species in the world, and that number represents about
40% of all mammal species. By far and away the most
diverse order of mammals, Rodentia is rivaled in
diversity only by Chiroptera, the bats (see chapter 8),
but globally bats have only about half of the species
represented by rodents.
The Neotropics harbor some of the most ecologically
interesting species, as well as the largest, of the vast
assemblage of rodents. Several are aquatic, others
arboreal, and still others are burrowers. Some are
familiar, similar to those found away from the tropics.
These include such groups as tree squirrels, pocket
mice, rice rats, and the familiar House Mouse (Mus
musculus), each of which descended from ancestors that
colonized the Neotropics from elsewhere. Others, like
the porcupines, spiny rats, agoutis, pacas, and capybaras,
members of what is known as the Caviomorpha (or
Hystricognathi) rodents, are evolutionarily unique to
the Neotropics, having originated there. Caviomorph
rodents include the familiar domestic guinea pig (Cavia
porcellus), chinchillas (Chinchilla chinchilla), and the
North American Porcupine (Erethizon dorsatum).
Agoutis (Dasyprocta spp.; plate 16- 24) are among
the most common of the larger rodents, represented
by 11 species that range from tropical Mexico to
northern Argentina and Paraguay. Each species has
a similar ecology. Primarily diurnal, agoutis are apt
to be encountered anywhere inside forests. One of
my students described an agouti (as well as its close
relative the paca) rather well by asking me, “What
are those little piggy things running across the trail?”
Agoutis do not look like “little piggy things” when seen
close up, but from a distance their chunky, 64– 75 cm
(25– 30 in) bodies, long legs, and delicate prancing gait
give an impression of a small, tailless (though they
have very short tails), hoofed animal with the head of
a mouse. Depending mostly upon species, they range
in coat color from buffy reddish brown to grizzled gray
and black. They eat by sitting upright on their hind
legs, holding their food (usually a fruit or seed) with
their front paws in a manner suggestive of mice and
squirrels. Agoutis are often important seed dispersers,
collecting more seeds than they can consume at once
and burying the remainder in a widely scattered
pattern. The wide- pattern burial behavior, termed
scatter hoarding, is possibly adaptive in protecting the
agouti’s cache from discovery by other seed consumers,
such as peccaries. During times of shortage, agoutis
dig up their buried seeds. Agoutis are vocal, and when
Plate 16- 24. The Central American Agouti (Dasyprocta
punctata) is a member of a New World branch of the rodents
known as the caviomorphs. Photo by Dennis Paulson.Plate 16- 26. The world’s largest rodent, the Capybara can be
up to 1.2 m (4 ft) long and weigh as much as 54.4 kg (120 lb).
Photo by John Kricher.Plate 16- 25. This is a rare sighting of a Lowland Paca during
the daylight hours, scurrying through the deeply shadowed
forest floor. Photo by Andrew Whittaker.330 chapter 16 from monkeys to tarantulas: endless eccentricities