Resource Science: Reforming the science used with the ESA

An excellent article in the March 30, 2026, WLJ by Charles Wallace describes a Senate subcommittee discussion on reforming the Endangered Species Act (ESA). Members of Congress and witnesses suggested more state involvement, incentives for landowners, staffing at the U.S. Fish and Wildlife Service (USFWS), and recovery criteria for wolves and grizzly bears. These are important considerations, but don’t focus on a primary problem with the ESA: science.

The ESA is supposed to use the best science available, but in my experience, it does not always do so. Consider four scientific considerations: the risk of extinction, foreseeable future, significant portion of a species’ range and the species definition. The risk of extinction is the likelihood a species will be reduced to zero. This is a prediction with inherent uncertainty. The foreseeable future is the time frame in which extinction is predicted to occur and is also a prediction. A significant portion of a species’ range is a judgment, not a fact. The definition of species includes species, and also subspecies and distinct population segments (DPS), which are not well-defined groups. The law requires USFWS to make decisions on these four criteria despite their indefinite nature. Because the science is uncertain, the ESA will always have conflicting opinions on science.

The definition of “species” is the primary science problem with the ESA. Science generally recognizes species as groups that can’t interbreed successfully, like cattle and sheep. Subspecies and DPS are populations in a geographic area that are capable of interbreeding with other populations of the same species (for example, grizzly bears in Alaska and in the Lower 48 states, see the References below). Subspecies and DPS are not species, so the ESA has a major science contradiction in considering groups that are not species. Listing subspecies and DPS makes it functionally an Endangered Population Act. Does the federal government have jurisdiction to manage wildlife populations? Lawyers can argue that, but it seems like overreach because states manage wildlife populations. I suggest the ESA could be changed to apply only to full species that are actually endangered with extinction, like California condors.

Consider grizzly bears and wolves. Grizzly bears are an endangered DPS in the Lower 48 states but not in Alaska. Their management is difficult because they have a low reproductive rate and because they kill livestock and sometimes, people. Information on the numbers, characteristics and locations of bear attacks on humans and predation on livestock, pets and game animals could be more widely publicized so people know what to expect if grizzlies expand their current range or are introduced to new areas.

Mexican wolves and wolves in Colorado are designated as experimental populations under the ESA. The Mexican wolf is a subspecies in Arizona and New Mexico and the wolves in Colorado are part of a DPS in the Lower 48 states. Wolves are more easily managed than bears because they have a high reproductive rate and are less likely to kill people. However, wolves kill livestock, pets and wildlife. As with grizzlies, information on the numbers, characteristics and locations of wolf attacks on humans and predation on livestock, pets and game animals could be more widely publicized so people know what to expect if wolves expand their current range or are introduced to new areas.

Also consider that Mexican wolves have been protected as a genetically unique subspecies but subspecies are not scientifically definite. The wolves in Colorado are a different northern subspecies and could disperse southward into Arizona and New Mexico and interbreed with Mexican wolves. There are plans to prevent this by capturing such wolves and returning them to Colorado. However, not all wolves in Colorado have radio tracking collars, so this will be hard or impossible to achieve.

Is it bad for Colorado wolves to interbreed with Mexican wolves? Probably not, biologically. Interbreeding will likely result in increased fitness through heterosis, as with crossbreeding cattle. Heterosis could improve reproduction and reduce inbreeding in Mexican wolves. But crossbreeding northern and Mexican wolves will also change the genetics of the Mexican wolf population which has been the basis of their ESA designation. This creates a management dilemma of allowing or preventing interbreeding of northern and Mexican wolves. Of course, the primary management issue with wolves is their killing livestock and their genetics is not a particularly practical management problem.

I think it is the responsibility of USFWS to better inform the public of this kind of information, especially the indefinite nature of subspecies and DPS. USFWS has a difficult job producing ESA documents and dealing with lawsuits. But such information is not easily available to most people and efforts to inform the public should be increased. I think that informing the public of the science on the indefinite nature of subspecies and DPS should be a priority because of the impact that wolves and grizzlies have on livestock, wildlife and people.

People have different opinions about wildlife management, including the ESA. All opinions are legitimate in our free country, but we should try to have them as informed as possible. — Matt Cronin, WLJ columnist

(Matt Cronin is a biologist with Northwest Biology and Forestry Company LLC in Bozeman, MT, and a teaching professor at Montana State University. He may be contacted at croninm@aol.com.)