The problems with getting high…

Not intoxicated high, but surviving the challenges of high altitude.

Does this look like an inviting place to live?

It’s cold, the air is thin — at 12,000 feet there is only 60% as much oxygen as there is at sea level, there is little food for animals that live this high, and there are strong winds and extreme weather.  Starkly beautiful, but potentially fatal if not appropriately adapted.

We were not appropriately adapted for high altitude — not enough clothing, not enough time at moderate altitudes to be hiking at 12,000 feet.  After teaching this topic for many years, I should have been better prepared.

So, how do animals cope with these challenges survive at high altitude?

The temperature:  animals stay warm with their heavy fur coats; hikers generally wear a number of layers, adding or peeling them off as the air temperature dictates.

Summer range of Bighorn Sheep is typically 10,000-14,000 feet. They descend in the winter to lower altitudes to find forage.  Sheep fur is composed of a thick underfur of hollow hairs that trap body heat and an overfur of guard hairs.

The lack of food:  summer is usually a productive period, even at high altitude, and animals cash in on this bounty by stockpiling resources (e.g., the pika collecting forage to turn it into hay or squirrels collecting nuts), or they consume so many calories during the summer, they are able to lay on an extra amount of fat to carry them through the winter while they hibernate.  Hikers carry their food around with them, and the added weight places an additional strain on the demand for oxygen.

A Chickaree or Douglas squirrel stockpiles nuts on a fall afternoon in the Sierras.

The lack of oxygen:  Now this is where the real macho high altitude physiology comes into play.  Animals (and humans) native to high altitude have bigger hearts, bigger lungs, more red blood cells, more oxygen-carrying hemoglobin, more capillary beds to carry oxygen to their muscles and other tissues, and a host of other biochemical advantages that their low altitude relatives lack.

Llamas (native to the South American Andes mountains) are particularly well adapted to high altitude, and exhibit many of the adaptations mentioned above.   By Richard Masoner (Lloyd the Llama) [CC-BY-SA-2.0 (http://creativecommons.org/licenses/by-sa/2.0)%5D, via Wikimedia Commons.

High altitude human hikers are limited in how far they can push their own biochemistry in the adapted direction.  We can’t grow larger organs, but we can make more red blood cells and hemoglogbin (it takes about three weeks though), and we can develop new capillary beds to tissues.  We can modify our biochemical enzymes slightly, but not to the degree that high altitude natives do.  However, these adjustments take time — much longer than 1-2 days, which makes our occasional visits to hike at high altitude problematic.

You can read or view more about this subject at the BBC Nature website on High Altitude.

Pine Squirrels – West vs East

While walking on the Tahoe Rim Trail late one evening last week, I spied a Chickaree, or Douglas’ Squirrel on a rock up ahead of me.  It was busily husking seeds from a pine cone and took off before I could get much of a photo of it.  John Muir, founder of the Sierra Club, and noted Sierra Nevada conservationist, thought this particular animal was one of the “most enchanting” and interesting to watch.

Although I didn’t get a chance to observe those enchanting behaviors, I got a good enough look to realize how similar this western Sierra version is to its cousin, the Red Squirrel, we see in the eastern US.

(I took this photo of a Red Squirrel in my backyard last December.)

Both species are about half the size of the common gray squirrel, but twice as feisty.  In fact, they are so aggressive, they chase the larger squirrels away from their favorite feeding sites.

Both species favor the cones (and seeds) of pine and spruce, and prefer to husk the cones when they are still green.  Both have that distinctive white eye ring, and both curl their tails over their back while sitting (probably keeps them warmer).  Since both species lack cheek pouches in which to store seeds, they bury the entire cone instead and harvest the seeds as they need them.

Like the other tree squirrels (Gray and Fox), these squirrels do not hibernate in the winter, but sleep the winter away in a cozy tree hole.  The stockpile of seeds usually lasts them well into the spring.

Here’s another look at the video of Red Squirrels harvesting pine seeds that I posted last December.