spent less time away from their roost a
t night and departed and returned more frequently than did other membe
rs of the harem. Adult females and one subadult male foraged mostly du
ring the first 2-3 h after sunset. Total time spent foraging by harem
males, adult females, and a subadult male, averaged 98, 152, and 115 m
in per night, respectively. On average, harem males engaged in 7.2 ran
domly spaced foraging bouts per night, compared with 2.1 bouts for har
em females and 2.0 bouts for a subadult male. Field metabolic rate, ex
pressed on a mass-specific basis (ml CO2 g(-1) h(-1)), averaged 3.4 +/
- 0.69 SD for harem males, 3.0 +/- 0.85 for adult females, 1.9 +/- 0.0
8 for a subadult male. These values varied predictably but did not dif
fer significantly. Similarly, daily energetic expenditure, expressed o
n a whole-animal basis (kJ/day), averaged 168.6 +/- 32.5 for harem mal
es and 124.9 +/- 38.9 for adult females but did not differ significant
ly. Because harem males allocate less time to nightly foraging activit
y compared with adult females, males should have more time and energy
available for vigilance at the roost and/or the defense of females.