Little Outlaw, the new colt of Stallion Renegade and mare Northern. Simply amazing.

We have been getting many questions about some of our litigation. We will address some of those questions over the next week in a series of articles.

Question related to the WHE and Carter Resevoir Mustangs, Inc. Carter/Buckhorn/Coppersmith case: What is “functional extinction” and what does it mean in your lawsuit?

What “functional extinction” means

Functional extinction describes a situation where a population has been reduced so much that it either no longer plays its natural role in the ecosystem, or it can no longer sustain itself as a genetically viable, reproducing population.

Animals may still exist on the landscape and on spreadsheets, but numbers, age structure, and genetics have been pushed past the point where the population can maintain healthy offspring without escalating inbreeding and loss of fitness.

For many species, functional extinction is a warning stage that often precedes complete extinction if nothing changes. Once a population reaches this point, conservation biologists treat it as an emergency because recovery becomes far harder, more expensive, and sometimes impossible. This is particularly critical when talking about a population that: 1) Contains a unique genetic make-up, 2) Occupies an isolated area with no corridor system to other populations that contain the same unique genetic markers.

It is important to understand “viability” in basic terms before we discuss what BLM intends to do to the Carter Herd Management Area (HMA).

“Functional Extinction” means urgency. 

“Functional extinction” doesn’t mean the last horse dies tomorrow. It means the herd is reduced to a size so small it can no longer maintain genetic diversity, demographic resilience, or natural herd behavior — so the irreplaceable primitive Iberian markers quietly vanish, generation by generation.

Once those 1000-year-old bloodlines are lost, no roundup, vaccine, or “introduction from outside” can bring the original Carter genome back.

Preservation has to happen now, at viable numbers, on adequate habitat.

Why numbers and genetics matter for wild horses

Conservation genetics and federal reviews of wild horse and burro management have long emphasized that herds must be large enough to maintain genetic diversity over time.

Scientific and (even) agency guidance typically places the minimum viable wild horse herd size at roughly 150–200 animals of breeding age, in order to keep inbreeding depression and genetic drift at bay. Smaller herds can see harmful recessive traits expressed more often, weakened immune systems, reduced fertility, and a loss of the adaptive capacity needed to survive drought, disease, and climate stress. BLM’s own genetic expert, Dr. Gus Cothran, concluded that the minimum viable wild horse herd is 150–200 animals. Within a herd that size, only ~100 are of breeding age, and just ~50 make up the genetic effective population (Ne) — the animals actually passing genes to the next generation. He stresses thid is the bare minimum.

Below: When looking at the number of HMAs where BLM actually sets and AML above their own minimum genetic threshold tells a story, where in practice, they simply don’t seem to care.

Breakdown of AML for the HMAs nationwide. Only 3 HMAs in the U.S. have an AML over 500. Only 31 have an AML over 150. These same ranges support thousands of cattle and massive extractive industries.

The Carter herd is unique; it is isolated and genetically distinct where genetic testing has documented Spanish–Iberian ancestry and unique markers in Carter horses, making them an irreplaceable heritage herd and genetic resource. Genetic testing has shown that Carter carries the highest ratio of individuals with specific ancient genetic markers (to date) that are, in part, responsible for the high number of horses with the “dun factor” coloration.  That same isolation which preserved this lineage also makes the herd more vulnerable when numbers are pushed down, because there is virtually no natural influx of outside horses to offset inbreeding or restore lost diversity.

New filly from stallion Royal and mare Anja. Vasilisa means “royal” and the perfect name for daddy’s little girl.

What reducing Carter to 25 horses really means

Current management plans for the Carter area envision reducing this already isolated herd to just 25 wild horses and then applying fertility control to all mares (and potentially gelding some of the stallions). This proposal comes on top of a history of removals and a massive reduction of habitat: more than 230,000–280,000 acres originally managed for wild horse use have been stripped away or reallocated (with no actual analysis), leaving the herd on a much smaller land base dominated by livestock use because the BLM simply said they wanted it this way.

At 25 animals, the Carter herd is far below any scientifically recognized threshold for long‑term genetic viability. With so few individuals and no exchange with other herds, almost every breeding pair is closely related, and the effective population size—the number that actually matters for genetics—is even smaller than the headcount. Adding fertility control on top of this tiny population shrinks the pool of breeding animals further and distorts age and sex structure, accelerating the slide toward inbreeding depression and demographic collapse. (Introducing other horses to solve this new BLM crafted problem, as BLM proposes in the EA where they recognize a population this small is not genetically sound, would destroy the unique genetic makeup that defines today’s “Carter Mustang.”)

In plain terms, reducing Carter to 25 horses under fertility control creates the conditions for functional extinction: technically, a few horses remain on paper, but the herd can no longer function as a healthy, self‑sustaining wildlife population on its designated range. That is the definition of “function extinction” of an existing subset population.

Shrinking both the herd and its range undermines any pretense of “multiple use” or “thriving natural ecological balance” for this population. A token remnant of 25 horses—confined to a fraction of their historically designated habitat, hemmed in by drift fencing, and subjected to fertility control—cannot fulfill the ecological and cultural role that Congress envisioned for wild free‑roaming horses on public lands. Instead, policy choices are turning the Carter herd into a museum display: visible enough to claim they still exist, but managed so tightly that their disappearance as a functioning wild “Carter herd” becomes a near‑certainty.

What’s at stake

Because Carter horses carry unusually strong Spanish–Iberian genetic signatures, their loss would erase a living link to the history of horses in the American West that cannot be restored once gone. For other species, a proposal to drive an isolated, genetically important population down to 25 animals and then deliberately suppress reproduction would be treated as a conservation emergency, not a routine and intentional management plan.

Recognizing the Carter situation as functional extinction by policy is the first step toward change: it reframes the debate from “overpopulation control” to “preventing the deliberate dismantling of a unique wild herd and its legal range.”

While we continue briefing on our emergency motion and prepare for the hearing, many of you want an action item.

You can sign on to a letter we may be able to utilize in the underlying case to demonstrate a strong public interest.

Stand With The Carters

Help protect this unique herd before low AMLs erase it from the wild.

Take Action  →  Sign the Letter

Every court case we bring, every mile we travel to cover roundups or assess a herd, every win, every action we take is only possible because of your support. Thank you!