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You can head to bespokepost.com/scishow20 and use code SCISHOW20 to grab your “box of awesome” and get 20% off your first box. [ intro ] When you think of hybrid animals, there are a few examples that probably come to mind, like mules or ligers. But both of those hybrids couldn’t exist without humans.

For example, lions and tigers, they do not live in the same places, so they would never have a chance to make a baby liger in the wild. However, that doesn’t mean that hybridization is always a human-caused phenomenon. Quite the opposite - there are wild hybridizations happening all the time!

And these wild hybrids can teach us a thing or two about the kind of pressures that cause closely related animals to cross the species line, and even give insight into how environmental changes might be pushing species to change, as well. In some cases, it can even be the first step in the formation of a new species. So here are five weird, wild-observed hybrids that not only are very cool, but actually have something to teach us, too.

Our first hybrid is the weird baby of two already weird parents - the beluga whale and the narwhal. If narwhals weren’t bizarre enough on their own as the unicorns of the sea, at least one individual decided to make things even weirder by breeding outside their species. And this unconventional crossing created an offspring with completely different adaptations from either parent!

Narwhals and belugas are both found in the frigid waters of the Arctic Ocean, and their mating habits, like a lot of their other habits, are pretty mysterious. After all, they typically, you know, do it under a thick layer of sea ice in the spring, making it pretty hard to study them in the act. So any clues we can get about what they’re doing down there go a long way.

And in this case, we ended up with two clues in one. When a biologist spotted a skull in an Inuk hunter’s collection in Greenland in 1990, it didn’t fit the bill, er, jaw, of either species. The hunter described seeing two other unique-looking whales along with the one whose skull he saved.

The three mysterious whales were all described as grayish in color, with the tail of a narwhal and the front flippers of a beluga. All these whales were killed, and the skull was all the evidence that remained of the three. Even so, there was still a lot that the research team could learn from this one weird skull.

DNA analysis confirmed that the animal was a first generation hybrid of a beluga and a narwhal. And after a closer look at its teeth, it turns out junior doesn't really take after Mom or Dad. Belugas have 40 teeth spread over both upper and lower jaws, whereas narwhals have no teeth at all on their lower jaw, probably to make some room for their one to two massive, spiraled tusks.

We also know that belugas and narwhals use their different teeth to eat different foods. Belugas catch fish around 500 meters below the surface, ripping into them with their teeth, while narwhals dive 800 meters or more in search of fish and squid, which they more or less slurp up whole. So what did the narluga have in its mouth?

Well, it had numerous teeth across both jaws, much like a beluga. But some of its teeth were grooved and pointed forward out of the skull, which is how male narwhal tusks grow. The researchers also analyzed isotopes from the narluga’s skull to figure out that its diet was unlike that of either of its parents.

Instead of feeding out in open water, it spent its time munching up grub close to the sediment surfaces of the ocean floor. And that’s probably thanks to its weird shaped teeth, which might not have been suitable for catching food out in the open ocean. Given that all the known instances of this hybrid have already been killed though, it’s hard to know if we’ll see another narluga anytime soon.

Now just as creamy white belugas and tusked narwhals are easy to identify as different species, no one is going to mistake a polar bear and a brown bear as the same animal. Polar bears and brown bears, also known as grizzly bears, eat different foods, live in different places, and of course - they are two completely different colors But it seems like some of those differences might be only skin deep - when they do cross paths in the wild, it turns out they can cross breed, despite their significant differences. Brown bears are found across the northern hemisphere, and in North America, they’re also called grizzly bears.

Grizzlies normally live on the mainland of the United States and Canada but they tend to move around a lot too, following the food sources in summer and fall in order to hibernate in the winter. Thanks to climate change, grizzly bears have been heading further north, and are becoming more common on Arctic Islands, where polar bears also live. In a past video we've talked about a strange instance from 2006, when a hunter was surprised to find that the polar bear he killed wasn’t very polar bear-y.

And genetic analysis of his catch later confirmed it was in fact a wild polar-grizzly hybrid. But the story went beyond this one bear. Researchers then compared the DNA of a number of other bears in the area over the next decade, and found eight wild hybrid bears.

Even more intriguing, all eight of these hybrids could be traced back to the same female polar bear, spread out over three generations. The DNA showed that when it came to males, she had a very specific type. She actually mated with two different grizzly bears over the years to produce at least four pizzly bear babies.

Her hybrid offspring appeared to stick around the Arctic Islands. At least one of her female offspring was fertile and would breed with grizzly bears, not polar bears. So this entire population of pizzly bears was started by one female who seemed to have a thing for her land-lubber neighbors from the south.

Unfortunately, this grizzly-loving polar bear, a long with 3 of her known first generation hybrid offspring, have all been killed. So far there’s no sign that any of her remaining descendants have interest in breeding back with polar bears, meaning that with time, the polar bear genes will likely drop out of the grizzly gene pool. And that means at least for now, the polar-grizz lineage may have reached its end.

But now that we know pizzly bears can exist, and are fertile, we can keep an eye out for more beige baby bears. As we travel down to the tropics from the frigid north, we’re next going to examine a hybrid cross between a species of land animals, and their semi-aquatic cousins, making them the mermaids of their lineage. Much like polar bears and grizzlies, the marine and land iguanas of the Galapagos Islands lead dramatically different lives.

These iguanas made their split about 4.5 million years ago, one taking to the frigid waters, and the other hanging out strictly on firm land. Marine iguanas are the only modern lizards in the world that have adapted to ocean life, feeding almost entirely on algae from the surrounding seas of many of the Galapagos Islands. These amazing swimmers are not particularly graceful on land, but they have to spend a lot of their time there anyway, to warm back up on rocks.

And they mate on land as well - not unlike their cousins, the land iguanas. Land iguanas are actually split into three different species and live over 8 different islands and islets of the Galapagos. They are not enthusiastic ocean swimmers or algae eaters, so they don’t have a great reason to stick too close to the shore, instead hanging out inland where there are plants to munch.

But on one islet, South Plaza, that’s not the case. Since this island is really small, the land iguanas are found closer to the shoreline because there’s not many other places to go. And given the very healthy population of marine iguanas along South Plaza’s shoreline, these two distinct iguanas overlap here more than any other location.

It’s on this island that marine and land iguanas have successfully hybridized, despite their very distant evolutionary split - again, these iguanas have been two separate lineages for 4.5 million years, and can still form hybrids! . The hybrids are similar in size and shape to the land iguanas, but have the unique dark mottled patterning of marine iguanas. A hybrid was confirmed in a 1997 study thanks to DNA analysis, but documented sightings of suspected marine and land iguana hybrids on South Plaza go back to the 1980s.

One hybrid was included in a study as recent as 2018, so these crossovers are still happening on occasion.. The jury however is out on if the hybrid offspring are able to reproduce, but so far that doesn’t appear to be the case. So these Galapagos iguana hybrids will likely remain pretty rare, even in their tiny ecosystem.

Meaning that it will still be quite difficult to see a lizard mermaid - but not impossible. Wild hybridization isn’t always as rare as the examples we’ve covered so far though. For some species, it’s a way of life.

The Australian blacktip and common blacktip sharks have formed multiple generations of hybrids. And this habit of interbreeding may even result in a new species one day. These two species have a lot of overlap in their range in Australia, although they’re pretty difficult to tell apart to begin with.

There are some subtle differences like variation in body and fin lengths, distinct markings, and the number of vertebrae. The similarities between the two species ended up posing a major problem for Australia’s fishing industry. In order for the fishers to fully understand how much each species is being harvested, researchers needed to collect genetic information to tell them apart.

In this case, they looked at mitochondrial DNA, which differs between the species and is passed down maternally, meaning that it should be a simple way to tell them apart. But during their investigation, they kept finding sharks with the mitochondrial DNA of the Australian blacktips, but physical features that better matched the common blacktips, and vice versa. With all these mixed-and-matched characteristics, it was suspected the sharks were interbreeding.

A deeper dive into their DNA analysis confirmed they were crossing the species line, and that their hybridization was pretty extensive. In their study from 2011, 57 hybrid individuals were found in five different locations spread across a range of 2,000 kilometers! Not only were they numerous, but these hybrids were fertile as well, and they backcrossed with other blackfin sharks.

The researchers think this sudden, frequent hybridization might be influenced by a changing environment, and may give the hybrids an edge in multiple ways. We think that hybridization may be beneficial in these sharks because the larger-bodied hybrids are better adapted for cooler water, while smaller hybrids are better-suited to warmer places.. This type of hybridization can shine light on the process of speciation and adaptive evolution.

If interbreeding occurs frequently, instead of just the occasional rendezvous, and the offspring have high fitness, a new species might come out of it! So researchers will continue to monitor the hybridization between these two species, as well as the fitness of their offspring, to find out what the future may hold for these sharks. Our final hybrids involve one very familiar species, the mallard duck.

Who do they interbreed with? … Well Basically, everything. Mallard ducks are doing pretty well for themselves, essentially found all across the Northern hemisphere and beyond. And yes, we’ve helped them become well established, since they tend to fare well in human-altered habitats.

And although we’ve bred a domestic lineage of mallard ducks, they don’t always stay put on the farm. Whether we’re talking about a feral, domestic, or a wild-type mallard, none of them are exactly discerning when it comes to choosing a mate. They’ve been found to hybridize with a whole slew of duck species.

A whopping 39 hybrid mallard combos have been documented! Mallard hybridizations most often happen with closely related species, like with the Mexican duck and spot-billed duck, but more distantly related combos have occurred, like with the red-crested pochard, and even with a greylag goose! And for some birds, frequent matings with mallards can pose a huge risk to their species’ survival.

Mottled ducks are found in Florida, and until recently they were the main ducks in town aside from Donald and Daisy. However, mallards are moving in on their territory, largely due to domestic ducks escaping from farms. And when mallards meet mottled ducks, they don’t waste time with the small talk.

In some of the mottled duck populations, the mottled-mallard hybridization rates are as high as 24%! And one problem is that the gene transfer is really only going in one direction. Mallards are only experiencing a small change in their genetic makeup from hybridization, showing just over a 3% change.

So mallard males may be in pursuit of mottled ducks, but the feelings do not seem to be mutual. Mallard duck males will frequently breed with mottled duck females, e hybrid genes stay in the mottled ducks’ gene pool. Since mottled duck males don’t breed with mallard females as frequently, the gene flow is less of a two way street as it is like a highway on-ramp.

This is a pretty different scenario than two species that are actively breeding back and forth, like the blacktip sharks. Since there's a more equal exchange of genes from one side to the other, it can lead to more stable hybrid zones, where new species may eventually evolve. So the mottled ducks’ population is headed towards getting completely swamped by mallard genes, which could eventually lead to their extinction.

This has already been a major problem for the American black duck, which has been pretty diluted genetically by both wild and feral mallard matings. And mottled ducks are already experiencing major population declines across their range thanks to droughts, wetland drainage, environmental degradation, and hunting, so these guys really don’t need another thing to worry about. We may like to think of species as neat little boxes we can categorize the world’s biodiversity into, but these wild hybrids are a reminder that living things don’t always play by our rules.

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