Biology and Conservation of Cicindela ohlone Freitag and Kavanaugh, the Endangered Ohlone Tiger Beetle (Coleoptera: Carabidae: Cicindelinae). I. Distribution and Natural History
2013
Knisley, C Barry | Arnold, Richard (Richard A.)
The objective of this study was to determine the current distribution and natural history of Cicindela ohlone Freitag and Kavanaugh, the endangered Ohlone tiger beetle, and to provide information essential for its conservation and recovery. Laboratory and field studies were conducted on the beetle's life cycle, seasonality, developmental times of immature stages, fecundity, and survivorship. The species is restricted to Watsonville loam soil in coastal terrace grassland in Santa Cruz County, California but was found at only 17 of over 200 sites of this habitat type surveyed. Most sites were unsuitable because they lacked bare ground surface needed by adults and larvae. During the course of our studies between 1996 and 2012, C. ohlone disappeared from eight of these sites as a result of land use changes that destroyed the habitat totally or altered it by eliminating sufficient bare soil due to increased vegetation. Laboratory studies yielded a mean high of 42 eggs per female over a 4-week period. Larvae reared at ad libitum feeding levels developed from first instar through third instar in 109 days compared to 144 days for larvae fed at lower levels. Field studies indicated a 12% survival rate for first instars after one year; 7% emerged as adults and 4% continued development into the second year. This species' unusual winter pattern of adult activity from late January into April coincides with the area's rainy season. Adult activity was limited to days with air temperatures above 16°C. Most of the bare or sparsely vegetated area occupied by C. ohlone adults and larvae is maintained by animal or human disturbances, including those by gophers, ground squirrels, feral pigs, cattle, horses, mountain bikers, and pedestrian foot traffic. Our studies suggest that this insect is seriously threatened by increased vegetation growth at most sites and is now more endangered than when we began our studies. New and expanded habitat management strategies must be quickly implemented at all sites to improve habitat conditions and increase recruitment.
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