Stephen Sharnoff and Roger
Rosentreter (Bureau of Land Management, Idaho)
Updated: February 2, 1998
Return to Lichens and Wildlife
Go to LICHENS AND INVERTEBRATES: A BRIEF REVIEW AND BIBLIOGRAPHY
Many species of hummingbird use lichens to decorate their nests. This is probably a Black-chinned hummingbird (Archilochus alexandri) and the nest was high in a large Pitosporum in Berkeley, California.
"By late March or early April the [polar bear] cubs weigh about 25 pounds, and the female, depending on the weather and the cub's condition, breaks out of her den. For the first days she might just sit drowsily in the sun at the den entrance. Or roll in the snow to revive her coat. Or nose about in a desultory way, looking for grasses and lichens to nibble." --from Arctic Dreams by Barry Lopez
With the exception of caribou, whose dependence on lichen is
well documented, references to lichens in literature on wildlife
are few. Lichens are less familiar to most researchers than
vascular plants; in animal studies they are frequently grouped with
other fungi or with mosses. Nomenclature is often vague,
particularly in the older literature. In the northern forests, and
in higher elevation habitats, lichen use seems to be heaviest in
winter, a season when fewer studies have been done.
This survey is an attempt to gather together those reports
that indicate significant use, primarily as food and nesting
material. For many of the animals discussed, there is some
research that does not mention lichens at all, or cites only trace
amounts of lichens being used. Lichens enhance wildlife habitat in
less direct ways as well: many species, especially the nitrogen-
fixing lichens, increase nutrient availability for vascular plants,
and lichens can be important in controlling soil erosion.
It is worth noting that a given forage may appear to be a
rather small percentage of an animal's yearly diet yet play an
important strategic role. In many instances lichens, perhaps the
least seasonal of forages, are one of the few foods available in
winter; they can be especially important during the most stressful
periods when the snowpack is deep or crusted. In these cases
lichens may be a crucial factor in ensuring survival until spring,
suggesting that lichens are a unique resource for many mammals
during this critical time of year.
It is generally useful to distinguish between forage
preference and actual importance in the diet. Some forage species
may be highly preferred, yet, because of scarcity, contribute
little to overall diet composition. Many animals, particularly
deer, eat a wide variety of plants, and their choices are based on
a complex set of factors. Certain plants are more palatable, or
more available, during certain seasons, and the nutritional needs
of animals change with the seasons, and with their sex, age, and
condition. Winter is always the heaviest, and sometimes the only,
season of lichen use by the mammals listed below--at least where
there is any information about seasonality. This pattern suggests
that lichens are not particularly preferred, but increasingly taken
as the seasonal forages become unavailable.
Lichens are generally regarded as low in protein but high in
carbohydrate, and this is true for the species most sought after by
caribou and deer. The fruticose Cladonia and Cetraria
genera, and the arboreal Alectoria, Bryoria, and Usnea, all of
which are the favored forage of caribou, contain a rough average of
2% crude protein, not enough for a complete year-round diet for
either caribou or deer. Most researchers feel that a variety of
other plants possessing a higher protein content is necessary for
caribou, although they apparently can sustain themselves for
extended periods on lichens alone. Interestingly, some of the
foliose lichens, such as Peltigera spp. and Lobaria spp. have much
more protein. Scotter (1964), found several species of Peltigera
containing from 17% to 21% crude protein. In spite of this, these
foliose lichens are less preferred by caribou, presumably because
other species are more important for their energy content. On the
other hand some reports suggest that mountain goats in some areas
eat considerable quantities of Lobaria (Fox 1989). Scotter found
that Stereocaulon, a genus whose palatability to caribou he found
to be moderate, had a fairly high protein content of 7.28%.
Digestibility of lichens is considered by most researchers to
be high, although tests done with animals not used to eating them
pointed to a very low digestibility. Hanley et. al (1989) found
the in-vitro dry matter digestibility (IVDMD) of Usnea and
Alectoria to be 15-26%, but points out that among animals whose
rumens contained microorganisms specifically adapted to lichens the
IVDMD was as high as 85.2%. Certainly, caribou (and many deer) in
northern forests are used to eating lichens. Lichens may be an
important dietary supplement to deer in another way. Rochelle
(1980) says, "Overall digestibilities of mixtures increased beyond
expected levels as increasing amounts of Alectoria sarmentosa were
added, suggesting that presence of this highly digestible species
enhances the degree to which the entire diet is utilized."
Apart from their food value, lichens may be important as a
source of free water during periods of cold temperatures. The
arboreal lichens in the genus Bryoria are dark-colored and
therefore a good absorber of solar radiation. They probably
provide liquid for the northern flying squirrel and other animals
(Thomas and Rosentreter, 1994.)
Both birds and small mammals who use lichens for nest building
undoubtedly benefit from the lichens' insulating properties.
One disadvantage of eating lichens, particularly for human
hunters who eat the meat of caribou and deer, is that lichens
absorb and accumulate radioactive fallout far more than vascular
plants and pass them along in the food chain. As Richardson and
Young (1977) put it, "Liden (1961)...showed that reindeer meat
contained 280 times the 137Cs level of beef produced in the same
general area." In a study in Alaska (Viereck, 1964) it was found
that "Lichens have concentrations of strontium-90 and cesium-137 of
from 10 to 100 times that of most other plants from either
temperate or northern regions...Caribou and reindeer have
concentrations of strontium-90 in meat and bones that are about 25-
30 times that found in meat in the average U.S. diet. Cesium-137
levels are from 3-300 times that found in beef...Strontium-90 in
bone in caribou-eating Alaskan Eskimos is being laid down at about
four times the rate of that of the average U.S. citizen...Inland
Alaskan Eskimos at Anaktuvuk in the summer of 1962 had whole body
counts of cesium-137 ...approximately 50-100 times the
concentration of cesium-137 in people of temperate latitudes."
After the Chernobyl disaster many reindeer in northern Europe had
to be destroyed without their meat being consumed.
All lichen names have been updated to conform with the Sixth
Checklist of the Lichen-forming, Lichenicolous and Allied Fungi of
the Continental United States and Canada (Esslinger and Egan,
1995). Where a lichen is listed below with an asterisk (*) the
identification is more than usually suspect.
Rangifer tarandus (caribou, reindeer)
In North America the species is divided
caribou (R.t. granti, R.t. groenlandicus, and R.t. pearyi) which
range over thousands of miles of arctic tundra and woodland caribou
(R.t. tarandus) whose home is the boreal forest. Large populations
live in Alaska and northern Canada. South of Canada, there is one
small herd, in the Selkirk Mountains of Idaho. This population
was declared endangered in 1984. European "reindeer" are a
different subspecies, some of which have been imported. These
subsequently interbred with barren-ground caribou. Likewise, some
populations of tundra caribou migrate into boreal forest areas
where they may interbreed with woodland caribou.
All caribou except for R.t.pearyi, the Peary caribou, depend
on lichens for food; their rumens contain microorganisms
specifically adapted for digesting lichens. Lichens are thought to
be the primary source of carbohydrate energy for caribou, and are
thus particularly important in winter. This energy is transferred
to the caribou's main predator besides humans, that is, wolves,
whose continued survival is directly linked to that of the caribou.
In the high arctic, the Peary caribou eat less lichen than
continental caribou, mostly subsisting on vascular plants and
increased use of moss, although they "do retain a preference for
foliose lichens in their winter diet" (Klein, 1979) even though
foliose lichens are rather scarce in that environment.
Barren-ground and woodland caribou feed on the mats of
terricolous lichens in both tundra and taiga (boreal forest), and
both eat substantial quantities of arboreal lichens as well.
Typical ingestion rates of ground lichens in northern Alaska in
winter range from 3.7 to 6.9 kg dry weight lichens per day for
adult females (Hanson et al. 1975).
Woodland caribou also eat lichens that grow on the ground.
Barrette and Vandal (1986) write, "We spent two winters studying
the social behavior of wild woodland caribou (Rangifer tarandus
caribou) at a time when their main food (ground lichens; Cladina
spp.) is available only at snow craters dug by the animals. The
competition for access to such craters was severe, the animals
constantly trying to take over the craters of others." Arboreal
lichens, especially Alectoria sarmentosa and Bryoria spp., are also of great
importance to woodland caribou. Edwards et al. (1960) say about
caribou in Wells Gray Provincial Park, British Columbia, "During
winter these lichens provide most of their food (Edwards and Ritcey
1960) and appear to be the only food available in quantity." In
all seasons caribou eat other forage besides lichens, but in winter
lichens comprise the bulk of their diet.
Overgrazing, and trampling of the tundra, have been problems
in some areas. Caribou were introduced to St. Matthew Island in
the Bering Sea in 1944. The herd rapidly increased to 6000 animals
by 1963, by which time they had eaten most of the lichens. That
winter less than 50 animals survived. In North America in general,
however, overgrazing seems not to have been a serious problem.
Caribou typically graze intermittently as they go, so that even
when a large herd has passed through an area many patches of
ungrazed forage remain.
Bergerud (1974) has discussed the decline of caribou in the
late 1800's and early 1900's. He argues that a combination of
hunting, predation, and possibly disease was responsible, rather
than destruction of the caribou ranges through overgrazing or fire.
He believes that caribou do not absolutely require lichens if
enough other forage is available. Scotter (1964) and Kelsall
(1968) emphasized the impact of fire and the slow post-fire
regeneration of lichens as possibly key factors in caribou decline,
but this view has been disputed by Bergerud (above) and Miller
(1979) who says, "Wildfire control as a caribou management tool is
no longer valid in northcentral Canada where caribou movements are
relatively unrestricted by human developments." In a recent review
of the "grand caribou controversy" (Cumming, 1993) that evaluates
the influence of both predation and habitat inadequacy on woodland
caribou, the author concludes that, "we should manage forests to
maintain lichen ares with few predators, and also manage to
maintain or increase the lichen supplies in those areas."
In many boreal forest regions, such as in northern Alberta,
intensive logging for pulp wood is destroying the lichen
communities upon which the woodland caribou depend. Oil and gas
development, with its road building and increased access by
hunters, is also stressing the herds. The number of woodland
caribou in Alberta has fallen from approximately 8000 in 1966 to
less than 2000 in 1990, and they may be in imminent danger of
extinction in that province. An increasing threat to the lichens
in the far north is local and global pollution, especially by
sulfur dioxide, fluorides, and acid rain. In Siberia, for example,
"Losses of terricolous lichens in the Taimyr from pollution
generated by the Norilsk metallurgical complex have been nearly
complete within a 300,000 ha area...and damage and reduced growth
extends over an area in excess of 600,000 ha. The Arctic also is
a sink for atmospheric pollution generated in the heavily
industrialized north temperate regions of the world." (Klein and
Vlasova, 1992.) Schofield (1975) says, "...all of the ingredients
necessary for lichen damage are present...The accelerated
industrialization of the Arctic makes this possibility of more than
It is probably fair to say that in most of the main ranges of
both barren-ground and woodland caribou there is no other forage
besides lichens which can provide the basis for their continued
Table 1. Lichens used by caribou.
Odocoileus hemionus (mule deer, black-tailed deer)
This deer ranges over most of western North America, from
coastal Alaska into Mexico. Wallmo (1981) recognizes seven
subspecies, of which two are known to make significant use of
lichens, the Sitka black-tailed deer (O.h. sitkensis) and the
Columbian black-tailed deer (O.h. columbianus). A third, the Rocky
Mountain mule deer (O.h. hemionus) is cited by Kufeld et al. (1973)
as occasionally eating lichens. Both anecdotal evidence and
several studies mentioned below suggest that lichens rank quite
high in deer preference, at least seasonally. The annual
productivity of lichens is generally low when compared with most
forbs and browse plants, so the impact of deer foraging on lichens
within their reach can be striking.
Odocoileus hemionus sitkensis (Sitka black-tailed deer)
Studies done in Southeast Alaska indicate that arboreal
lichens, in particular the "beard" lichens Alectoria sarmentosa and
Bryoria spp., are critical winter survival food for these deer.
When other forage is buried under snow, or in a dormant state, the
lichen litterfall is the energy source which can provide the
"bridge" to springtime. Rochelle (1980) states about deer in
winter on northern Vancouver Island, British Columbia, "Alectoria
spp. occurred at 100 percent frequency in rumens of 12 deer
collected in mature conifer stands. These lichens made up 35.5
percent of the volume of rumen contents of these deer." The deer
eat lichens in smaller amounts throughout the year. Another study
(Schoen and Kirchhoff, 1983) found that fecal samples collected in
early March in Southeast Alaska contained as much as 43% lichen,
and that presence of lichen in the samples correlated well with
increasing snow depth.
The dependence of deer on lichens, and the fact that the
lichens are abundant only in mature forests, has important
management implications. Rochelle remarks, "With harvest rotations
of 100 years or less, it is unlikely that significant biomass of
lichens will develop in second-growth forests." Hanley et al.
(1989) say, "Retention of old-growth forests for winter range
during periods of snow will remain an important feature of habitat
management for deer while techniques for increasing the carrying
capacity of even-aged stands are sought."
Table 2. Lichens used by Sitka black-tailed deer.
Odocoileus hemionus columbianus (Columbian black-tailed deer)
Columbian black-tailed deer are found from central California
to British Columbia. On Vancouver Island they are heavy consumers
of beard lichens, especially in winter. Deer rumen in one winter
study contained 26% lichens by volume (Stevenson and Rochelle
1984). In this same area, digestibility of A. sarmentosa by mule
deer was found to be high; Robbins (1987) says, "This lichen can be
an important source of energy to wintering cervids."
On the University of California Hastings Reserve east of Carmel,
California, mule deer eat many kinds of lichens that grow on the
oaks. They nibble litterfall lichens and frequently rear up on
their hind legs to reach for lichens in the trees, thus creating a
marked browse line. In March, 1992 the author observed two deer
exclosures at Hastings, a two-year and a six-year exclosure. In
the latter, the Ramalina menziesii hung right down to the ground,
the only place in the preserve where this was the case. Lichen
consumption reaches its peak in early winter.
Linsdale (1953) characterizes lichens as among those plants
"avidly sought." He describes one incident as follows: "In
afternoon in early February...a doe discovered a clump of lichen
about 2 feet long dislodged from a large valley oak in a recent
storm. When the doe began eagerly to feed on the clump, another
doe 10 feet away rushed over and drove her off by striking with the
left forefoot. She missed her mark only because the first doe
leaped off to the side. The aggressor fed on the lichen, allowing
her yearling to join without interference."
At the University of California Hopland Field Station in
communities of grassland, mixed hardwood, Douglas-fir (Pseudotsuga
menziesii), and chaparral, black-tailed deer eat a variety of
lichen species, most conspicuously the hanging Ramalina menziesii.
In "cafeteria" feeding trials at Hopland, set up to determine
forage preference, the deer chose R. menziesii over every other
forage except mistletoe (Phoradendron villosum). In the same
trials domestic sheep chose lichens third, after black oak (Quercus
kellogii) and mistletoe. For both deer and sheep poison oak (Rhus
diversiloba) was the next most favored forage after lichens; they
were given a choice of 31 items. This study (Longhurst et. al
1979) found that lichens ranged from 7.7% volume in rumen samples
in December to 0.1% in January, with a yearly mean of 2.0%, and a
frequency of occurrence of 56.7% for the year. These figures
placed lichens as third highest in both volume and frequency among
the 93 plants listed. Interestingly, a different study from the
same area at the same time (Menke and Fry, 1979) found similar
levels of lichen consumption, but use was highest in April (6.7%
volume) and July-August (6.3%), with only a trace in December and
The deer at Hopland were found by Book et. al (1972) to have
elevated levels of the radioisotope 137Cs because of the lichens
they were eating: "Oak woodland deer ate appreciable amounts of
lichens at all seasons; these lichens contained up to 140 times the
137Cs activity of other forage."
Table 3. Lichens used by Columbian black-tailed deer.
Usnea fillipendula *
Usnea florida *
Odocoileus virginianus (white-tailed deer)
"A marked "browse line" on arboreal lichens...and substantial
use of lichens at feeding stations all suggest these epiphytes are
an important winter forage of White-tailed deer in Maine." (Hodgman
and Bowyer 1985). "Use of arboreal lichens by deer dropped
precipitously in early May as succulent forbs and grasses became
available in nearby fields. Crude protein and energy available
from arboreal lichens compare favorably with other winter
Llano (1956) cites R.S. Palmer of the New York State Museum as
noting, "...Usnea is one of the best foods in baiting traps for
northern white-tailed deer, that on overbrowsed ranges Usnea was
completely cleaned out as high as the animals could obtain it, and
that, when trees are being felled, tame deer will come running to
feed on this lichen." Jenks and Leslie (1988) remark, "Available
lichen may enhance energy balance during winter when poorly
digested browse species make up the bulk of winter
diets...availability of lichen in winter could have important
implications for deer management in boreal habitats." George
Pauley found that white-tailed deer were eating lichens in northern
Idaho during winter storms, when the deer remained confined in old-
growth timber stands (personal communication, 1997). Lichens
reportedly used by white-tailed deer include Evernia mesomorpha and
Oreamnos americanus (mountain goat)
Lichen use by mountain goats varies widely, depending on
location and season. While many studies report no use on summer
ranges and little use in winter, others indicate substantial
foraging for lichens. Harmon (1944) claims that mountain goat
diets in the Black Hills of South Dakota in winter consisted of
about 60% mosses and lichens. Eight goats had been introduced to
the region in 1929 as escapees from captivity and had since
multiplied rapidly. One might speculate that their reportedly
heavy use of lichens may have outstripped the lichens' ability to
regenerate. In the mountains of Idaho Brandborg (1955) observed
goats spending 24% of their feeding time nibbling foliose lichens.
A study by Saunders (1955) showed 7% utilization of lichens in
summer in Montana, and Smith (1976) found 14% use in winter in the
In Southeast Alaska one study found mountain goat fecal
samples in winter contained from 18% to 30% lichen, mostly Lobaria
spp. (Fox and Smith 1988). These authors (1989) make the point
that, "Winter is a period of severe nutritional deprivation and
food scarcity for mountain goats." They believe, "The importance
of conifers and arboreal lichens in the winter diets of coastal
mountain goats suggests that removal of timber may produce a
serious decline in forage availability for goats in Southeast
Table 4. Lichens used by mountain goats.
unspecified lichen spp.
crustose lichen spp.
Antilocapra americana (pronghorn antelope)
Thomas and Rosentreter (1989) have reported that the vagrant
(non-attached) forms of several lichens that are common on
windswept gravelly ridges in southeastern Idaho valleys may be an
extremely important winter forage for pronghorns. These ridges are
often the only snow-free areas for much of the winter and early
spring. In addition to supplying energy the lichens may be a
source of free water when they are exposed to direct sunlight,
during a time of very low temperatures. One rumen sample of an
antelope in winter in this area contained 51% lichen (Bernt 1976).
Domestic sheep graze some of the same ranges and may be competing
with the antelope for the same lichens.
Wildlife biologists with the Bureau of Land Management and the
USDA Forest Service in Nevada and New Mexico have used the presence
of "ground lichen" (Xanthoparmelia chlorochroa) as an indicator of
excellent antelope range for a number of years. They have
considered it to be "fair" forage in spring, and "poor" forage in
summer (Suminski, unpublished letter).
Table 5. Lichens used by pronghorn antelope.
Xanthoparmelia spp. (vagrant forms)
Ovibos moschatus (muskox)
Muskox and caribou are the only ungulates adapted to life on
the arctic tundra. Modern studies have shown that the primary
foods of the muskox are sedges and willows, and that very early
opinions that their main diet consisted of lichens and mosses were
incorrect. Nonetheless, there are enough reports of muskoxen
eating lichens at least occasionally, to not entirely discredit
these early naturalists. McKendrick (1981) for example, says,
"They browsed on willow and alder, grazed on sedges and fed upon
lichens during the normal course of their daily feeding in the
summer." During winter the animals tend to feed on the ridgetops,
where lichens are a much higher proportion of the total vegetation,
and it may be that they use lichens as a supplementary food when
their preferred forages are scarce. During the 1930s Palmer (1944)
conducted feeding trials with a number of captive big game animals;
he found that muskoxen gained weight readily on a diet of lichens.
The lichens used by muskoxen are largely unknown, but presumably
similar to that of caribou; Palmer used Cladina/Cladonia and
Cetraria spp. in his trials.
Alces alces (North American moose)
Moose are browsers of trees and shrubs, primarily in wet
habitats of northern North America. Willow, balsam fir, aspen, and
birch are all important foods. At times, however, moose will eat
substantial amounts of lichen. Thomas (1990), who studied winter-
type pellets in Jasper National Park, reported that arboreal
lichens ("Alectoria/Bryoria type") appeared in the sample from that
area with a relative density of 30% while Cladonia spp. occurred
with a density of 4%, and Peltigera spp. 3%. Particularly for the
arboreal lichens this figure seems too high to be merely incidental
to their browsing, and tends to confirm other observations of moose
seeking out lichens. On Isle Royale, for example, Risenhoover
(1987) found that moose spent considerable time eating arboreal
lichens. LeResche and Davis (1973) observed that 23% of the bites
of tame moose on browse-depleted range in Alaska were of lichens,
primarily Peltigera spp. It may well be that lichens function as
a kind of back-up food source for these animals.
Table 6. Lichens used by moose.
Ovis dalli (Dall's sheep)
These wild sheep, closely related to bighorn sheep, eat a wide
variety of grasses and forbs. For several bands on Alaska's Kenai
Peninsula it was found that "grasses and grass-like plants...made
up most of the animals' diet except in mid-winter when they were
replaced in importance by lichens." (Nichols, 1974.) One of these
bands in February, 1973 had a diet that contained 42% lichens,
listed as "Cladonia spp.," probably mostly Cladina, the most common
form of "reindeer lichen." Lowell Suring (pers. comm., 1994) has
reported that Dall's sheep have been seen eating lichens in the
Chugach National Forest, Alaska.
Cervus elaphus (elk or wapiti)
Schwartz and Mitchell, 1945, referring to Rosevelt elk (C.e.
rosevelti) found that lichens were "common on the trunks and limbs
of trees" on the Olympic Peninsula and that "during winter,
especially at higher elevations, they are important in the diet and
are taken from as far up as the animals can reach. On the high
ridges at this season, the elk apparently depend largely upon
lichens and the browse from broken limbs of fir and hemlock."
Marcum, 1980, reported an average of 3% volume of lichens occurring
in 33% of the rumen samples of a western Montana herd in Oct.-Nov.,
1972. Most forage studies of elk do not list lichens; they are
probably an occasional winter forage, especially during times of
Table 7. Lichens used by elk.
Bryoria trichodes, ssp. americana
Usnea sp. (U. barbata and U. plicata, cited, are
Other ungulates whose diet is reported to include some lichen:
Ovis canadensis bighorn sheep
(Banfield 1974, Brown and Yde 1988)
Bison bison wood bison
Larter (1990) found that the bison he was studying in the
Northwest Territories, generally grazers, "also feed heavily on
terrestrial lichen (Cladina mitis) during the fall..." when they
move from meadow habitats into the forests.
Glaucomys sabrinus (northern flying squirrel)
Northern flying squirrels are important
animals in western
coniferous forest communities in two ways: they are one of the
main prey species of both northern spotted owls and boreal owls,
and they are agents of dispersal of mycorrhizal fungi. In many
areas, they are heavily dependent on lichens for both food and
Over the range of the spotted owl, from British Columbia to
southern California, "70% to 90% of the prey biomass is
contributed by just two or three species, particularly northern
flying squirrels, dusky-footed or bushy-tailed woodrats, and
various lagomorphs (hares and rabbits)...flying squirrels are
especially important in mesic forests of the Western
Hemlock/Douglas-Fir Zones..." (Thomas 1990). In the HJ Andrews
study area on the western slope of the Oregon Cascades, Forsman
(1984) found that "flying squirrels comprised over 60% of all prey
taken during fall and winter...by midsummer flying squirrels
comprised only 27% of the diet." Boreal owls live across a wide
area of western North America, and have been listed as a
"sensitive" species by the USDA Forest Service (Hayward and Verner
1994). In the Rocky Mountain region their primary prey was found
to be the red-backed vole (another lichen consumer; see below), but
it was found that in the study area in Idaho, "The squirrels
represented 45% of prey biomass recorded for female owls during
Lichen consumption by flying squirrels is highest in the drier
forests east of the Cascade crest, but it is has been reported on
the west side as well. Maser et al. (1985) report that in
northeastern Oregon lichens comprised 93% of the stomach contents
by volume in winter and spring, dropping to 22% by July. In
southwestern Oregon, lichens totaled 64% of stomach contents in
Jan, 33% in Feb, and 0% in March (Maser et al. 1986). Rosentreter,
et. al., 1997, reported 86% occurrence of lichen algae in winter
scats, and 25% in summer. In a set of "cafeteria-style" feeding
trials conducted in summer in Lassen National Forest, northeastern
California, trapped flying squirrels chose Bryoria fremontii third
out of the eight foods offered, only slightly behind two species of
truffle and ahead of other species of fungi, Abies seeds, and the
lichen Letharia vulpina. (Zabel and Waters, 1997). Letharia
vulpina contains the unpalatable vulpinic acid; it has been widely
assumed that this makes it one of the least preferred species.
Because lichens in the genus Bryoria, favored by the flying
squirrel, are dark brown, they are good absorbers of solar
radiation; in winter they melt snow and become a source of liquid
water as well as food. The main staples of the squirrels' diet in
the months of mild weather are hypogeous (underground-fruiting)
fungi. These fungi are, for the most part, mycorrhizal, and they
do not produce airborne spores. They are critical to the trees'
ability to absorb water and nutrients, and "play a vital role in
nutrient cycling, productivity, and plant succession in
ecosystems...as they travel through the forest [the squirrels]
disperse the fungal spores in their droppings" (Maser et al. 1986).
Lichen consumption is highest during the winter months when the
fungi are least available.
Flying squirrels also build their nests from Bryoria (Hayward
and Rosentreter, 1994.). Maser et al. (1985) say, "The major foods
(90-100%) of the flying squirrel's diet in northern Oregon were
fungi and lichens...The lichen (Alectoria [Bryoria] fremontii) was
not only the squirrel's predominant food in northeastern Oregon
from December through June but also its sole nest material: from
July on hypogeous fungi were the principal [diet] item...." In
British Columbia a few nests were found made of twigs and shredded
bark, but one was constructed entirely of "old man's beard lichen"
(Usnea longissima--possibly a misidentification of Ramalina
thrausta), and the stomach of the squirrel which occupied it
contained nothing but Usnea (Cowan 1936). In the northern Rockies
Hayward and Rosentreter (1994) found that 96%, by volume, of the
material of squirrel nests (built in artificial boxes in trees) was
lichen, and that more than 95% of the lichen consisted of three
species of Bryoria. They suggest that these nests may function as
larders during winter, particularly since the species of Bryoria
used, especially B. fremontii, are more digestible than other
species of lichens that contain higher levels of acidic secondary
compounds. Roger Rosentreter has collected nests from the interior
of British Columbia made of Ramalina thrausta (Hayward and
Rosentreter, 1994) and lichen nests have been reported from
interior Alaska as well (Mowrey and Zasada, 1984.)
Unpublished data from the West Virginia Natural Resources
Department (Mitchell, 1994) indicated that in the Monongahela
National Forest lichens were the single most abundant (80.3%)
constituent in northern flying squirrel fecal samples in spring and
summer. Unlike southern flying squirrels, northern flying
squirrels are rare in West Virginia.
It is worth noting how these elements of the forest are
interrelated. The trees depend on mycorrhizal fungi for nutrients.
The lichens and squirrels both depend on the trees for a structural
environment. The fungi depend on the squirrels for dispersal. The
squirrels depend on the lichens and fungi for food, and on the
lichens for nests. Flying squirrels "also become food for such
nonclimbing predators as bobcats (Felix rufus), cougars (Felix
concolor), and coyotes (Canis latrans) while foraging on the forest
floor..." (Maser et al. 1985). It appears that the lichens are one
essential element in a matrix of functional relationships which
sustain the forest ecosystem. As Rosentreter et.al. (1997) put it,
"...the interdependence and functional relationships among
mycorrhizal fungi, conifers, flying squirrels, and arboreal lichens
suggests a coevolution requiring each component for the optimal
functioning of the interior coniferous forest."
Table 8. Lichens used by the northern flying squirrel.
B. fuscescens complex
Usnea ceratina* ("staghorn lichen"...possibly misidentified)
Clethrionomys californicus (California red-backed vole)
California red-backed voles are common in coastal coniferous
forests from northern Oregon into California. Like the flying
squirrel, the vole is a frequent prey of the northern spotted owl.
In a study done in Oregon's coast range it was found that, "The
major types of food for the vole...were fungal sporocarps and
lichens. Sporocarps accounted for 85.7% of the total
diet...Lichens...comprised the second largest food class. Lichen
consumption was negatively correlated with fungus consumption...and
played the greatest role in vole diets in February, but decreased
gradually through spring as sporocarps increased...Sporocarps and
lichens together accounted for 98.4% by volume of the Coast Range
California red-backed vole diet." (Ure and Maser 1982).
The California red-backed vole is closely associated with
coarse woody debris and with old-growth forests (Clarkson and
Mills, 1994). This association may be due both to behavioral
characteristics, and to the food habits of the vole. In addition
to spotted owls, the vole is preyed upon by the marten,
short-tailed weasel, long-tailed weasel, bobcat, spotted skunk,
great horned owl, and saw-whet owl. (Maser et al. 1981). Lichens
reportedly used by the California red-backed vole include species
of Alectoria and Usnea.
Clethrionomys gapperi (boreal red-backed vole or Gapper's
red-backed vole or southern red-backed vole)
Boreal red-backed voles are found all across the northern
states and Canada in moist coniferous habitats. They are commonly
prey of owls, including the northern spotted owl.
In the coastal forests of the west the vole's diet is similar to
that of the California red-backed vole, eating mostly hypogeous
fungi and lichens (Maser and Maser, 1988). These authors also
emphasize the particular importance of lichens in winter: "In the
Cascades, harsh weather renders fungi unavailable early in the
year, forcing small mammals to turn entirely to lichens. By late
winter, most of the readily available fruticose lichens in the snow
column have been consumed, and the subnivean red-backed voles are
forced to turn to vascular plants and mosses." One should note
that none of the voles (Clethrionomys spp.) hibernate but are
In the Rocky Mountains, their diet includes more seeds and
vascular plant material. In northern Ontario, Martell (1981) found
that red-backed voles made heavy use of lichens both in mature
forests, where they consumed ground-growing lichens, and in recent
clear cuts, where they ate arboreal lichens off the branches and
trunks remaining on the ground. He points out that the local
disappearance of C. gapperi following logging in Ontario is no
doubt related to their "feeding on a declining food source."
In another study of small mammals, in clearcuts in the western
Cascades of central Washington, Gunther et al. (1983) found that
"Fungi and lichens were the major foods eaten by most rodents,
particularly red-backed voles...".
Roger Rosentreter has described (personal communication, 1992)
finding many red-backed voles in "owl boxes"--nesting boxes placed
in trees by Greg Hayward (discussed in a USDA Forest Service
report) to study boreal and saw-whet owls. The voles, which had
been killed by owls and brought to the nests to feed their young,
still had lichen sticking out of their mouths. A recent USDA
Forest Service report (Hayward and Verner, eds. 1994) on
flammulated, boreal, and great gray owls, three species listed as
"sensitive" by that agency, cited Clethrionomys gapperi as the
single most important prey species of the boreal owl. This study
charts the ecosystem linkage between Bryoria spp. lichens, red-
backed voles and northern flying squirrels, and boreal owls.
Table 9. Lichens used by the boreal red-backed vole.
There are reports of other small mammals using lichens; they
are listed below.
Table 10. Small mammals reported to eat lichens, or to use lichens
in nest building.
Arvicola sp. (vole)--food (Llano 1956)
Clethrionomys rutilus northern red-backed vole--food (Bangs, 1984)
Dicrostonyx richardsonii) collared lemming--food, habitat [lives in
lichen heaths] (Llano 1956, Scott 1989,)
Eutamias ruficaudus redtailed chipmunk--nest material (Broadbooks
Lemmus sp. (lemming)--food (Llano 1956)
Lepus sp. (rabbit or hare)--food (Llano 1956)
Lepus americanus snowshoe hare--food (observed eating lichens of
downed trees in the winter in the Frank Church Wilderness, Idaho--
pers. comm., Greg Howard, 1994)
Marmota caligata hoary bat--nesting sites ( Richardson and Young
1977) and food (Hanson 1975)
Microtus pennsylvanicus terraenovae insular meadow vole--food
(Riewe 1973, Bangs, 1984)
Microtus sp. (meadow vole)--food (Llano 1956)
Microtus townsendii Townsend vole--food (Gunther et. al 1983)
Neotoma cinerea bushy-tailed woodrat--food (Maser, et. al 1978)
Neurotrichus gibbsii shrew mole--food (Gunther et. al 1983)
Ochotona princeps North American pika--food (Conner 1983)
Peromyscus maniculatus deer mouse--food (Gunther et. al 1983, Li
et. al 1986, Martell and Macaulay 1981)
Phenacomys intermedius heather vole--food, nest material
Phenacomys longicaudus red tree vole--nest material, possibly food
(Denison 1973, Gillesberg and Carey 1972, Zentner 1977)
Sorex monticolus dusky (or montane) shrew--food (Gunther et. al
Sorex trowbridgii Trowbridge shrew--food (Gunther et. al 1983)
Spermophilus parryii arctic ground squirrel--food, nest material
Tamias townsendii Townsend's chipmunk--nest material (Banfield
1974, Carey 1991, Gunther et. al 1983, Maser et. al 1981)
Tamiasciurus douglasii Douglas' squirrel, chickaree--nest material
Tamiasciurus hudsonicus red squirrel--food (P. Neitlich, personal
Richardson and Young (1977) list 45 North
American birds which
use lichens in building their nests; these are listed in Table 11
below. These authors point out that many birds actively seek out
the lichens, frequently using them for camouflage. John W. B.
Thomson has remarked (personal communication, 1993) that birds are
"good taxonomists", knowing just which lichen species they prefer.
In an striking example from northern Sweden, birds,
invertebrates, lichens, and forestry, were all found to be
functionally connected (Pettersson, et. al, 1995). The authors
state that, "Natural forests had significantly greater invertebrate
diversity than managed forests and nearly five times as many
invertebrates per branch...The number and biomass of invertebrates
were related to the number of lichens, even after controlling for
sampling location and branch size. Other studies have implicated
forestry in the decline of non-migratory passerine birds in
northern Europe through the destruction and fragmentation of
forests, but our study indicates that it may also reduce foraging
habitat quality through a reduction in lichen abundance." It might
be reasonable to postulate similar effects in North America.
Table 11. Birds that use lichens for nest building. From
Richardson and Young, 1977.
Common merganser Mergus merganser
Red-shouldered hawk Buteo lineatus
Red-bellied hawk Buteo lineatus elegans
Swainson's hawk Buteo swainsoni
Ruby-throated hummingbird Archilochus colubris
Black-chinned hummingbird Archilochus alexandri
Anna's hummingbird Calytpe anna
Broad-tailed hummingbird Selasphorus platycercus
Rufous hummingbird Selasphorus rufus
Allen's hummingbird Selasphorus sasin
Rivoli's hummingbird Eugenes fulgens
Buff-bellied hummingbird Amazilia yucatanensis
White-eared hummingbird Hylocharis leucotis
Broad-billed hummingbird Cynanthus latirostris
Coue's flycatcher Contopus pertinax
Eastern wood pewee Contopus virens
Olive-sided flycatcher Nuttallornis borealis
Vermilion flycatcher Pyrocephalus rubinus
Boreal chickadee Parus hudsonicus
Common bushtit Psaltriparus minimus
Black-eared bushtit Psaltriparus melanotis
Wrentit Chamaea fasciata
Varied thrush Ixoreus naevius
Swainson's thrush Hylocichla ustulata
Gray-cheeked thrush Hylocichla minima
Blue-gray gnatcatcher Polioptila caerulea
Black-tailed gnatcatcher Polioptila melanura
Golden-crowned kinglet Regulus satrapa
Silky flycatcher Phainopepla nitens
White-eyed vireo Vireo griseus
Yellow-throated vireo Vireo flavifrons
Solitary vireo Vireo solitarius
Black-whiskered vireo Vireo altiloquus
Philadelphia vireo Vireo philadelphicus
Parula warbler Parula americana
Olive warbler Peucedramus taeniatus
Townsend's warbler Dendroica townsendi
Hermit warbler Dendroica occidentalis
Cerulean warbler Dendroica cerulea
Blackburnian warbler Dendroica fusca
Yellow-throated warbler Dendroica dominica
Blackpoll warbler Dendroica striata
American redstart Setophaga ruticilla
Rusty blackbird Euphagus carolinus
White-winged crossbill Loxia leucoptera
The marbled murrelet (Brachyramphus marmoratus), recently
listed as endangered, nests in mosses and lichens covering the
limbs of large coastal conifers from central California to Alaska.
Lichens have been found in murrelet nests in the Santa Cruz
Mountains, California (Singer et al, 1991) and in Prince William
Sound, Alaska (Naslund, unpuplished report, 1991). Most murrelet
nests have been reported to be simple depressions in the moss and
lichen cover of the branches, but the Santa Cruz Mountains study
found one nest that was constructed of lichen-covered twigs.
Lichens cited were Usnea sp., Hypogymnia enteromorpha, Evernia sp.,
Parmelia sp., and Sphaerophorus globosus.
The golden-plover (Pluvialis dominica) is cited by both
Richardson (1974) and by Thomson (1984) as using Thamnolia
vermicularis to build its nests; Richardson remarks it is "well
camouflaged" by the lichen. This same lichen, an arctic-alpine
species, was recently discovered in the coastal hills just north of
San Francisco, California, far from its usual range; it has been
plausibly speculated (Wright 1992) that it might have been brought
there on the feet of a golden plover. This same bird is listed by
Gabrielson and Lincoln (1959) as lining its nests with "reindeer
moss", i.e., Cladina spp. Forsman (1984) mentions barred owls
"sometimes lined their nests with lichen". Ellison, (1966) found
evidence of the spruce grouse (Canachites canadensis) eating
ground-growing lichens, particularly Peltigera spp. This genus is
much higher in protein than the fruticose lichens favored by most
Lichens are a key element in the food chain of the northern
spotted owl and boreal owl (see small mammals, above). Many of the
most important prey species of the boreal owl (Aegolius funereus)
are small mammals that consume lichens, including the northern
flying squirrel, and several species of voles (Hayward and Hayward,
Two species of frog, the common or gray
versicolor) and the bird-voiced tree frog (Hyla avivoca) look so
much like the lichens that grow on the trees where the frogs live
that it seems clear they are using lichen camouflage to avoid
predation. (Richardson and Young 1977).
The green salamander (Aneides aeneus) also is hard to spot
among the lichen-covered rocks in which it lives (ibid.).
A possible link between lichens and the
(Gopherus agassizii) a species formally listed as endangered, is
suggested by Harper and Pendleton (1993). They found that forage
plants growing in soil that was covered by microbiotic crusts,
particularly the cyanolichen Collema tenax, exhibited markedly
greater uptake of nutrients such as phosphorus, magnesium, and
calcium. One reason for the tortoise's decline appears to be the
high incidence of diseases related to dietary deficiency (Jarchow,
1984, and Robbins, 1983). The authors suggest that destruction of
soil crusts may be impacting the tortoise, particularly with regard
to the availability of phosphorus and magnesium.
Many lizards around the world show coloration which may well
be evolved to blend against a background of lichens. One possible
example from North America is the chuckwalla (Sauromalus obesus),
which has a mottled appearance that mimics the lichen-covered rocks
among which it lives.
This compilation is an ongoing project, and more information
is welcomed. Please send to: Stephen Sharnoff, 2406 Roosevelt
Avenue, Berkeley, CA 94703, or e-mail: email@example.com.
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Maser, C., J.M. Trappe and R.A. Nussbaum. 1978. Fungal-small
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Hayward, G.D. and P.H. Hayward. 1993. The Birds of America, No. 63:
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Riewe, R.R. 1973. Food habits of insular meadow voles, Microtus
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Wilcox, B.A. and D.D. Murphy. 1985. Conservation strategy: the
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Northwestern California. M.A. thesis in biological sciences,
California State Univ., Sacramento, CA.
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