Leon M. Lederman Science Education Center

American Bison

How Large is the Fermilab Herd?

The 80-acre pasture at Fermilab is large enough to comfortably hold about 70 head, however the size of the herd varies seasonally. In the winter of 1996 the herd consisted of 36 cows. In the spring 4 two-year-old bulls were purchased. Also at this time, 26 calves were born bringing the herd size to 66. In the fall about 30 will be sold to bring the herd back to about 40. Fermilab bison have a reputation for being large and healthy animals and are much sought after by breeders. The sale of the bison covers a large part of the expenses of maintaining the herd.

Why are there Tags in their Ears?

The tags in the ears of the bison (see photo) have numbers on them to identify individual animals. The number on the right tag indicates the year the animal was born and the animal's individual number. For example, 413 means that the animal was born in 1994 and is number 13 in the herd. The left tag repeats the animal's individual number.