regarding rodent conservation. These attitudes empha-
size the need to focus conservation efforts on entire
communities rather than on focal species.- We need to greatly expand our knowledge of rodents in
most parts of the world. - Rodents are subject to the same principles of conser-
vation biology as other organisms, and in fact be-
cause of their extraordinary diversity (2,021 species in
twenty-nine families) they comprise a representative
subsample of mammals, except that there are few large-
bodied species. Observed demographic patterns cover
the full range of commonness, all forms of rarity, and
ephemerality (migration, hibernation, multiannual
cycles, irruptions). - Social behavior is a significant factor in rodent conser-
vation, and collectively rodents exhibit a wide range of
social complexity. - Social factors affect: (1) spatial structure, (2) genetic
structure, (3) the chances of small-population extinc-
tion by modifying the minimum threshold density,
(4) colonization ability, (5) dispersal behavior, (6) resis-
tance to immigration, (7) the success of metapopula-
tions, and (8) responses to landscape features such as
edges and corridors. - Our understanding of what constitutes effective conser-
vation action has expanded greatly as we have moved
from a focus on simply measuring population vital
rates to an appreciation for the complex array of fac-
tors that generally influences these rates, and that can
vary over time and space. Moreover, we have begun
to incorporate community context and landscape ele-
ments into our conceptual framework. - Research on rodents has been an essential component
in this intellectual development, and hopefully they will
reap the benefits of this continuing enterprise, along
with the rest of the Earth’s biota, including most partic-
ularly our own species.
SummaryRodent conservation is disadvantaged by widespread indif-
ference and complacency. Yet, rodents comprise a large pro-
portion of the mammalian fauna on six continents. Rodents
are extremely diverse (438 genera in twenty-nine families),
and often play key roles in the communities in which they
live. Rodents impact human welfare as agricultural pests,
carriers of zoonoses, pilferers of stored food, and as adept
and damaging alien invaders of natural communities. How-
ever, they also are incredibly valuable in biomedical re-
search, as components of healthy ecosystems, as pets, fur-
bearers, and even food. Most importantly, rodents provide
innumerable opportunities for evolutionary, ecological, and
behavioral research. In spite of their overwhelming impor-
tance, rodents are poorly known on most continents. Even
in relatively well-known areas such as North America and
Australia, 40.3 and 39.3% of extant species respectively are
currently of conservation concern. Rodents show all of the
known patterns of demographic behavior, the various types
posing different modalities of conservation concern. Distri-
bution in space depends on geographic range, habitat frag-
mentation, dispersal capabilities, and social system. Small
ranges, fragmented habitat, poor dispersal ability, and com-
plex social systems all increase the risk of extinctions. Small
populations carry additional risks from stochastic impacts
as well as deterministic antiregulating forces, which gener-
ate minimum threshold densities often well above zero. So-
cial behavior often contributes to such minimum thresh-
olds. Effective conservation requires an understanding of
the often complex community context of focal populations,
and this may vary spatially and temporally. This context
includes community dominance relations as well as the na-
ture and magnitude of interspecific interactions. Finally, it
is critical to understand how species respond to landscape
factors such as habitat patch size, quality, and distribution,
and edge effects, corridors, and matrix features.462 Chapter Thirty-Eight