Biology and Conservation of Cicindela ohlone Freitag and Kavanaugh (Coleoptera: Carabidae: Cicindelinae), the Endangered Ohlone Tiger Beetle. II. Population Ecology of Adults and Larvae and Recommended Monitoring Methods

Abstract

Population ecological and monitoring results are presented for the endangered Ohlone tiger beetle, Cicindela ohlone Freitag and Kavanaugh, at six study sites near Santa Cruz, CA, covering the years 2000 through 2017. Mapping of larval burrows and nearest neighbor analysis found a highly clumped distribution pattern. The numbers of both larvae and adults exhibited substantial year-to-year fluctuations. The range of adult seasonal activity varied over the years, with extreme dates from 13 January to 21 May. Daily, study period, and generation population sizes of adults were estimated using three absolute population estimation methods: capture-recapture; frequency of capture; and repeated counts along fixed belt transect routes throughout the entire adult activity period. In a 12-day capture-recapture study, daily population estimates using four different models ranged from 35 to 146 adults, with estimated average life spans of 3.0–7.2 days. Estimated adult generation sizes using belt transect counts over the 18 years ranged from 136 to 1,025 at Glenwood, 139 to 1,000 at Marshall Field, 284 to 944 at Grey Whale, and 504 to 1,808 at Moore Creek. Temporal trends in generation sizes at these four sites were associated with land use and habitat management activities, including grazing, controlled burns, and trail use by hikers and bikers, plus annual and seasonal precipitation amounts. Results of these studies suggest that both larvae and adults should be monitored as part of adaptive management programs specifically designed for this endangered beetle.