Annual Yosemite National Park Butterfly Count

Jeffrey Glassberg, Karen Amstutz, and Ryan Carlton searching for butterflies.
Jeffrey Glassberg, Karen Amstutz, and Ryan Carlton searching for butterflies.
Yosemite National Park initiated its fifth annual butterfly count in the Tuolumne Meadows area in summer 2015. 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. Participants spend the day gathering data toward long-term monitoring; raising public awareness toward butterfly conservation; and socializing and having fun with other butterfly devotees.
Watercolor showing Sierra sulphur, heather blue, American copper, rockslide checkerspot, and Sierra Nevada parnassian with a lake in the background. Illustration by Liam O'Brien 8/16

On July 25, 2016, butterfly experts and enthusiasts met in the morning glow of Lembert Dome in Tuolumne Meadows in anticipation of finding as many butterflies in a single day as possible. Expert lepidopterists came from around the state to lead their groups in butterfly quests and to share their knowledge and intense appreciation for butterflies and natural history.

Following introductions, instructions, and dissemination of count datasheets, the larger group divided up into seven smaller groups, each led by one or two butterfly experts. Each group was responsible for counting and identifying butterflies in their respective area. The butterfly count area included such hotspots as Dana Meadows, Gaylor Lakes, Saddlebag Lake, Ellery Lake, Hall Natural Area, lower Lee Vining Canyon, Mono Lake County Park, and Lundy Lake.

A clear sky, calm winds, and relatively wetter conditions compared to past years allowed for optimal butterfly viewing. Butterfly counters systematically searched all habitats for species that specialize on specific plants, varying degrees of moisture, and that exhibit different behaviors at different times of the day or under different conditions. Each person learned to conjure a particular search image, depending on the conditions, circumstances, and target species. The leaders enthusiastically taught the participants tips for identifying different species and all facets of butterfly identification and ecology.

At the end of the day, the group reconvened back in Tuolumne Meadows to share highlights from the day, report count results, and enjoy pizza. As expected, lively discussions ensued concerning difficult species identifications.

Clodius parnassian butterfly; gray with four red spots
This year’s final tally broke previous records for the number of participants, butterfly species, and individual butterflies. Forty eight participants counted 70 butterfly species composed of 1,954 individuals. The four most frequently detected butterflies were Sierra sulphur (287 individuals), greenish blue (190 individuals), Edith’s checkerspot (125 individuals), and orange sulphur (124 individuals). Missed butterflies included lilac-bordered copper and Behr’s hairstreak. Four new species observed during the Yosemite Butterfly Count included square-spotted blue, red admiral, "California" common ringlet, and queen.

All the groups except for the lower East Side group were rewarded with the subtle beauty of both male and female Sierra sulphurs, California’s only high elevation Colias. The Yosemite count is the only one in the country that regularly reports this species, due to its extremely small range. Mono Lake yielded several butterflies not observed by other groups, including Becker's white (1), cabbage white (2), Sylvan hairstreak (18), gray hairstreak (1), western pygmy-blue (4), Nokomis fritillary (2), red admiral (3), common ringlet (4), Great Basin wood-nymph (7), and queen (1) The Mono County Park was particularly productive this year and contributed the majority of novel species to the count.

The combination of the butterflies themselves, people brimming over with natural history knowledge and passion, and beautiful scenery makes this one day very special. As Liam O’Brien put it, “the Yosemite Butterfly Count quickly has become Center Court/Wimbledon of the California Butterfly Count Season.” See you at next year’s count on Monday, July 31, 2017!

Related Information

Group photo of people in Tuolumne Meadows
2016 Butterfly Count participants

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