O’SHEA, CRYAN & BOGAN: UNITED STATES BAT SPECIES OF CONCERN 
197 
sion of Wildlife Resources 
(2015, Sutter et al., 2005): 
Species of Greatest Conservation 
Need. 
Description. — The big 
free-tailed bat (Fig. 39) is among 
the larger bats found in the Unit¬ 
ed States. Forearm lengths range 
from 58 to 64 millimeters, body 
mass ranges 22 to 37 g, and 
wingspans range to 436 millime¬ 
ters (Barbour and Davis, 1969; 
Milner et al., 1990; Parish and 
Jones, 1999; Higginbotham and 
Ammerman, 2002). The hairs are 
bicolored and lighter at the base, 
and the pelage varies from gray Figure 39. Big free-tailed bat, Nyctinomops macrotis (photo by J. Scott 
to medium and darker shades of Altenbach). 
brown (Milner et al., 1990), with considerable color variation among individuals within a colony 
(Borell, 1939). The upper lips are wrinkled. As typical for a molossid bat, the tail extends beyond 
the interfemoral membrane, the ears are large, rounded airfoils joined at the midline, and the long 
narrow wings render these bats capable of rapid flight (Vaughan, 1966). 
Distribution and Systematics. — Although the species is widely distributed throughout the 
Americas and the Caribbean, in the United States populations seem localized and the core of the 
range appears to be the rugged, rocky landscapes of the Four Comers states (Fig. 40). Extralimital 
records are widespread in North America and include places as far from the typical range as British 
Columbia, Kansas, Iowa, Missouri, Oklahoma, and South Carolina (Cary, 1911; Bowles, 1975; 
Dalquest et al., 1990; DiSalvo et al., 1992; Nagorsen and Brigham, 1993; Pitts et al., 1996; Sparks 
and Choate, 2000); these may represent post-breeding wandering juveniles of this rapid and pow¬ 
erful flyer (Milner et al., 1990). The big free-tailed bat is referred to as Tadarida molossa and as 
Tadarida macrotis in earlier scientific writings, but it was elevated to the genus Nyctinomops based 
on morphological analysis (Freeman, 1981). Molecular genetic studies have been conducted on this 
species that confirm its distinctiveness and provide interpretations of its relationships to other 
species of molossid bats (Ammerman et al., 2012b; Dolman and Ammerman, 2015). There are no 
named subspecies. Milner et al. (1990) provided a complete taxonomic synonymy of past scientif¬ 
ic names for the big free-tailed bat. Another English common name is the Tacubaya free-tailed bat. 
Habitats and Relative Abundance. — Big free-tailed bats have been captured in mist nets 
in a range of habitats in the western United States, including lowland deserts, pinon-juniper, pon- 
derosa pine, and mixed conifer vegetation assemblages ranging to over 2,800 meters in elevation 
(for example, Borell, 1939; Cockrum and Ordway, 1959; Zimmerman, 1970; Jones and Suttkus, 
1972; Easterla, 1973; Carothers and Ruffner, 1974). However the distribution seems localized. A 
few areas have been documented where they are likely to be taken in surveys, but they are rare in 
many other surveyed areas within the general distribution. They have not been captured in several 
intensive mist-netting surveys within their general distribution (for example, Black, 1974; Cock- 
rum et al., 1996; O’Shea et al., 2011a; Geluso and Geluso, 2012; Jones, 2016), again suggesting 
only localized abundance. In a few other studies, this species has not been captured but has been 
detected based on vocalizations or echolocation, perhaps at significant distances from roosts. 
