Above: A griffin is a mythological creature with the head and wings of an eagle, and the body and tail of a lion. Image © iStock, ganjarlex

Griffins, sphinxes, hippogriffs, centaurs, mermaids and more! You’ve probably encountered plenty of mythological creatures in books and movies. But could these strange creatures actually exist? Could an eagle and a lion or a human and a horse actually mate? And could they produce a griffin or a centaur?

It is possible for animals from two different species to mate. The offspring is called a hybrid. For example, you might be familiar with mules, which are hybrids of horses and donkeys. Other hybrids include camas (camels and llamas) and zorses (zebras and horses), as well as ligers or tigons (tigers and lions).

But even though hybrids are possible, they’re relatively rare in the animal world. Only about 10 percent of animal species can produce hybrids. There are simply too many conditions that animals from different species need to meet in order to successfully mate. And even when they do succeed, their offspring usually can’t reproduce.

Did you know? Most hybrids get their names from a combination of their parents’ species’ names. Words that come from combining two other words are called portmanteaus.

Reproductive Isolation

So why are hybrids so uncommon? What’s preventing an eagle from mating with a horse to produce a hippogriff? In many cases, animals from different species simply can’t get together to mate. In other words, they can’t produce a hybrid because they’re reproductively isolated.

So even if you really wanted a hippogriff, you would have a very hard time getting an eagle and a horse to mate. Here are some of the reasons why.

  • Behavioural isolation: The eagle and horse would have to be attracted to each other. But eagles and horses have different mating rituals. Eagles like to put on an aerial show, while horses like to sniff and nuzzle each other. Species that can’t mate because they have different mating behaviours are behaviourally isolated.
  • Temporal isolation: The eagle and horse would have to want to reproduce at the same time. But eagles tend to mate in winter, and wild horses tend to mate in spring and summer. Species that can’t mate because they have different mating seasons are temporally isolated.
  • Spatial isolation: The eagle and horse would have to physically meet. This means they’d have to live in the same environment. But eagles like to soar high above clouds, while horses enjoy keeping their four legs on the ground. Species that can’t mate because they live in different environments are spatially isolated.

Did you know? Usually, the first half of a hybrid’s name represents the father, and the second half represents the mother. Now you know the difference between a liger and a tigon!

Physical and genetic compatibility

But let’s say the horse and eagle were attracted to each other, were both in the mood, and were in the same place at the same time. Before they could start making hippogriffs, they would still need to meet some other important conditions.

  • Physical compatibility: The horse and eagle would have to actually mate. In other words, they’d have to have sex. But an eagle and a horse have very different morphologies (physical structures) that would probably prevent their sexual organs from fitting together!
  • Genetic compatibility: The two animals’ gametes (sex cells) would have to be able to combine their genetic information. For example, an eagle’s egg would have to fuse with a horse’s sperm to create an embryo. Furthermore, the resulting DNA instructions would have to be clear.

So even if the horse and the eagle succeeded in making an embryo, the combined genetic instructions created from their DNA might not make any sense. And without proper instructions on how to develop, the embryo wouldn’t be able to grow into an organism.

Those are some big obstacles to overcome. You can see why there aren’t a lot of hippogriffs flying around! But why are some hybrids fairly common and others virtually impossible? Basically, the more similar two species are, the more likely it is that their mating behaviors, anatomy and DNA will overlap. And that all makes them more likely to create a hybrid baby!

Sterility and hybrid speciation

But what if they tried really, really hard? For the sake of argument, let’s say that an eagle and a horse were able to mate and produce a hippogriff. Would you start to see a whole lot of other hippogriffs flying around? Probably not, because hybrids tend to be sterile. In other words, they can’t make babies.

It’s not clear exactly why hybrids are usually sterile, but the problem may be related to impaired meiosis. Meiosis is the process by which gametes are created. During meiosis, chromosomes must pair in such a way that they’ll be evenly distributed in the gametes they create. Think of this as a puzzle: the pieces must fit together. Without proper pairing, certain vital genes (or puzzle pieces) might be missing in certain cells. The puzzle can’t be completed, and no viable organism can come from these cells.

However, if a hybrid is fertile, it has a chance of becoming its own species. If it can thrive in its environment, it has a good chance of surviving to create more of its kind. This process is called hybrid speciation.

Did you know? Hybrid speciation is more common in plants than animals.

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So there you have it! Under just the right conditions, it might be possible to create a griffin, a sphinx or a centaur. But it’s extremely unlikely to happen. There are simply too many behavioral, anatomical and genetic differences between animals from different species that prevent them from mating. And even when hybrids are born, they tend to be sterile. But don’t let that stop you from enjoying your favourite books and movies!

Learn more!

What is the best way to define species? (2016)
Linda Jewell, CurioCity by Let’s Talk Science

The role of meiotic drive in hybrid male sterility (2010)
Shannon R. McDermott & Mohamed A.F. Noor, Philosophical Transactions of the Royal Society B: Biological Sciences 365

Hybrid (2009)
Encyclopaedia Britannica

Hybridization and Gene Flow (2008)
Laurie Stevison, Nature Education 1

Moushumi Nath

 I am a graduate student at the University of Toronto in the Department of Physiology. I study how the brain functions in learning and memory! This means I get to play with mice, visualize the brain, and listen in on how neurons communicate with each other. My interests in learning and memory began during my undergraduate degree at McGill University, where I completed a BSc in Honours Neuroscience. I look forward to continuing to engage in the fields of science communication and science policy. Sidenote: I am an avid free-food scavenger.

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