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Prairie Mole Crickets at Downs Prairie Natural Area

Arkansas Natural Heritage Commission - Tuesday, June 01, 2010

In 2008, the September edition of Natural News reported on a tallgrass prairie project restoring an abandoned railroad right-of-way at Downs Prairie Natural Area (Breaking ground: Grand Prairie restoration). The work is supported through a grant from the Arkansas Game and Fish Commission’s (AGFC) State Wildlife Grant Program. Over the past two years, ANHC staff have been busy with our partners, the AGFC and Arkansas Forestry Commission (AFC), and have recently completed planting the abandoned railroad with native prairie seed collected from Downs Prairie. As part of this project, surveys were undertaken to monitor the response of grassland bird and insect species of conservation concern to habitat restoration activities, the latter of which is the subject of this article.

During the past two months, ANHC staff and volunteers conducted surveys for a rare orthopteran insect (an order of insect classification), the prairie mole cricket (Gryllotalpa major), which is native to tallgrass prairie in the south-central United States. Historically, this species range included areas in Kansas, Missouri, Illinois, Kentucky, Tennessee, Mississippi, Arkansas, and Oklahoma. Today, populations are known only from tallgrass prairie relicts in Kansas, Missouri, Arkansas, and Oklahoma. Populations have declined with the reduced availability of suitable grassland habitat. For example, in the Grand Prairie of eastern Arkansas, less than one percent of tallgrass prairie remains as much of the land was converted to other uses, primarily agriculture.

Prairie mole crickets are the largest of North American crickets, with recorded lengths up to 5.0 cm and masses up to 2.6 grams. Little is known about their life cycle because they spend the majority of their time underground. Most common crickets have large hind legs adapted for jumping, but prairie mole crickets have hefty front legs designed for digging.

In late spring, the crickets emerge for courtship and reproduction. Males construct an acoustic underground burrow used to amplify their courtship call (click link to hear call), which is made by rubbing their forewings together to produce the sound. Humans can hear the calls at distances up to 400 meters from burrow. In Arkansas, calling usually begins in April and continues through early May. Weather conditions such as moisture, temperature, and wind speed play an important role during the courtship period. Males generally will not call unless evening temperatures are above 55-60°F and wind speeds are less than 25 miles per hour. Soil conditions (moist or dry) also affect the acoustics of the burrow. When conditions are right, males begin to call shortly after sunset and continue for approximately 45 minutes after dark. In response, females flying over the area drop to the ground, enter a male’s burrow, mate, and disperse to lay eggs.

Surveys at Downs Prairie documented 52 acoustic burrows occupied by calling males in April and 18 active burrows in May. A decrease in activity during May was expected because the courtship period comes to an end during this time. Most all burrows were located in the high quality tallgrass prairie areas with a few located along the edge of the abandoned railroad. A survey conducted seven years ago reported active burrows in the quality tallgrass prairie areas but none in the abandoned railroad which, at that time, was overrun by dense trees, shrubs, and vines.

During the past two years, the vegetation was removed from the abandoned railroad, the site was prepared to receive native prairie seed, and then was planted this past April. Prairie seed often germinates over a period of two to three years, and perennial prairie plants devote most of their efforts in the first few years to developing root systems with little visible above-ground growth. Therefore, it may be several years before prairie plants are seen growing in the abandoned railroad bed.

Restoring the abandoned railroad increases the productivity of this natural area for species of concern, such as the prairie mole cricket, by providing additional foraging and breeding habitat, and eliminating fragmentation within the natural area. For more photos from the survey, visit the photo gallery on our website.



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