Saying that their concerns about trigger-happy hunters have been validated, 12 conservation and animal-rights groups have sued to get the gray wolf re-listed as an endangered species. The 1,500 wolves that roam through Wyoming, Montana, and Idaho were delisted on Mar. 28 and can now be shot at will; a total of 37 have been killed in the last month. Conservation groups filed suit Monday, saying that the wolf population should be 2,000 at a minimum to protect genetic diversity. But federal biologists have a goal of maintaining a minimum population of only 300 wolves, and predict that even with willy-nilly killing, the population will stabilize well above that goal in the next few years.