Repopulating a Rare Butterfly Species

Dec 05 , 2019

Repopulating a Rare Butterfly Species

Long gone from their home in San Francisco, the California pipevine swallowtail is back thanks to one man transforming his yard into a habitat for them.

For centuries the beautiful butterfly thrived in San Francisco and around the Bay Area.  But as the region became increasingly urbanized in the early 1900s, the pipevine swallowtail began to disappear.  Today, it’s an extremely rare sight.

Aquatic biologist Tim Wong at the California Academy of Sciences has made it his personal mission to bring the butterfly back, and he’s off to a very promising start.

In 2012, he set out on a quest to find California pipevine, the pipevine swallowtail’s sole food source, which had disappeared in tandem with the butterfly in the city.

He was finally able to find this plant in the San Francisco Botanical Garden and they allowed him to take a few clippings of the plant.

Wong propagated the plant in his backyard, weeding, watering and tending it until he had created a pipevine swallowtail paradise.  He also built a large screen enclosure to protect the butterflies which allowed them to mate under outdoor environmental conditions—natural sun, airflow, temp fluctuations, etc.  This special enclosure protects the butterflies from some predators, increases mating opportunities, and serves as a study environment to better understand the criteria female butterflies are looking for in their ideal host plant.

After the habitat was ready, Wong secured 20 caterpillars from a few residences outside the city and collected them with permission.  He carefully transported them home and set them loose in their new feeding and mating grounds.

About six weeks later, the hungry caterpillars turned into butterflies, and the females began laying tiny red eggs on the stems of the pipevine plant.

After several generations, the butterflies began to multiply exponentially.  Having more than he knew what to do with, Wong started donating caterpillars to the Botanical Gardens where their food originated from.

While other conservationists have repopulated the pipevine butterfly in neighboring Santa Cruz and Sonoma counties, Wong has made the first and only successful attempt in San Francisco.

Wong attributes his success to the habitat he created for the caterpillars and by weeding by hand and by not using herbicides or pesticides.


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