Washington Post science writer Brian Vastag reports on the story of the last four chimps that remain at a controversial research facility in Maryland. Bioqual has been experimenting on chimpanzees for 30 years. Soon, that era will end, as part of "a historic shift away from using apes in medical experiments."

On Monday morning, a truck hauled six chimps from Bioqual. Last week, five others were removed. The last four, including Tiffany and Torian, will depart later this summer.

They are returning to where they were born — the much larger New Iberia Research Center, part of the University of Louisiana at Lafayette — where they will be available for more research before they're retired — someday — to a sanctuary.

"This is another indication that chimpanzee research is on the decline," said Kathleen Conlee of the Humane Society of the United States, which has painted Bioqual's chimp research as unethical.

While about 1,000 research chimps live in the United States — down from 1,500 in 1997 — a landmark report from the influential Institute of Medicine (IOM) last December labeled nearly all chimpanzee research as scientifically unjustified.