BCI and Mexican biologists join in a mutual concern:
protection of the bats that cross our borders...
BCI and Mexican biologists join in a
mutual concern: protection of the bats that cross our borders...
Mexico's largest bat populations are in serious trouble. In
addition to being victims of habitat loss, pesticides, and roost
disturbance, they also are targets of intense eradication
efforts. Throughout much of Latin America, people do not
discriminate between the single vampire bat species that harms
livestock and the hundreds of other species that are essential to
the health of tropical ecosystems. War is declared on all bats,
and beneficial species, especially those that form large colonies
in caves, are the most often killed.
Many of Mexico's more than 130 bat species may be in trouble,
though almost nothing is known about the status or needs of most.
Last fall BCI staff, Patricia Morton, Paul Robertson, and Merlin
Tuttle, along with scientific advisory board member Don Wilson
from the Smithsonian Institution, met with Mexican scientists to
take the first steps in developing a comprehensive conservation
plan for Mexico's exceptionally rich, but threatened, bat fauna.
The meeting, chaired by Rodrigo Medellin, a bat ecologist, was
held at the Ecology Center at the University of Mexico in Mexico
City and was attended by fellow ecologists Hector Arita, Joaquin
Arroyo, Gerardo Ceballos, and Oscar Sanchez. Participating
scientists agreed upon several stages of conservation
initiatives, ranging from surveys to identify the most important
bat caves and their protective needs, to developing vampire
control training and public education materials.
Mexico's largest remaining overwintering colonies of Mexican
free-tailed bats (Tadarida brasiliensis) are believed to
be in the most immediate jeopardy. Although free-tailed bats
still form colonies numbering in the millions (the world's
largest aggregations of warm-blooded animals), there is cause for
serious concern. A large proportion of the species population is
migratory, traveling north each spring to rear young in only
about a dozen suitable caves in the southwestern U.S. Alarming
declines have been documented at several of these sites. Eagle
Creek Cave in Arizona once housed the world's largest bat
population, estimated in 1963 to be 25 to 50 million individuals.
In just six years, the population plummeted to only 30,000, a
99.9% reduction! Even the famous Carlsbad Caverns, New Mexico,
population has dropped from a reported 8.7 million bats in the
1930s to only about 250,000 today.
Following the Mexico conference, Paul Robertson conducted an
exhaustive search for information on important bat caves of
Mexico and interviewed leading authorities on Mexican caves and
bats. Of the over 200 caves identified as important for bats, he
selected the 20 believed to harbor the largest overwintering
populations of free-tailed bats. He targeted those for immediate
status surveys and organized a BCI field team that included Jesse
Villalobos, an assistant from Trinity University, and Mexican bat
biologists Arnulfo Moreno and Jorge Medellin. During February,
they visited eight of the largest overwintering caves
historically known to be used by Mexican free-tailed bats.
What the team found highlights the urgency of current efforts.
Half of the eight caves visited had lost their entire
colonies--an alarming discovery, considering they had
historically ranked among Mexico's most important. The owner of
the fifth cave estimated a 90% loss of bats over the past five
years. The colony in the sixth had dropped from many millions to
just 100,000, and the final two caves still housed 30,000 and
100,000 respectively, having apparently undergone substantial
decline as well. The primary cause appeared to be human
disturbance and vandalism, including ill-timed phosphate mining
and guano extraction.
Tires that had been burned in one cave entrance had so covered
the interior with thick soot that it was totally unusable by
bats, and fire also seriously damaged a second cave. Another that
had housed a large free-tailed colony only five years ago had
been entirely blocked off with plastic and cardboard, preventing
further use. Burning tires in caves is disastrous, the noxious
smoke killing entire ecosystems of unique life. Such fires not
only destroy millions of bats at a time, but without extensive
clean-up by conservationists, bats cannot even use the caves in
the future. These disastrous incidents likely are examples of
misdirected efforts to kill vampire bats.
This summer the eight caves visited in February will be
rechecked, and owners contacted regarding possible protective
measures. The remaining 12 of the top 20 Mexican bat caves also
will be visited this summer and again during the winter of
1991-92. Ongoing monitoring is greatly needed on both sides of
the Mexican border. Following completion of initial surveys,
plans will be developed to educate people and gain conservation
measures in the locations where help is most feasible and needed.
One of BCI's current priorities is to develop educational
programs in Spanish for use throughout Latin America. These will
focus both on broad public education and on training for vampire
control personnel. The many values of bats, as well as specific
vampire control techniques, will be emphasized, especially in
areas where the most important or endangered bat populations are
Mexico's bats are an essential heritage shared by many North
Americans. The bats that cross our borders create some of our
most spectacular bat flights, from those at Carlsbad Caverns in
New Mexico to the Congress Avenue bridge in Austin, Texas. We
must work together with the people of Mexico to ensure a future
for our bats and the many other plants and animals that rely on
by James H. Fullard
Colonies of Mexican free-tailed bats often number in the
millions, but there is still cause for serious concern. The few
roosting caves suitable for the species are increasingly
disturbed, and dramatic declines have been documented.
Half of the caves surveyed have completely lost their bat
populations. Although Tio Bartolo is one of the least disturbed,
evidence suggests a much larger past population.