Endangered, colorful garter snakes released into the wild for the first time

Most people have never seen a San Francisco garter snake (Thamnophis sirtalis tetrataenia). Native only to California’s San Mateo and Santa Cruz counties, the brilliantly colored reptile was one of the initial entries in the United States Fish and Wildlife Service’s first endangered species list in 1967. After nearly 60 more years of droughts, invasive species, disease, low genetic diversity, and poaching, researchers estimate only a few thousand San Francisco garter snakes still exist in the wild. However, conservationists recently scored a major win for the snakes. For the first time, 62 of young serpents born at the San Francisco Zoo were released at specific sites across San Mateo County earlier this fall. The successful rewilding of dozens of the endangered snakes marks a huge moment for population rehabilitation efforts, and hopefully clears the way for similar releases in the future. “Seeing these young snakes returning to the wild represents years of research, collaboration, habitat restoration and careful conservation work,” Midpeninsula Regional Open Space District (Midpen) biologist Karine Tokatlian said in a statement. “This first release is an important step toward building healthy, resilient populations that can sustain themselves over the long term.” Although slender, the brightly colored San Francisco garter snake can grow anywhere from 18 to 55 inches long. Its eyes are larger than most of its fellow garter snakes, allowing it to keep active during daylight hours. With no fangs and only mildly toxic saliva, the snake is essentially harmless to humans, although its bites are fatal for prey like smaller reptiles and rodents. The process of releasing young animals like these snakes that were reared in captivity is known as head-starting. It is an effective way to protect creatures during the most vulnerable stage of their lives. Head-starting the first batch of San Francisco garter snakes began in 2025, when conservationists collected multiple pregnant females from a healthy preserve in California’s Midpeninsula. Researchers later released the adult snakes back into their habitats after they gave birth, but kept the infants at the San Francisco Zoo. While there, zoologists conducted genetic testing on each snake to select the best possible locations for their eventual release. Conservationists deposited about one-third of them in the same area as their mothers, then placed the other two-thirds at locations particularly in need of greater genetic diversity pools for breeding. As biologists continue to monitor the first generation of head-started snakes, another generation is already waiting for its time to shine. More than 130 garter snakes have been born at the San Francisco Zoo this year alone, with an eye to release them sometime in 2027. “This species is special in many ways, but unfortunately its critical status is not unique,” added Midpen wildlife ecologist Ariel Starr. “The success of this project and the associated research will not only benefit the San Francisco garter snake but will also hopefully inform the recovery of many imperiled reptile species.” The post Endangered, colorful garter snakes released into the wild for the first time appeared first on Popular Science.