Life at High Altitude is a Wonder

 

 

My wife and I visited Grayson Highlands State Park (GHSP) in VA recently and marveled at the diversity of life at high altitudes and how it differs from that at lower elevations. Conditions are much harsher as one approaches the peaks of mountains, and climates approximate those that occur much father north. Thus as we stood on Little Pinnacles overlook at 5089 feet, the beautiful vista reveals a recovering red spruce forest that was logged off more than 100 years ago. After the clear cutting there were fires and many areas became pastures and were over grazed for years by cows and subsequently by unnaturally abundant white-tailed deer. This often led to colonization of the pastures by forests of unpalatable hawthorn trees; thus the name of “Haw Orchard Mountain” was applied by early settlers. In GHSP this process has now been reversed and red spruce, yellow birch, sugar maple and beech are returning to replace the inappropriate hawthorn forests. You can still observe this human caused effect at places such as Tater Hill near Boone where the bald on the top of the mountain contains an “orchard stand” of large hawthorns.

A characteristic of habitats that are abiotically harsh, such as mountain tops, is that some species develop local adaptations and become genetically separated from their low elevation counterparts. For example the wide spread elderberry has a high elevation counterpart, the red berried elder, Sambucus pubens. The great spangled fritillary butterfly is very common at lower elevations, but on mountain tops it is primarily the closely related sibling species, the aphrodite fritillary, that is common.

The presence of many boulders at high elevations increases the occurrence of strange rock tripe lichens. These are said to be edible, but they are certainly not palatable. Early explorers who were starving were reported to prefer eating their boots to consuming this strange lichen, which can be made into a purple dye by fermenting it in ammonia water.

Although I have never seen this snake before in VA or NC, I found two high altitude eastern milk snakes in GHSP on one day. They were both very dark individuals, possibly a means of maximizing heat gain during basking in a cool climate. This species is quite unusual in that it intergrades with a banded and colorful variant of the same species (but called the scarlet kingsnake) in the southeastern coastal plain. The latter banded subspecies presumably is involved in a mimicry complex with the poisonous coral snake.

An example among birds of habitat separation by altitude is found among the thrushes. The hermit thrush breeds at higher altitudes, whereas the wood thrush is found lower down. Yet in winter the hermit thrush descends to the piedmont and coastal plain to escape the punishing weather at high altitudes.

Bill Dunson

About Bill Dunson

Bill Dunson, born in rural Georgia, skipped 12th grade and went directly to Yale. Bill subsequent-ly received a PhD in Zoology from the University of Michigan, studying softshell turtles. Bill is Professor Emeritus of Pennsylvania State University thanks to a career spent entirely at that institution, teaching and doing research on the physio-logical ecology and ecotoxiciology of reptiles, amphibians and fish. Always curious about nature, Bill has dedicated his life to learning and sharing his knowledge with others. He has served on many advisory boards here in Southwest Florida to preserve the water that gives life to our region.

View all posts by Bill Dunson