Rocky Mountain Arsenal


brochure Rocky Mountain Arsenal - Bisons

Bisons at Rocky Mountain Arsenal National Wildlife Refuge (NWR) in Colorado. Published by the U.S. Fish & Wildlife Service (USFWS).

U.S. Fish & Wildlife Service American Bison at Rocky Mountain Arsenal National Wildlife Refuge - July 2018 Overview Since reintroducing the American bison (Bison bison) in 2007, the Rocky Mountain Arsenal National Wildlife Refuge (Refuge) has played an important role in the conservation of this iconic prairie species. Characteristics Bison have dark brown fur and horns that can grow to 2 feet in length. They have a hump on their back and stand between 5 and 6.5 feet tall at the shoulder. Bison are the heaviest land animals in North America, with bulls (males) weighing up to 2,000 pounds and cows (females) weighing up to 1,200 pounds. They usually live between 12 and 20 years and are often referred to as buffalo, though this name is incorrect. True buffalo are native to Africa and Asia. Bison are fast and agile animals. They can reach speeds of up to 35 miles per hour and jump more than 5 feet high. These abilities, combined with their massive size and horns, make them formidable opponents to predators. Grizzly bears and wolves are predators of bison, although these species are not found at the Refuge. faster and returning nutrients to the soil. Bison also push seeds into the soil with their hooves, encouraging new grasses to grow. Social Life Cows, juvenile bulls, and calves (young bison) live together while mature bulls remain alone or form small bachelor herds throughout most of the year. Bulls only join the larger herd during the rut (mating season), which peaks in July and August. Bulls bellow at each other and fight using their heads or horns during the rut to establish dominance. Some bulls wallow (roll in dirt) to demonstrate their strength. Wallowing has the added benefit of removing molted fur, deterring flies, and creating low spots that serve as seasonal wetlands. After a pregnancy lasting 9 to 9.5 months, cows give birth to a reddish-brown calf weighing between 30 and 70 pounds. Calves can walk within an hour of birth and are fiercely protected by the entire herd. If calves are in danger, adult bison will form a circle around them. During calving season, Grazing please give the Bison eat between 15 and 30 pounds of grass each day animals extra and move continuously as they forage, sometimes walking distance with up to 20 miles to find enough food. Grazing bison help your vehicle. keep prairie plants healthy and diverse. They break up dead plants with their hooves, helping them to decompose Population Decline and Conservation An estimated 30 to 60 million bison once roamed North America until overhunting caused their population to dwindle to about 1,000 in the mid-1880s. As a result, the government and private landowners intervened. Punishments for poaching bison were strengthened and bison recovery efforts were initiated on the National Bison Range in Montana and other public lands. Due to these conservation measures, bison populations began to increase and there are now more than 500,000 animals in North America, the majority of which are privately owned. To promote the continued conservation of bison, the Department of the Interior launched the Bison Conservation Initiative in 2008. The goal of the initiative is to restore bison to their ecological and cultural role on appropriate landscapes by maintaining herds on public lands and controlling disease. The initiative seeks to ensure that bison are free of cattle genes and have high genetic diversity as well. Bison Recovery at the Refuge In support of the Department of the Interior’s bison conservation efforts, 16 bison were transferred from the National Bison Range to the Refuge in March 2007. The herd has since grown to more than 180 animals, largely as a result of calves being born at the Refuge. A small number of bison from other refuges were also added to the herd to ensure genetic diversity. Refuge staff will continue to expand the size of the bison enclosure until approximately two-thirds of the Refuge is bison pasture. As a result, the Refuge will be able to support about 200 bison. A roundup of the bison is conducted annually in the late fall or winter to ensure the health of the herd. Genetic information is collected by taking blood, fat, and tail hair samples and microchips are implanted in the calves at the base of their ear. Microchips are similar to barcodes on products at the grocery store. They individually identify the bison and retrieve information about the specific animal when they are scanned. Bison to be sent to other refuges are separated out during the roundup. Viewing Opportunities The bison herd at the Refuge may be viewed by taking the Wildlife Drive Auto Tour. While driving through the bison pasture, please remain in your vehicle as bison are large and unpredictable animals. Pull off the road completely if stopping to view these burly animals and observe posted 30 mph speed limit as bison and other wildlife may be crossing the road. Learn More To learn more about the Rocky Mountain Arsenal National Wildlife Refuge please visit refuge/rocky_mountain_arsenal/ or call the Visitor Center at 303-289-0930. The Refuge is open seven days a week from sunrise to sunset and is closed on Thanksgiving, Christmas and New Year’s Day only. The Visitor Center is open Wednesdays through Sundays from 9 am - 4 pm.

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