I want to use the next few posts to respond to comments some people have made on the blog.
First, a number of you noticed some of the differences between plains zebra and Grevy’s zebra and were interested to know more about zebras in general.
Isn’t it interesting how well-known zebras are in so many cultures – what’s the first thing you think of when you think of black and white stripes? Or the letter “z”? – and yet, how many people know that there are three different species of zebra in the world?
First there’s the plains zebra – the most numerous and most familiar species of zebra. Plains, or Burchell’s zebras, are the ones you usually see on TV documentaries about African wildlife. There are more than a million of them and they’re found in the savannahs of eastern and southern Africa all the way from Kenya through Tanzania, Zambia, Zimbabwe, Botswana, Namibia, and down to South Africa. There is some variation in their stripe patterns and the habitats in which they’re found, but it’s the same species throughout this large geographical range. Basically, they are the stocky, bold-striped zebra familiar to most people.
The second species is the mountain zebra. This zebra is endangered and only found in a few reserves in South Africa and Namibia. They look a lot like the plains zebra – with bold, broad stripes – but their bellies are white, they have a grid-iron pattern on their back and rump, and their muzzles are thicker and browner than plans zebras’. In terms of behavior, they are quite similar to plains zebras.
Finally, there is the zebra I care about the most – Grevy’s. It’s the largest and prettiest and most interesting of the zebras (I’m not biased 🙂 ). Ancestors to this zebra have been found as widely separated as China, Uzbekistan, and South Africa, so they were once quite a cosmopolitan zebra! It’s thought that they may have evolved separately from the other two species of zebras.
Grevy’s are about 33% larger than plains zebras, with fine stripes and a white belly. They have big, round ears (they’re really cute) and a slightly brownish muzzle. Here’s a photo of several Grevy’s and plains zebras together. The tight group of plains zebras on the right is a harem of females nuzzling each other.
Socially, Grevy’s and plains zebras are quite different. Plains zebras form harems – one male (the stallion) guards and defends a group of females (anywhere from 2 to 12) and their foals. This group stays together, moving as a unit. Sometimes many harems may join together to form large herds, but these herds are usually ephemeral. Males that are unable to gather a harem live in “bachelor” herds – waiting until they have a chance to challenge a stallion for his harem. This type of society is better adapted to plains (and mountan) zebra habitats which tend to be less arid than the areas where Grevy’s live.
Grevy’s, by contrast, have a looser social structure. Females live in groups, but these groups do not always stay the same. The members of these groups may change daily or weekly, or occasionally they last even longer. In the dry lands that Grevy’s live in, females must wander in search of grass and water, sometimes parting ways with their friends. Males who want to mate with females cannot defend any one group – because the group is always changing members! Instead, a male chooses to hold onto a piece of real estate that he knows will attract females. Males will patrol and defend their territories from other males. The picture below shows a typical male posture – head held high, standing guard over his territories (“monarch of all he surveys”?)
Here’s another male standing guard over his territory – battle scarred (see his ears and neck) from fighting off challengers to his land…
By occupying and defending areas with good grass and good access to water, a Grevy’s stallion knows that he has what every girl wants – a safe place to eat and drink and raise her babies!
Finally, an interesting factoid – Equids, the mammal family to which zebras belong, first appeared and thrived in North America millions of years ago. Yet, today all zebra species are found only in Africa! In fact, none of the remaining wild equids are found in North America. Why might that be? And what makes some species – like Grevy’s – more endangered than others?