Population Densities of Butterflies in the Pikes Peak Region
The following records, drawn from my field logs of the last 59 years, sift out the average and the greatest observed densities of many of the common butterflies in the Pikes Peak Region. This work has been done so that future workers in this field can compare observations to see if populations are becoming more or less dense with time.
The “average number per trip” is calculated as the total number of individuals observed divided by the number of trips afield during which the species was encountered. Thus, if I found a total of 320 individuals of a species on 70 trips afield, the average density would be recorded as 320/70 = 4.6 / trip (not per hour). The “maximum density” is derived from the single trip afield during which the observed number of individuals of a species divided by the time afield equals the largest quotient. For example, if a three-hour trip found 29 individuals, the recorded density would be 29/3 = 9.7/hour. If on another trip, two and a half hours turned up 27 individuals, then 27/2.5 = 10.8/hour, a greater observed density. Thus, the greatest density observed is reported. “TNTC” means too numerous to count, usually reflecting population explosions.
The Pikes Peak Region is herein defined as including all of El Paso and Teller Counties, and portions of adjacent Park, Lincoln, and Kiowa Counties. Sites north of the Monument Divide are excluded, as they were poorly sampled, and in many cases include clear ecological differences from the Pikes Peak area itself. The Rampart Range is included north only to Mount Herman and Carroll Lakes. A radius of roughly thirty-five miles from Pikes Peak is roughly 3850 square miles or 2.46 million acres. The life zones include the Sonoran short grass prairie, the pinyon-juniper and oak-pine transition woodlands, the Canadian (Taiga), a thin, poorly resolved Hudsonian, and the Arctic-Alpine (Tundra) on Pikes Peak itself. At least 206 butterfly species fly in El Paso County alone, although many of them are occasional or stray species from the south and east.