A monthslong conflict over a plan to send eight chimpanzees from a laboratory in the United States to a wildlife park in England intensified this week when animal welfare groups and primate sanctuaries went to court for the second time to stop the move.

The New England Anti-Vivisection Society, an animal rights group, is leading the effort to block the United States Fish and Wildlife Service from allowing the move. After the society brought a similar lawsuit in November to stop the transfer, the wildlife service pulled back from its initial decision to grant the permit and reopened public comment.

The chimpanzees in question are longtime residents of the Yerkes National Primate Research Center at Emory University in Atlanta.

Yerkes is trying to reduce the number of its chimpanzees because of a change in research focus. Also, medical experiments using chimpanzees have become almost impossible because of new regulations. Yerkes gave seven chimps to the Chattanooga Zoo in Tennessee, but still has more than 50 and arranged to donate eight to Wingham Wildlife Park in Kent, England.