Info from AGFD Abstract: http://www.azgfd.gov/w_c/edits/documents/Macrcali.fi.pdf

HABITAT: Mostly found in the Sonoran desertscrub; primary summer and winter range essentially the same; primarily roost in mines, caves, and rock shelters. Day roosts in mines are usually within about 80 feet of the entrance. Prefer roost sites with large areas of ceiling and flying space. In colder parts of their range, during winter, they are found in mines where temperatures are well above external ambient temperatures. During this time they are found in roosts with temperatures 80°F and are usually found 100 ft or more back from the entrance. Nocturnal roosts are found in places that provide overhead protection and an adequate flight approach. Such places including a variety of manmade structures, rock shelters and mines.

ELEVATION: All Arizona records below 4,000 feet (1,220 m) with most below about 2,500 feet (7,625 m). Based on records in the Heritage Data Management System, elevation ranges from 160 - 3,980 ft. (49 - 1,214 m) (AGFD unpublished data, accessed 2001).

FOOD HABITS: Primarily takes prey while hovering close to the ground or by gleaning from vegetation often within 3 feet of the ground. It does not crawl well, so it does not forage on the ground as does Antrozous pallidus but rather lands on its prey from above and then takes it to a night roost to feed. Feeds on large, flying insects such as grasshoppers, moths and flying beetles. Also capable of taking prey in flight. Insect larvae, especially lepidopterans, and other flightless, or daytime active prey are taken from bushes and off the ground. Daytime insects are especially important during winter months.

AIDS TO IDENTIFICATION: M. californicus may be identified by the combination of large ears and nose-leaf. No other large-eared bat has a nose-leaf and no other bat with a nose-leaf has such large ears. It is easily distinguished from Choeronycteris mexicana and Leptonycteris curasoae by its much larger ears (>29.0 mm [>1.16 in.)] in M. californicus, < 19.0 mm (0.76 in.) in C. mexicana and L. curasoae) which are joined together near their base. M. californicus also has a shorter rostrum, shorter tongue, no bristle-like papillae on the tongue and its first upper premolars contact its canines and usually also its second premolar. Guano of this bat is reported to have a distinctive odor that maybe used to help identify a roost.

Roosting Macrotus give clues to their identity by where they hang and how they cluster. They generally prefer to hang from the ceiling of caves and mines in groups of up to several hundred. Although they roost close to each other they are not usually touching or tightly packed as are the individuals of many other colonial bat species. If they do come into contact they become restless and move.