What do forests have to do with global climate change? What do ...

Froglogging in East Texas
by Zoë Hoyle
The decline of frog populations
across the world has received
a lot of attention in the last few
years because of the key role frogs
play in aquatic ecosystems as both
predator and prey. Frogs and other
amphibians, with their permeable
skin and unshelled eggs, can also be
seen as indicator species—canaries in
nature’s coal mine—for the health of
aquatic ecosystems. So far, no single
cause has been found for declines in
frog populations, though chemicals,
disease, and loss of habitat have been
identified as possible causes.
Changing weather patterns from
global climate change could also be
a contributing factor, particularly for
frog species using ephemeral water
sources. In eastern Texas, some frog
species rely on ephemeral sources—
sometimes literally a rain puddle—
while others rely on permanent ponds.
“It’s widely known that the
breeding activity of amphibians like
frogs is closely tied to weather,” says
Dan Saenz, SRS research wildlife
biologist. “However, the specifics of
these relationships have barely been
explored.”
Saenz, along with other scientists
from the Nacogdoches, TX, team of
the SRS Southern Pine Ecology and
Management group, is currently
studying the effects of rainfall and
temperature on the breeding activities
of 13 different species of frogs in
eastern Texas. Information from the
research will make it possible to
predict potential effects of a changing
climate on frog populations.
“There’s a particularly high level
of diversity in frog species in eastern
Texas,” says Saenz. “There’s also a lot
of seasonal variation in temperature
and rainfall, so we suspected that
Gulf coast toad (Bufo valliceps). (Photo by Daniel Saenz, U.S. Forest Service)
weather might be a major factor
influencing breeding activity in frogs.”
Frogs call at night to advertise for
mates. To study breeding activity in
relation to weather, Saenz and fellow
researchers used “frogloggers” to
record calls at eight different ponds
every night for 2 years. Additional
dataloggers recorded hourly air
temperature and daily rainfall for each
site.
After identifying calls from the
tapes and relating them to weather
data, the researchers were able to
map out 5 different breeding patterns
among the13 frog species that vary
from total independence from local
weather patterns to dependence on
specific rainfall patterns in specific
temperature ranges.
“Our research has shown how frog
breeding activity is related to rainfall
and temperature,” says Saenz. “A
prolonged change in the weather
will have different effects on different
species—some negative, others
positive or neutral. We don’t know
how this will affect the diversity of frog
species, but our research has given
us a good foundation to begin making
predictions.”
For more information:
Dan Saenz at 936–569–7981 or
dsaenz@fs.fed.us
www.srs.fs.usda.gov 23