A coalition of 15 environmental groups criticized Interior Secretary Cecil Andrus yesterday for firing a veteran scientist who wrote to one of Andrus' favorite restaurants and asked that rattlesnake steaks be taken off its menu.

The group, which calls itself Monitor, demanded that Andrus withdraw the pink slip issued Thursday to Kenneth Dodd, a GS-12 herpetologist specializing in endangered species, for writing the letter -- on department stationery -- to Dominique's.

Dodd made a "good faith effort to save the species from extinction" when he asked restaurateur Dominique D'Ermo to "respectfully" banish the Pennsylvania timber rattler from the menu, said Monitor in a letter delivered yesterday afternoon to Andrus. The letter, from such wildlife groups as the Sierra Club, Friends of the Earth, The Greenpeace Foundation, the Humane Society of the United States, Defenders of Wildlife and The Fund for Animals, called Dodd's use of official stationery, "a good faith mistake of the kind we need more of. His action brought credit" to the Interior Department.

A Department spokesman, however, failed to see it that way, and said that Andrus, who predicted the rattlesnake stew would blow over in four or five days, would have no comment on the letter.

The letter would receive a reply, however, said spokesman Harman Kallman. "The action is by no means closed," he said, stressing that Dodd had yet to exhaust the government's 30-day appeal process.

Dodd, 29, who holds a doctorate in zoology, has been praised by superiors as the most productive scientist in the endangered species branch of the U.S. Fish and Wildlife Service. He has helped write proposals to protect some 25 animals, among them the Plymouth Red-Bellied Turtle.

But yesterday, Dodd said his scheduled trip to a public hearing in Plymouth, Mass., to discuss granting endangered status to the turtle, which is nearing extinction in the ponds outside Boston, had been mysteriously canceled.

Department officials said that Dodd's trip was canceled because another qualified herpetologist was found to field questions from the public. Endangered Species Program Manager Hal O'Conner said Dodd's attendance "wasn't essential, so we relieved him of that responsibility."

O'Conner said Dodd had indicated the trip would cut into the 30 days he has to appeal the firing and had requested an extension.Rather than extend the 30-day period, though, Interior "checked with (the) Boston (regional office) and found that his presence wasn't essential," he said.

A disappointed Dodd, who indicated that he had spent a great deal of time studying the plight of the turtle, attributed the abrupt cancellation to "politics."

Among the charges Interior presented to Dodd last Thursday in its letter of dismissal was that his "unauthorized" letter to Dominique's, which was leaked to The Washington Star's gossip column, The Ear, had "jeopardized sensitive endangered species legislation" before Congress.

The coalition of wildlife groups that rallied to Dodd's defense contended, in their letter to Andrus yesterday, that the scientist's letter "had absolutely no effect on the negotiations" over the Endangered Species Act on the Hill.