Monteverde : Ecology and Conservation of a Tropical Cloud Forest

Table 5.5. Distribution of species of anurans, lizards, and snakes

among broad habitat strata in the Monteverde area.

Habitat Stratum

Taxon

Anurans (N = 53)

Percentage of N

Lizards (N = 29)

Percentage of N

Snakes (N = 72)

Percentage of N

Subterranean

3

5.7

0

0.0

0.0

8.3

Ground and

Leaf Litter

15

28.3

5

17.2

40

55.6

Aboveground

Vegetation

35

66.0

24

82.8

26

36.1

Each species is assigned to the stratum where observed most often (see Appendix 8).

palmata), which on Costa Rica's Cerro de la Muerte
is largely terrestrial (Vial 1968). The Ring-tailed Sala-
mander is most commonly found under debris on the
forest floor. Anurans that frequent bromeliads at
Monteverde include seven species of rain frogs
(Eleutherodactylus), plus the Meadow Treefrog, the
Drab River Frog, and the Crowned Frog (Hayes et al.
1989). Male Common Dink Frogs often call from
within these plants, and the non-aquatic eggs of this
and several other species of rain frogs are found there
(Taylor 1955, Myers 1969, Scott 1983c). The aquatic
eggs and tadpoles of the Crowned Frog develop in
water-filled tree cavities and bromeliads (Taylor 1954,
Robinson 1961). The possibility that other arboreal
anurans (e.g., the Giant Fringe-limbed Treefrog) use
bromeliads should be investigated. Eyelash Vipers and
Blunt-headed Tree Snakes may take refuge in these
epiphytes during the day, but Bromeliad Lizards are
the only reptiles in the area thought to use them as their
principal microhabitat (Heyer 1967). Secretive forms
that are not well studied (e.g., the Green-bellied Caiman
Lizard) might also use bromeliads.
Future studies should monitor epiphytes. A long-
term study of seed germination and seedling establish-
ment and growth in bromeliads and orchids would be
valuable. Monitoring should also examine growth and
possible dieback of epiphytic mosses, which may be
sensitive indicators of changes in orographic cloud
banks and tradewind-conveyed precipitation (see Sec.
5.4.3; see Chap. 2, Physical Environment). The abun-
dance of epiphytes, one of the defining characteris-
tics of cloud forests, may decrease if climate change
continues on its current trajectory.

5.7. Conservation

In this section, I discuss action—how policy makers,

managers of parks and preserves, and the public in

general might respond to the population declines. A

large segment of Monteverde's herpetofauna is miss-

ing from seemingly undisturbed habitats 11 years

after a multispecies population crash that led to a

spate of disappearances. Bob Carlson, Director of the

MCFP, sees the unexpected erosion of diversity as

"the single greatest problem facing the Preserve." He

worries about the possible implications for the rest of

the area's biota.

Only recently has the scientific community reached

a consensus that amphibian declines are a serious

conservation threat (Wake 1998). The issue of "stan-

dards of proof" has been central to the debate (McCoy

1994). Under the strictest standards, there may be

insufficient long-term data to judge how unusual the

declines are in the context of natural demographic

variability (Pechmann et al. 1991, Pechmann and

Wilbur 1994). The same would be true, however, even

if there were baseline data demonstrating that species

composition had remained constant for, say, 50 years

before the 1987 crash. The most extreme fluctuations

might occur only once per century or even less fre-

quently. What constitutes an adequate time period for

assessing natural variability is unknowable. As con-

servationists, we cannot wait decades to form an

opinion when so much is at stake. The observed pat-

terns, viewed in relation to known variability, war-

rant concern, which justifies action.

To identify the most appropriate courses of action

and avoid the pitfalls of well-meaning but misguided

efforts, ongoing research is needed (Beebee 1993). The

results obtained so far suggest that climate change and

epidemic disease may be key factors in the popula-

tion declines and disappearances (see Sec. 5.4.3).

There is growing evidence that global warming is a

real phenomenon with potentially devastating bio-

logical consequences (Peters and Lovejoy 1992, Barry

et al. 1995, Graham 1995, Diaz and Graham 1996,

Houghton et al. 1996, Parmesan 1996, Santer et al.

1996). Ultimately, conservation action geared to this

problem must be global in scope. We must educate

169 Amphibians and Reptiles