Further reading:

http://messybeast.com/genetics/hybrid-equines.htm

Show transcript:

Welcome to Strange Animals Podcast. I’m your host, Kate Shaw.

I stumbled across an interesting mystery animal recently and thought it would make a great topic for a Patreon episode. It’s supposed to be a hybrid animal, but as we’ll soon learn, it can’t possibly be what it’s said to be.

The animal is called a jumar or jumart, or sometimes a kumrah. The oldest record of a jumar dates to 1546 but there are many other accounts up to the beginning of the 20th century. The jumar is supposed to be the hybrid offspring of a horse and a cow, usually a bull and a mare. Sometimes it was supposed to be the offspring of a bull and a donkey mare.

Whatever its supposed origins, the jumar was said to look like a horse except for cow-like hindquarters and head, although with no horns. The hooves were usually solid like a horse’s hooves but occasionally cloven. A jumar was supposed to be stronger but smaller than an ordinary mule, which is a cross between a horse and a donkey.

There are plenty of reports of jumars, including individuals examined by naturalists, so it’s obviously a real animal. Could it really be a horse-cow hybrid? How closely related are horses and cows, anyway?

Not closely related AT ALL. The horse is almost as closely related to whales as it is to cows. They belong to totally different orders, and if you remember from the hybrids episode, it’s unusual for a hybrid to result from animals that share a genus, but extremely rare for animals that only share a family. Order is a step above family. There is literally no way that a horse and a cow could crossbreed successfully, but if somehow they did, the baby would not survive long enough to be born.

So the jumar can’t be a horse-cow hybrid, but at the same time, the jumar was a real animal. So what was it?

The first hint of a solution came from a French naturalist who lived in the 18th century. He wrote in 1771 about two dead jumars he bought and dissected. Both of them turned out to be ordinary mules. Specifically, they were hinnies, which are the offspring of a female donkey and a male horse. Most mules are offspring of a male donkey and a female horse.

Part of the reason that the hinny is a less common hybrid is because of the differences in chromosomes between horses and donkeys. Horses have 64 chromosomes, donkeys have 62. Mules and hinnies have 63 and are almost always sterile. In the case of a pair of animals with mismatched chromosomes, a baby is more likely to result when the father has the lower chromosome count, as is the case with the male donkey. A male horse has more chromosomes than a female donkey, so it’s less likely that a baby will result. Hinnies are almost always smaller than horses or mules because the mother donkey is a smaller animal than the mother horse.

Like any other animal, mules are sometimes born with genetic issues that may affect their appearance. One relatively common issue is a type of dwarfism that can affect certain bones in the body, which makes the animal’s conformation look different from an ordinary mule’s. A disorder called chondrodysplasia, which can have a number of different causes, results in the upper portion of the animal’s skull being underdeveloped. This means its face appears dished like a cow’s face, its upper jaw may be much shorter than its lower jaw, and its eye sockets and forehead may look more cow-like too.

It’s most likely, then, that jumars are just horses, mules, or hinnies with a genetic abnormality. That would also explain why no one talks about jumars anymore. These days if a weird-looking foal is born, the owner calls the vet, who recognizes a genetic issue right away. In the olden days people didn’t know what caused genetic issues and assumed it had something to do with parentage. If a mare had a baby that looked a little bit like a cow in some ways, that must be because its father was a bull.

If you remember the Patreon episode we had a long time ago about horses with extra hooves on one or more feet, it’s probable that this is the trait leading to reports of jumars with cloven hooves. We even have one account from 1830 by a veterinarian who examined a jumar who had three legs with ordinary horse hooves but one leg with a cloven hoof that looked like a cow’s.

That’s pretty much it for the jumar, but a quick reminder as we finish talking about hybrid horses and donkeys, if you cross a zebra with a donkey, the resulting offspring has stripes and is called a zedonk, my favorite word.

Thanks for your support, and thanks for listening!