Skip to content

SANParks.org Forums

View unanswered posts | View active topics






Post new topic Reply to topic  Page 7 of 8
 [ 120 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next
Author Message
 Post subject: Re: Zebra
Unread postPosted: Sun Dec 12, 2010 4:39 pm 
Offline
Junior Virtual Ranger
Junior Virtual Ranger
User avatar

Joined: Fri Apr 03, 2009 10:18 pm
Posts: 1541
Location: johannesburg (but soon in Kruger)
ImageLarge


Last edited by Elsa on Wed Jun 25, 2014 2:17 pm, edited 1 time in total.
pic resized.


Top
 Profile  
 
 Post subject: Re: Zebra
Unread postPosted: Wed Dec 15, 2010 10:30 pm 
Offline
Junior Virtual Ranger
Junior Virtual Ranger
User avatar

Joined: Thu Dec 24, 2009 6:03 pm
Posts: 866
Location: Planning to be in kruger again.........
Hope you enjoy
ImageLarge

_________________
Matti

:yaya: CLICK HERE TO JOIN THE FUN FORUM ON SANPARKS

:yaya: Take a look at my Lion TR


Last edited by Elsa on Wed Jun 25, 2014 2:20 pm, edited 2 times in total.
pic resized.


Top
 Profile  
 
 Post subject: Re: Zebra
Unread postPosted: Tue Dec 21, 2010 2:05 pm 
Offline
Junior Virtual Ranger
Junior Virtual Ranger
User avatar

Joined: Fri Apr 03, 2009 10:18 pm
Posts: 1541
Location: johannesburg (but soon in Kruger)
nice pics mattib :clap: :thumbs_up:


Top
 Profile  
 
 Post subject: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Mon May 16, 2011 6:13 pm 
Offline

Joined: Fri Sep 18, 2009 11:23 am
Posts: 5
Many wildlife guides confidently state that temperature differences between the black and white stripes on a zebra set up convection currents that help to control its body temperature.

Does anyone know where this comes from ? - an internet search of the scientific literature does not provide any sources at all.

Or is it a modern version of a just so story ?

Peter Apps


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Mon May 16, 2011 7:33 pm 
Offline
Junior Virtual Ranger
Junior Virtual Ranger

Joined: Tue May 19, 2009 7:47 am
Posts: 192
Location: Amanzimtoti, KZN, RSA.
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 ?


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: 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


Top
  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Wed May 18, 2011 6:39 pm 
Offline
Virtual Ranger
Virtual Ranger
User avatar

Joined: Wed Jan 02, 2008 4:57 pm
Posts: 3183
Location: Randburg, SA
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


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Wed May 18, 2011 7:06 pm 
Offline
Legendary Virtual Ranger
Legendary Virtual Ranger
User avatar

Joined: Sat Oct 06, 2007 7:05 am
Posts: 7414
Location: Back home in the caravan at Malelane camp, KNP
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 gate leaflet? Do you KNOW the regulations?

Completed over 5 years in Kruger in my caravan.

If I were normal I wouldn't be me!


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: 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:


Top
  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Wed May 18, 2011 7:37 pm 
Offline
Legendary Virtual Ranger
Legendary Virtual Ranger
User avatar

Joined: Sat Oct 06, 2007 7:05 am
Posts: 7414
Location: Back home in the caravan at Malelane camp, KNP
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 gate leaflet? Do you KNOW the regulations?

Completed over 5 years in Kruger in my caravan.

If I were normal I wouldn't be me!


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Mon May 23, 2011 4:47 pm 
Offline

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


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: 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:


Top
  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Tue May 24, 2011 9:23 pm 
Offline

Joined: Wed Jul 23, 2008 8:50 pm
Posts: 175
Location: JHB, Gauteng
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


Top
 Profile  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: 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).


Top
  
 
 Post subject: Re: wildlife myth ? zebra stripes and temperature control
Unread postPosted: Wed May 25, 2011 1:19 pm 
Offline

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


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 120 posts ]  Go to page Previous  1 ... 4, 5, 6, 7, 8  Next



Who is online

Users browsing this forum: No registered users and 1 guest


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot post attachments in this forum

Powered by phpBB © 2000, 2002, 2005, 2007 phpBB Group

Webcams Highlights

Addo Nossob Orpen Satara
Addo Nossob Orpen Satara
Submitted by ritad at 13:28:30 Submitted by Foxy at 14:17:58 Submitted by Leanawel at 15:29:03 Submitted by Mrs. S.K.L.Gauntlett at 08:53:55