Tobias is a Labrador retriever with one job: sniffing out invasive Argentine ants wherever they hide. He’s really good at it, and with his help, a fragile island ecosystem may be spared a repeat inundation with the pests.

Santa Cruz Island is 25 miles off the coast of Southern California, part of Channel Islands National Park. The island’s rich, rugged environment — which includes more than 1,000 kinds of plants and animals, including the bald eagle and the island fox — is threatened by Argentine ants, one of the world’s most successful and wily invasive species.

The ants are one in a long line of threats that The Nature Conservancy has worked to overcome since it bought most of the island in 1978. In one section, the ants chased away flower-pollinating bees, native ants, spiders and other insects crucial to local ecology.