The simple answer is that they are hidden.

The three largest populations are at Covance, the Wisconsin National Primate Research Center, and the Harlow Primate Psychology Laboratory.

Covance, at 3301 Kinsman Boulevard near the Dane County Regional Airport, reported using 7,313 monkeys in 2007. Most, if not all, were wild-captured. The US Department of Fish and Wildlife Service's live primate importation records from January 1 to June 30, 2009, list Covance as the number one importer of monkeys.

Only two companies Imported more that 1000 monkeys during that seven month period. 5,577 were imported by Covance (most of these animals probably ended up here in Dane County, and 2,648 were imported by Boston-based Charles River.

Wisconsin National Primate Research Center, at 1220 Capitol Court, just off Regent St, is part of the University of Wiscosnin-Madison. Most of the monkeys used at the primate center are from their breeding program. The primate center reported in 2008, that it had 1,570 monkeys on hand.

Harlow Primate Psychology Lab, at 22 North Charter Street, just a few feet away from the primate center, is also a part of UW-Madison. In 2006, they reported having 500 monkeys on hand.