variable periods immediately after oviposition (mean
clutch size = 20) but do not return to the clutches. The
developing embryos, usually on the upper surface of
a leaf or other exposed site, depend on moisture from
the environment. Male Reticulated Glass Frogs appear
to guard eggs against predation (McDiarmid 1983).
They attend clutches 24 hr/day, whereas male Bare-
hearted Glass Frogs (Fig. 5.10) leave theirs unattended
during the daytime. Embryos of the latter species suf-
fer greater mortality due to visually hunting preda-
tors, particularly wasps.
The diversity of oviposition sites exhibited by spe-
cies that have declined or disappeared at Monteverde
casts doubt on the hypothesis that UV radiation has
caused the declines by reducing hatching success (see
Sec. 5.4.3). Eggs of the Golden Toad, typically laid in
dark recesses beneath masses of tree roots, are rarely
exposed to direct sunlight. Embryos of the Tilaran
Rain Frog, which disappeared from the area along
with the Golden Toad (Pounds et al. 1997), develop
in underground nests where they receive no UV radi-
ation. Although Emerald and Fleischmann's Glass
Frogs both declined in the late 1980s (see Sec. 5.4.1),
eggs of the former are laid on exposed surfaces, whereas
eggs of the latter are shielded on the undersurfaces of
leaves (see Sec. 5.5.2).5.5.4. Tadpole Feeding Ecology
Feeding ecology of anuran larvae at Monteverde needs
further study. Tadpoles of the Meadow Treefrog, which
develop in temporary pools where food is presumed
to be limited, cannibalize eggs and hatchlings (Crump
1983, 1991b). In laboratory experiments, larvae that
were fed conspecific tadpoles developed at the same
rate as those fed tadpoles of another treefrog species
but grew larger before undergoing metamorphosis
(Crump 1990). Larger tadpoles generally transform
into larger froglets, which presumably have higher
survivorship. Another solution to the problem of food
scarcity in temporary pools is to forego eating. Golden
Toads lay relatively few, large eggs that are well-Figure 5.10. A male Bare-hearted Glass Frog
(Hyalinobatrachium colymbiphyllum) attend-
ing eggs. Photograph by Michael and Patricia
Fogden.165 Amphibians and Reptiles