Monitoring Colorado’s Pawnee Montane Skipper

August 31, 2011 at 5:28 pm Leave a comment

Monitoring Colorado’s Pawnee Montane Skipper

Amanda Accamando – Curatorial Manager

I’ve chased butterflies through the rainforests of Puerto Rico, visited butterfly farms in Costa Rica, observed butterflies puddling in Nicaragua, and even spent a summer monitoring butterflies in the most exotic of places – New York City. But it wasn’t until last week, in the depths of Pike National Forest, that I observed my first federally ‘threatened’ butterfly – the Pawnee montane skipper (Hesperia leonardus montana).   I was lucky enough to join a team from the US Forest Service and the Colorado Natural Heritage Program as a volunteer in monitoring this butterfly throughout its habitat, the ponderosa pine forest

Skipper butterflies in North America aren’t your typical colorful and charismatic butterflies that one usually hopes to attract to a garden. Skipper butterflies (in the family Hesperiidae) tend to be small, often brown colored and well camouflaged butterflies. These butterflies are fast fliers darting from flower to flower, deriving their name ‘skipper’ from this flight pattern. Pawnee montane skippers are not especially distinctive, except in one respect – they are found in only one place in the world!

Pawnee montane skippers are endemic to Colorado. Actually, they are restricted to a very small area of about 40 square miles in the Upper South Platte River drainage system. Although their larval host plant, blue grama grass, is abundant in the area, recent forest fires may have impacted population sizes, putting this butterfly at risk for extinction.

To understand the habitat needs and how forest management techniques, such as tree-thinning, are affecting Pawnee montane skippers, the US Forest Service has embarked on a long term monitoring study of the butterflies. So, for about one month every August, a group of biologists and volunteers hike through ponderosa pine forest along 400 meter transects (lines) trying to count Pawnee montane skippers. On August 24, I joined the group hoping to spot one of these skippers to help out the study and to add the butterfly to my life list!

Before heading out to the transects a biologist prepared the group for monitoring by teaching us how to distinguish Pawnee montane skippers from a more common skipper, the Colorado skipper (Hesperia colorado). The main difference between the Pawnee montane skipper and the Colorado skipper is found on the off-white colored patches on the underside of the wings. Common skippers have very defined patches outlined in black on their wings, whereas Pawnee montane skippers have less defined patches that ‘bleed’ into the surrounding wing color, and will sometimes not have patches at all. We were also taught how to spot differences between male and female skippers – males have much more angular wings and a black pheromone patch on the inside of their wings. 

Once we were skipper identification experts we headed out to the field armed with liters of water and our binoculars! My group of four people was responsible for monitoring 5 transects, each 400 meters long and 10 meters wide. The four of us walked together in a straight line stopping each time we thought we spotted a butterfly. Using our binoculars we tried to focus in on the butterfly to identify what species it was and whether it was male or female.

We saw about 30 skippers that day, both Pawnee montane skippers and Colorado skippers. Many of the skippers were spotted nectaring on their preferred nectar plant, prairie gayfeather (Liatris punctata). However the highlight of the day was watching a female Pawnee montane skipper oviposit (lay an egg)! We placed a fluorescent orange flag near the egg and recorded the location of the egg with a GPS, so that the biologists could check on the egg in the upcoming months.

 Overall, it was an amazing day hiking through ponderosa pines to contribute to our knowledge and ultimately the recovery of the Pawnee montane skipper!

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