More on Ground Squirrels

by Steve Ayala

Kathleen Wong's article "Lord of the Burrows" (Jan-Mar 2008) describes the California ground squirrel's role in a network of grassland residents. That network expands the closer you look.

A group of California sandflies coevolved with ground squirrels. The flies spend their daylight hours in the burrows and lay eggs in the squirrels' latrine chambers. Female sandflies need a blood meal to mature their eggs. Their hosts are not squirrels but reptiles and amphibians that live in the burrows.

Sandflies carry viruses, bacteria, and protozoa that infect their blood meal hosts. California sandflies carry malaria parasites that live in fence lizards and a blood-inhabiting trypanosome that lives in another burrow resident — the western toad.

The story of how this community evolved through the Ice Ages may be even more fascinating. One of that toad's closest Old World relatives lives in eastern China, in a habitat very similar to Central California. And in the blood of the Chinese toad lives a trypanosome (probably sandfly-transmitted) almost identical to its California relative.