Nick Maloney / 2025 
Julien Ueda Annual Event SummaryEvery year, the Yosemite Butterfly Count is made possible by dedicated volunteers, coordinated in partnership with the North American Butterfly Association (NABA). NABA conducts long-term monitoring of butterfly populations across North America, using standardized counts to determine the number of species and individual butterflies within a 15-mile diameter circle over a 24-hour period. With approximately 450 counts nationwide, this initiative provides invaluable data on the geographical distribution and relative population sizes of butterflies across the country. Participants not only gather critical data but also raise public awareness about butterfly conservation and enjoy connecting with fellow naturalists. On July 28, 2025, dozens of butterfly enthusiasts returned to Tuolumne Meadows, eager to document as many butterflies as possible in a single day. This year saw a record 86 participants, ranging from professional lepidopterists to young, excited naturalists. Each group was assigned a specific zone, where they were responsible for counting and identifying all the butterflies they encountered. The count area included hotspots such as Dana Bench, Gaylor Lakes, Saddlebag Lake, Mono Lake County Park, Log Cabin Mine Road, Dana Meadows, and Lundy Canyon. Participants were greeted by clear skies as they set off into the high country, forming teams that blended old friends with new faces. Throughout the day, they honed their ability to spot target butterfly species, guided by habitat, elevation, and the presence of specific flowering plants. Group leaders enthusiastically shared their expertise on butterfly identification and ecology, offering tips for recognizing tricky species. In the evening, the groups reconvened in Tuolumne Meadows to compile their findings over pizza. Since its inception in 2011, the Yosemite Butterfly Count has recorded an impressive diversity of 100 butterfly species. This achievement is thanks to the experienced and knowledgeable leaders, the growing number of informed participants, and the diverse habitats encompassed by a 5,000-foot elevation gradient. While one group might explore the shores of Mono Lake at 6,400 feet, another could be observing butterflies on the Dana Bench at 11,000 feet. 
Alison Sheehey In 2025, the participants counted 1073 individual butterflies and identified 58 species. Although this year’s count was lower than average—typically, about 1,471 butterflies are observed annually—it still yielded a rich variety of species. The five most frequently detected species in 2025 were the Great Basin fritillary (171), Clodius Parnassian (90), mormon fritillary (70), Sierra sulfur (51), and Shasta blue (51). Every year brings both similarities and differences compared to previous counts. In 2024, the top five species also included the Shasta blue, as in 2022 and 2023, but the other species varied. The explosions of Great Basin fritillary and Clodius Parnassian were unusual, reaching the highest counts for these species since the Yosemite Butterfly Count began in 2011. Similarly, both Acmon blue (30) and lupine blue (13) were more common than any other year. Some species that are usually present, like anise and Indra swallowtails, small wood-nymph, and California crescent, were notably absent this year. 
Alison Sheehey Given the short growing season in the high Sierra, many butterfly species only fly for a few weeks before breeding and dying, with some species active only once in early summer, while others breed multiple times and are found into the fall. Because of this, small differences in temperature and precipitation patterns and between years can influence the exact timing of butterfly activity, interacting with the specific biology of each species to produce complex responses of butterfly behavior and abundance. This subtle variation in climate and its impact on ecological networks explain much of the variation we see in the Yosemite Butterfly Count across years, making each new count unpredictable and exciting. While 58 species were recorded this year, no new species were added to the count. As the years of data accumulate, the list of potential new species diminishes, a testament to the dedication and hard work of participants over more than a decade of the Yosemite Butterfly Count. 
Alison Sheehey Each year, the leaders strive to document all butterfly species to gain a deeper understanding of Yosemite's butterfly fauna. Some rare species, like the Sierra Nevada Parnassian, rockslide checkerspot, and Chryxus arctic, all seen in 2025, are highly specialized alpine butterflies that make Yosemite National Park and its Butterfly Count unique. We are still waiting for the return of other specialized species like heather blue, which has been absent since 2020. The combination of butterflies, the wealth of natural history knowledge and passion among the participants, and the stunning scenery make this annual event truly special. As Liam O’Brien aptly described it, “the Yosemite Butterfly Count has quickly become the Wimbledon of the California Butterfly Count Season.” A heartfelt thank you goes out to this year’s group leaders, volunteers, and the National Wildlife Federation for their generous pizza donation. We look forward to seeing you at the next Yosemite Butterfly Count on Monday, July 27, 2026! Raw Data Results from 2011–2025Each year, Yosemite coordinates its Yosemite Butterfly Count event with the North American Butterfly Association, an organization that conducts long-term monitoring of butterfly populations all over North America.This event takes place in summer in the Tuolumne Meadows area.
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Last updated: March 6, 2026