R
odents are a hard sellwhen it comes to
conservation. In most human cultures, rodents are
generally viewed as vermin. Only in one country,
Canada, is a rodent considered a national symbol; namely,
the beaver (Castor canadensis). At least two rodents have
positive images as mascots of American university football
teams (beaver, gopher [ground squirrel]). And in some
cases, rodents supplement human diets (several species in
parts of Southeast Asia and the capybara, Hydrochaeris hy-
drochaeris[Macdonald et al., chap. 33 this volume] and
nutria [Myocaster coypus] in South America). Admittedly,
rodents are in fact often pests, being guilty of damaging
crops, pilfering stored grains, invading households, and
spreading zoonoses. However, these faults, from a human
perspective, are perpetrated by a very small percentage of
rodent species. A recent compilation of species (Wilson and
Reeder 1993; see also Honeycutt, Frabotta, and Rowe,
chap. 2 this volume) lists 2,021 species of rodents. These
species are arranged in 438 genera and twenty-nine fami-
lies, and they occur in all the continents except Antarctica.
Thus rodents comprise the largest and most diverse Order
of living mammals.
Aside from their numbers and diversity, there are many
reasons why rodents should be major concerns in conser-
vation planning. Perhaps of least importance, there are ac-
tually some quite charismatic species. These include beavers
(Castor), dormice (twenty-six species in the Family Myo-
xidae), hamsters (especially Mesocricetus auratus), flying
squirrels (forty-four species), chinchillas ( species in the fam-
ily Chinchillidae), and the huge (up to 79 kg) capybara. A
few species have been harvested commercially for their fur:
muskrat (Ondatra zibethicus;fig. 38.1), beavers (C. can-
adensis, C. fiber), chinchillas (Chinchilla brevicaudata, C.
lanigera), and nutria. Several species have been domesti-
cated for use as pets, and particularly for biomedical re-
search: house mice (Mus musculus), rats (Rattus norvegi-
cus, R. rattus), hamsters (Mesocricetus auratus), and guinea
pigs (Cavia porcellus). The contributions of these species of
rodents to human welfare, while often under-appreciated, is
so tremendous that it defies quantitative estimation. More-
over, there is a huge potential for many more species to
serve human needs in this way.
Of course the important reasons for conserving rodent
species are their taxonomic and ecological diversity, and the
fact that they are major players in ecological communities
worldwide. Rodents occur in all of the terrestrial biomes;
because of their generally small size and mostly herbivorous
food habits they often provide the foundation for all higher
trophic levels in a community. Life forms run the gamut,
from subterranean and semiaquatic to arboreal and gliding.
Some species are carnivores (e.g., Onychomys, Hydromis
Mayermys) and many are omnivores. Among herbivores,
there are grazers, browsers, granivores, bark-feeders, frugi-
vores, and root and /or bulb specialists. Behaviorally, ro-
dents exhibit the full range of social systems found among
mammals, and this includes the only eusocial (social insect-
like) species known for mammals (the naked mole-rat, Het-
erocephalus glaber;Sherman et al.1991; Faulkes and Ben-
nett, chap. 36 this volume). Rodents, therefore, are not
only essential components in the functioning of communi-
ties everywhere, they provide innumerable opportunities for
evolutionary, ecological, and behavioral investigations.