Last week, the U.S. Geological Survey (USGS) announced scientists had successfully produced hybrid pups from a captive male western gray wolf and female western coyote. This is an important step in determining whether the eastern wolf of southeastern Canada is a unique species eligible for protection under the U.S. Endangered Species act.

A press release from the USGS said scientists attempted to artificially inseminate nine captive coyotes with sperm from eight different gray wolves. Three became pregnant, and one was able to bear and nurture six healthy hybrid pups. Scientists believe the project shows it’s possible for western wolves to procreate with western coyotes, and sheds light on the theory that eastern wolves are merely a smaller version of western wolves.

“Our findings leave the eastern wolf debate open by adding further merit to the hybrid theory rather than disproving it,” said David Mech, USGS scientist and the report’s lead author. “However, the findings are applicable to captive animals and are not necessarily true under natural conditions, so the counter-hybrid theory is not disproved either.”