One.
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The George River Caribou herd.
Caribou (Rangifer tarandus) is the North American name, this animal as known as reindeer the Arctic.
A group of caribou is called a herd. Reindeer are also grouped in herds.
The herd of caribou ran across the field with pride, speed, and honor.
These tracks indicate that a small herd of caribou has recently passed through our yard.
Caribou calves are born out on the tundra in the spring and stick with their mothers--travelling long distances with them, avoiding predators, sticking with the caribou herd and suckling from them--until they are about a year old. If female they are weaned but stay with the female caribou herd. If male, they are also weaned, but they go off and join the bachelor caribou herd that comprises of males young and old.
caribou
A caribou can live from the age of 6 up to 13, depending on how healthy the herd is.
A group of reindeer is called a herd.
a herd moose
They can live in herds of 100,000 to 1,000,000. But, that usually depends on how strong the herds are. Such as if the herds are sick and weak with little food, ( There can be competition between the bison and the caribou for food)or if they might have a sickness sweeping through the herd, or on the other hand; Maybe the herd has a good food supply and a lucky breeding season!
They don't. Muskox and caribou quite often don't even mix, and naturally avoid each other. And, since caribou are migratory animals and fast runners, they don't stop to graze for very long, unlike muskox. So there's no need to fight over one single plant when there are billions more to choose from and the herd to keep up with.