Tarantulas

Tarantulas appear on Mount Diablo in late summer as part of a short, sharply defined mating season. Hundreds of males emerge after the first fall rain, moving through mountain vegetation in search of females; their conspicuous nighttime crossings end in a life cycle that does not lead back to their underground holes.

Seasonal Emergence

In late August and early September, following the first fall rain, hundreds of male Tarantulas come out of holes in the ground. They skitter through mint-scented mountain sage, searching for burrows delicately draped in silk, where females are ready to mate. Their emergence is tied to a narrow seasonal window and a specific purpose: finding those burrows.

Seen After Dark

The tarantulas’ movement draws visitors to Mount Diablo around sunset and just after dark, when flashlights make them easier to spot. Beams sweeping across the trails sometimes reveal what first looks like a moving piece of earth; closer inspection shows a scuttling Tarantula as large as a saucer. Bats wheel over gray pines and live oaks, while great horned owls call in the dark, placing the search for the spiders within a larger scene of nocturnal activity.

Mating and Death

The males’ search ends in mating, but they never return to their holes. They mate as much as they can and then die, either from starvation or from the cold. The seasonal spectacle therefore carries its own stark ending: the same movement that brings the males out into view also takes them away from the burrows to which they will not go back.