# The Implications of Habitat Management on the Population Viability of the Endangered Ohlone Tiger Beetle (Cicindela ohlone) Metapopulation

> The endangered Ohlone tiger beetle survives in just five patches of coastal prairie in California. By reading the size and state of larval burrows and the exit holes of emerging adults, researchers followed the beetles through their life cycle for three years. Their models show that more bare ground and slower cyclists could keep four of the five populations growing.

Summary by Kersey Lawrence, Original Wisdom. Updated 9 November 2026. Page: https://www.originalwisdom.com/tracking-literature/2013-cornelisse-bennett-implications-habitat-management-population/

## Citation and access

- **Authors:** Tara M. Cornelisse, Michelle K. Bennett and Deborah K. Letourneau
- **Year published:** 2013
- **Journal or source:** PLoS ONE
- **Full citation:** Cornelisse, T. M., Bennett, M. K. and Letourneau, D. K. 2013. The implications of habitat management on the population viability of the endangered Ohlone tiger beetle (Cicindela ohlone) metapopulation. PLoS ONE 8(8): e71005.
- **DOI:** 10.1371/journal.pone.0071005
- **Access status:** Open access (CC BY)
- **PDF:** https://www.originalwisdom.com/wp-content/uploads/2026/11/2013_Cornelisse_and_Bennett_etal_habitat-management-and-population-viability-of-the-endangered-ohlone-tiger-beetle.pdf

## Tags

- **Species:** Invertebrates > Ohlone tiger beetle
- **Region:** North America > United States
- **Tracking:** Burrows; Tracking; Tracks and signs identification
- **Behaviour and ecology:** Behaviour; Dispersal; Human disturbance
- **Methods and technology:** Global Positioning System (GPS); Logistic regression; Pearson correlation; Simulation
- **Data type:** Modelling or theoretical; New field data
- **Observer qualification:** Not reported
- **Discipline:** Behaviour and ecology; Wildlife tracking
- **Year published:** 2013

## Detailed keywords

- **Species:** Studied: Ohlone tiger beetle (Cicindela ohlone), an endangered insect: eggs, three larval stages (instars) and adults. Livestock (cattle and horses) are mentioned as grazers used to keep the ground bare. Other tiger beetles (Coleoptera: Cicindelinae) are discussed from the literature.
- **Location and habitat:** Santa Cruz County, California, United States: five remaining populations in coastal terrace prairie within a 24 km² area. Lower Marshall (1.5 ha) and Wilder Ranch (3.5 ha), 1.3 km apart in the centre of the range; Moore Creek (9.6 ha) and the University of California Santa Cruz campus (7.8 ha), 0.75 km apart in the south; Glenwood (2.9 ha), 10 km north of the others, grazed by horses year round and managed by the Land Trust of Santa Cruz County. Mediterranean climate; bare ground is needed for mating, hunting and egg-laying. Threats: invasive grasses, loss of natural disturbance (grazing, fire), fast cycling on recreational trails.
- **Topics:** endangered insect conservation; population viability analysis (PVA); metapopulation dynamics; stage-structured life cycle (egg, three larval instars, adult); larval burrow surveys; survival and fecundity; density dependence; habitat management (artificial bare-ground plots, grazing); recreation management (slower bicycle speeds); migration between habitat patches; extinction risk; recolonization of extirpated patches.
- **Statistics or models:** Stage-class population projection matrix models (Morris and Doak 2002) in Matlab; stochastic log growth rate by simulation (50,000 iterations) and Tuljapurkar’s approximation; quasi-extinction simulations; stochastic sensitivity and elasticity analysis (limitsens.m; maximum likelihood estimates with Kendall.m); management scalar h in a deterministic model (vitalsens.m); metapopulation simulation (DemoMetaSim.m, 100 years, 500 runs); logistic regression (SPSS) for density dependence; Pearson correlation of vital rates among sites. Inconsistencies in the paper: (1) the migration multipliers are written “m = 1/25 = 1.04” and “10% m = 1.10” (1/25 is 0.04; the multipliers of 1.04 and 1.10 appear to be meant); (2) the Results say vital rates were “largely correlated among sites” with some asynchronous pairs, while the Discussion says vital rates “were generally asynchronous among sites”; (3) the Discussion says slower cycling “increased population growth by 42–58%”, which matches the elasticity values (0.458 to 0.582) rather than a reported percentage change; (4) the status quo growth rates in Figure 4 (deterministic, averaged vital rates) differ from the stochastic growth rates in the text (for example, the campus site is about 1.35 in the figure and 1.163 in the text); (5) the y-axis of Figure 5 has repeated and uneven labels.
- **Data type:** New field data: adult counts and larval burrow monitoring, January 2010 to August 2012 (the campus site was surveyed only in 2011 and 2012). Modelling: population projection and management scenarios built from these data and published fecundity estimates.

## Synopsis

### 1. What they did

Insects are often overlooked in conservation planning. The Ohlone tiger beetle lives only in the coastal prairies of Santa Cruz County, California, where five populations remain from a group of 10 to 15 habitat patches in the last 25 years. Adults hunt prey on open ground, and larvae wait at the mouths of burrows flush with the soil to catch passing arthropods, so both need bare ground. Grazing, scraped bare-ground plots and recreational trails now keep the ground open, but fast cycling can disturb adult mating and hunting.

To find out how management affects the beetles’ chances of survival, the researchers:

- Counted adults once or twice a week from late January to early June, 2010 to 2012, at all five sites.

- Marked larval burrows. They found first-stage larval burrows (and in 2012, egg-laying burrows), told the stages apart by burrow diameter, and took a burrow as active when its entrance was clean and clearly outlined. Each group of burrows was mapped under a gridded quadrat, marked with metal washers and nails, and located with a Global Positioning System (GPS) unit.

- Followed survival. They revisited the burrows in spring and summer. A wider entrance showed the larva had moulted to the next stage. The next winter, an irregular exit hole of 6 mm or more showed an adult had emerged.

- Tested crowding. They checked whether the number of burrows in a quadrat affected larval survival.

- Built population models for each site and for all sites together, then tested the effect of more bare ground, slower cycling (8 to 12 kilometres per hour) and different rates of migration between the two central sites.

### 2. What they found

Survival and crowding

- Numbers and survival rates varied between sites and years. Egg survival was lowest at Wilder Ranch (0.06 in 2012).

- Larvae never stayed in the first stage between visits.

- Quadrats held 1 to 13 larval burrows (average 3.3). Crowding had no effect on larval survival.

Population growth

- Four populations were growing: Glenwood (1.41, the highest), Moore Creek (1.164), the campus (1.163) and Lower Marshall (1.03). Wilder Ranch was shrinking (0.598).

- Wilder Ranch was certain to go extinct within 21 years in every model; every other population had zero risk in all time frames modelled.

- Growth was most sensitive to egg survival. At Lower Marshall it was also sensitive to the growth of third-stage larvae.

Management

- More bare ground and slower cycling both raised growth rates at every site, bare ground more than slower cycling. Neither did much for Wilder Ranch.

Metapopulation

- Any combination of sites that included Glenwood, Moore Creek and the campus had zero risk of falling to very low numbers.

- Wilder Ranch and Lower Marshall alone had a 52% chance of falling to 10 individuals per stage within 100 years with no migration. Migration of 2%, 4% and 10% of adult females lowered this to 49%, 46% and 43%.

### 3. What they concluded

- The Ohlone tiger beetle has four viable populations that, with habitat management, could recolonize extirpated sites and avoid extinction.

- Glenwood shows how good habitat and management can lower the risk for an isolated patch. Wilder Ranch shows how a well-connected patch can fail as habitat declines.

- Protecting occupied habitat is not enough on its own: bare ground must be kept open and accidental deaths reduced. As little as 9 m² of bare ground per site would be beneficial.

- Three years of data are not enough to predict insect population swings, and how far the beetles disperse between patches is unknown. Future studies should focus on dispersal, to judge whether the beetles can recolonize on their own or need to be moved.

### 4. How tracking was or was not used

The study relied on reading the beetles’ signs in the soil rather than seeing the larvae themselves. The researchers identified larval burrows, told the three larval stages apart by entrance diameter, judged burrows active by a clean, clearly outlined entrance, read a widened entrance as a moult to the next stage, and took an irregular exit hole of 6 mm or more as a sign that an adult had emerged. Adults were counted by sight. No trailing was used.

### 5. Tracker or observer certification

Not reported. The survival estimates rest on burrow interpretation, but no training or skill check is described. Tara Cornelisse and Michelle Bennett carried out the fieldwork, with field help from M. Hash.

### 6. Other technologies, skills or innovations

- GPS and metal washers and nails (found again with a metal detector) to relocate marked quadrats without disturbing the larvae.

- Gridded quadrats and matching datasheets to map individual burrows.

- Population viability modelling in Matlab, adding management actions as a multiplier on survival and egg numbers.

### 7. Implications for conservation (from the paper)

- Making bare ground and slowing cyclists in occupied habitat can raise beetle survival and population growth.

- Habitat should also be managed at recently extirpated sites and in potential coastal prairie habitat, so beetles can recolonize.

- Wilder Ranch needs more habitat management; the area between Wilder Ranch and Lower Marshall is protected, but improving extirpated patches there is a necessary first step.

### 8. Implications for tracking (Original Wisdom's observations)

_These are Original Wisdom's observations, not the authors'._

- Population estimates for animals that are rarely seen can rest entirely on signs: here, burrow size, the condition of the entrance and the shape of exit holes stood in for direct counts of larvae.

## Cite this summary

Lawrence, K. 2026. Summary of: The Implications of Habitat Management on the Population Viability of the Endangered Ohlone Tiger Beetle (Cicindela ohlone) Metapopulation (Cornelisse and Bennett et al., 2013). Original Wisdom, Tracking Literature. https://www.originalwisdom.com/tracking-literature/2013-cornelisse-bennett-implications-habitat-management-population/