Los Farallones

Dispatches from Point Blue’s field station on the Farallon Islands National Wildlife Refuge

Cricket Time!

Once each season we set out to survey the population of endemic Farallon Cave Crickets on the island, and that time has come again! This entails three nights of surveys and two day surveys to get an accurate estimate of the number of crickets currently present. On three evenings, we got our headlamps on and surveyed five different locations across the island.

Rabbit Cave (seen above), the deepest cave we search, extends 75m back and varies in size from tight squeezes to large spacious rooms. After surveying the mouth of the cave, it’s time to crawl in, counting off the crickets along the walls as we go.

We break down our counts by age and sex classes, from the tiny nymphs, to the middle sized juveniles and larger breeding adults. An adult male can be seen above. This is determined by the lack of an ovipositor, an egg laying organ that extends off the rear end of female crickets.

During the day, there is one more cricket hang-out to survey. Cricket cave, properly named for its abundance of crickets, gets a visit to count the total number of individuals present. The winter time is not the most abundant time of year for crickets, but we counted over 2000 individuals in Cricket Cave alone!

There’s also some pretty cool geologic formations inside the caves too!