Cool Headed Oryx - thoughts on new science.

Danger, Vernon doing science. Seriously, I am not an academic, but of course certain things are relevant and as a guide one really wants to be communicating the most correct info available at the time...which is hard if you are working out in the field. Here is something I am just getting to grips with which will have a big impact on how I guide.

The Southern Oryx or Gemsbok, the sub-species of Oryx gazella that we find in Southern Africa must have some specific adaptations to arid conditions. Some of the popular ideas about this, however, appear not to be correct in the face of new studies. Since it affects what I tell people when I am guiding, it was important to try to understand it.

Without going to much into desert ecology, lets just say an animal living in a desert environment has two main problems that feed off each other...dealing with heat and dealing with a lack of moisture. By a long way the best way to deal with heat is through some form of surface cooling through evaporation off the surface of an animal. In mammals...sweating. Works great, but what if you have a very limited water supply...obviously sweating becomes expensive.

Adaptations that relate to dealing with this double problem (heat/moisture scarcity) come in two forms, and again it is a little obvious...gain more moisture and loose less moisture. It may be obvious, but it helps to look at it like that. And of course, the implementation is a little more tricky than the concept. Of course, for a tour guide in the desert these mechanisms are a chunk of our bread and butter, and the more exotic and exciting they are, the better.

Now, a popular idea for many years was that Oryx could do something really amazing...that they could choose to stop sweating and use brain cooling through the carotid rete system. I have been telling this story for years. I love it. But, one small problem with this popular idea is that it appears not to be true.

The idea went something like this - Veins from the nasal cavity cools arterial blood going to the brain in a network of blood vessels called the Corotid Rete. This method of brain cooling occurs in a number of mammals. It was believed that Oryx could simply choose to stop sweating and let their body temperature go, even beyond mammalian norms, and have the brain stay cool enough by using this system.

The idea was proposed based on the anatomy of the brain, not because of temperature measurements. That was mainly because you couldn't measure the brain temperature of an animal living outside for a period of time as it went through it's normal duel with the environmental conditions. But now it is possible. Small data loggers can be inserted into the brain and give an accurate picture of just how much this cooling actually does.

What they are finding is that the cooling effect is minimal, and not enough to allow Oryx to stop sweating. What's more, the body temperature of the animals are higher at night, rather than in the day time. The Corotid rete does assist in survival in hot, dry places, but most likely, I take it, for periods of high activity, such as running away from a predator.

This is my understanding. I don't have good access to scientific literature (and I am not cleaver enough to always understand these things in depth). This is mainly made from reading between the lines (or reading the abstracts of papers). If anyone has any good knowledge on this or an accurate popular article, please (please, please, please) let me know...I would be most interested.

Note: I didn't intend to write a blog post about this when I was first reading about it, and can't remember all the links I visited. I started out just trying to understand the functioning of the theory as it was, a little better. It soon became apparent that the whole thing was based on a number of assumptions, and so I started trying to dig a little deeper.

The carotid rete and artiodactyl success
The eland and the oryx revisited: body and brain temperatures of free-living animals
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Meiring Borcherds said...

Very interesting Vern, I will re-post this and see if some one can send you good info. Just goes to show that science is a living thing and can change over time as time is not constant.....

John said...

If I am right, you left a comment on my blog regarding the two Oryx fighting at Etosha. Your monica was Namib Naturalist, but the link did not allow me to go anywhere. Think I have found you via google; am I correct? Will post more Namibia shots over the coming weeks.

Vernon said...

Yes, it's me. I guess I have disconnected my blogger profile because, but I guess I can just connect it again. I don't reference it in my blogs anymore, I wasn't thinking about comments.

My name, as you probably gathered, is Vernon. I use Namibnat or names like that only because often my own name is taken. I much prefer using my own name and usually leave comments on blog posts with my name and specified URL.

Anyway, I'll check out some of your pics if I get a chance.