extremes on record immediately preceded the col-
lapse of amphibian populations and the first major
influx of premontane birds into lower-montane habi-
tats. The patterns suggest that climate may have
crossed a biologically important threshold during the
1986-87 El Nino.likely to escape regional extinction than species asso-
ciated with aquatic habitats (Pounds et al. 1997; see
Sec. 5.6.1). The lizards and snakes known to have de-
clined (see Sec. 5.4.1) lay eggs. Hence, the species for
which declines have been documented include repre-
sentatives of all breeding modes except live-bearing.5.5. Reproductive EcologyWe know little about reproductive cycles, courtship
and mating, oviposition, parental care, and life-his-
tory traits such as clutch size and frequency for most
amphibians and reptiles at Monteverde. Here I sum-
marize breeding modes, review anuran reproductive
behavior, and discuss breeding phenology.
5.5.1. Breeding ModesAmphibians are known for their diverse breeding
modes, whereas reptiles are comparatively uniform
in this regard. Amphibian breeding modes in the
Monteverde area fall into four classes: (1) eggs and
larvae aquatic; (2) eggs laid out of water but larvae
aquatic; (3) direct development (no larvae) within
encapsulated, terrestrial eggs; and (4) live-bearing
(viviparous). The caecilians are the only known live-
bearing amphibians in the area. The fetuses of these
elongate burrowers hatch from eggs retained in their
mother's oviduct and feed there on glandular secre-
tions (Wake 1983). Using specialized fetal teeth (lost
at birth), they scrape the lining of the oviduct to stimu-
late food production. The five species of salamanders
follow mode 3; the young hatch as miniature repli-
cas of the adults (Wake and Lynch 1976). The same
is true for the rain frogs that have been studied and
may apply to all 18 species (Hayes 1985, Hayes et al.
1989). Of the remaining 35 anuran species, 24 follow
mode 1 and 11 follow mode 2. Treefrogs in the gen-
era Agalychnis and Phyllomedusa and glass frogs
(Centrolenidae) lay eggs on vegetation above water
(Duellman 1970, Pyburn 1970, McDiarmid 1983,
Hayes 1991). Smoky Jungle Frogs lay eggs in a foam
nest built in a hollow that is likely to be flooded (Scott
1983e). Most lizards and snakes at Monteverde are
egg-laying (oviparous), although a few are live-bearing.
The latter include the Bronze-backed Climbing Skink,
the Green Spiny Lizard, the Boa Constrictor, and the
four species of pit vipers.
The species of amphibians and reptiles that have
declined or disappeared in the Monteverde region
represent a wide range of life histories. For frogs and
toads, there was no association between the probabil-
ity of disappearance and breeding mode, although
species not dependent on bodies of water were more
5.5.2. Courtship and Mating in
Frogs and Toads
Much of the variation in anuran mating behavior is
best understood in the context of competition among
males for access to females. This competition varies
in form according to the spatial and temporal distri-
bution of receptive females (Wells 1977). Both "ex-
plosive" and "prolonged" breeders have been stud-
ied at Monteverde.
Golden Toads and Meadow Treefrogs are examples
of explosive breeders. Intense physical competition
between male Golden Toads characterizes their 5-10-
day mating bouts at temporary pools (Jacobson and
Vandenberg 1991; Fig. 5.2). Males ordinarily out-
number females 8-to-l, and unpaired males attempt
to dislodge rivals who have achieved amplexus. Balls
of up to 10 struggling males sometimes envelope in-
dividual females. In the fray, males often clasp one
another and sometimes clasp anurans of other species
(e.g., Pin-striped Treefrogs) or even tree roots. Single
males not engaged in physical interactions with other
males may utter a soft "tep-tep-tep" like wooden
spoons clicking together, but the most common sound
is the release call. Males produce this low-intensity
trill along with body vibrations when clasped by
other males. When rains fill a seasonal pond, Meadow
Treefrogs gather suddenly and breed in a frenzy that
may continue night and day (Crump and Townsend
1990). The males, mostly tan and brown at night, of-
ten turn bright yellow during the day (Crump 199lb).
They greatly outnumber the females, and "mating
balls" with up to 16 males have been observed. The
principal vocalization is an unmusical "waaank."
Glass Frogs are prolonged breeders. Throughout
much of the rainy season, male Fleischmann's Glass
Frogs deliver loud, frequent "peeps" from territories
along streams, and the females arrive asynchronously
(Greer and Wells 1980, Jacobson 1985, Hayes 1991).
When a female approaches a calling male, who is
usually on the underside of a leaf, he intersperses
peeps with "mew" calls. After lengthy preliminaries
in which she appears to assess egg-laying sites or other
qualities of his territory, she initiates amplexus by
backing under him (Fig. 5.1). Mew calls also serve
in aggressive interactions between males. A male
Emerald Glass Frog sporadically emits two to five loud
"beeps," typically from the upper side of a leaf. When163 Amphibians and Reptiles