The term domesticated carries weight in science, ethics, and law—but what does it really mean? A new paper by Lord and Karlsson challenges long-held assumptions, proposing that animals should be considered domesticated if they depend on humans to survive — regardless of whether that dependence arose through breeding, captivity, or other means.

This proposal marks a significant departure from traditional views rooted in selective breeding and human intent. It could blur the lines between truly domesticated animals, self-domesticating animals, feral animals, wild animals and those that are merely socialised and tamed. Those that are not dependent on humans and can survive without us are not domesticated.

If this shift takes hold, selectively bred silver foxes might be considered no more domesticated than animals born in the wild but they still carry genetically altered traits humans specifically selected for. That has major implications—not only for animal welfare and legal classification, but for how we understand human-animal relationships altogether.

A New Way of Defining “Domesticated”

Scientists are now rethinking what it really means for an animal to be domesticated. Traditionally, we’ve thought of domesticated animals as those that humans have bred and raised over generations—like dogs, cats, horses, and farm animals. Even stray or feral animals are often seen as "domesticated but gone wild."

But a new scientific definition, proposed by evolutionary biologists Dr. Kathryn Lord and Dr. Elinor Karlsson, published in Proceedings of the National Academy of Sciences, May 2025, shifts that view. Their definition focuses not on breeding history, but on survival:

It’s all about ecological dependency—in other words, whether the animals could live without us.

Why This Redefinition Matters

At Black Foxes UK, we welcome clearer scientific terminology, but we believe this new definition overlooks key realities—especially for animals like captive-bred silver foxes. Silver foxes have not followed a single, uniform path to domestication. Instead, there are two main domesticated fox populations, both bred by humans for very different purposes—yet both irrevocably altered by our influence.

There are two domesticated populations:

• Russian domesticated pet foxes (Vulpes vulpes forma amicus; from lineages once considered Vulpes fulva), bred for tameness and aggression.

• Farmed silver foxes (Vulpes vulpes; once considered Vulpes fulva), bred primarily for fur colour varieties (over 80 types), many suffer from serious genetic health problems, including lethal mutations, painful diseases, and reproductive issues.

These foxes have been selectively bred for fur colours and other traits that do not occur naturally in the wild. Many display physical characteristics and health problems that make surviving in the wild difficult or impossible.

Lord and Karlsson’s ecological dependency model states that animals are considered domesticated only if they have evolved to depend on humans or human-made environments for survival. By this definition, silver foxes that survive independently in the wild—even if selectively bred—are not considered domesticated.

However, many silver foxes carry genetic changes from human influence that mark them as domesticated in a broader biological and ethical sense. This creates a grey area in classification. Therefore:

• If a silver fox depends on humans (due to health or other factors), it fits the domesticated category.

• If it survives fully independently, it would be classified as wild under that definition—even if selectively bred.

This is exactly where the debate lies, and why some argue Lord and Karlsson’s definition is too narrow for animals like silver foxes. Not accepting their “domesticated” status risks erasing their vulnerability—and the human responsibility that comes with it.

So, What Counts as Domesticated Now?

Domesticated animals, as detailed in the new definition, are those that can no longer survive on their own in the wild. This includes:

• Sewer rats, which rely on human waste systems to survive and are rarely found outside of these environments.

• Lactic acid bacteria, used in food production like yogurt and cheese. These microbes have adapted so specifically to human-made environments (like milk and fermentation tanks) that many strains can no longer survive or reproduce in the wild.

• Brachycephalic dogs (such as pugs and bulldogs), whose extreme physical features—like short limbs and breathing difficulties—make it nearly impossible for them to survive, hunt, or thrive outside of human care.

Animals that are not considered domesticated in the new definition, are those that live near humans but could still survive without us. These include:

• Feral cats and dogs, which may have descended from pets but are able to hunt, reproduce, and survive without any human help.

• Feral Pigeons, once domesticated for communication and for the creation of saltpeter, that scavenge human food but don’t rely on us directly—they nest, feed, and thrive without needing care.

• Silver foxes, which are selectively bred for non-naturally occurring fur traits that live with people, but are still capable of surviving on their own in the wild.

What About Feral and Stray Animals?

The new definition even changes how we see strays.

• A dependent stray (like a Chihuahua that can’t find food without people or human waste) would still count as domesticated.

• But an independent stray (like a feral cat that hunts on its own) would not.

So now, how an animal lives matters more than what it is. The same dog breed might be “domesticated” in a home but considered wild if living self-sufficiently in nature—even if genetically identical.

Where the Definition Fails

The new definition conflates adaptation with domestication. Urban foxes exploiting bird feeders or trash bins are adapting; silver foxes with non-molting coats or overgrowing gums are broken by design. Calling both "wild" ignores humanity’s role in creating (and often harming) the latter.

• It ignores human intent and intervention

• It could misrepresent genetic alteration as natural adaptation

• It undermines accountability and welfare protections

Domestication isn’t accidental—it’s deliberate manipulation. Russian lab foxes didn’t "evolve" tameness; humans forced it via selective breeding, with collateral damage (e.g., floppy ears = unhealthy and unintended genetic mutation).

So what’s really at stake here?

The Core Problem

The new ecological definition is dangerously reductionist—it treats domestication as a passive accident of dependency rather than what it really is:

• Active human manipulation of genomes (whether via selective breeding or CRISPR)

• Intentional creation of non-wild phenotypes (regardless of survivability)

• Irreversible divergence from wild ancestors (even if some traits are neutral or beneficial in nature)

So how should we define domestication in a way that acknowledges both science and ethics?

How to Fix This: A No-BS Definition

An animal population is domesticated if:

• Its genetic or behavioural traits have been deliberately shaped by humans through breeding, engineering, or other directed interventions, including the intentional creation of environments that promote dependency or tameness (e.g., proximity, provisioning, or confinement).

  AND

• It exhibits heritable traits not found in wild populations (whether harmful, neutral, or adaptive).

Ecological dependency is irrelevant to the classification—only relevant for welfare/policy considerations.

An alternative approach—sometimes proposed—is to allow different fields (e.g., ecology, law, animal welfare, or genetics) to use their own definitions of domestication based on the priorities of that discipline.

While this may offer short-term utility within specific contexts, it risks undermining conceptual clarity and cross-disciplinary coherence. For that reason, we do not favour this fragmented model and instead advocate for a consistent, biologically grounded definition that can be applied across domains.

Populations, Not Species—But At What Cost?

One positive aspect of the new definition is its emphasis on populations, not entire species. This framework is meant to serve evolutionary biology—not animal welfare or public education.

This subtlety recognises that domestication is rarely absolute. Just as not every dog lives in a house, not every fox is wild. In the UK, for example, we increasingly see a blurred line between wild native foxes and the domesticated, non-native silver foxes kept as pets or animal ambassadors.

However, definitions used in science don’t stay in science. They shape how animals are understood, classified, and treated. This population-level framing does little to help those of us working with silver foxes when the definition still discounts the profound effects humans have had on them. Is the silver fox wild or domesticated?

If science rewrites “domesticated” to exclude animals who have not lost the ability to function outside human environments—what then happens to their legal protections, husbandry standards, or public understanding? At worst, this reframing risks obscuring the responsibilities we bear towards animals we have irreversibly altered.

Definitions Shape Our Responsibilities

This reclassification raises important questions:

• If we exclude animals altered by humans from being called domesticated, do we risk losing legal protections and ethical care standards for them?

• Does intent matter if the consequences of breeding are irreversible dependency and health needs?

• Should definitions account for the ethical and welfare responsibilities humans have towards animals they have changed?

  
  

The Bird Feeder Paradox

The Bird Feeder Paradox A 2017 University of Oxford study found that British garden birds, like great tits, are evolving longer beaks—likely in response to widespread bird feeder use. In some areas, these birds may now depend on feeders to meet their nutritional needs.

Under Lord and Karlsson’s ecological dependency model, this could signal early domestication. But that raises odd contradictions: if bird feeders can "domesticate" wild birds, while dogs, cats, and silver foxes—animals deeply shaped by human breeding—are excluded, something doesn’t add up. 

A similar paradox is unfolding with released red squirrels and urban foxes. Some are becoming bolder, more human-tolerant, even food-dependent, with morphological changes appearing. Social media is filled with videos of people hand-feeding foxes everything from raw steaks to birthday cakes. This isn’t just adaptation—it’s behavioural change driven by human interaction. Some foxes now rely entirely on handouts.

Like the birds, these squirrels and foxes reflect human-induced dependency. But with more direct influence—social conditioning, diet changes, and increasing conflict with people. It goes even further with the CRISPR editing of the grey squirrel to reduce reproduction. CRISPR is domestication on steroids, (human-directed evolution through genetic engineering). 

Here's the deeper inconsistency: many “domesticated” animals—like feral dogs, silver foxes, and even humanised and chimeric laboratory mice—can survive in the wild. Meanwhile, wild animals are becoming dependent on us, despite no breeding history.

This exposes a flaw in the ecological model: it focuses on survival, but misses the bigger picture. Domestication isn't just about where an animal can live—it's about how humans have altered their bodies, behaviour, and choices. And with that influence comes responsibility.

Dependency isn’t binary. A lab mouse engineered to possess human genes (domesticated, but can still survive in the wild) and an urban fox raised to beg instead of hunt (wild, but self-domesticating), both defy neat categories. This definition draws a line that real life constantly blurs.

Evolution Is Not the Whole Story

Lord and Karlsson argue that domestication is “just plain old evolution”—that it is not special, merely the result of natural processes adapting animals to human environments. But it’s evolution hijacked.

We cannot neatly define what constitutes a species—nor can we clearly define domestication. Generalisations are necessary, but they are not the rule. Human intent—whether driven by companionship, utility, or mere curiosity—shapes the course of adaptation in ways that demand ethical responsibility.

• A wild European fox scavenging bins is a native subspecies adapted to its environment and may be partially self-domesticating through handouts, social media impacts, and close proximity to humans.

• The silver fox, however, is a domesticated and intensively farmed form of a different subspecies, bred for traits and temperament that can hinder natural survival—such as overgrown gums and tameness towards humans (like the Russian domesticated pet foxes, fur foxes were also bred for even temperament, on welfare grounds under Welfur policies).

Treating both as the same “wild” animal ignores these biological differences and overlooks our responsibility for the silver fox’s vulnerability.

Summary

At Black Foxes UK, we recognise the importance of a clear, consistent scientific framework to study domestication across species. Defining domestication through ecological dependency may help evolutionary biologists make comparisons—but scientific precision must be balanced with practical consequences.

Definitions useful in research do not always translate well into the real world. Welfare, law, and public understanding can suffer when the language becomes too narrow—or too abstract. Rigour is essential, but so are compassion, clarity, and context.

We urge scientists, policymakers, and animal professionals to approach this redefinition with care. Terminology shifts do not happen in isolation. They influence perception, inform policy, and ultimately affect how animals are treated.

For animals like the silver fox—caught between categories of wild and domestic—the stakes are particularly high. At Black Foxes UK, we will continue to refer to silver foxes as domesticated, (as farm animals or as pets—in the case of the Russian foxes). Because they are.

No matter what science calls them, their welfare depends on us understanding their domestication. And our responsibilities—to protect, care, and advocate—must not be lost in semantics.

Sources:

• A universally applicable definition for domestication

• National Geographic: Dogs. Bedbugs. Corn. They all have this one thing in common

• Unravelling domestication: introduction to the theme issue

• What defines a species? Inside the fierce debate that's rocking biology to its core

• British birds adapt their beaks to bird feeders

• Urban foxes may be self-domesticating in our midst

• Feeding British red squirrels is changing their skulls

• Gene tool holds promise of managing invasive species