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.
After many years of observation, I have compiled my data on butterfly visits to flowers. The results are shown in two graphs. This is from a database consisting of 11,392 observed visits to 110 species of flowers in the Pikes Peak Region.
This is a summary of my 37 years of data on the butterflies of the Pikes Peak Region. The following graphs show trends in abundances as measured by butterflies observed per hour afield. Each data point is a record of the number of butterflies observed per hour of observation time. First, the whole data set for the Pikes Peak Region, with tons of scatter:
This shows an almost flat line, but slightly increasing (from 69/h to 78/h). But when I restrict the data to only Bear Creek, where I have spent most of my time, we find:a negative slope (from 87/h to 80/h). And when graphed according to the average number per hour for each year, we get:a more negative slope (from 102/h down to 79/h). This is surprising to me, as 11 years at an Austin Bluffs site shows no such decline:even when plotted according to annual averages:I also created box and whisker plots for the numbers of butterflies per hour for each summer month in Bear Creek!
In sum, butterfly numbers appear generally stable in this region, but further study is always needed as we enter a hotter earth with more fires.
After 33 years of collecting moths in the Pikes Peak Region, I finally have begun to let it go to the C. P. Gillette Museum in Fort Collins at Colorado State University. The first installment, 36 drawers of mostly Noctuidae (the owlet moths) were shrink-wrapped and dispatched on August 29. One drawer is shown here.
And here is the first load.
And in their new home.
Many more to go in the next few weeks. Sad to see them go, but I know that they’re in a better place. (!)
This paper was rejected by the Lepidopterists Society because I did not make a clear enough distinction between “perching” and “roosting.” The latter involves shade-seeking, while perching means sitting on an elevated leaf or flower and watching for passing insects to harass. Anyway, the point of the paper should be clear. Atalopedes skippers modify their behaviors at high temperatures to avoid overheating. They can’t tolerate temperatures above about 40°C, so if the Texas thorn-scrub savanna warms beyond that, they’ll move north. I would.
Albinism and leucism are rare in Lepidoptera. If you google “Albinism and Leucism in Lepidoptera” you’ll find thousands of photos of mammals, birds, and reptiles, but only a scattering of leps, some of which are white species, not leucistics. The obvious exception is a white luna moth, which is normally green. But the photo is labeled “Albino,” while the dark ocelli stand out on all four wings. It is a leucistic. Leucism is caused by recessive alleles that don’t produce the normal pigments. Albinism is an extreme case of this in which all of the alleles are dysfunctional.
I found a Vanessa cardui that is partially leucistic, feeding with hundreds of normal morphs on Chrysothamnus bushes. I show it here with a normal form below.
Adelpha bredowi, the Sisters butterfly, is a species of the southwestern U.S. and Mexico. By 1981, Ferris and Brown had recorded specimens from eight Colorado counties, mostly in the southwestern corner of the state, but including El Paso and Douglas.
Although the foodplant is oak, which is abundant here, the species does not appear to thrive this far north. I never found it in my early years (1959-1983), but it has shown up four times since 2001. One of these records was a dead specimen on a street in Broadmoor (29 August 2003), where it was killed by a passing car. Two others are from Bear Creek Canyon (2 June 2001 and today, 25 August 2017), and the fourth is from an ephemeral pond immediately west of the large, disused landfill northwest of Bear Creek Road (26 June 2005). The June and August dates might suggest a double brooded species, or it might have a very long flight period. My suspicion is that as the autumns get longer and the springs get earlier, this species might be more often encountered here. I paid for this spectacular find, however, by stepping in a yellow jacket nest. They got me five times before I could escape. Here it is on my forearm, twenty-four hours later, even after aloe vera and benadryl cream. Geez.
Here is a one-night collection of moths from Rock Creek, taken with a small blacklight trap late in June, 2008.
It includes about 120 species. By contrast…
For those of you who were there, and curious, and for others who may find this of interest, my little moth trap in Rock Creek on the night of 12 August captured a measly 50 species and 169 individuals. This is a very poor night by any measure. But it all adds up. When I combine several nights (all better than this one) I find a current total of 260 species and 2494 individuals. This produces a Fisher’s Alpha score of 73, which can be used to further estimate the moth biodiversity of this site. Because each doubling of the sample size would theoretically increase the species numbers by (0.693)(alpha), doubling the sample size 50 times, which would mean an exhaustive study, estimates about 2789 species.
A similar study done at the Catamount Field Station south of Woodland Park produces a Fisher’s Alpha score of about 56. Doubling this sample 50 times produces an estimate of about 2227 species of moths. This is close to theoretical, as species diversity diminishes with altitude. Rock Creek is at about 6000 feet, while Catamount Field Station is close to 9000 feet.
The butterfly sights in Bear Creek are worth waiting for, even in a season that has been damaged by extremely early emergents, late hard freezes, and the wettest July on record, including a couple very heavy rains in Bear Creek. Here are a few beauties. First, Polites mystic, the mystic skipper. I feel pretty mystical when I find one.
Not to be confused with Ochlodes sylvanoides, the sylvan skipper. These look similar, but note the very black “stigma” on the mystic skipper. The sylvan’s stigma is brown, and less imposing.
This is the banded hairstreak, Satyrium calanus. It was one of only two species of Lycaenidae, or gossamer winged butterflies, I saw all day. I love his six-point stance, like a linebacker.
The other Lycaenid was the tailed copper, Lycaena arota. This one is taking nectar from Eriogonum (wild buckwheat) flowers.
And last for today, a police car moth (one of the better named species!), Gnophaela vermiculata.