The Oklahoma City Zoo and Botanical Garden’s 22-year-old female bison, Mary Ann, was humanely euthanized on Tuesday, March 21, 2023. 

Mary Ann arrived at the OKC Zoo in 2001 from Sedgwick County Zoo in Wichita, Kansas and instantly became a fan favorite. She was one of the first species to relocate to the Zoo’s Oklahoma Trails habitat when it opened in 2007, becoming an important ambassador for educating guests about Oklahoma’s unique biodiversity.

At 22, Mary Ann, was considered a geriatric animal and the OKC Zoo’s veterinary and animal care teams had been monitoring her for end-of-life care. Mary Ann was showing signs of decline from age-related issues and more recently experiencing decrease of appetite and increased respiratory effort, compromising her quality of life. Animal care team members were treating Mary Ann’s age-related conditions with medications, but when it became evident that her health issues could no longer be mitigated with treatment, the veterinary and animal care teams made the decision to humanely euthanize her.

“Caring for Mary Ann was a joy and privilege for myself and the entire team,” said Tracey Dolphin, OKC Zoo’s curator of hoofstock and primates. “She brought smiles to guests of all ages through experiences like our Wild Encounters and annual enrichment activities, and will be missed by many.”

Mary Ann shared her habitat with two younger bison, Yarrow and Verbena, both 3-years-old. These energetic youngsters definitely kept Mary Ann active but knew she was the matriarch when it came to herd dynamics. Mary Ann always had her first pick of browse and tasty enrichment treats before the “littles”! According to Mary Ann’s caretakers she was a fan of foraging for food and interacting with enrichment particularly cedar trees, and would enthusiastically rub her head and body on the tree branches. Mary Ann could be seen exploring her habitat year-round and enjoyed the seasonal weather including the occasional snow zoomie or mud wallow after a spring rain!

The American bison is the largest mammal in North America with an average weight of 1,000 pounds for females and 2,000 pounds for males, and standing at approximately 6.5 feet tall and 12.5 feet long. These horned mammals are a force of nature and can run up to 35 miles per hour. Bison are herbivores and can eat 15 to 18 pounds of greenery per day. In order to drink enough water, bison will sometimes eat snow if they can’t find an open water source!

Just 200 years ago, there were over 30 million bison blanketing the United States. However, by the late 1800’s they were nearly hunted to extinction. The population was brought back from the brink when 15 bison from the New York Zoological Society (Bronx Zoo) were relocated to Cache, Oklahoma, in 1907. They were released into the first national bison preserve, which later became the Wichita Mountains National Wildlife Refuge. Descendants of this original herd still roam there today.

Bison are currently listed as near threatened by the International Union for Conservation of Nature. Designated as the official state animal in 1972, the American bison has a special place in Oklahomans’ hearts. The Zoo has committed itself to bison conservation through the support of its legacy partner, The Nature Conservancy in Oklahoma (TNC), an organization dedicated to conserving Oklahoma wildlife and open spaces. TNC manages 12 nature preserves in Oklahoma, covering nearly 100,000 acres, and encompassing much of the state’s diverse habitat for native species, including bison. The OKC Zoo has provided over $125,000 in financial support to TNC through its Round Up for Conservation program funds, an initiative that invites guests to round up their Zoo purchases to the nearest dollar in support of the Zoo’s various conservation projects.

The OKC Zoo is proud to share that Mary Ann, and several other animals, were the subject for world-renowned wildlife photographer, Joel Sartore, for the National Geographic Photo Ark.  

If you have memories or photos of Mary Ann, we encourage you to post them on the Zoo’s social platforms.

Photo Credits:

“Mary Ann” OKC Zoo, ©Joel Sartore/National Geographic Photo Ark 

Cover photo: Andrea J.


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