Wood Bison

The Wood Bison is the larger subspecies of the American Bison, with the other one being its southern cousin – the plains bison. This beast, in fact, is the largest of North America’s land mammals, as also, all theterrestrial living animals. However, presently, the population of these historic animals is decreasing at a rapid rate. As of May 2013, the population of the wood bison in Canada is approximately 11,000.

Physical Description/Characteristics

Size: The range length of the wood bison is 3.04 – 3.8 m, excluding the tail, and a height of around 1.67 – 1.82m at the shoulder.

Weight:They can weigh anything between 350 and 1000 kg.

Bodily Features: A huge, wide head and a large shoulder hump close to its front legs. The shoulders and forelimbs are covered with shaggy golden to dark brown fur.The hindquarters are somewhat shorter than the front ones.

Tail: They have a distinctive short, tasseled tail, with a small tuft of dark hair at the tip.

Horns: Both the sexes have short black horns.

Sexual Dimorphism: Not visually present, except that the males are around a foot larger than the females.

Wood Bison vs. Plains Bison:The Differences

There are quite a few visual differences between the two subspecies:

1. Compared to the plains bison, the wood bison is larger and heavier, attaining a weight of almost 200 pounds more.
2. The hump of the plains bison is rounded, while the wood bison’s is somewhat squared.
3. The wood bison is darker in color than the plains bison.
4. The facial beard, the hairs in the throat latch, ventral neck mane, chaps, and penis tuft of the wood bison are smaller and more pointed, whereas the plains bison’s hairs are larger and rounded.

Lifespan

Wood bison can live for 18-22 years in the wild andmore than 30 years in the zoo/captivity.

Distribution

This subspecies is native to North America and is distributed throughout the western Northwest Territories, Alaska, Yukon, northeastern British Columbia, northwestern Saskatchewan, and northern Alberta.

Habitat: Where do Wood BisonLive

The wood bison are found in a wide variety of habitats including meadows along riverbanks, boreal forests, muskeg swamps, and scrub-land. As the spring and summer arrive, they begin foraging in the relatively drier, grassy meadows, parklands, andshrubby savannahs. During winter, they shift to the wet meadows, as well as in the lake areas, when they freeze.

Behavior

Wood bison are social animals that live in herds and are found roaming in small groups all throughoutthe year. The herds primarily comprise of adult females, sub-adults,and calves. It is their social norm to mingle with the bulls only during the mating season.

Because they are primarily ruminants, they spend a long time every day chewing their cud, and hence, are seen spending less time grazing in meadows.

The mood swings of these animals can easily be understood from the movement of their tails. When the tail hangs downward and switches naturally, it means, the beast is in a calm temperament, but if standing upright, accompanied by bellow sound/calls, it may be ready to charge.

These animals are very protective of the members of their group. Not only that, they would also maintain a hierarchy, with the leader usually taking various decisions. The males that have passed three years of age are subjected to leave the herd, and instead, form bachelor herds.

Diet

These bison are completely herbivorous beasts. 85% of the diet of the bison is made up of sedges and grasses, while the remaining 15% consists of herbs, some shrubs, lichen, and willow leaves.

Mating and Reproduction

The mating season of the wood bison falls between July and early September. The females of the species generally give birth to its first calf at the age of three years. In the case of the males, strong competition bars the young animals to defeat the larger and mature bulls to win over a mate.

At times, such combats lead to serious injuries, and if the challenged male is not intended to fight, it walks away from the competitor male. Hence, the former need to wait until they are around seven to eight years old and get stronger to defeat the others.

These beasts are usually polygamous and indulge in copulating with more than one female. With the arrival of the breeding season, the dominant male bison maintain and protect a harem of female bison until they are sexually ready for mating.

Life Cycle

The female bison generally gives birth to one calf at a time, and a total of two calves in a three-year period. The offspring are born in around May after a gestation period of about 277-293 days.

When a female is about to give birth, it leaves the herdand rejoins only after the baby is born, and is able to run. This takes about three hours from the birth of the young.

The juvenile begins spending time with the members of the herd and gradually gain strength with the care and cooperation of the entire group. Very soon, it becomes ready to run with its herd members by autumn.

Interestingly, the individuals that are born earlier tend to mature faster with the advent of autumn and become more dominant when they grow up to adults.

The young bison are weanedwhen they are seven monthsold and are nursed for up to a year. They remain with their mothers for three years, by which time they attain the age of sexual maturity. The female juveniles attain complete physical maturity at the age of three years, and males at six years.

Adaptations

• They have extremely strong horns and powerful hooves, so much so, that, getting a chance, they can often invade carnivorous predators.
• The rate of metabolism in these animal decreases with the fall in temperatures. Hence, they are adapted to living on a very limited amount of food during the winter months.
• As a behavioral adaptation, the wood bison are highly alert and suspicious in nature, and a mere cracking of a branch, or just the sound of a footstep,can result in the entire group leaving the area.

Predators

By virtue of their large size and immense strength, healthy adults are practically safe from predators. However, injured/sick/young individuals can fall prey to predators like mountain lions, wolves, and even humans.

Conservation Status

Considering their decreasing population, the IUCN 3.1 has marked them as a ‘NT’ (Near Threatened) species.

Interesting Facts

• Apart from hunting, diseases, including tuberculosis, brucellosis, etc., have always played a vital role in the degradation of their population, killing very large numbers of these animals in a short time period.
• Though it is often mistakenly termed as ‘buffalo’, but scientifically, it is considered as a misnomer, since it is only a distant relative of the two ‘true buffalo’ species – the Asian water buffalo and the African buffalo.
• Yellowstone National Park is the only place in the U.S. where these bisonhave continuously been living since prehistoric times.
• Because of their reddish body tinge, the baby bison have earned the nickname ‘red dogs’.
• The wood bison is the official ‘National Mammal’ of the United States.