CO-Horts Blog

Thursday, October 29, 2015

Native Tree Squirrels

This blog's emphasis is on the two native tree squirrels you might encounter while hiking through the Colorado forests:  Abert’s and pine squirrels.

(Abert's Squirrel)
The Abert’s squirrel (Sciurus aberti) is associated almost solely within the montane (8,000-10,000 foot) forest ecosystem.  They are quite distinct because of their tufted, or tasseled, ears and black coat.  Interestingly, their ear tufts diminish in the spring and summer months, while their fur color may range from the typical black, to gray.

Abert’s squirrels make their home among mature ponderosa pine, using taste to select trees with the most nutritional value.  They rely on the ponderosa for all aspects of their life including food, nesting, and cover. They are not known to defend territories, perhaps because their home range is quite large, averaging nearly 20 acres. 

Their preferred food is the seeds of the ponderosa cone although their summer diet contains a high proportion of fungi.  You might observe them holding the cone like an ear of corn, slowly rotating it as they remove the cone scales to unveil the meaty seeds.  Unlike many of their relatives, Abert’s squirrels do not store large caches of food in their nest, although they occasionally bury a cone.

(Pine Squirrel)
 The pine squirrel, red squirrel, or chickaree (Tamiasciurus hudsonicus) is a solitary squirrel that is easily identified as they scold intruders by growling, screeching, or chirping.  These squirrels are much more aggressive than the Abert’s squirrels and will jealously defend their territories.  Their home range is restricted to mature pine, Douglas-fir, fir, spruce, and mixed wood riparian forests. They generally have multiple nests in tree hollows, or underground tunnels, and numerous food caches.  

The pine squirrel is the smallest tree squirrel in Colorado with an average length of 12 to 13 ½ inches.  Its coloration is rust red to grayish red, and its tail is outlined with a broad, black band edged with white.  Most of the squirrels I’ve encountered in the Pikes Peak region tend towards the gray coloration.

(Pine Squirrel Midden)
Generally, pine squirrels have a favorite feeding tree where they eat and drop leftover cone pieces. The shredded cones at the base of its feeding tree may accumulate into huge piles, called middens, which may be 30 feet across and up to two feet deep. Very large middens are evidence that several generations of squirrels have used the same feeding tree.  Territories are usually centered around middens because they contain one to two years of cone resources.  Because of this, their territory averages approximately two acres, depending on food availability. 

(Ponderosa Pine tips sheared off)
If you have hiked in the montane ecosystem during the winter months, you may have noticed needled tips littering the ground under select ponderosa pines.  This is the work of both species as they feed on the shoots, slicing completely through the branch.  The mule deer enjoy this delicacy and tend to clean up the mess left behind.

Neither squirrel hibernates, but if the weather is very cold, they will stay in their nest until the temperatures warm up.

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