(plate 16- 86). In some areas in western Amazonia there
can be as many as 80 species of anurans at single sites
within lowland rain forest.
Although many species of anurans reproduce in the
manner described above, many also show dramatic
departures. In Costa Rica, where 119 anuran species
are found, some have live birth, bearing fully formed
miniature adults (skipping the egg and larval phases);
others lay eggs on plants, from which larvae hatch and
drop into water; and some lay eggs in nests of foam
on land, in bromeliads, or in tree cavities. The species-
rich genus Eleutherodactylus (plate 16- 87) reproduces
by direct development, laying eggs that hatch into
tiny but fully formed frogs. Courtship patterns are
also sophisticated. Frogs and toads vocalize, the
males emitting a specific call that serves to attract
the females. Many species are territorial. Anuran
reproductive behavior has undergone an impressive
adaptive radiation in the tropics. This is largely possible
because the tropical rain forest maintains a constantly
high humidity that facilitates keeping an anuran’s skin
constantly moist, a prerequisite to its survival.Tree Frogs
Tree frogs of the family Hylidae are arboreal, attaching
to leaves and stems by tiny suction disks on their feet.
Most are small and cryptic, though some are brightly
colored. One of the most common is the Red- eyed Tree
Frog (Agalychnis callidryas; plate 16- 88). This Central
American species has bulging, blazing red eyes, a
bright green upper body with a scattering of white
spots, bluish marks on the sides, white on the belly, and
orange on the hands and feet! Males and females have
a prolonged mating ritual, in which the female, with
the male clinging to her, attaches eggs to a leaf as the
male fertilizes them. Hatching occurs in approximately
five days, and the larval tadpoles drop off the leaf into
water.
One of the most intriguing examples of the complexity
of frog life cycles is provided by the Strawberry Poison-
dart Frog (Oophaga pumilio). In this species, whose
life history has been painstakingly documented, both
male and female parents are involved in caring for the
eggs and tadpoles. The male guards the eggs for 10 to
12 days. Once the eggs hatch into tadpoles, the female
takes over, transporting each tadpole to a bromeliad
containing water. Each tadpole is placed in a different
bromeliad plant, to which the female returns regularlyAnuran Defenses
As discussed in this section, anurans exhibit warning
coloration (poison- dart frogs) and toxic irritating
chemicals as defenses. They have two other defense
tricks. Some species that are normally cryptic display
flash colors when threatened. The flash color is revealed
when the frog raises a foot or other body part, revealing
a bright patch of color, usually red, orange, yellow, or
blue. The sudden appearance of the bright coloration
may momentarily confuse a predator, interrupting its
search image long enough for the frog to use its most
obvious defense tactic, its jumping ability.Plate 16- 86. The Small- headed Tree Frog (Dendropsophus
microcephalus) ranges from Central America to Brazil. It
demonstrates the expanded throat that enhances the loud
vocalization of these animals as well as the flattened toes
adapted to attach to vertical surfaces, such as leaves and
stems. Photo by Dennis Paulson.
Plate 16- 87. The 2.5 cm (1 in) long Central American Common
Tink Frog (Eleutherodactylus [Diasporus] diastema) is named
for its tink call. This species brings forth fully formed adults
from the gelatinous egg, with no free- swimming tadpole
stage of the life cycle. Photo by Dennis Paulson.
356 chapter 16 from monkeys to tarantulas: endless eccentricities