There’s no evidence that wolves and foxes have ever bred with each other, and all the science suggests they wouldn’t be able to produce viable young, says James Fair.
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Can wolves and foxes interbreed?
There are a number of reasons for this. First, red foxes belong to the genus Vulpes, and grey wolves to Canis, and it’s thought the fox lineage split from its closest relatives nearly 12 million years ago. So, though both species belong to the dog, or canid, family, they are about as closely related as humans and baboons.
What’s actually stopping wolves and foxes breeding?
Because they are so distantly related, the most important factor is that wolves have 78 chromosomes and foxes only 34. Such as a big difference between the two makes it extremely unlikely that a viable zygote could be created were the sperm of one to meet the egg of another.
Anything else?
While red foxes and grey wolves do overlap in where they live – they are both found extensively throughout Europe and much of Asia (as well as in North America, though red foxes were introduced and not native) – they vary a great deal in size.
Foxes are relatively small, typically weighing between 5-8kg and standing 40cm at the shoulder, while wolves can range between 30 and 65kg, and so are six to eight times larger. They are very different animals in terms of their behaviour, too – wolves are pack animals, while foxes are largely solitary and only come together to breed. If they ever come across each other in the wild, the chances are that foxes quickly make themselves scarce.
If all this is true, how did a dog breed with a fox in Brazil?
This is true. In 2021, an animal was taken to an animal refuge after it had been hit by a car, and – after noting its odd appearance and strange behaviour – scientists determined it was indeed a hybrid that was the result of a domestic dog breeding with a pampas fox. It was called the ‘dogxim', because the Portuguese name for the fox is graxaim-do-campo. Scientists reported that its pricked ears were reminiscent of the fox, while it barked like a dog.
And dogs are very closely related to, and can interbreed with, wolves – so that suggests foxes and wolves could interbreed?
No, because the pampas fox of South America is not what scientists call a true fox. It is a member of the genus Lycalopex, not Vulpes, and it has 74 chromosomes, much closer to the domestic dog (and wolf’s) number of 78. The dogxim was found to have 76 chromosomes.
But what’s the ‘dox’ then?
It’s true that the Grosvenor Museum in Chester has a specimen known as the dox – the museum says it is the offspring resulting from a male fox mating with a female dog on a canal boat near Beeston, south-east of Chester and that it is the only known example of dog-fox hybrid in the world. But there is no evidence the dox has ever been genetically tested to see whether its true origins can be determined.
Who was Wilhelm Niemayer?
He was the director of Hannover Zoological Gardens in Germany in the 19th century, and he gives an account of breeding a female domestic dog and a captive male fox. After mating, he reports, the dog “was kept strictly away from other dogs, and produced a litter of four young, one of which was dead at birth.
The others died during the next few days.” If accurate, this account demonstrates that dog-fox hybrids cannot happen, making wolf-fox ones even less likely. Besides, who ever heard of a wox – or a folf?
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