Terry A. Vaughan

“ More than seasonal differences in length of pelage is indicated by measurements of additional specimens of each subspecies taken at different times of the year.
Considering its extensive geographic range and its occurrence in many contrasting environments, Myotis velifer varies little; and the variation that does occur is continuous. The change from the large, dark Mexican subspecies to the small, pale Arizonan subspecies is gradual. The reason may lie in the ecology of M. velifer. It seems that there are few barriers separating populations. ”

“ Waterless areas and regions lacking suitable roosting places such as fissures in cliffs and outcrops of rocks, caves and buildings, may exclude the species from certain areas, but there are few areas of any great size within [Pg 512] the range of the species that lack these features. Also, these bats are strong fliers; even between fairly distant colonies there may be considerable gene flow. The geographic variation observed probably is the result of adaptation, on the part of populations in different parts of the range of the species, to different environments. ”

“ These sparsely-furred areas are less evident in live animals than in study skins and specimens in alcohol, because the back of the head in life lies against the depression between the shoulders and conceals most of the thinly furred areas.
The pelage of Myotis velifer brevis is shorter than that of either M. v. velifer or M. v. incautus and gives the impression of being less dense. The dorsal hairs average approximately 4.5 millimeters long in M. v. brevis taken 35 miles north of Blythe, Riverside County, California, in May, eight millimeters in M. v. ”