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We have compared the echolocation and feeding behaviours of Myotis lucifugus, M. californicus, M. volans, and M. auriculus based on observations and recordings of bats in the field. Myotis lucifugus and M. californicus appeared to detect prey at close range (≤ 1 m) and regularly made several attempts to capture insects over short distances; both used similar frequency-modulated echolocation calls. Myotis volans detected prey at greater distances (5–10 m), made only one attempt to capture insects per pass through a feeding area, and used an echolocation call with a distinct constant-frequency component. Myotis auriculus fed mainly on resting insects, mostly moths. The echolocation calls of this species were of shorter duration, lower intensity, broader frequency range with a higher frequency of maximum energy, and showed an initial upward sweep in frequency relative to the calls of the other Myotis we studied. Myotis auriculus did not increase their pulse repetition rate as they closed with stationary prey, and they appeared to fix on resting insects from about 2 m. This species rarely made more than one attempt to capture an insect per pass through a feeding area.

Behavioural tests were used to examine the visual acuity and sensitivity of Macrotus californicus , a 12–14-g desert bat known to use vision in the location of terrestrial prey. Optomotor responses indicate single point visual acuity as fine as 3′38″ of arc. For comparison, the same tests were applied to two other species of bats. Antrozous pallidus , a desert gleaner which locates prey by the sounds they produce, exhibited acuity of 15′ of arc, and Eptesicus fuscus , an aerial foraging species that uses echolocation to find prey, 60′ of arc. Both M. californicus and A. pallidus retained their acuity at light levels as low as 2×10 −4 mL (approximately 2×10 −3 lux), comparable to ground luminance on a clear, moonless night. The eyes of M. californicus were more anteriorly directed, and had twice the binocular overlap of the other species examined. Comparison of our data with results from other studies indicate that M. californicus has vision superior to other insectivorous bats, and at least equivalent to larger-eyed frugivorous and nectarivorous bats examined in previous studies.

Energy metabolism, thermoregulation, and water flux ofMacrotus californicus, the most northerly representative of the Phyllostomidae, were studied in the laboratory using standard methods, and energy metabolism and water fluxes were studied in the field using the doubly labelled water method together with a time budget. Daily energy expenditures of free-living bats averaged 22.8 kJ during the winter study period. Approximately 60% of this was allocated to resting metabolism costs while in the primary roosts (22 h/day).Macrotus californicus is unable to use torpor. The thermoneutral zone (TNZ) in this species is narrow (33 to 40 °C) and metabolic rate increased rapidly as ambient temperature decreased below the TNZ. Basal metabolic rate was 1.25 ml O2/g·h, or 24 J/g·h. Total thermal conductance below the TNZ. was 1.8 mW/g·°C, similar to values measured for other bats. Evaporative water loss showed a hyperbolic increase with increasing ambient temperature, and was approximately 1% of total body mass/h in the TNZ. The success of these bats as year-round residents in deserts in the southwestern United States is probably not due to special physiological adaptations, but to roosting and foraging behavior. They use geothermally-heated winter roost sites (stable year-round temperatures of approximately 29 °C) which minimize energy expenditures, and they have an energetically frugal pattern of foraging that relies on visual prey location. These seem to be the two major factors which have allowedM. californicus to invade the temperate zone.

I examined the habitat use patterns of an Arizona insectivorous bat community using ultrasonic sensing equipment which allowed field identification of bat species based on their echolocation calls. Response to prey patchiness by the species encountered was tested using ultraviolet lights to attract swarms of insects. No partitioning of habitat or time was observed, there being a high degree of species overlap, and many species of bats appeared to be positively associated. All species responded to light-induced prey patches on at least some occasions. Analysis of prey populations indicated that food, though abundant, was extremely patchy in distribution, both spatially and temporally. These data indicate a bat community in which species are highly adapted to an abundant, but patchy food source.

Hipposideros ruber use CF/FM echolocation calls to detect the wing flutter of their insect prey. Fluttering prey were detected whether the insects were flying or sitting on a surface, and prey in either situation were captured with equal success (approximately 40% of capture attempts). Stationary prey were ignored. The bats did not use visual cues or the sounds of wing flutter to locate their prey. Wing flutter detection suggests that H. ruber exploit the Doppler-shifted information in echoes of their echolocation calls. These bats fed primarily upon moths, usually those of between 10 and 25 mm wingchord, although moths of less than 5 mm and greater than 40 mm wingchord were also attacked and captured. They showed no evidence of selecting moths on the basis of species or other taxonomic distinction, and occasionaly captured other insects.