Did you know narwhals and belugas can reproduce in the wild and create a Narluga hybrid? Scientists found evidence of the Narluga’s existence in Greenland. In this post, we give you an in 3D exclusive first look at the Narluga’s skull, courtesy of the Natural History Museum of Denmark.
They can interbreed! How do we know that?
On 30th March 1990, researchers found an unusual skull in Disko Bay in Greenland. However, it is not the first time humans observed Narlugas. Inuit hunters have known about them for a while.
Narlugas, according to Inuit hunters, look like a mix of both narwhal and beluga skulls. They have a narwhal tail, beluga pectoral fins, and grey body coloration. From DNA analysis, Skovrind et al. (2019) confirmed that the mating between a female narwhal and a male beluga produced a male Narluga. This skull is the first evidence of a hybrid Narluga specimen. It is housed at the Natural History Museum of Denmark (NHMD) in Copenhagen.
Hybrids usually show a dominant phenotype of one of their parental species, meaning their appearance is more similar to their dad or mum. We will soon know if the Narluga is more similar to its father (beluga) or its mother (narwhal)!
The skull of a beluga is very different from the skull of a narwhal. Both species have elongated skulls. Yet, narwhals show a shorter and robust ‘beak’ (rostrum) compared to belugas. Belugas have teeth while narwhals have tusks (which are also teeth). Male narwhals have one (in some rare case two) tusk protruding from the left side of the skull (females don’t usually have tusks). The Narluga has a wider and longer ‘beak’ than a beluga and several horizontal teeth, similar to the tusks in narwhals. This is its strongest characteristic of the strange Narluga’s skull.
To see if the Narluga’s appearance is closer to one of its parental species, scientists have also studied its morphology. You can find exactly how they did it in the last section of this post.
How can mating between beluga and narwhal be possible?
Cetaceans have, for the most part, the same number of chromosomes. Scientists say they are “karyologically” uniform. Indeed, most cetaceans have 44 chromosomes in every cell, and only seven species have 42 chromosomes. This is one of the reasons why they tend to have more hybridization cases than other mammals.
Scientists have recorded 57 cases of hybridization in whales and dolphins. Hybridization usually occurs even between two very close species, like the blue whale and the fin whale (at least 14 known hybrids). It happens more often in dolphins and whales than seals, but it still makes the narwhal-beluga breeding unique!
Species range and migrations
Belugas and narwhals live in the Arctic. Their habitats overlap, especially during the winter migrations towards Disko Bay in West Greenland. The dramatic changes in sea ice due to climate change might help interbreeding between the two species because they live close to each other. It was shown in aerial surveys. Disko Bay is the only right “exchange area” known by scientists for narwhals and belugas at the moment. It could explain why we found the skull in Disko bay. It seems that mama narwhal and daddy beluga met ‘at the Disko’!
Are hybrids fertile?
It is still unknown if Narlugas are fertile. A bottlenose dolphin and a common dolphin hybrid once gave birth to a fertile baby in captivity. The Narluga from the skull scientists found is a first-generation hybrid, and we know that it is an adult from the degree of fusion of bones in the ‘beak.’ What we do not know is if it was fertile or not.
Does the Narluga have different behavioral traits from its parents?
Skovrind et al. (2019) analyzed the chemical composition of the Narluga’s teeth. They found out that its diet was different from its parents. Belugas and narwhals dive to catch fish and squid, while the Narluga’s diet is closer to a bottom feeder. The Narluga must have used its teeth for scraping the sea’s depths to catch prey. Hybrids may have developed their feeding technique, different from their parental species.
Cetaceans are challenging to study because most species spend only a few minutes at the surface to breathe. 3D reconstruction of their bones can thus be useful to study toothed whales’ morphology. It also compensates for the lack of data in certain species. Plus, it gives us access to much more information that we cannot get in the field.
Keep reading to find out more about morphology analyses.
How can scientists study cetacean skull morphology?
Researchers reconstruct the specimens in 3D by using different devices. The most affordable equipment they can use is a good old photo camera. They use a technique called photogrammetry to reconstruct 3D models from a set of photographs.
Then, they proceed in the following steps:
In this way, researchers can take all the measurements directly on the 3D model by placing several landmarks. Landmarks are points of correspondence (with an X, Y, and Z, coordinates) on specific anatomical features. The distance between each pair of landmarks is equal to linear measurement. Then, with many landmarks, we obtain an increased number of measures on the same specimen. Successively, these measurements will be entered into the software for data analyses. This way, the study of the morphology in hundreds of skulls becomes easy!
3D Narluga skull
Footage of the 3D model hybrid specimen (MCE 1356). Courtesy of the Natural History Museum of Denmark (NHMD) – Made by Deborah Vicari
The study of their morphology can be an excellent way to start a PhD linked to marine mammals. Once you have had access to a lot of skulls, it will give you quicker outputs and a broad set of statistical skills!
Come read our other posts on belugas.
- Heide‐Jørgensen, M. P. and Reeves, R. R. (1993) ‘Description of an anomalous monodontid skull from west Greenland: a possible hybrid?’, Marine Mammal Science. Wiley Online Library, 9(3), pp. 258–268.
- Heide-Jørgensen, M.-P. & Laidre, K. Greenland’s Winter Whales: The Beluga, the Narwhal and the Bowhead Whale. (2006).
- Kelly, B. P., Whiteley, A. and Tallmon, D. (2010) ‘The Arctic melting pot’, Nature. Nature Publishing Group, 468(7326), p. 891.
- Preuß, A. et al. (2009) ‘Bear-hybrids: behaviour and phenotype’, Der Zoologische Garten. Elsevier, 78(4), pp. 204–220.
- Skovrind, M., Castruita, J. A. S., Haile, J., Treadaway, E. C., Gopalakrishnan, S., Westbury, M. V., … & Lorenzen, E. D. (2019). Hybridization between two high Arctic cetaceans confirmed by genomic analysis. Scientific reports, 9(1), 1-10.
- Wiig, Ø. et al. (2012) ‘Geographic variation in cranial morphology of narwhals (Monodon monoceros) from Greenland and the eastern Canadian Arctic’, Polar biology. Springer, 35(1), pp. 63–71.
- Zornetzer, H. R. and Duffield, D. A. (2003) ‘Captive-born bottlenose dolphin× common dolphin (Tursiops truncatus× Delphinus capensis) intergeneric hybrids’, Canadian Journal of Zoology. NRC Research Press, 81(10), pp. 1755–1762.