Grizzly bears, bald eagles and sundry other constituents from the political wilds are back on the government's agenda, and you might say hunting season has opened.

The Endangered Species Act, designed to protect imperiled flora and fauna from man's bulldozers and oil rigs, is itself on the endangered list, under the sharpest attack since it was enacted by Congress in 1973.

The act is up for reauthorization this year, and industrial and development interests, buoyed by what they see as administration sympathy to their cause, are proposing major changes to bring "balance" to the law.

Critics have another term for it. "They want to gut the act," said a congressional observer.

But some conservationists fear that the act is being eviscerated by the administration even before Congress gets a crack at it.

Interior Secretary James G. Watt has asked for a one-year extension of the act with only minor changes, saying he wants time to find administrative solutions to industry's problems. Critics say the real reason for Interior's low profile on the reauthorization is that it wants to avoid a potentially divisive political issue in an election year.

Meanwhile, the budget for Interior's Office of Endangered Species has been sliced by more than 50 percent, from $4.1 million to $1.9 million, forcing the office to cut back on contracts for the biological studies it uses to identify endangered species.

About 60 proposals for new listings under the act that have come in during the Reagan administration are bottled up in the solicitor general's office, awaiting clearance under the Reagan administration's stringent rules for cost-benefit analysis.

Only one species has made it through the cost-benefit hoops--the Hays spring amphipod, a tiny shrimp-like creature initially proposed for listing during the Carter administration. Considering that the amphipod lives only in a spring in the heart of Washington's National Zoo, conservationists note archly, the administration could list it safely without offending any industrial interest.

A major reason for the bottleneck, according to Ron Lambertson of the endangered species office, is that the office had no guidelines to determine the possible benefit of, say, a Hays spring amphipod, versus the cost of modifying or scrapping development projects that might destroy it.

Scientists point to important medical research being done with certain plants--some of them endangered--and argue that it is not yet possible to determine the potential value of some humble organisms.

Industry, however, sees the conflict in more concrete terms, and it is mindful of the tiny snail darter that held up the $120 million Tellico Dam for years until Congress granted it an exemption from the act.

One of the changes in the act proposed by industry associations, among them the American Mining Congress and the National Forest Products Assocation, would severely limit the listing of "lower forms of life"--plants, insects and invertebrate animals.

Interior's Lambertson says higher life forms get priority in his office as well, all other factors being equal, albeit under a different rationale. By protecting the habitat of a higher life form, such as the grizzly bear, he says, "you're protecting lower life forms as well."

But another industry proposal would remove the grizzly bear, along with other popular species such as the bald eagle and the sea otter, from the protection of the act, on the grounds that the animals are abundant in Alaska and there is no need to "conflict with other national needs" by protecting them in the lower 48 states.

Conservation groups say the act has worked just fine and should be reauthorized for three years with no major changes. Meanwhile, they are devoting their time to rebutting charges that the act has placed an unreasonable burden on industry.

The Endangered Species Act Reauthorization Coordinating Committee, a coalition of environmental and conservation groups, says that of 9,686 consultations conducted by the U.S. Fish and Wildlife Service in the last three years, only 185 led to preliminary findings that a proposed project would jeopardize a protected species.

"In virtually every case, the project was able to go forward with modification," says Ken Berlin of the National Audubon Society, who will be presenting the coalition's case to a House subcommittee today. Only two "minor" projects were halted, he says.