On the morning of July 28th, Yosemite National Park held its fourth annual butterfly count in the Tuolumne Meadow area.

Expert lepidopterists and approximately 40 butterfly enthusiasts from around the state convened in Yosemite’s high country to conduct long-term monitoring of butterfly populations and determine how many species and individual butterflies can be observed within a 15-mile diameter circle during a 24-hour period.

Participants of the count received instructions, were disseminated count datasheets, and divided into small groups, each lead by at least one butterfly expert, and dispatched to a specific location. Each group was responsible for counting and identifying as many butterflies as possible in their respective area.

Butterfly count areas included locations within the park and outside the park, including Dana Meadows, Gaylor and Granite Lakes, Saddlebag Lake, Ellery Lake, Warren Canyon, Hall Natural Area, lower Lee Vining Canyon, Mono Lake County Park, and Lundy Lake.

Typically, during butterfly counts, the ideal weather is sunny with little to no breeze. On the day of the butterfly count in Yosemite, the weather proved to be intermittently raining. Normally, butterflies do not fly in inclement weather, making this specific count more difficult than normal.

Experts 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. The leaders were not only adept at identifying species, but also enthusiastic teachers, helping the other participants learn all sorts of facets of butterfly identification and ecology.

After several hours, the groups reconvened in Tuolumne Meadows to share highlights from the day and report count results. Lepidopterist, author, poet, and founder of the Xerces Society, Robert Michael Pyle, led the compilation, while sharing entertaining butterfly stories, and facilitating lively discussions about difficult species identifications.

The final tally for the day included a total of 40 butterfly species composed of 680 individuals. The three most frequently detected butterflies were Sandhill Skipper (133 individuals), Shasta Blue (102 individuals), and Greenish Blue (72 individuals). Of all the species detected, four were new species (Becker’s White, Sylvan Hairstreak, Reakirt's Blue, and Common Checkered-Skipper) never before observed during a Yosemite Butterfly Count.

This event is coordinated in association with the Northern American Butterfly Association. The next butterfly count in Yosemite will occur on July 27, 2015.