Site by Bennett Web & Design Co.
2006 SOUTHEASTERN NATURALIST 5(2):355–360
Use of Fungal Rhizomorphs as Nesting Material by
Glaucomys volans (Southern Flying Squirrels)
Suzanne Prange1,2,* and David H. Nelson1
Abstract - We examined 53 nests of southern flying squirrels constructed within
nest boxes in Mobile County, AL. Of those containing a bedding layer (n = 35),
80% contained fungal rhizomorphs of Marasmius brevipes. Rhizomorphs of this
genus have been reported in bird-nest descriptions, but have not been documented
in flying squirrel nests. M. brevipes was common on our study site, and its use by
flying squirrels may be unique to the area. Nevertheless, this and similar species of
rhizomorph-producing fungi occur in other portions of the flying squirrel’s range,
and the nondescript nature of rhizomorphs may lead to their misidentification. Our
observations appear to constitute the first description of an ecological relationship
between this fungus and a mammalian species.
Glaucomys volans (L.) (southern flying squirrels) are largely a cavitynesting
species, although outside nests have been reported (Dolan and
Carter 1977, Ivey 1959, Landwer 1935, Moore 1947, Snyder 1921). Nests
in cavities or nest boxes, particularly those used during summer, may
consist of only a thin layer of leaves or mosses (Gilmore and Gates 1985,
Muul 1968). Nests used during cooler periods and those constructed by
pregnant or lactating females, however, are often designed more elaborately
and typically include a layer of soft bedding material on top or
within a layer of leaves and/or mosses (Gilmore and Gates 1985; Muul
1968, 1974; Sonenshine et al. 1979). Material in the bedding layer is
usually woven into a chamber in the form of either a cup-like structure or
an enclosed ball. This layer is most often composed of finely shredded
inner bark (Gilmore and Gates 1985; Goertz et al. 1975; Heidt 1977;
Jackson 1961; Layne 1958; Muul 1968, 1974; Sollberger 1943), although
Tillandsia usneoides (L.) L. (Spanish moss) was most commonly used in
Florida (Ivey 1959, Moore 1947).
Outside nests are typically constructed externally of leaves and twigs,
and frequently contain a bedding layer of shredded bark (Ivey 1959,
Landwer 1935, Snyder 1921). As in cavity nests, however, Moore (1947)
reported the extensive use of Serenoa repens (Bartr.) Small (palmetto) and
Spanish moss in outside nests in Florida, with nests occasionally constructed
within fresh streamers of the latter. Other nesting materials have been
reported in both cavity and outside nests, including: hair, wool, feathers,
1Department of Biological Sciences, University of South Alabama, LSB 124, Mobile,
AL 36688. 2Current address - Max McGraw Wildlife Foundation, PO Box 9,
Dundee, IL 60118. * Corresponding author - email@example.com.
356 Southeastern Naturalist Vol. 5, No. 2
lichens, grass, pine straw, and chips of outer bark (Dolan and Carter 1977,
Goertz et al. 1975, Heidt 1977, MacClintock 1970, Muul 1974).
Glaucomys sabrinus (Shaw) (northern flying squirrels) also utilize both
outside and cavity nests, and nest construction is similar to that of G.
volans (Jackson 1961, Wells-Gosling and Heaney 1984). From the few
available descriptions of nests in cavities or nest boxes, however, it appears
the primary bedding material varies by location. In British Columbia,
Cowan (1936) described a hollow tree containing the remains of 14 nests
that consisted primarily of shredded bark, and Harestad (1990) similarly
reported shredded bark as the primary material in nest boxes, although the
use of moss was also observed. Ten cavity nests examined in the Pacific
Northwest (Oregon and Washington), however, were all lined with moss,
and moss constituted > 90% of the material in nest boxes (Carey et al.
1997). In central Idaho and western Montana, cavity nests were constructed
almost entirely of arboreal lichens (Hayward and Rosentreter
1994). Likewise, some descriptions of outside nests have noted bedding
layers of shredded bark (Cowan 1936, Manville 1942, Weigl and Osgood
1974), whereas others have reported the primary constituent of the bedding
layer to be moss (Carey et al. 1997) or lichens (Rust 1946). Other materials
found in both cavity and outside nests of G. sabrinus have included: wool,
grass, conifer needles, polyester batting (stolen from live-traps, where it
was used to provide insulation), paper, fern fronds, beargrass, feathers, and
egg-shell fragments (Bailey 1929, Carey et al. 1997, Cowan 1936, Hayward
and Rosentreter 1994).
Use of fungal rhizomorphs of the genus Marasmius has been reported for
bird nests (Foster 1976, Hedger 1990, McFarland and Rimmer 1996, Pérez-
Rivera 1993, Young and Zuchowski 2003). McFarland and Rimmer (1996)
examined 54 nests of 10 species of birds in a subalpine spruce-fir community
in the northeastern United States and found 85% of the nests contained
rhizomorphs of M. androsaceus (L. ex Fr.) Fr. Interestingly, this was the
first reported use of marasmioid rhizomorphs as a nesting material by birds
in North America. The authors, however, speculated that previous descriptions
of nesting material as “black roots,” “rootlets,” “moss stems,” or “hair”
may have actually described rhizomorphs.
Although its use by birds is now well documented, use of marasmioid
rhizomorphs has not been reported for flying squirrels or, to the best of our
knowledge, any other small mammal. In this paper, we describe the use of
fungal rhizomorphs as nesting material by southern flying squirrels.
During a larger study examining habitat use by southern flying squirrels
(Hatten 1992), we deployed 100 nest boxes (internal dimensions: 15 x 15 x 30
cm) similar to those of Sonenshine et al. (1973). Our study site was a 6-ha oakpine
woodland within a suburban park (Cottage Hill Park) in Mobile County,
AL. The canopy was comprised primarily of Pinus palustris Mill. (longleaf
2006 S. Prange and D.H. Nelson 357
pine), Quercus hemisphaerica Bartr. ex Willd. (laurel oak), Q. virginiana
Mill. (live oak), P. taeda L. (loblolly pine), and Q. falcata Michx. (southern
red oak). We used a grid system with 25-m intervals and hung nest boxes at 3–
4 m height on the tree nearest each grid point. We checked nest boxes for
occupancy every 2 weeks from June 1991 through May 1992 and made
detailed observations on the construction of nests when present.
Results and Discussion
Overall, 53 nest boxes contained southern flying squirrel nests. In general,
nest construction was similar to that previously reported (Gilmore and
Gates 1985; Goertz et al. 1975; Heidt 1977; Muul 1968, 1974; Sollberger
1943). Eighteen nests (34%) consisted solely of leaves and/or pine straw,
whereas 35 (66%) contained an additional bedding layer. As in previous nest
descriptions, shredded inner bark was a major constituent of the bedding
layer, occurring in 33 (94%) of these nests. Most of these nests (n = 28,
80%), however, also contained numerous black, hair-like fibers interwoven
with the bark shavings. The incorporation of these fibers appeared to add
stability to the bedding chamber. Furthermore, in 2 cases the bedding layer
consisted exclusively of this material woven into a cup-like structure. Upon
closer examination, minute fruitbodies were observed growing directly from
the black hair-like fibers.
Mycologist Juan Luis Mata (University of South Alabama; Mobile, AL)
identified these fibers as rhizomorphs of Marasmius brevipes (Berkeley and
Ravenel in Berkeley and Curtis). This species and several other members of
the genus Marasmius are saprotrophic or parasitic on tree branches, deciduous
leaves, and conifer needles (Desjardin and Petersen 1989, Gilliam
1976). A subset of these species are often referred to as “horsehair fungi”
and are characterized by copious production of thin, wiry rhizomorphs,
which allow for the colonization of leaves and branches (Seaver 1944).
Marasmius brevipes occurs throughout the southeastern United States
(Desjardin and Petersen 1989) and was abundant on our study site on
decaying wood and leaves, as well as on branches and leaves of living trees.
Although this species has been previously documented in Alabama (one
record in Monroe County, near Uriah; Desjardin and Petersen 1989), this
appears to be the first record of its occurrence in Mobile County, located
approximately 100 km southwest of Uriah, AL.
Southern flying squirrels are highly adaptable and opportunistic in their
choice of nesting material (Muul 1974). Flying squirrels at our suburban
study site also made use of anthropogenic items, including synthetic fibers
similar to upholstery stuffing (n = 18 nests, 34%; the source of this material
was never located), shredded newspaper (n = 1, 2%), plastic bags (n = 1,
2%), and candy wrappers (n = 1, 2%). As noted by Muul (1974), choice of
nesting materials by G. volans appears to reflect what is locally available.
Species of Marasmius, as well as Marasmiellus (which also contains
rhizomorph-producing species), occur widely within the southern flying
358 Southeastern Naturalist Vol. 5, No. 2
squirrel’s range. Therefore, it is possible fungal rhizomorphs in nests of
flying squirrels have been overlooked or misidentified in previous descriptions,
as appears to be the case for a number of bird species in North America.
Very little is known about M. brevipes, and the few studies reporting on
this species were limited to taxonomic and anatomical issues (Desjardin and
Petersen 1989). To our knowledge, no study has dealt with their ecology or
their ecological relationships within natural communities (J.L. Mata, pers.
comm.). As such, our observation of M. brevipes use by southern flying
squirrels not only documents extensive use of a previously unreported
nesting material, but also provides the first description of an ecological
relationship between this fungus and a mammalian species. Several species
of Marasmius produce antibiotic agents (Melin et al. 1947), as do many
species of lichens (Huneck 1999, Muller 2001), which are a common component
of flying squirrel nests (Dolan and Carter 1977, Hayward and
Rosentreter 1994). Thus, the incorporation of rhizomorphs of Marasmius
into nests might protect against pathogens and parasites (McFarland and
Rimmer 1996); however, this remains unconfirmed.
Use of M. brevipes by southern flying squirrels raises further questions
regarding potential ecological relationships. For example, northern
flying squirrels commonly incorporate lichens in their nests, which serve
not only as structural material, but also as food (Cotton and Parker 2000,
Cowan 1936). Thus, G. sabrinus may function as an important dispersal
agent for certain lichens (Hayward and Rosentreter 1994). We do not
know if southern flying squirrels consume M. brevipes, or whether collection
and transport of rhizomorphs to nests facilitate dispersal of this
fungus. Additional research is needed to determine to what extent southern
flying squirrels use marasmioid rhizomorphs, and to explore potential
ecological relationships between flying squirrels and M. brevipes, as well
as other rhizomorph-producing species. Regardless of any broader ecological
relationship, fungal rhizomorphs appear to provide an abundant,
easily manipulated, and structurally stable nesting material for southern
We are grateful to the Mobile Parks Department for access to Cottage Hill Park.
We are likewise grateful to the Environmental Studies Center for use of their
facilities. We thank the following individuals who assisted with fieldwork: D. Biggs,
T. Legarduer, and L. White-Buchanan. Helpful criticisms were received from two
anonymous reviewers and guest editor, Thomas J. Maier. Finally, we are grateful to
Dr. Juan Luis Mata for identifying our fungal specimens and providing us with
additional information on rhizomorph-forming fungi.
Bailey, B. 1929. Mammals of Sherburne County, Minnesota. Journal of Mammalogy
2006 S. Prange and D.H. Nelson 359
Carey, A.B., T.M. Wilson, C.C. Maguire, and B.L. Biswell. 1997. Dens of northern
flying squirrels in the Pacific Northwest. Journal of Wildlife Management
Cotton, C.L., and K.L. Parker. 2000. Winter activity patterns of northern flying
squirrels in sub-boreal forests. Canadian Journal of Zoology 78:1896–1901.
Cowan, I.M. 1936. Nesting habits of the flying squirrel Glaucomys sabrinus. Journal
of Mammalogy 17:58–60.
Desjardin, D.E., and R.H. Petersen. 1989. Studies of Marasmius from eastern North
America. III. Marasmius brevipes and Micromphale Sect. Rhizomorphigena.
Dolan, P.G., and D.C. Carter. 1977. Glaucomys volans. Mammalian Species 78:1–6.
Foster, M.S. 1976. Nesting biology of the Long-tailed Manakin. Wilson Bulletin
Gilliam, M.S. 1976. The genus Marasmius in the northeastern United States and
adjacent Canada. Mycotaxon 4:1–144.
Gilmore, R.M., and J.E. Gates. 1985. Habitat use by the southern flying squirrel
at a hemlock-northern hardwood ecotone. Journal of Wildlife Management
Goertz, J.W., R.M. Dawson, and E.E. Mowbray. 1975. Response to nest boxes and
reproduction by Glaucomys volans in northern Louisiana. Journal of Mammalogy
Harestad, A.S. 1990. Nest-site selection by northern flying squirrels and Douglas
squirrels. Northwestern Naturalist 71:43–45.
Hatten, S. 1992. Population ecology of the southern flying squirrel (Glaucomys
volans) in Alabama. M.Sc. Thesis. University of South Alabama, Mobile, AL.
Hayward, G.D., and R. Rosentreter. 1994. Lichens as nesting material for northern
flying squirrels in the northern Rocky Mountains. Journal of Mammalogy
Hedger, J. 1990. Fungi in the tropical forest canopy. Mycologist 4:200–202.
Heidt, G.A. 1977. Utilization of nest boxes by the southern flying squirrel,
Glaucomys volans, in central Arkansas. Proceedings of the Arkansas Academy of
Huneck, S. 1999. The significance of lichens and their metabolites. Naturwissenschaften
Ivey, R.D. 1959. The mammals of Palm Valley, Florida. Journal of Mammalogy
Jackson, H.H. 1961. Mammals of Wisconsin. University of Wisconsin Press, Madison,
Landwer, M.F. 1935. An outside nest of a flying squirrel. Journal of Mammalogy
Layne, J.N. 1958. Notes on mammals of southern Illinois. American Midland Naturalist
MacClintock, D. 1970. Squirrels of North America. Van-Nostrand Reinhold Co.,
New York, NY.
Manville, R.H. 1942. Notes on the mammals of Mount Desert Island, Maine. Journal
of Mammalogy 23:391–398.
McFarland, K.P., and C.C. Rimmer. 1996. Horsehair fungus, Marasmius
androsaceus, used as nest lining by birds of the subalpine spruce-fir community
in the northeastern United States. Canadian Field-Naturalist 110:541–543.
360 Southeastern Naturalist Vol. 5, No. 2
Melin, E., T. Wiken, and K. Oblom. 1947. Antibiotic agents in the substrates from
cultures of the genus Marasmius. Nature 159:840–841.
Moore, J.C. 1947. Nests of the Florida flying squirrel. American Midland Naturalist
Muller, K. 2001. Pharmaceutically relevant metabolites from lichens. Applied Microbiology
and Biotechnology 56:9–16.
Muul, I. 1968. Behavioral and physiological influences on the distribution of the
flying squirrel, Glaucomys volans. Museum of Zoology, Miscellaneous Publication
134. University of Michigan, Ann Arbor, MI.
Muul, I. 1974. Geographic variation in the nesting habits of Glaucomys volans.
Journal of Mammalogy 55:840–844.
Pérez-Rivera, R.A. 1993. Notes on breeding of the Puerto Rican Tanager
(Nesospingus speculiferus). Caribbean Journal of Science 29:262–264.
Rust, H.J. 1946. Mammals of northern Idaho. Journal of Mammalogy 27:308–327.
Seaver, F.J. 1944. The horse-hair fungi. Mycologia 36:340–342.
Snyder, L.L. 1921. An outside nest of a flying squirrel. Journal of Mammalogy
Sollberger, D.E. 1943. Notes on the breeding habits of the eastern flying squirrel
(Glaucomys volans volans). Journal of Mammalogy 24:163–173.
Sonenshine, D.E., D.G. Cerretani, G. Enlow, and B.L. Elisberg. 1973. Improved
methods for capturing wild flying squirrels. Journal of Wildlife Management
Sonenshine, D.E., D.M. Lauer, T.C. Walker, and B.L. Elisberg. 1979. The ecology of
Glaucomys volans (Linnaeus, 1758) in Virginia. Acta Theriologica 24:363–377.
Weigl, P.D., and D.W. Osgood. 1974. Study of the northern flying squirrel,
Glaucomys sabrinus, by temperature telemetry. American Midland Naturalist
Wells-Gosling, N., and L.R. Heaney. 1984. Glaucomys sabrinus. Mammalian Species
Young, B.E., and W. Zuchowski. 2003. First description of the nest of the silveryfronted
Tapaculo (Scytalopus argentifrons). Wilson Bulletin 115:91–93.