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PROCEEDINGS OF THE CALIFORNIA ACADEMY OF SCIENCES 
Series 4, Volume 65, Supplement I 
boat sheds (Rice, 1957; Bain, 1981; Felts and Webster, 2003). These bats will shift to warmer 
roosts in buildings during cold snaps in Florida (Bain, 1981). 
Southeastern myotis also will roost in hollow trees during winter in the southern parts of the 
distribution that lack caves. Two males radio tracked in winter in Georgia switched roosts in trees 
every 2.8 days with distances between successive roosts ranging from 15 to 2,237 meters (Clement 
and Castleberry, 2013b). Trees used as roosts in winter were smaller and had smaller but higher 
roost openings than trees used in summer, perhaps to avoid trees with entrances subject to winter 
flooding. As during summer, bats did not use trees with chimney-like openings at the top; winter 
roosts were in hardwood forest with lower flooding than the cypress-gum swamps used in summer 
(Clement and Castleberry, 2013a,b). The seasonal differences in tree roosts found in the Georgia 
study indicate that in some areas findings from summer studies alone may not reveal a full suite of 
roost attributes necessary for year-round management (Clement and Castleberry, 2013b). 
In eastern Mississippi, trees with cavities used by southeastern myotis in winter had larger 
girths and larger cavity volumes than trees with cavities that were unoccupied, but in spring, trees 
that were selected were similar in girth and cavity size (Fleming et al., 2013a). On the landscape 
scale, roost trees found in winter during the eastern Mississippi study were at lower elevations, and 
during spring they were farther from roads than unoccupied trees with cavities (Fleming et al., 
2013a). Availability of water in winter was a possibly important landscape characteristic for this 
species at Noxubee National Wildlife Refuge in Mississippi, where colony sizes in both winter and 
summer were 50 or fewer bats and larger trees were used as winter roosts than were used as sum¬ 
mer roosts (Stevenson, 2008). As in summer, only water tupelo trees with basal hollows and no 
upper openings were observed to be used by individuals during winter at Upper Ouachita Nation¬ 
al Wildlife Refuge in northeastern Louisiana, with some individual trees used much more fre¬ 
quently than other roost trees (Rice, 2009). Most winter observations were of solitary bats; larger 
roosting groups in winter were often inactive, but left roosts to forage on warmer days (Rice, 2009). 
Warm Season Roosts in Caves: In Florida, caves used by maternity colonies often have per¬ 
manent water and large areas of horizontal ceilings at least 2 meters above the water surface (Rice, 
1957; but see below). Although clusters of these bats have been observed in dry areas in some 
caves (Mumford and Whitaker, 1982; Gore and Hovis, 1994), colonies in caves are often found 
over water, a roosting habit which may deter predators as well as increase humidity for the clusters 
of developing young (Rice, 1957; Foster et al., 1978). Banding returns in Florida caves suggest that 
adults have a strong fidelity to specific caves, but that juveniles are more likely to wander (Rice, 
1957). Many caves used as nursery sites in Florida have large, horizontal high ceilings as well as 
permanent bodies of water, and bats may desert caves when the water level is low (Rice, 1957; 
Bain, 1981). However, there is conflicting evidence for the importance of over-water roosts for this 
species, and additional study of this topic is desirable (Gore and Hovis, 1994). 
Maternity colonies of southeastern myotis numbering from about 2,000 to 90,000 adults form 
in dense clusters (1,600 per square meter) in Florida caves during late March and early April (Rice, 
1957). Young are bom from late April to late May, with young bats taking flight at five to six weeks 
of age; adult males join maternity colonies in large numbers after this time, with most bats dis¬ 
persing from these sites in October (Rice, 1957). A colony of about 1,000 southeastern myotis uti¬ 
lized a cave in Mississippi when visited in both July and October (McCartney, 2007). 
Warm Season Roosts in Trees: Colonies in trees include maternity groups but tend to be 
smaller than those found in other stmctures (Clark, 2003; Mirowsky et al., 2004). A count of 101 
bats was reported from a hollow water tupelo in southern Illinois (Gardner et al., 1992; Hofmann 
et al., 1999). Roost trees utilized by southeastern myotis maternity colonies in bottomland forests 
will be abandoned during periods of unusually high flood waters (Gardner et al., 1992; Hofmann 
et al., 1999). 
