Endangered Species in Santa Cruz County - Species Account


Ohlone Tiger Beetle
(Cicindela ohlone)


This information was excerpted from the following publications, which are available for reference use at the Central Branch Library:

Description and Taxonomy

The Ohlone tiger beetle, Cicindela ohlone, is a member of the Coleopteran family Cicindelidae (tiger beetles), which includes over 2,000 species worldwide and over 100 species in the United State (Pearson and Cassola 1992). Tiger beetles are day-active, predatory insects that prey on small arthropods. Because many tiger beetles often feed on insect species that are injurious to man and crops, they are regarded as beneficial (Pearson and Cassola 1992; Nagano 1982). Adult tiger beetles are medium-sized, elongate beetles characterized by their usually brilliant metallic green, blue, red, and yellow coloration highlighted by stripes and spots. Adults are ferocious, swift, and agile predators that seize small prey with powerful sickle-shaped jaws.

Tiger beetle larvae are also predatory. They live in small vertical or slanting burrows from which they lunge and seize passing invertebrate prey (Essig 1926; Essig 1942; Pearson 1988). When a prey item passes near a burrow, the larva grasps the prey with its strong mandibles (mouthparts) and pulls it into the burrow, and once inside the burrow, the larva will feed on the captured prey (Essig 1942; Pearson 1988). Tiger beetles share similar larval body forms throughout the world (Pearson and Cassola 1992). The larvae, either white, yellowish, or dusky in coloration, are grub-like and fossorial (subterranean), with a hook-like appendage on the fifth abdominal segment that anchors the larvae inside their burrows. 1

The Ohlone tiger beetle is endemic to Santa Cruz County, California, where it is known only from coastal terraces supporting remnant patches of native grassland habitat. Specimens of this species were first collected northwest of the City of Santa Cruz, California, in 1987, and were first described in 1993 (Freitag et al. 1993). Both male and female specimens have been collected.2

The Ohlone tiger beetle has a relatively small adult body size compared to closely related Cicindela pupurea and other species in the purpurea group. Males range in length from 9.5 to 10.5 millimeters (0.37 to 0.40 inch); the females are slightly larger, ranging in length from 10.5 to 12.5 millimeters (0.40 to 0.49 inch). The adults have a bright light green dorsum with tints of bronze on the pronotal disc (hardened body wall plate on the prothorax) and elytra (leathery wing covers), particularly around the middle band. Other closely related species have a darker green or blue green dorsum with indistinctive, or no brown highlight. The elytral maculations (spotted markings on the wing covers) of the Ohlone tiger beetle are broad; the closely related species have narrower markings. Females have a deep notch in the lateral portion of the gonapophysis (the process in the anal region of the beetle that serves in copulation or oviposition), and the male has sharply defined lacteroapical flanges on its median lobe (Freitag et al. 1993).3

Two principal distinguishing features of the Ohlone tiger beetle are its early seasonal adult activity period and its disjunct distribution. While other tiger beetle species, such as Cicindela purpurea, are active during spring, summer, or early fall (Nagano 1982; Freitag et al. 1993), the Ohlone tiger beetle is active from late January to early April (Freitag et al. 1993). The Ohlone tiger beetle is the southernmost of the purpurea group species in the Pacific coast region; its distribution is allopatric (geographically separated) to those of similar species (Freitag et al. 1993).

Ohlone tiger beetle larvae are currently undescribed. However, tiger beetle burrows, measuring 4 to 6 mm in diameter (0.16 to 0.23 in), were found in the same habitat areas where adult Ohlone tiger beetles were collected (David Kavanaugh, California Academy of Sciences, pers. comm. 1997; V. Cheap, in litt. 1997). The surface openings of these burrows are circular and flat with no dirt piles or mounds surrounding the circumference (Kim Touneh, Service, pers. obs. 1997). These burrows are similar to larval burrows belonging to other tiger beetle species. Larvae and inactive adults have been excavated from these burrows, and the inactive adults collected from these burrows were fully mature and easily identified as Ohlone tiger beetles (D. Kavanaugh, pers. comm. 1997; V. Cheap, in litt. 1997). Based on these collections, Kavanaugh (pers. comm. 1997) concluded that the larvae found in these burrows were Ohlone tiger beetle larvae. Further investigations of these recently collected larvae are being conducted to scientifically characterize and document the morphology of the Ohlone tiger beetle larvae (D. Kavanaugh, pers. comm. 1997).4

Habitat Description

The known habitat of the Ohlone tiger beetle is described as coastal terraces with remnant stands of open native grassland containing Stipa pulchra (purple needlegrass), Danthonia californica (California oat grass), Perideridia gairdenera (Gairdner's yampa), and/or Perideridia kelloggii (Kellogg's yampa) (Morgan, in litt. 1992; Freitag et al. 1993). Soils at these level or nearly level sites are shallow, poorly-drained pale clay or sandy clay soils over bedrock of Santa Cruz Mudstone. (Freitag et al. 1993). Adult tiger beetles generally occupy sun-exposed or open areas within their habitat to thermoregulate or hunt (Knisley et al. 1990; Knisley and Hill 1992).5

Ohlone tiger beetle habitat is associated with specific soil types in Santa Cruz County, either Watsonville loam or Bonnydoon soil types. Soil core analyses were conducted for three out of the five known population sites; the soil types for these three sites were determined to be either Watsonville loan or Bonnydoon (Richard Casale and Ken Oster, U.S. Department of Agriculture, Natural Resources Conservation Service, pers. comm. 1997).

Adult Ohlone tiger beetles have been observed in remnant patches of native grassland on coastal terraces where bare areas occur among low or sparse vegetation. Trails (e.g., foot paths, dirt roads, and bicycle paths) are also used. When disturbed, adults will fly to more densely vegetated areas (Freitag et al. 1993; Richard Arnold, private consultant, pers. comm. 1995). Oviposition by females and subsequent larval development also occur in this coastal prairie habitat (i.e., open areas among native vegetation) (D. Kavanaugh, pers. comm. 1997; V. Cheap, in litt. 1997). The density of larval burrows decreases with increasing vegetation cover (G. Hayes, in litt. 1997).6

Range and Distribution

The historic range of the Ohlone tiger beetle cannot be precisely assessed because the species was only recently discovered, and no historic specimens or records are available. The earliest specimen recorded was collected from a site northwest of the City of Santa Cruz in 1987 (Freitag et al. 1993). Based on available information on topography, substrates, soils, and vegetation, it is likely that suitable habitat for the Ohlone tiger beetle was more extensive and continuous prior to the increase in urban development and agriculture. ... . However, we have no evidence or data indicating that this species occurred beyond the present known occupied areas of Santa Cruz County. Currently, the extent of potentially suitable habitat for the Ohlone tiger beetle is estimated at 81 to 121 hectares (ha) (200 to 300 acres (ac)) in Santa Cruz County, California (Freitag et al. 1993).7

Through surveys conducted in San Mateo, Santa Cruz, and Monterey Counties, the current known range of the Ohlone tiger beetle is from Scotts Valley City to the southern coast of Santa Cruz City. Because the beetle is known to be restricted to coastal terraces of clay or sandy soils and based on soil maps, it may once have historically extended from southwestern San Mateo County to northwestern Monterey County, California (Freitag et al. 1993). Much of this habitat has been destroyed, degraded, and fragmented by urban development and invasion of non-native vegetation.8

The available data indicate a restricted range and limited distribution of the Ohlone tiger beetle. This finding is supported by the following considerations. First, many tiger beetle species are known to be restricted to specific habitats (Pearson 1988; Knisley and Hill 1992; Pearson and Cassola 1992), such as the open native grassland occupied by the Ohlone tiger beetle. Second, tiger beetles are widely collected and well studied, yet no historic specimens were found in the extensive collections of the California Academy of Sciences (Freitag et al. 1993). The Ohlone tiger beetle's specialized habitat and restricted range may account for the absence of collection records prior to 1987. Because Cicindela is a very popular insect genus to collect (Chris Nagano, Service, pers. comm. 1993), and because entomologists commonly collect out of season and out of known ranges in order to find temporally and spatially outlying specimens, one would expect more specimens to have been collected if the Ohlone tiger beetle were more widespread and common.

Only five populations of Ohlone tiger beetles are known to exist. All known populations are located on coastal terraces supporting remnant stands of native grassland. One population occurs northwest of the City of Soquel at 60 to 90 meters (m) (200 to 295 feet(ft)) elevation. A second population is located in the City of Scotts Valley at 210 m (690 ft) elevation; a third is located west of the City of Santa Cruz at 110 m (360 ft) elevation on property owned by the County of Santa Cruz; a fourth population is found in a preserve northwest of the City of Santa Cruz and owned by the City and occurs at about 110 m (360 ft) elevation; and the fifth population is found northwest of the City of Santa Cruz on properties owned by the University of Santa Cruz (University) and the California Department of Parks and Recreation, at about 340 m (1115 ft) elevation (Freitag et al. 1993; R. Morgan, in litt. 1994; G. Hayes, in litt. 1997). The abundance of individuals in each population in unknown. However, each population is localized to areas of less than 2 ha (5 ac) (G. Hayes, pers. comm. 1995).9

Population Status and Current Threats

The Ohlone tiger beetle is limited to only five populations in the mid-county portion of coastal Santa Cruz County. Four are threatened by habitat fragmentation, degradation, and destruction due to proposed developments of residential housing, ballfields, parks, parking lots, and an entrance road. One population occurs within the range of the other taxa included in this [recovery] plan, in the area of Scotts Valley.

Ohlone tiger beetle habitat sites are also threatened by invasion of nonnative vegetation (e.g. French broom [Cytisus monspessulanus], velvet grass [Holcus sp.], filaree [Erodium sp.], and Eucalyptus sp.) (Morgan, in litt. 1992). These nonnative plants convert sunny, open grassland habitat needed by Ohlone tiger beetles to habitat dominated by an overstory that shades the grasses and possibly eliminates areas necessary for thermoregulation, foraging and oviposition (laying eggs). In addition to shading areas used by the beetle, nonnative vegetation will directly eliminate the open spaces by creating an unsuitable, densely vegetated habitat.10

Nonnative vegetation may also affect the numbers and diversity of the beetle's prey, predators, and parasites ... . Increased vegetation encroachment is the primary factor attributed to the extirpation of several populations of other Cicindela species (e.g., C. abdominalis and C. debilis) (Knisley and Hill 1992). Without management efforts to reduce and control nonnative species, the populations of Ohlone tiger beetle will likely decline because of habitat degradation.11

The species' restricted range and small population size increase its vulnerability to local extirpations resulting form random, naturally occurring events, such as erosion, disease, or predation. Recreational use of habitat (i.e. bicycling or off-road motor vehicle use), over-collection, and pesticides are recognized as potential threats.12

Conservation Efforts

The Ohlone tiger beetle is not State-listed and receives no protection under the California Endangered Species Act. However, the species is given consideration during the environmental review process conducted under the California Environmental Quality Act.13

The final rule to list the Ohlone tiger beetle as endangered was published in the Federal Register October 3, 2001.

Needed Conservation Measures

Specific actions that would provide protection for the Ohlone tiger beetle include:

  • Habitat Conservation Plans with the County of Santa Cruz, City of Santa Cruz, and City of Scotts Valley that minimize loss of habitat from urban development
  • Protection of habitat through acquisition or conservation easements on habitat in the City of Santa Cruz and Scotts Valley
  • Conduct research focusing on habitat requirements for long-term survival.14

Footnotes:

1 Federal Register: February 11, 2000 (Volume 65, Number 29). "Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the Ohlone Tiger Beetle (Cicindela ohlone)," p. 6952.

2Ibid., p. 6952.

3U.S. Fish and Wildlife Service. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." Portland, Oregon. The Service, 1998, p. 38.

4 Federal Register: February 11, 2000 (Volume 65, Number 29). "Endangered and Threatened Wildlife and Plants; Proposed Endangered Status for the Ohlone Tiger Beetle (Cicindela ohlone)," p. 6953.

5 U.S. Fish and Wildlife Service. "Draft Recovery Plan for Two Insects (Polyphylla barbata and Trimerotropis infantilis) and Four Plants (Chorizanthe pungens var. hartwegiana, Chorizanthe robusta var. hartwegii, Erysimum teretifolium, and Polygonum hickmanii) from the Santa Cruz Mountains, California." Portland, Oregon: The Service, 1997, p. 33.

6 Op. Cit., Federal Register: February 11, 2000 (Volume 65, Number 29), p. 6953.

7 Ibid., p. 6953.

8 U.S. Fish and Wildlife Service. "Draft Recovery Plan for Two Insects (Polyphylla barbata and Trimerotropis infantilis) and Four Plants (Chorizanthe pungens var. hartwegiana, Chorizanthe robusta var. hartwegii, Erysimum teretifolium, and Polygonum hickmanii) from the Santa Cruz Mountains, California." Portland, Oregon: The Service, 1997, p. 34.

9 Op. Cit., Federal Register: February 11, 2000 (Volume 65, Number 29), p. 6953.

10U.S. Fish and Wildlife Service. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." Portland, Oregon. The Service, 1998, p. 39.

11 Op. Cit., Federal Register: February 11, 2000 (Volume 65, Number 29), p. 6955.

12U.S. Fish and Wildlife Service. "Recovery Plan for Insect and Plant Taxa from the Santa Cruz Mountains in California." Portland, Oregon. The Service, 1998, p. 39.

13 Ibid., p. 39.

14 Ibid., p. 40.