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When cave crickets go out
for dinner, they really go, researchers say
Life Sciences Editor
photo to enlarge
by by Jean K. Krejca
Steven J. Taylor has found that cave crickets travel
farther from their homes to forage, which means that
protective buffers around caves may need to be extended
to protect endangered invertebrates that live inside
and depend on the crickets.
— Cave crickets travel farther from their homes to forage –
by about double – than their previously reported range, researchers
have discovered. In Texas, that means protective buffer areas around
caves may need to be extended to protect endangered invertebrate species
that live inside and depend on the crickets.
Reporting in the journal American Midland Naturalist, a team of researchers
led by Steven J. Taylor, an entomologist with the Illinois Natural History
Survey and University of Illinois at Urbana-Champaign, reported
that the crickets, Ceuthophilus secretus, journey at night in high numbers
up to 80 meters (262 feet) from the entrances of central Texas caves.
A few crickets traveled up to 105 meters (344 feet) to feed.
Previous research indicated that most crickets stay within 50 meters
(164 feet) from their caves. As part of the formula for a buffer zone
proposed by the U.S. Fish and Wildlife Service, a range for cricket
foraging was recommended. The buffer zone also extends outward to control
for the effects of invasive red imported fire ants (Solenopsis invicta
Buren). The buffer-zone formula helps to guide where to apply treatment
applications against the ants.
Buffer zones are designed to help maintain a healthy vegetative community,
including woodland and grassland species, around cave entrances to protect
cave life from disturbance, including that created by encroaching urban
“Our findings suggest that a relatively large area may be needed
to protect the crickets’ foraging area and to shield them from
fire ants,” Taylor said. “Based on the foraging range we
saw, we believe that cave resource managers may wish to create buffers
around the footprint of a cave – not just the entrance. It could
be that there are other small openings that allow crickets to leave
caves on their way to forage.”
The U.S. Fish and Wildlife Service has listed 16 cave invertebrates
– including a variety of spiders, pseudoscorpions and beetles
– in the Austin-San Antonio region as federally endangered species.
These invertebrates depend on nutrients brought into caves primarily
by crickets after foraging. Crickets also lay their eggs inside.
Taylor and colleagues studied the crickets around a cave at Fort Hood,
a sprawling military base northwest of Austin. Both cave crickets and
fire ants are found in large numbers around the cave, in which several
invertebrates related to endangered species live.
Researchers collected crickets as they emerged from the cave during
late spring and summer in 2003. Using a fine-tipped brush, scientists,
in the course of 17 nights, marked more than 2,000 crickets with fluorescent
The crickets were then released each night within a meter of the cave
entrance. Later each night, the crickets were located using portable
black lights, with their locations plotted with GPS equipment. On subsequent
days, the locations were measured and analyzed.
On average, adult crickets were found farther from the cave entrance
than were the nymphs. While 51 percent of all crickets were found to
be within 40 meters (131 feet) of the cave entrance, 8 percent were
found at locations 80 meters (262 feet) and beyond.
Previous studies of cave-cricket foraging depended on the use of bait
stations, which, Taylor said, could have biased the distribution and
movements of the crickets by attracting them to energy-rich locations.
The use of paint on the crickets, he said, made it “more likely
that observed foraging distances are natural.”
“Our results provide a quantitative measure of cave cricket foraging
range,” the researchers wrote, “and indicate that Ceuthophius
secretus routinely forages out to 80 meters or more from the cave entrance,
and is relatively uniform in density out to this distance.”
Co-authors on the study were Jean K. Krejca of Zara Environmental LLC
in Buda, Texas, and Michael L. Denight of the Engineer Research and
Development Center at the Construction Engineering Research Laboratory
in Champaign, Ill. The Engineer Research and Development Center and
the U.S. Department of the Army funded the research.