It's a bouncing baby bison.
And another one. And another one.
Two have been born this week, one Sunday and one Monday. The lab expects another eight to 10 to come along soon.
Bison have a 9-month gestation period; the calves can weigh up to 66 pounds, according to the American Bison Society. For the record, though, there was one born at a zoo last year that weighed 125 pounds. The sex and the weight of the Fermi babies had not yet been determined as of Tuesday.
The lab has 24 bison. It will sell any of the females born, to limit the herd to the 20s, because a part-time worker manages it. The lab also wants to avoid inbreeding.
Fermilab's first director, Robert Wilson, brought in a herd in 1969. He wanted to honor the heritage of the laboratory site, and preserve an iconic image of the American prairie.
They have become a symbol of Fermilab's work on the frontiers of high-energy physics.
The babies will grow up to stand 5 to 6.5 feet tall and eventually weigh as much as 2,500 pounds.