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Archive for the ‘Cetaceans’ Category

narwhal hybrid.png

a: beluga skull b. “narluga hybrid” c. male narwhal skull.

In the 1980s, an Inuit subsistence hunter in Greenland killed three gray whales that looked suspiciously like belugas at first. However, they were oddly gray. The fins resembled a beluga’s, while the tail looked like that of a narwhal.

The hunter kept one of the skulls, eventually donating it to science, where became the property of the Greenland Fisheries Research Institute. A scientist working for that institute, Mads Peter Heide-Jørgensen,hypothesized that this skull came from a hybrid between a narwhal and a beluga.

It was only today that a study was released in the journal Nature that revealed that this whale was indeed a hybrid. The DNA analysis revealed that male beluga mated with a female narwhal to produce the creature.

The skull was quite strange. Belugas have 40 homodont teeth. Narwhals are toothless, except males. The males have one really long canine tooth that sticks out as a tusk. Sometimes, they have two, but most have only one true tooth. It is spiraled like what is expected form the mythical unicorn. They do have only a few vestigial teeth.

The hybrid had 18 teeth, many of which were pointed out horizontally and spiraled like the vestigial teeth of the narwhal.

Isotopic analysis also revealed that the hybrid had a different diet from either parent species, both of which catch fish or squid in the open water. The beluga hunts fish at depths of up to 500 meters, while the narwhal hunts fish or squid at depths exceeding 800 meters. The isotopic analysis revealed that the narluga was eating mostly benthic prey, which means it was eating mostly shellfish from the sea floor.

So this study raises so many questions. Analysis of the narwhal genome revealed that gene flow between the two species stopped between 1.25 and 1.65 million years ago. The initial split happened around 4 million years ago, and that study thought that an viable hybrids would be unable to reproduce. However, the authors of the study cautioned that a larger sample size of individual narwhal and beluga genomes from across their range might reveal more recent dates on when gene flow stopped (if it did at all).

So it is not entirely clear that this hybrid would have been sterile, but we also have no further evidence of hybrids anywhere else.  It is quite possible that these hybrids could be fertile, and if they are, climate change could cause the eventual genetic extinction of the narwhal.

The morphology and feeding behavior this odd whale might point to the origins of the narwhal. Perhaps the ancestral narwhal was a benthic feeding whale that later lost its teeth to become a whale that hunts squid and fish at great depths with an almost toothless mouth.

Having teeth like the hybrid is a great adaptation for this particular diet, because the forward pointing teeth can poke around and dislodge shellfish more easily.

If these hybrids are fertile, then one could see the eventual development of a hybrid whale species that has its own niche as a benthic feeder in the arctic.

It is an amazing find, and chances are there will be more discovered. Further, as scientists examine genomes from belugas and narwhals from a wide geographic distribution, we might see evidence of some hybridization.

Hybridization could also increase genetic diversity in narwhals, but if these hybrids must eat a fundamentally different diet than narwhals do, it might become difficult for these hybrids to add their genes to narwhal populations. They just cannot hang out for extensive periods of time, before they have to split off and engage in divergent feeding behavior.

So this discovery does generate lots of speculation and raises several important questions that need to be addressed.

Pretty cool.

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new peru whale

A lot of the popular reaction to new discovery  of a 42.6-million-year-old amphibious whale in Peru has focused on the fact that this whale had four legs.  Yeah, four-legged amphibious whales first appeared in South Asia 50 million years ago, with most famous one being Pakicetus.

However, this reaction to this new discovery merely tells me that most people are unaware of how much we know about whale evolution.  Whales and dolphin, in case you didn’t know, are actually a subset of artiodactyls.  Artiodactyla is the same order that includes pigs, sheep, antelope, giraffes, cattle, and camels, and when scientists began to classify whales and dolphins this way, some creationist wag posted a strawman that scientists believed that whales evolved from cows.

No. Whales and dolphins are actually derived an ancestor that was very close the common ancestor of hippopotamuses. The clade that includes hippos and whales and dolphins is called Whippomorpha.  Literally, they just combined the word “whale” and “hippo” to create this name.

Hippos are actually much more closely related to whales and dolphins than they are to other artiodactyls, and because whales and dolphins are so well-nested in Artiodactyla, some experts now call the order Cetartiodactyla, combing the word “Cetacean” with the word “Artiodactyla.”  I personally don’t do this because we could just as easily renamed Carnivora “Pinnipedavora” because phocid seals, otariid seals, and the walrus are all derived from caniform ancestors.

Whales and dolphins, though, are derived from land-based artiodactyls. They are not derived from cows or any ruminants, though. Ruminants are highly specialized plant-eating mammals, which have a multi-chambered stomach to deal with the hard cellulose and fiber of their diets.

50 million years ago, though, there were many omnivorous and carnivorous artiodactyls.  Mesonychids, which were quite numerous millions of years before whales evolved, were essentially artiodactyl wolves that ran down their prey on hoofed feet.  When I was first reading about whale evolution as a teenager, it was believed that whales derived from Mesonychids, but now we have a more complete view of their evolution.

Pakicetus first appeared in the fossil record of South Asia. It was a sort of a semi-aquatic artiodactyl wolf, which then gave rise to Ambulocetus, a sort of mammalian crocodile-like creature.

From South Asia, these primitive whales entered the sea, and over time, they evolved into more and more specialized animals.

Four-legged whales have been found North America and Africa, but there has long been a debate about how whales dispersed from South Asia into the oceans of the world.

The discovery of this new extinct whale species called Peregocetus pacificus in Peru suggests that South Asian amphibious whales entered the now defunct Tethys Sea (which included the Mediterranean but went much further east), swam down around the Atlantic Coast of Africa, crossed the narrow distance of the Atlantic to enter South America, and then colonized North America. This colonization took about 10 million years after the whales began to become creatures of the water.

So yeah, we know a lot more about whale evolution now because of this discovery, and now the public knows that four-legged whales really were a thing.

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Source.

The documentary is in German, but I don’t know where this was filmed.

Tiger sharks and blue whales are both wide ranging species.

This is not a big blue whale. It’s only about 60 feet long!

Nature isn’t always so nice.

This would be like a human being eaten alive by pack of weasels.

Not a great way to go.

 

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When I was growing up, I spent a large part of my summers at the beach. My aunt and uncle had a condo on the Outer Banks, and my family used to spend three weeks a summer there. We would go when school was out for the summer, and then we would go again for the Fourth of July. We would make a final trip before school started again. It was a way to spend the summer– part of it in the bucolic countryside of West Virginia and part of it only sea-salted air of the Outer Banks.

I am not a person who sunbathes. I don’t think we humans are meant to be walruses, hauling our bodies onto the shore and letting the sun beat down on us. I am a beach comber, and I have always been interested in what animals use the littoral zone. I am pretty good at identifying the shorebirds of the North Carolina coast, and I have seen sea turtle tracks that reach from the surf to their nesting places on the beach. However, to get to really experience these things, I would always walk as far as  I could from the public bathing areas and the resorts. Only the intrepid would ever go so far, for the sand flies and mosquitoes tended to be rather strong at certain points during the summer and narrow barrier islands are rather hard to negotiate during high tide.

I have seen lots of interesting things wash ashore.

I remember walking along the beach during what we call “spring break” in the US. It actually happens in the late winter. In fact, it was snowing in West Virginia when we left. However, the beach in winter can be a remarkable place. I saw lots of cormorants diving among the waves. I also watched large numbers of brown pelicans dive into the water. Now, in the summer months, I rarely saw cormorants, and the number of pelicans diving from the sky was much lower.

But that was not the most interesting bird I saw on that trip.

I saw a dead white bird that had washed ashore in a raft of seaweed. When I approached it I could see it was a northern gannet, a bird I had only read about but had never seen. It was too bad that I had come across a dead specimen rather than a living one.

But even that bird wasn’t the most interesting thing I’ve found while beach combing.

One summer I was walking along the coast early in the morning. The tide was out, but at the narrow points on the beach the surf was beginning to come in. The surf was starting to nip at my heels as I passed the public bathing area.

As soon as I was through, the beach opened up in all its white sandy glory. Joggers were running down the coast. Some of them at the far end of the island were but tiny specs.  The sea breeze was blowing gently. The gulls were lining the shore, while the turns squabbled over their position on the beach. A skimmer hovered over the surf, occassionally lowering its thick bottom jaw into to the water to troll for small fish. All was as beach on the Outer Banks should be.

As I walked on, I saw a grey shape looming ahead. I noticed a mother and a daughter stopping to look at it. They had baskets full of shells, and I assumed they had found some interesting shells around that grey lump of flotsam or jetsam.

I continued on, keeping my eye peeled for the dolphins I had seen the day before. They were Atlantic bottlenose dolphins. I had often seen them foraging just a few yards off shore.  The day before the dolphins had come in really close. I surmised that there had been a shoal of small bait fish close to the coast that day, and the dolphins had cornered them up against the beach for easy picking.

As I kept walking, I noticed that the grey lump had a tail. In fact, the tail had a fluke, just like a dolphin. Could it be a dolphin that beached on the shore?

I  hastened my pace. I did not full out run, because I knew that if I started running towards the shape, it would definitely draw attention to it. So I kept walking, just at quicker pace.

When I got close enough to the grey lump, I realized that I had come across something really interesting. It was a cetacean. And unfortunately, it was quite dead.

However, it was not a bottlenose dolphin.

It head was thick and rounded, much more like a whale than any dophin I had seen. Its bottom jaw was tiny by comparison. Its jaw was lined with thick, sharp teeth.

I knew what I had come across. A few months before, I had purchased a guide book to the marine mammals of North America. I had learned that there were three species of sperm whale. One was the cachalot, the great whale that grappled with giant squid many fathoms down below the surface. It was the species immortalized in Melville’s Moby Dick.  The other two were much smaller. The one most common on the East Coast is the pygmy sperm whale, and it is better known for being a light shade gray and a more conical head shape. The other species of sperm whale is also small. It is called the dwarf sperm whale. It has a squarer head and darker coloration. It also has a larger dorsal fin in proportion to its body size.

I knew that I had come across a pygmy sperm whale. I was quite surprised. I ran back to tell my parents, who followed me closesly back to the whale. By then a crowd had gathered aroud the whale. And suddenly found myself like George Costanza, an impromptu marine biologist. I explained the taxonomy of the species and how it was related to the bigger sperm whale that everyone knows. I explained how its jagged teeth helped it catch squid, which are its primary food source.

I suppose someone from Marine Fisheries collected the animal. It wasn’t there when I went on my afternoon excursion down the beach.

The whale had a large gash on its head. I had guessed that it had been cut by teh propeller of a boat, which had mortally wounded the whale. It had then staggered in closer to shore, hoping that coming closer to shore would keep the sharks at at distance.

But then I began to wonder about the dolphins. Perhaps the dolphins had been attracted to the whale’s distress cries and had come to its aid. Maybe they hadn’t bunched up a shoal of bait fish against the beach after all.  Perhaps the propeller had damaged the whale’s melon, and it couldn’t find its way back to deeper water. Or maybe its brain was damaged, and it went to shore to die. The dolphins could have been trying to lead the whale back to deeper water.

My suspicions were furth substantiated when I read about this Indo-Pacific bottlenosed dolphin in New Zealand. This dolphin had helped a female pygmy sperm whale and her calf that came to close to the shore. The dolphin guided the whales back away from the beach and into deeper water. Perhaps that was what the Atlantic bottlenose dolphins were doing that day in North Carolina.

So a pygmy sperm whale is the most interesting thing I’ve found on the beach. It’s not the Montauk Monster, but it was far more interesting.

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