Caribou (Rangifer tarandus), known as reindeer in Eurasia, are large migratory ungulates that inhabit the northern tundras and boreal forests. They are the only deer species where both males and females grow antlers, making them recognizable across their vast circumpolar range. These animals are powerful herbivores, with adult males reaching shoulder heights of up to 120 centimeters and weights between 109 and 318 kilograms.
Caribou Temperament and Physical Capabilities
Caribou are generally docile animals that exhibit a shy disposition toward humans, whom they perceive as predators. Their primary defense mechanism against perceived threats involves rapid flight, as they are capable of running at speeds up to 80 kilometers per hour. A bull caribou possesses large, complex antlers that can weigh up to 9 kilograms and span over a meter in length. These antlers are primarily used during the autumn rut for sparring with other males to establish dominance. The large, concave hooves are also formidable tools, designed to support the animal on soft snow or muskeg while also serving as scoops to dig for winter forage. While serious physical encounters with humans are rare, the sheer weight and momentum of a charging caribou could cause significant injury.
Situations That Heighten Defensive Behavior
A caribou’s avoidance behavior can quickly shift to defensive action under specific circumstances. The most common time for aggression is during the autumn rutting season, when bull caribou are driven by elevated hormone levels. These males become highly focused on establishing breeding rights and may view any nearby large presence as a threat or competitor. Female caribou, or cows, are also intensely protective of their young. A mother may charge to defend her vulnerable offspring if she feels a person or a dog is approaching too closely. The animals are also highly sensitive to disturbance, and a rapid or unexpected approach, such as by a person on a snowmobile or ATV, can induce stress and cause a panicked flight. This can be dangerous when encountering a massive, stampeding herd, as being caught in the path of thousands of rapidly moving animals can result in trampling.
Health Risks Beyond Physical Encounter
Beyond the immediate physical danger, caribou can pose a health risk through the potential transmission of zoonotic diseases. Brucellosis, caused by the bacterium Brucella suis biovar 4, is a disease of concern found in caribou populations. Humans can acquire brucellosis through direct contact with infected animal tissues or fluids, such as when processing a carcass. In people, this bacterial infection can cause flu-like symptoms, including a fever that comes and goes, and joint pain. Parasites also present an indirect risk, such as the tapeworm Echinococcus granulosus, which forms cysts in the caribou’s liver and lungs. While consumption of properly cooked meat is generally safe, exposure to contaminated wolf or dog scat can transmit the infective stage of this parasite to humans.