Natural history and conservation.—Most of the information
available on the ecology, reproduction, and natural history of
M. midastactus comes from museum labels and from L.
Aguirre’s fieldwork in Bolivia. This information is synthesized
under accounts for M. simus in Espinoza (2007) and Moratelli
(2012). Myotis midastactus has day roosts in holes in the
ground, under thatched roofs, and hollow trees (Espinoza 2007;
Moratelli 2012). In the first 2 roosts, it was found together with
the Argentine brown bat, Eptesicus furinalis d’Orbigny and
Gervais, 1847 (Espinoza 2007).
According to Aguirre et al. (2003), 1 or 2 individuals of M. midastactus have been found
in hollow trees (Handroanthus heptaphyllus: Bignoniaceae) in
mixed groups with the lesser bulldog bat, Noctilio albiventris
Desmarest, 1818; and 1 was found sharing a roost with N.
albiventris and the Pallas’s mastiff bat, Molossus molossus
(Pallas, 1766). Individuals of M. midastactus and N. albiventris
from these roosts had similarly colored fur, texture, and smell;
on the basis of the number of individuals, M. midastactus is
solitary or forms very small groups (Aguirre et al. 2003).
Myotis simus is another species that shares roosts with N.
albiventris; cohabitation records are from Paraguay (Myers and
Wetzel 1979) and northern Brazil (Patterson 1992). Population
samples from northern Brazil unquestionably represent M.
simus, but those from Paraguay were not included here and
their identification is pending.