Julien Ueda Yosemite National Park held its 13th annual Yosemite Butterfly Count in the Tuolumne Meadows area in summer 2024, thanks to the dedicated scientists and volunteers that make it possible each year. Yosemite coordinates this event in association with the North American Butterfly Association (NABA), an organization that conducts long-term monitoring of butterfly populations all over North America. The purpose of the NABA counts is to determine how many species and individual butterflies can be observed within a 15-mile diameter circle, during a 24-hour period, within the same date-span year after year. The approximately 450 counts nationwide contribute a tremendous amount of information about the geographical distribution and relative population sizes of butterflies across the country. Participants spend the day gathering data, raising public awareness toward butterfly conservation, and socializing with other naturalists. On July 29, 2024, dozens of butterfly enthusiasts returned to Tuolumne Meadows to find as many butterflies as they could in a single day. This year had a record number of 80 participants from professional lepidopterists to excited young naturalists. Each group was assigned to a specific zone and was responsible for counting and identifying all the butterflies they detected within that area. The butterfly count area included such hotspots as Dana Bench, Gaylor Lakes, Saddlebag Lake, Gardisky Lake, Mono Lake County Park, Log Cabin Mine Road, Dana Meadows, and Lundy Canyon. Clear skies greeted everyone as old friends and new faces gathered into their groups and raced into the high country. Over the course of the day, participants developed a search-image for target butterfly species, depending on the habitat, elevation, and the presence of specific flowering plants. The leaders enthusiastically shared their knowledge about butterfly identification and ecology, including tips for identifying tricky species. In the early evening, the groups rejoined in Tuolumne Meadows and compiled their findings over pizza. Since its inception in 2011, the Yosemite Butterfly Count has recorded a remarkable diversity of 100 butterfly species. This diversity is the result of experienced and knowledgeable leaders, a growing number of learned participants, and diverse habitats comprising a 5,000 feet elevation gradient between the lowest and highest zones. One group can search for butterflies along the shores of Mono Lake at 6,400 feet elevation, while another group can observe butterflies on the Dana Bench at 11,000 feet elevation. 
Alison Sheehey This year (2024), 80 participants counted 744 individual butterflies and found 57 species. When compared to previous years, this year had less individual butterflies than usual. An average of 1502 butterflies are found every year, but less than half of that (744) were found this year, and only two other counts had less (679 in 2014 and 602 in 2011). Many group leaders, who have participated in multiple years of Yosemite Butterfly Counts, noted budding autumn flowers and thought that the summer peak of butterfly activity has passed. Each species of caterpillar can only eat a few species of plants that have a short growing season in the High Sierra, so many butterflies only fly for a few weeks before breeding and dying. Some species fly and breed only once in the early summer, while others breed multiple times and are found into the fall, but most species overlap in the mid-summer. However, this activity peak may have occurred earlier than usual this year. Where groups last year found fifty butterflies at a puddle, this year they found four. However, this year’s participants faced the challenge and still found a diverse array of 57 butterfly species, just above the average of 56. The five most frequently detected species in 2024 were the Shasta Blue (120), Mormon Fritillary (90), Sandhill Skipper (58), Sierra Sulfur (43), and Orange Sulfur (36). This year also set the Yosemite Butterfly Count record for the Lorquin’s 
Alison Sheehey Every year has its similarities and differences to previous years. Like 2022 and 2023, the top five species in 2024 shared the Shasta blue and the sandhill skipper but differed otherwise [2023 top five: Mexican cloudywing (206), sandhill skipper (101), Shasta blue (95), orange sulfur (80), and checkered white (74)]. Compared to 2023, far less Mexican cloudywing were found this year (206 in 2023 compared to one in 2024), but far more Sierra Sulfurs were found (one in 2023 compared to 43 in 2024). Some species that are found almost every year, like the sonoran skipper, painted lady, anise swallowtail, and California crescent were missed. However, this year brought a revival of a couple species, notably the Monarch, which had not been seen on the count since 2019, and the cabbage white, which had not been seen on a count since 2018. While an incredible 57 species were found this year, no new species for the count were found. With each year of butterfly counting, the species list grows and the chance of observing a new species diminishes. Though, the difficulty of finding a new species demonstrates the hard work participants have put into more than a decade of Yosemite Butterfly Counts. 
Alison Sheehey In 2024, alpine groups enjoyed an abundance of Shasta blues, cheered at an endemic Sierra Nevada parnassian, and found a doe and her three spotted fawns! Meanwhile, the low elevation group celebrated swallowtails and monarchs beside the tufa of Mono Lake. Every year, the leaders continue to seek all butterfly species to better understand how many call Yosemite home. Some rare species, like the Sierra Nevada parnassian, rockslide checkerspot, heather blue, and Chryxus arctic, are highly specialized alpine butterfly species that make Yosemite National Park and its Butterfly Count unique. The combination of the butterflies themselves, people brimming with natural history knowledge and passion, and beautiful scenery makes this annual event very special. As Liam O’Brien put it, “the Yosemite Butterfly Count has quickly become Center Court/Wimbledon of the California Butterfly Count Season.” A huge thank you to this year’s group leaders, volunteers, and the National Wildlife Federation for their pizza donation. See you at the next Yosemite Butterfly Count on Monday, July 28, 2025! Learn More
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Last updated: August 19, 2024