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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
roosted in a building at Bosque Del Apache National Wildlife Refuge (Mumford, 1957), and a 
maternity colony of several hundred Arizona myotis was reported from an attic of a seminary in 
San Miguel County that was the subject of several physiological ecology studies during 1966-1971 
(for example, Studier and O’Farrell, 1972; O’Farrell and Studier, 1973; Geluso and Studier, 1979). 
This colony sharply increased in size during 1970, peaking at about 15,000 individuals (O’Farrell 
and Studier, 1975). An attic of a home in the same region was reported to house a maternity colony 
estimated at 4,400 at peak summer size (O’Farrell and Studier, 1975). Hundreds of individuals 
were found roosting in diurnal colonies in narrow cracks and crevices under nine highway bridges 
over the Rio Grande in southern New Mexico during 2004-2006, including two maternity colonies 
in bridges constructed of timbers; roosting sites were at least 1.1 meters above ground (Geluso and 
Mink, 2009). A maternity colony of unreported size was found in the attic of an abandoned home 
in the Verde Valley of Arizona in 1960 and 1961 (Hayward, 1963). In human-made structures, Ari¬ 
zona myotis colonies will often occur with colonies of other species, including Yuma myotis, big 
brown bats, and fringed myotis (Studier, 1968; Geluso and Mink, 2009). 
Population Ecology.— Litter Size, Natality, and Female Reproduction: Surprisingly lit¬ 
tle has been published on litter size in the Arizona myotis, although the presumption that only one 
young is bom each year is likely valid. Single embryos were found in an adult female from Bosque 
Del Apache National Wildlife Refuge, a female from Santa Rosa, and an unspecified number of 
females from near Montezuma, all in New Mexico (Bailey, 1931; Mumford, 1957; Studier and 
O’Farrell, 1972; O’Farrell and Studier, 1973; Studier et al., 1973). 
Natality has been investigated in this species at several locations, but proportions of females 
breeding may be biased high in samples taken at maternity roosts. In New Mexico, all of 240 
females examined at a maternity roost in Las Vegas were reproductive in 1969 (O’Farrell and 
Studier, 1975; it is unclear if reproductive bats were intentionally selected), “about 90%” were 
pregnant the following year (O’Farrell and Studier, 1975:370; number examined not stated), and 
43 of 47 (91%) captured both at roosts and over water in the Mogollon Mountains (including adja¬ 
cent Arizona) during June and July in 1959-1962 were reproductive (C. Jones, 1964). In southern 
Colorado during 1968, 67 of 70 (96%) adult (greater than one year old) females examined at mater¬ 
nity roosts at three locations were reproductive (Davis and Barbour, 1970). However, females do 
not all breed in their first year of life. Only one of 35 one-year-old females examined at four loca¬ 
tions (including maternity colonies) in Colorado and New Mexico in summer 1968 were repro¬ 
ductive, compared to 97 of 109 (89%) older adults (Davis and Barbour, 1970). 
In northern Arizona, 12 of 38 (32%) females captured over water in ponderosa pine forest dur¬ 
ing 1993-1995 were reproductive, whereas 39 of 51 (76%) females captured over water in pine- 
oak forest during summers 1994-1995 were reproductive (Morrell et ah, 1999). In New Mexico, 
12 of 16 (75%) females captured over water at Bosque del Apache National Wildlife Refuge in 
1997 were reproductive (Chung-MacCoubrey, 1999), and 19 of 28 (68%) examined at a night roost 
at Eagle Nest in 1968 were reproductive (Davis and Barbour, 1970). At Mesa Verde National Park 
in southwestern Colorado 18 of 22 females (82%) captured over water during 2006 and 2007 were 
reproductive, with no differences between years despite a prolonged drought and reduced insect 
abundance in 2006; it was suggested that these bats maintained higher reproductive rates because 
of foraging access to the irrigated Mancos Valley where roosts were located (O’Shea et ah, 2011a). 
The proportion reproductive for the cumulative total females taken away from maternity roosts 
over all U.S. locations and years was 65% (100 of 155 bats). 
Survival: Diamond et ah (2015) investigated population dynamics of Arizona myotis roosting 
in wooden bat boxes placed on six ponderosa pines (four boxes per tree) within each of 24 one- 
hectare study plots in northern Arizona during 2005-2012. Bands were placed on 227 individuals 
