Saturday, 26 September 2015

The quaggas' coat colour variation

The 23 preserved quagga skins tell us that there was quite considerable variation regarding stripe reduction in this animal. This is not only an interesting fact for itself but also of importance for the Quagga Project. So I tried to capture this colour diversity in one picture, so that we can see it at one glance.
I decided only to use the skins as a reference. There are plenty of old drawings depicting quaggas, but most of them are from a time after its extinction. And those that might be contemporaneous are, just as many the others, mostly just copies of the widely used photo of the mare at London zoo (by the way,  I decided not to include the London mare, which is identical with the Edinburgh skin, because I already did an illustration of that specimen and it does not differ substantially from the other quagga individuals). The webpage of the QP project provides a nice overview over all preserved skins with background information. A quick google research will result in more pictures of the respective specimen. 
However, I did not include all of the skins in my drawing. For the simple reason that many of them do look much alike and I did not want the image to become all too large. Therefore the relation of the individuals with the weaker stripe pattern and the stronger stripe pattern is not exactly the same as in the preserved skins, because the excluded individuals are mostly of the weakly-striped type. So the latter was the prevailing one, probably by far.

While the skins give a very good idea of the colour pattern, telling the exact tone was difficult because none of those is younger than 132 years (today). Therefore, all of them must be bleached today (I consider it very likely that the Berlin specimen is bleached as well, eventhough the QP webpage speculates it is not). So it is not easy to say when stripes were deep black or just dark brown, and if the neck and head region was always black-white or maybe striped in a dark brown and light brown pattern. So I used the hair on the legs as reference, which were probably always white in life. So if the hair of the space between the stripes was the same colour as those on the legs, they probably where white. And for black, I used the colour of the dark stripes on the mane as reference. I had to speculate about the shade of the background colour in the Frankfurt, Tring and Mainz (female) specimen. I am not sure if it really was that light on the trunk. But mostly the skins were sufficient to get an overall idea of the colour. But for the brown regions, it was not easy to tell which tone they had - chestnut, dark brown, orangish? So I had to guess and preferred a chestnut-like colour (note that I use that word in its universal meaning, not its meaning as a horse colour). 

It was tempting to arrange the specimen as a kind of colour pannel and therefore suggesting the stripe pattern reflects an ecological cline within the quagga, as it is hypothized by some. But unfortunately, it seems that the actual localities where the animals have been obtained have not been noted or are not known in most cases. That makes it impossible to test this hypothesis, as long as no research has been done to find out the respective origins of the skins. It would be a small sample size anyway. 

Doing these drawings confirmed my notion I have done several times already. While the reduced stripe pattern on the trunk of the quagga and the Rau zebras of the QP sometimes looks much alike, the reduction of stripes follows a different pattern on the anterior part of the body. The stripes on neck and face are almost always thicker than the space between them, sometimes more than twice as much. In most of the Rau zebras, the stripes on the neck region seem not to be thicker than in other Burchell's zebras and often have "shaddow stripes" (as some quagga did), which are not counted in the QP's scoring system. The stripes on the head of some Rau zebras are very reduced, creating much white space, while the stripe pattern on a quagga's had is actually to be called intensified.

The way of stripe reduction in Rau zebras resembles that of specimens like Darmstadt, Mainz (male) and Munich. In other cases, such as the Tring specimen, the Rau zebras have a similar pattern but it is not that "squiggely". The stripes of the specimen from Berlin and Amsterdam seem to be numerous but they get smaller and their contours smoother, and their colour continues to merge with the background towards the end of the trunk. Some quaggas, on the other hand, have stripe patterns that I think do not occur neither within Rau zebras or other living Plains zebra populations, such as the Basel and Frankfurt specimen, which have these broad, horizontal and smooth stripes, regularly arranged along the trunk. Other cases, such as the female Mainz specimen or that at Vienna (not included in the drawing) show striping to an extreme extent in a way that I have not seen it in living P. zebras yet. Again in a kind of "squiggled", or irregular somehow. 

The explanation for that is simply that the quagga had some unique traits, which would be the result of population genetics in any way if the quagga was just the end of a cline or a separate population. Nothing would hinder new traits to evolve.

I also have the suspicion that the mane of the quagga was a few centimetres shorter than in other P. zebras. It looks like this is the case in all skins. That might be due to preservation, but the photos of the alive mare at London zoo also show an animal with a comparably short mane. Measurements of the mane length in the specimen might provide some insight, it would be interesting to have this suspicion confirmed.

1 comment:

  1. nice research. I had no idea there were so much color variations...