Squirrels of the World

Glaucomys volans 95

year have been reported, although, as in G. volans, it is un-
likely that the same female produces more than one litter
annually. The young are 5–6 g at birth; details of their devel-
opment are available in the literature. Population densities
typically average 0.25 to 2.5 animals/ha, but have been ob-
served to reach 12/ha. In the Oregon Cascades (USA), G. sa-
brinus averages about 2 animals/ha in both secondary and
primary Douglas fi r (Pseudotsuga menziesii) stands. Home
range sizes vary considerably with habitat and location;
reports typically diff er across studies—from 1 to 7 ha per
animal—but their ranges have been observed to reach 35 ha
in the east. Supplementation experiments show that in the
Pacifi c Northwest (USA), food (but not nest cavities) limits
the densities of northern fl ying squirrels. Where this spe-
cies is sympatric with G. volans, it may be excluded from
nest cavities. In Pennsylvania (USA), G. sabrinus and G. vo-
lans converge on stands of hemlock (Tsuga) for nesting, and
the two species have even been observed to nest together.
Here, G. volans spends most of its time foraging in adjacent
hardwoods, whereas G. sabrinus restricts nearly all of its ac-
tivity to the hemlocks.
A number of avian and mammalian predators are re-
ported to take northern fl ying squirrels, and this species is
a preferred food item of the Northern Spotted Owl (Strix
occidentalis) in the Pacifi c Northwest (USA). G. sabrinus hosts
relatively high numbers of both ecto- and endoparasites for
a sciurid. More ectoparasites are found on males than on
females, and they more heavily infest smaller males than
larger ones. At least 9 fl ea species, 3 louse species, and 10
mite and tick species are reported. Endoparasites include 2
species of Eimeria (protozoans), 6 nematodes, and 4 species
of cestodes. The nonoverlapping geographic ranges of G.
volans and G. sabrinus may result from parasite-mediated com-
petitive exclusion, wherein the nematode Strongyloides ro-
bustus, a common parasite of G. volans, is potentially lethal
to G. sabrinus. Fossils of this species are reported since the
late Pleistocene. Cytochrome b sequence data from mito-
chondrial DNA is signifi cantly more variable in G. sabrinus
than in G. volans, and it shows two separate lineages in G.
sabrinus, suggesting the possibility of a third species of Glau-
comys. Loss of genetic variation and genetic diff erentiation
are evident in populations on coastal islands in the Pacifi c
Northwest (USA). Despite previous evidence of diff erences
in chromosome number and bacular structure, the two spe-
cies of Glaucomys have been reported to hybridize, produc-
ing viable off spring that are intermediate in pelage charac-
teristics and size. Such hybridization in the northeastern
part of the range may be due to climate change, habitat loss,
or a combination of the two, which has increased sympatry
between the two species.

general references: Anthony 1928; Arbogast 1999; Ar-

bogast et al. 2005; Bakker and Hastings 2002; Bidlack and

Cook 2001; Bradley and Marzluff 2003; Carey 2000, 2001,

2002; Carey, Horton, et al. 1992; Carey, Kershner, et al. 1999;

Demboski et al. 1998; Garroway et al. 2010; Hackett and Pa-

gels 2003; D. S. Hall 1991; Holloway and Malcolm 2007; How-

ell 1915a; Krichbaum et al. 2010; A. W. Linzey and Hammer-

son 2008a; Loeb and Tainter 2000; Meyer, North, et al. 2005;

D. Mitchell 2001; Odom et al. 2001; J. L. Payne et al. 1989;

Perez-Orella and Schulte-Hostedde 2005; Pyare and Long-

land 2001; Ransome and Sullivan 1997, 2002, 2003, 2004; Ra-

phael 1984; Rosenberg and Anthony 1992; Scheibe et al.

2007; W. P. Smith 2007; W. P. Smith, Gende, et al. 2004;

Vernes 2001; Vernes et al. 2004; P. D. Weigl 2007; Wells-

Gosling and Heaney 1984; Witt 1991, 1992; Zittlau et al. 2000.

Glaucomys volans (Linnaeus, 1758)

Southern Flying Squirrel

description: G. volans is a small fl ying squirrel, usually

weighing approximately 60 g. It is easily identifi ed by its

grayish brown dorsum; white, cream or yellowish venter;

and the dark brownish edge of the dorsal and ventral sur-

faces of the patagium (“wing”). The head is gray, and the

cheeks are white. The dorsal pelage consists of fi ne dense

fur. G. volans is distinguished from the only other fl ying

squirrel in North America—G. sabrinus—by its smaller size

and the whitish base of the ventral hairs (which are dark

gray in G. sabrinus). Despite diff erences in the bacula and