be an important threat in cloud forests, as concentra-
tions in mist and cloud water may greatly exceed those
in heavy rainfall. Climate change may increase this
threat, because concentrations might reach critical lev-
els when light precipitation punctuates long dry peri-
ods. Climate change could also encourage pathogen
outbreaks via several possible mechanisms.
At Monteverde, there is a 26-year trend toward
increasingly severe dry seasons and concordant bio-
logical responses to this trend, Variability of daily
precipitation has increased, leading to drier extremes
without producing trends in monthly or yearly means.
Days with no measurable precipitation have become
more frequent and have increasingly coalesced into
dry periods. The patterns suggest the hypothesis that
global warming has raised the mean height at which
condensation of trade-wind-conveyed moisture begins
and thereby has increased the average altitude at the
base of the orographic cloud bank. As predicted by this
lifting-cloud-base model, many premontane breeding-
bird species have invaded lower-montane habitats,
whereas some lower-montane species have retreated
up the mountain slopes. Patterns of daily precipita-
tion during the dry season, which account for most
of the interannual variation in the rate of invasion by
premontane bird species, are strongly correlated with
abundance in the lizard populations that have de-
clined and disappeared. The driest extremes imme-
diately preceded the multispecies crash of amphib-
ian populations and the first major upslope movement
of premontane breeding birds. These changes, which
suggest that climate may have crossed a biologically
important threshold during the 1986-87 El Nino, may
foreshadow an uncertain future for natural commu-
nities in general, including humankind.
Acknowledgments I thank M. Crump for introducing
me to Monteverde. She and many others, especially M.
Fogden, M. Hayes, J. Savage, W. Timmerman, and R.
Van Devender, have contributed to our knowledge of
the herpetofauna. For financial support, I am grateful
to the Tropical Science Center, the University of Florida,
the Organization for Tropical Studies, the Jessie Smith
Noyes Foundation, Stanford's Center for Conservation
Biology, the Mac Arthur Foundation, Chicago's Brook-
field Zoo, the University of Miami, and the U.S. Na-
tional Science Foundation (Grant DEB 9200081 to
J. Savage). I thank G. Barboza, G. Bello, F. Bolaiios,
R. Bolanos, J. Calvo, B. Carlson, G. Gorman, R. Heyer,
R. and M. Lawton, D. and M. Lieberman, K. Masters,
R. Solorzano, J. Tosi, M. Wainwright, D. Wake, and
V. Watson for valuable discussion and assistance; F.
Bolanos, J. Campbell, M. Fogden, W. Guindon, N. Rios,
C. Rojas, and J. Savage for sharing unpublished data
or observations; M. Fogden for providing photographs;
and M. Brenes, B. Carlson, M. Donnelly, M. and
P. Fogden, C. Guyer, R. Heyer, C. Rojas, and the edi-
tors for commenting on the manuscript. I dedicate this
chapter to the memory of Archie F. Carr, who was never
afraid to admit his attachment to frogs.
Editors' note (added in proof): The study cited as J. A.
Pounds, M. P. L. Fogden, and J. H. Campbell, unpubL,
was reported in Nature (Pounds et al. 1999). This work,
widely discussed by the media, was quoted in a speech
by U.S. President Clinton (June 3, 1999) as "disturb-
ing new evidence of climate change."THE DISCOVERY OF THE GOLDEN TOAD
jay M.Savagey initial response when I first saw Golden
Toads was one of disbelief. Instead of the
somber tones of gray, brown, or olive char-
acteristic of most toads in the genus Bufo, the males
were solid bright orange (Fig. 5.2). I wondered if some-
one had dipped them in enamel paint, but the color
proved to be genuine. The females were equally as-
tonishing. Lacking any hint of orange in their col-
oration, they were olive to black with large blotches
of the brightest scarlet outlined in yellow. This marked
difference between the sexes was as unexpected as the
brilliant hues. I first learned of this singularly strik-
ing toad in October 1963. During a visit to Monte-
verde, Norman J. Scott, Jr. and I spoke with local resi-dent Jerry James, who brought the species' existence
to our attention. Because it was the wrong time of year,
however, we were unable to find any examples. When
James delivered several specimens to the University
of Costa Rica the following May, we returned to the
cloud forest at once.
Scott, James, and I hiked up to the ridge above the
Monteverde community on 14 May 1964. On reach-
ing the toads' habitat at midafternoon, I was impressed
by the eerie atmosphere created by the dark soil, the
gnarled, moss-covered trees, and the billowing fog
that passed overhead. As we stepped into the forest,
everywhere we looked we saw bright blotches of or-
ange standing out against the black soil. Each blotch171 Amphibians and ReptilesM