It is hard to understand how the caribou can live in regions that average well below freezing temperatures for six to eight months out of the year. This extreme cold, often with high winds, makes the frigid temperatures even harder to handle. Let’s see how it is possible for caribou to survive in the extreme cold and wind.
First, caribou have two coats that cover their skin to help keep them warm. The undercoat, is dense and wooly, while the other is an overcoat consisting of long, quill-like, air-filled hairs. This is the primary insulation for the caribou, helping to regulate their core body temperature, and enabling them to stay warm.
During the many months of below-freezing winter, made more dangerous by the wind, caribou often walk in snow deep enough to reach their bellies. Their body organs and brain have to be kept at a temperature of about 101 degrees or they will die. But despite their warm core temperature, their legs are only about one degree above freezing; however, they never freeze. Why? An amazing process known as rete mirabile, the same process that keeps birds’ legs and feet from freezing and keeps the blood from rushing to a giraffe’s head when they bend down to get a drink. It works this way: the 101-degree blood coming down the artery from the heart is in close proximity to the vein with cold blood going up from the legs back to the heart. In a process called countercurrent exchange, the heat is transferred from the artery to the vein, which warms the blood going back to the organs and brain. Hence the legs, which don’t have a great need for warm blood, are kept just above freezing and the blood returning to the body is warmed, which helps maintain their core temperature. Only a “heating and cooling engineer” like God could design this in a living being.
The nose structure of the caribou contributes to its heat and water balance. The nose has turbinates that resemble a rolled-up newspaper. When the caribou breathe air in, which, in an 80-mile-an-hour wind could be minus 60 degrees, the massive surface area of these turbinates does two things: it pulls out the moisture, helping to maintain their water balance and warms the air before it gets to the delicate structures of the bronchial tubes and lungs. When they exhale, most animals breathe out producing steam, but not the caribou. On exhalation, the turbinates again pull out the moisture keeping the water in the system. The moisture conservation is very important because caribou do not drink water. There are minerals in the water of lakes and streams, and drinking water would require an increased filtering workload on the kidneys increasing their water loss. The turbinates also absorb the heat from the air further heated by the lungs, thus helping to maintain their 101-degree core body temperature. All of these heat and moisture conservation mechanisms are critical to help keep them alive in their extreme environments.
None of the mechanisms worked into the bodily systems of the caribou can be the result of gradual evolutionary changes and mutations. Every minute detail was created to allow them to live in their cold and harsh surroundings. It is absolutely amazing that our Lord has thought of everything for the survival of the caribou. “O give thanks to the Lord for He is good.” Psalm 136:1
Adapted from God’s Living Treasures, Volume 2, Amazing Animals of Alaska, Hosted by Dr. Jobe Martin