Hybrid Animals Are Trouble, Scientists Say, No Matter How Cute They Are

The recent announcement of the discovery of a dog-fox hybrid, the so-called “dogxim,” was strange and adorable and a little otherworldly. But scientists warn that such crossbreeds are generally evidence of nature going awry under pressures created by humans.

As agriculture and other forms of human development encroach on natural areas, wild and domesticated animals (not to mention people and their automobiles) are frequently coming into close contact with each other.

In the case of dogxim, the medium-sized animal was hit by a car in Vacaria in Southern Brazil, a small city of about 66,000. Vacaria is surrounded by rugged farm fields and patches of forest, and four different species of canids live in the area, the Rio Grande do Sul State.

Upon inspection, an academic team from two different local universities determined that the animal was a hybrid between a domestic dog (Canis lupus familiaris) and the sandy-coated pampas fox (Lycalopex gymnocercus).

The hybrid had dark, coal-colored fur, large, pointed ears, and refused to eat dog food. Although it barked like a dog, it preferred to eat rats and at one point climbed a bush in its enclosure, a fox-like behavior.

The odds are stacked against such a crossing ever occurring, which may explain why examples of hybrids are so rare, and dogxim is the only one ever confirmed by modern science. Dogs and foxes belong to not just separate species but separate genera and have different numbers of chromosomes.

Two zoo directors from years gone by, from the 19th and early 20th Centuries, claimed to have crossed a fox and a dog. But those cases never received the same scrutiny as dogxim.

Read More: 5 Dog Breeds That Have Changed Over The Past 100 Years

Genetic testing found that the hybrid had 76 chromosomes, halfway between the dog’s 78 and the pampas fox’s 74. Overall, the rare mixing of animals from two different genera resulted in a genetic interweaving of the two species, which had diverged from a common ancestor some 6.7 million years ago.

Hybrids are often fantastical to consider, such as ligers (a lion-tiger cross) or wholphins (dolphin and killer whale), but they tend to result from some sort of human influence, scientists say, and they typically do more harm to the species involved than good.

In dogxim’s case, the animal was born with a coat poorly suited to its environment, according to the team’s paper. It may also have been born infertile and susceptible to a host of canine diseases, such as parvovirus, distemper, and brucellosis. (Information about Dogxim’s fertility was never released publicly before she died in a conservation facility in early 2022.)

“Hybridization between species with different evolutionary trajectories can be a powerful threat to wildlife conservation,” the paper said.

Read More: Dogs Have Co-Evolved With Humans Like No Other Species

While some hybrids go on to outperform the original species, many others suffer from abnormalities or from the blotting out of useful DNA evolved over centuries.

A 2022 report quantified the effects of hybridization by reviewing 115 studies and found that 49 percent of the effects described therein were negative and only 13 percent counted as positive. The study also found that hybridization was surprisingly common and had affected 25 percent of plant species and 10 percent of animal ones.

The downsides of hybridization included “outbreeding depression” in which hybrid individuals are born, as in dogxim’s case, lacking in one or more important adaptations. Should one of those hybrids then go and breed with a member of a wild population, the damage is even greater.

Hybrids can also introduce reproductive issues to wild groups, as when interbreeding injected fin whale DNA into blue whale populations and slowed their reproduction.

As for the breeding of dogxim – the only confirmed dog-fox hybrid in history – how much damage could have been done to the local fox population?

“So far, we have no scientific evidence that there are other hybrids in this region,” researcher Bruna Szynwelski of Universidade Federal do Rio Grande do Sul told Newsweek. “However, we suspect that this case we have described is not the only one.”

Read More: These Rare Adaptations Help Animals Survive in the Desert