August 18, 2016

What's in your stomach?

by Barbara Pepper-Rotness, MHS Research Center Reference Assistant

Museum accession # x1963 42 01
"Does anyone know what this object is?" asked Amanda Streeter Trum during a behind-the-scenes tour of the museum's stored artifacts.

  • It's a rock. No.
  • It's a prehistoric weapon. No.
  • It's, um... No.
The Curator of Collections for the Montana Historical Society Museum had us all stumped. And, we received an answer that was just as perplexing.
  • It's a bison hairball. What? That thing was in an animal?
Yes, in fact, much like hairballs in cats, hairballs in bison can be created by licking their own and other bisons’ fur. Unlike feline hairballs, bison hairballs can become trapped in the gastrointestinal tract and oftentimes a shell is formed around them. Technically called 'bezoars', these balls develop around not only masses of fur but also antler tines, twigs, gravel, bullets, pebbles – potentially any foreign object that isn’t expelled from the body.

The term ‘bezoar’ purportedly derives from the Persian words for ‘protection from poison’[1], and bezoars were once treasured - particularly by royalty afraid of poisoning by opponents - for this specific medicinal property. “It is said that a gold-framed specimen was included in the 1622 inventory of Queen Elizabeth I’s crown jewels.”[2]    

Example of bezoar pendant that could be dipped in a drinking cup for poison testing.
Netherlands, ca. 1600-1650. bezoar and gold filigree, 11cm.
BK-NM-7082 Rijksmuseum, Amsterdam.
Image used with permission.
Bison and other ruminants, such as cows and oxen, can carry bezoars because of the unique anatomy and physiology of their four-compartmented stomachs. Anything swallowed makes its way to the first compartment - the rumen. From the rumen, food is regurgitated as ‘cud’ for rumination. The cud is swallowed and then travels to the reticulum. [3] “Bezoars are frequently found in the rumen and reticulum and are formed through the rolling movements of these two forestomachs during rumination.”[4] This mass remains lodged in the animal, potentially causing digestive problems or life-threatening situations “if obstruction of the esophagus, cardia, pylorus, or intestinal tract occurs.” [5] 

"University of Minnesota Extension --Dairy", University of Minnesota, Accessed July 22, 2016.
Used with permission.

In the case of the museum’s four inch wide and four inch high bison bezoar, openings in the outside layer allow us to see the "matted, compacted brown hair inside"[6]. One can see the rock-like formation surrounding the hairball. In an email several years ago, Dan Sharps, former biologist at the National Bison Range in Moiese, Montana, stated that whatever is at the core of a bison bezoar is “coated with minerals present in the animal’s diet in an attempt to protect the animal from harm” and this shell is described as a calculus or concretion. One wonders how long this particular heavy-looking and obtrusive bezoar was carried around by the animal.

Museum Director, Jennifer Bottomly-O’Looney, suggests visiting the Montana Historical Society Museum to see an example of a bison bezoar in the Neither Empty or Unknown: Montana in the Time of Lewis and Clark exhibit. 

Works Cited:
[1] “Hairballs: Myth and Realities Behind Some Medical Curiosities,” National Museum of Health and Medicine, last modified October 5, 2015, accessed June 24, 2016,
[2] Stefi Weisburd. "Chemistry." Science News 132, no. 12 (1987): 190.
[3] Amy Lisk, email message to author, July 20, 2016.
[4] Jacqueline M. Zdziarski and Bush Mitchell. "Clinical Challenge: Case 3." Journal of Zoo and Wildlife Medicine 22, no. 4 (1991): 508.
[5] Ibid.
[6] “Bison Bezoar.” x1963 42 01. Montana Historical Society Museum.
Thank you to previous National Bison Range (NBR) biologists, Dan Sharps and Brendan Moynahan for their expertise and contributions; and to current NBR biologist, Amy Lisk for her expertise and for reviewing this article.