Dec 14, 2017
Every December, Western Monarch butterflies begin their winter migration to Rob Hill Campground, one of 400 known “overwintering” sites in California (check out the Xerces Society website to learn more). Once common, the monarch butterfly is experiencing an alarming decline primarily due to the loss of overwintering and breeding habitat, pesticide use, and climate change. Over the past 20 years, Monarch numbers have fluctuated at Rob Hill; in 2016/2017, we saw record numbers there with approximately 250 Monarchs spotted and in 2020/21 there were no overwintering monarchs observed. But in 2022, we saw a bit of a come back with ten seen in the park and many more seen in other parts of California.
In 2016, Presidio Wildlife Ecologist Jonathan Young and local butterfly expert Liam O’Brien made a visit to Rob Hill to participate in the annual Western Monarch Butterfly Count with the Xerces Society. Information from these surveys help paint a more complete picture of the wintering butterflies’ population size at this site as well as their movements. Check out this brief video and learn more about these colorful creatures.
Photo Credit: Fue Her