Skip to Content

Zebra

Find, identify and discuss the animals of all the SANParks

Moderator: RosemaryH

100ponder
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 192
Joined: Tue May 19, 2009 7:47 am
Location: Amanzimtoti, KZN, RSA.

Re: wildlife myth ? zebra stripes and temperature control

Unread postby 100ponder » Mon May 16, 2011 7:33 pm

Sorry if I am ignorant, but why do a zebra require such sophisticated cooling while the wildebeest and buffalo grazing next to him are much darker in color without such space-age cooling technology ?

Richprins

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Richprins » Wed May 18, 2011 5:51 pm

Hello, Peter!
I don't know, but an interesting bumshot I posted under "quizzes" a while back shows a clear difference in the consistency of the black and white hairs, shown up by more mud sticking to the black ones...interesting! :hmz:

Maybe the black ones are indeed hotter? :shock:

Image

User avatar
oddesy
Virtual Ranger
Virtual Ranger
Posts: 3183
Joined: Wed Jan 02, 2008 4:57 pm
Location: Randburg, SA

Re: wildlife myth ? zebra stripes and temperature control

Unread postby oddesy » Wed May 18, 2011 6:39 pm

Welcome to the forums Peter :thumbs_up: :thumbs_up:

I once read a paper outlining a number of theories related to the evolutionary fitness benefits of the zebra coat.
The main theories they looked at were that the coat evolved as a predatory avoidance characteristic, making the zebra look bigger, as well as the fact that stripes blend in with tall grass.
Also along these lines is the idea that moving stripes dazzle predators and that the colouration and patterning are hard to pick out in poor light.

The next major theory looks at the evolutionary development along the lines of social benefits ITO group bonding as a marker for grooming and as a means to identify individuals in the group.

Then comes the idea of thermo-regulation which is basically the question you have asked, but unfortunately from an evolutionary and therefore fitness point of view this theory has little merit.

Then lastly my favourite theory.
Where the coat is believed to have evolved as a means of protection from tsetse flies.
This theory has quite allot of evidence to support it and makes logical sense too.
Waage showed experimentally that there was a significant difference between the number of flies attracted to solid colours and those attracted to striped patterns (horizontal).

All of the theories have their advantages and disadvantages and I would list them but a bit short of time.
If anyone has access to the paper the reference is:

Ruxton, G.D. 2002. The possible fitness benefits of striped coat colouration for zebra. Mammal Review 32(4):237-244.
The beginning of knowledge is the discovery of something we do not understand.

"We are what we repeatedly do. Excellence, then, is not an act, but a habit." Aristotle

User avatar
ecojunkie
Legendary Virtual Ranger
Legendary Virtual Ranger
Posts: 9427
Joined: Sat Oct 06, 2007 7:05 am
Location: On the road again......

Re: wildlife myth ? zebra stripes and temperature control

Unread postby ecojunkie » Wed May 18, 2011 7:06 pm

In 'Beat about the bush - mammals' Carnaby states that research has shown more capillaries under the black stripes and this is thought to be to do with dissipating heat. Probably where the guides get the information from. (see page 229)
Smiling is contagious. Start an epidemic today!

Have you read the entrance permit? Do you KNOW the Conditions of Entry?

Completed over 6 years in Kruger in my caravan.

If I was normal I wouldn't be me!

Richprins

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Richprins » Wed May 18, 2011 7:20 pm

Maybe the capillaries developed there to counter the added heat, rather than the other way around? Presumably blood heat-loss would be directed to cooler areas?

Interesting point! :thumbs_up:

User avatar
ecojunkie
Legendary Virtual Ranger
Legendary Virtual Ranger
Posts: 9427
Joined: Sat Oct 06, 2007 7:05 am
Location: On the road again......

Re: wildlife myth ? zebra stripes and temperature control

Unread postby ecojunkie » Wed May 18, 2011 7:37 pm

Hi RP!

I think I also read somewhere the theory about temperature gradients and micro-breezes too, but cannot remember where.

Some of the theories scientists come up with really amuse me - they can never just accept that some things maybe just are like that! And some are just totally contradictory too......try the white marks round eyes to make it easier to collect light and focus....vs the dark marks on a cheetah's face to reduce glare!!!!
Smiling is contagious. Start an epidemic today!

Have you read the entrance permit? Do you KNOW the Conditions of Entry?

Completed over 6 years in Kruger in my caravan.

If I was normal I wouldn't be me!

Peter Apps
Posts: 5
Joined: Fri Sep 18, 2009 11:23 am

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Peter Apps » Mon May 23, 2011 4:47 pm

I cannot find any original reference to proper scientific work on this micro-convection story.
This rather strengthens my suspicion that it is a plausible hypothesis that seems eminently reasonable and has some corroborating evidence of a kind;
the different distribution of blood under the black and white areas, but which has never been rigorously tested.
It has the allure of sophisticated science about it, and is more convincing than telling a client that nobody really knows why zebras have stripes.
Before long it becomes a sort of accepted wisdom and before you know it is being repeated on TV and all over the internet, and when it appears in a book - well it must be true, I read it in a book !

For what it is worth, the explanation that I find most convincing is that contrasting black and white stripes allow zebras to see one another under conditions of poor visibility, thus allowing them to stay closely bunched when fleeing from predators at night in clouds of dust.
Zebras are the only species that have this particular anti-predator behaviour, and the only species with black and white stripes.

If anyone does find the original reference, please post the citation.

Thanks again Peter

Richprins

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Richprins » Tue May 24, 2011 8:59 pm

Well, some other species also have stripes, tigers being the obvious example, but probably just camouflage...

The other herbivore that comes to mind is the rare okapi, which has similar attempted stripes along its buttocks, but is related to giraffe!

Kudu and nyala also have stripes!


Curiouser and curiouser! :hmz:

ross hawkins
Posts: 176
Joined: Wed Jul 23, 2008 8:50 pm
Location: JHB, Gauteng

Re: wildlife myth ? zebra stripes and temperature control

Unread postby ross hawkins » Tue May 24, 2011 9:23 pm

Hi Peter

I wasn't aware of this at all, until I read an article about it in a copy of Africa Geographic about research being done into biomimicry and how this can benefit the human world.
But now I cannot find that article for you.

But ye it did pertain to the view that the Zebra strips were a possible cooling system for the Zebra in that the darker stripes allowed the animal to dump heat from these dark stripes.

Sorry its a bit vague without the article I read

Richprins

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Richprins » Tue May 24, 2011 9:44 pm

Thanks, and welcome down here, Ross! :thumbs_up:

Here's an excerpt from the link:

Thermoregulation

The thermoregulatory hypothesis’ basis is that the black and white stripes work together to keep the animal cooler than if it was solid colored (Ruxton 2002).
Through experiments, it was seen that there was no difference in the temperature of striped objects as solid colored objects (Ruxton 2002).
Although the theory of black and white stripes as a cooling mechanism has been dispelled, it is interesting to note that zebras have a stripes of fat that coincide with the black stripes that seem to function as heat absorbers (Elzenga 1992).
As Ruxton believes that thermoregulation is the least plausible explanation for striping and said, “If black and white stripes were an effective method of dissipating heat from structures, then I think that thermal engineers would know about it” (2002).

Peter Apps
Posts: 5
Joined: Fri Sep 18, 2009 11:23 am

Re: wildlife myth ? zebra stripes and temperature control

Unread postby Peter Apps » Wed May 25, 2011 1:19 pm

So, it is fair to summarize that there is no hard evidence that zebra stripes are a cooling mechanism.
The differential fat distribution and blood supply suggest that they could serve that role (and these biological features were not covered by the simple comparison of striped and plain solid objects), but micro-convection will be disrupted by even the tiniest of breezes, and so if there is a significant difference in heat exchange between black and white stripes it is probably due to radiation rather than convection.
It is important to stress though that nobody has ever taken any measurements of heat flow and body temperature that support the thermoregulation theory.
Or, if they have taken the measurements, for some reason they have not published them.

It is time for this myth to die.
The next time you hear a wildlife guide spouting off about it, or see it in a magazine or on the web, please ask them where they got the information.
And put them right, in the nicest possible way of course.

Peter

johanrebel
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 566
Joined: Sun Mar 05, 2006 4:34 pm

Re: wildlife myth ? zebra stripes and temperature control

Unread postby johanrebel » Sun May 29, 2011 10:10 pm

Slightly off-topic, but anybody who wonders how (not why) zebras get their stripes, should read

Shapes. Nature's Patterns: A Tapestry in Three Parts, by Philip Ball.

A bit too complicated to briefly summarize here, except to say that it all boils down to constraints imposed by the fundamental laws of physics and chemistry, which rule out, say, squares and triangles, but not stripes (or spots).

Johan

User avatar
ice
Posts: 391
Joined: Fri Jun 10, 2005 11:42 am

Re: Zebra

Unread postby ice » Sun Jun 12, 2011 10:57 am

what are these zebras doing?

[video]http://www.youtube.com/watch?v=AokjnmM1S80[/video]

yeah, I can imagine they try to watch out for predators - but why do they stand so close to each other? lots of other herd animals position themselves in different directions to look out for threats but I've never observed others so closely together. bonding? or just laziness (I rest my head on your back, so I don't have to carry as much load on my shoulder muscles)?

thanks

User avatar
adw
Junior Virtual Ranger
Junior Virtual Ranger
Posts: 702
Joined: Thu Dec 28, 2006 3:30 pm
Location: Back Home

Re: Zebra

Unread postby adw » Thu Jul 07, 2011 4:06 pm

This young (sub-adult) Zebra stood out in that it had a magnificent mane.

Image
Rhino Poaching - Highlight's man's stupidity and greediness.

User avatar
Impisi08
Posts: 204
Joined: Thu Mar 02, 2006 7:40 pm

Re: Zebra

Unread postby Impisi08 » Tue May 08, 2012 4:24 pm

Image


Return to “Mammals”