Given the overwhelming importance of rodents to hu-
man welfare, both directly and indirectly, it is pertinent to
ask how we are doing in our efforts to keep the Earth’s ro-
dent fauna intact. The answer seems to be “Not well,” al-
though it is difficult to be very precise about this, as the ro-
dent fauna in much of the world is poorly known. Basic
information on life-history traits, ecological relations, and
demographic patterns of most species remains unknown or
poorly understood. A particularly grievous example of our
conservation failures is that of the Vancouver Island mar-
mot (Marmota vancouverensis). There are only two species
of mammals endemic to Canada (both rodents); this is one
of them, and it is on the brink of extinction (Johnson 1989).
There have been two reviews of the conservation status
of rodents on a continental scale. The first of these (Lidicker
1989) attempted to survey rodents worldwide. However,
Central America was not covered, and South America and
most of Asia received only superficial coverage. This report
was a product of the Rodent Specialist Group, Species Sur-
vival Commission, International Union for the Conserva-
tion of Nature and Natural Resources (IUCN), and served
mainly to call attention to the conservation needs of rodents
and to set a baseline for future research. In 1998, the North
American contingent of the Rodent Specialist Group pub-
lished a detailed survey of the conservation status of North
American rodents, including action plans where appropri-
ate (Hafner et al. 1998). Table 38.1 is compiled from the
summarizing statistics in that report. In addition, The Na-
ture Conservancy lists two extinct subspecies that are not
included in table 38.1; adding in these would raise the per-
centage of recently extinct subspecies to 0.6. These data
clearly illustrate that even in North America, which has
a relatively well-known rodent fauna and supports a rela-
tively strong conservation program, extinctions have oc-
curred, many more species and subspecies are in a precari-
ous state, and data are inadequate for determining the sta-
tus of many more. The only other continent-sized area with
a comparable level of knowledge and concern is Australia
(Calaby and Lee 1989; MacPhee and Flemming 1999). For
this continent, at least eight species of rodents are known
to be extinct since European colonization (14.3%), nine
more are considered vulnerable (16.1%), and at least five
are insufficiently known, for a total of twenty-two species
of conservation concern (39.3%). MacPhee and Flemming
(1999) reported that over the last 500 years, forty-three
species of rodents have disappeared from Australia; and
this represents 52.3% of all mammalian losses known for
that period.
In this review, I will summarize the known factors that in-
fluence the conservation status of the Earth’s rodent fauna.
This will be addressed in the context of life-history vari-
ables, as they may impact demographic behavior, spatial
structure, movements, and interspecific relations. Special
emphasis will be given to the role of social behavior as a
contributing variable. As a group, rodents face the same
suite of threats to their welfare and existence as do other or-
ganisms. Paramount are habitat destruction and introduc-
tion of exotic species. Other well-known factors are pol-
lution, over-exploitation by humans, and disease. A new
threat of unknown but potentially major influence is rapid
global warming. Additionally, rodent conservation is ham-
pered by indifference and complacency. The former is the
result of a conservation focus on larger, more charismatic
and generally familiar species, as well as residual negative
attitudes toward rodents. The latter stems from the view
that rodents are abundant, have high reproductive rates,
widespread distributions, and are adaptable. Therefore,
they can take care of themselves, or so it is thought.454 Chapter Thirty-Eight
Figure 38.1 Muskrat (Ondatra zibethicus), a popular and widespread rodent
furbearer. Ogden Bay, Utah; 20 July, 1950; photo by author.
Table 38.1 Numbers and percentages of North American
species and subspecies of rodents in various categories of
conservation concernSpecies SubspeciesStatus No. % No. %Extinct 0 — 7 0.5
Endangered 3 1.5 19 1.3
Vulnerable 6 2.9 25 1.8
Low risk 69 33.5 37 2.6
Insufficient data 5 2.4 36 2.5
Totals 83 40.3 124 8.7SOURCE: Data from Hafner et al. (1998).
NOTE: N206 species and 1,426 subspecies.