ECONOMY OF HAREM MAINTENANCE IN THE GREATER SPEAR-NOSED BAT, PHYLLOSTOMUS-HASTATUS

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.