Beaver

Beaver - Castor canadensis
There are two adult beavers that live/work the area I hike along the Elbow River. The beavers have been active since mid April when the ice on the river melted. Mostly I see them around Kingfisher Island, which is the most likely location of the den, but they range the entire course of my hike.

May 29, 2013 Cruising the Elbow River.

The eyes, ears and nose are located at the extreme upper side of the head, which allows the beaver to cruise with only this small portion of the head above water. When the beaver dives, the furred lips close behind the incisors so food may be carried in the teeth without risk of water filling the mouth. Air only enters the lungs through the nostrils, so the beaver can even eat underwater without aspirating water.

June 2, 2013 Beaver swam up onto one of the small Kingfisher Islands.

Spotted a tasty bush in his natural garden and started to cut the base with the notorious teeth. Typically a beaver turns the head to a 45 degree angle to cut the wood. They prefer poplar and willow.

Carried the bush to the other side of the small island. 

Entered river and eventually swam to the center of the group of Kingfisher Islands, where I presume the den is located. 

Mate (likely female since smaller) of the feeding beaver above, spotted on same day in different location on river. There has been a lot of feeding activity in the last week. I presumed this implied a new litter and this was confirmed on June 10th when I spotted a kit. Beavers are monogamous and breeding occurs during winter. The incubation is an average of 105 days and the average litter is 2 to 4 babies or "kits." 

Close up of photo above.  

June 3, 2013 Feeding down a small inlet off the Elbow River. The beaver has a double coat of fur. The underfur provides insulation and traps a layer of air against the skin. The outer "guard" hair protects the underfur and directs water away from the skin. Two oil glands behind the anus continuously secrete an oily substance, that waterproofs the fur. Most of the photos give a good sense of how oily the fur is. 

A routine beaver dive can last 3 to 5 minutes but 15 minutes without a new breath is possible because the beaver can exchange at least 75% of their lung capacity with each breath. By comparison and human exchanges only 15 to 20%.  

June 4, 2013 This beaver looked smaller than the adults that I usually see and I wondered if this were a second year from the litter in 2012. If so, this beaver is due to relocate to establish an independent dam and lodge. 

References
Gadd Ben. Handbook of the Canadian Rockies. Corax Press. Alberta. 1986.
Naughton Donna. The Natural History of Canadian Mammals. UofT Press. Toronto. 2012.