Caribou Migration

Caribou Survival Adaptations:
Article and Activity

While we sit in our comfortable and heated homes during these cold winter months, all the wild creatures must cope with these winter extremes with only what Mother Nature has provided them. There are no fireplaces or extra logs for the fire in their daily routine. So how do they do it? Some like bears or ground squirrels hibernate and yet others, like many species of birds, migrate south to much warmer climates. But what of our most northern caribou herd? How do they survive or adapt to the extremes of our northern winters?

Behavioral Adaptations
The most important behavior caribou have adapted for survival is their annual migration from their summer range along the north coast to the boreal forests of the Richardson and Ogilvie mountain ranges. This 700 km trip allows the caribou to seek conditions essential for survival. The summer feeding grounds of the north coast become unpredictable with intolerable weather and feeding conditions. Caribou have survived over the centuries by traveling to the more temperate climate of a boreal forest. While these migrations will not rival that of the bird world, they are just as vital to their survival. The boreal forests offer favorable snow conditions that allow the caribou ready access to their favorite winter food source, lichens, of which they need to eat approximately 3 kilograms each day.

Physical Adaptations

Shape
Caribou have compact bodies, small tails, and short ears. Because of this compactness, their surface area is exposed to the cold so they can keep their body heat in. The caribou's normal body temperature is set at 105 degrees F. Their circulatory system is uniquely adapted to northern climate extremes.

Legs
Even though their legs are long, the veins and arteries run close together and the warm blood pumping from the heart keeps the colder blood in the veins warm. The legs are kept at a safe 50 degrees F. These long legs are well suited for quick turns on rough ground, for ploughing deep snow, and for swimming.

Fur
To keep the heat in, caribou have two layers of fur covering their bodies. They have a fine crinkly under-fur and a thick coat of guard hairs on top. Guard hairs are hollow like straws. The air trapped inside the hollow hairs act as insulation to keep in the caribou's body heat. Caribou are excellent swimmers. The hollow hairs help them to be buoyant in the water.

Feet and Hooves
The caribou's large feet have 4 toes. Two are small and called "dew claws." Two are large crescent-shaped toes that support most of their weight. These large concave hooves offer stable support on wet, soggy ground and on crusty snow. The pads of the hoof actually change from a thick, fleshy shape in the summer to hard and thin in the winter. Additional winter protection comes from long hair between the toes that covers the pads so the animal walks only on the horny rim of the hooves.

Muzzle
Dozens of times a day, caribou thrust their muzzles into the snow to sniff for food or push snow aside to find food. Caribou muzzles are unique among the deer family in that they are densely covered with short hairs; even their nostrils are covered with short hairs. The hairs help warm the intensely cold air before it is inhaled into the lungs.

Sense of Smell
Another adaptation for living in snowy conditions is the caribou's fantastic sense of smell. Key to their winter survival is the low-growing lichen. Even under as much as 5 feet of snow, a lichen plant can be sniffed out by a hungry caribou.

Specialized Stomach
Caribou, like other members of the deer family, have a four-chambered stomach and a complex digestive system that allows them to thrive on vegetation, like lichens, their main winter food source. Lichen may be low in nutrients but available in large quantities. They digest every bit of nutrients possible out of the food they eat. This ability to thrive on winter food sources that do not contain as high a level of nutrients as sources available in the summer is an important adaption for winter survival.

Activity: Build or Draw a Caribou

Discuss animal adaptations. Use examples such as long necks on giraffes for reaching high branches of vegetation or large eyes on owls for hunting at night. Brainstorm other examples of animal adaptations. Discuss adaptations of the caribou for their environment.

Use an Attribute Chart to gather all the facts about caribou adaptations.
Make a large Concept Map to display all the facts.

A. "Building" a Caribou

Break into small groups and brainstorm ways to build a model of a caribou using materials that symbolize caribou body parts.
Build your model caribou. Display your group's creation and share it with the class.

B. Drawing a Caribou

Draw the basic outline of a caribou on a huge piece of paper.
Using your class Attribute Chart or Concept map, decide how you will show the adaptations on your paper caribou.
Divide the class into small groups. Give each group a specific adaptation or body part: feet, stomach, muzzle, legs, and fur. Have each group draw details on the paper caribou to showcase the adaptation. Have them write descriptions of the adaptation on the drawing.

*Adapted from PROJECT CARIBOU, An Educator's Guide to Wild Caribou of North America.