When Cave Crickets Go Out For Dinner, They Really Go, Researchers Say

Reportingin the journal American Midland Naturalist, a team of researchers ledby Steven J. Taylor, an entomologist with the Illinois Natural HistorySurvey and University of Illinois at Urbana-Champaign, reported thatthe crickets, Ceuthophilus secretus, journey at night in high numbersup to 80 meters (262 feet) from the entrances of central Texas caves. Afew crickets traveled up to 105 meters (344 feet) to feed.

Previousresearch indicated that most crickets stay within 50 meters (164 feet)from their caves. As part of the formula for a buffer zone proposed bythe U.S. Fish and Wildlife Service, a range for cricket foraging wasrecommended. The buffer zone also extends outward to control for theeffects of invasive red imported fire ants (Solenopsis invicta Buren).The buffer-zone formula helps to guide where to apply treatmentapplications against the ants.

Buffer zones are designed to helpmaintain a healthy vegetative community, including woodland andgrassland species, around cave entrances to protect cave life fromdisturbance, including that created by encroaching urban development.

“Ourfindings suggest that a relatively large area may be needed to protectthe crickets’ foraging area and to shield them from fire ants,” Taylorsaid. “Based on the foraging range we saw, we believe that caveresource managers may wish to create buffers around the footprint of acave – not just the entrance. It could be that there are other smallopenings that allow crickets to leave caves on their way to forage.”

TheU.S. Fish and Wildlife Service has listed 16 cave invertebrates –including a variety of spiders, pseudoscorpions and beetles – in theAustin-San Antonio region as federally endangered species. Theseinvertebrates depend on nutrients brought into caves primarily bycrickets after foraging. Crickets also lay their eggs inside.

Taylorand colleagues studied the crickets around a cave at Fort Hood, asprawling military base northwest of Austin. Both cave crickets andfire ants are found in large numbers around the cave, in which severalinvertebrates related to endangered species live.

Researcherscollected crickets as they emerged from the cave during late spring andsummer in 2003. Using a fine-tipped brush, scientists, in the course of17 nights, marked more than 2,000 crickets with fluorescent water-basedpaint.
The crickets were then released each night within a meter ofthe cave entrance. Later each night, the crickets were located usingportable black lights, with their locations plotted with GPS equipment.On subsequent days, the locations were measured and analyzed.

Onaverage, adult crickets were found farther from the cave entrance thanwere the nymphs. While 51 percent of all crickets were found to bewithin 40 meters (131 feet) of the cave entrance, 8 percent were foundat locations 80 meters (262 feet) and beyond.

Previous studies ofcave-cricket foraging depended on the use of bait stations, which,Taylor said, could have biased the distribution and movements of thecrickets by attracting them to energy-rich locations. The use of painton the crickets, he said, made it “more likely that observed foragingdistances are natural.”

“Our results provide a quantitativemeasure of cave cricket foraging range,” the researchers wrote, “andindicate that Ceuthophius secretus routinely forages out to 80 metersor more from the cave entrance, and is relatively uniform in densityout to this distance.”

Co-authors on the study were Jean K.Krejca of Zara Environmental LLC in Buda, Texas, and Michael L. Denightof the Engineer Research and Development Center at the ConstructionEngineering Research Laboratory in Champaign, Ill. The EngineerResearch and Development Center and the U.S. Department of the Armyfunded the research.