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Counting technique

How does one use photos to "monitor" Grevy’s anyhow? Our field assistant, Hussein, regularly conducts surveys for zebra and livestock on Mpala. Over the course of three days, he covers as much of the ranch’s 48,000 acres as possible by driving a standardized network of roads and tracks.

Along the route, each time he encounters a group of Grevy’s, he attempts to
photograph every individual:

This is a simple task when he encounters a lone territorial male, but can become quite difficult when he stumbles upon a tightly spaced group of 20+ females and their young! He records the number of animals seen, as well as the group structure. We therefore know how many males (territorial or bachelor), females (pregnant, lactacting, or non-lactating), juveniles, and foals of different age categories there were. See for yourself how hard it can be to get a photo (and data) for every member of a group!

This isn’t the only data he collects, however. Each of these sightings is associated with a location, weather conditions, vegetation characteristics, and what the group was busy doing when they were first sighted. This teaches us about the Grevy’s habitat preferences and behavior.

All of this same habitat information is recorded for plains zebra and livestock (cattle, sheep, camels and donkeys) as well. Not only can we use this information to make comparisons across species, but we can see how Grevy’s interact with other competing grazers.


Monitoring Grevy’s Using Photographs

Hi everybody,

You have probably heard a lot about GPS collars and how they can be used to track the whereabouts of critters like Grevy’s zebra (you may recall that we adorned five lucky Grevy’s with GPS collars here on Mpala last June). But these collars are not the only means we have for seeing where animals go and who they hang out with.

Using photo identification software, we can recognize individual zebra from our collection of photos that date back to 2002. Just as a human fingerprint is a unique identifier, zebra stripes patterns are one-of-a-kind and can be recognized by a computer. The photos are stored in a database and ‘matched’ against any new pictures. That way we can tell whether we have a new photo of a zebra or if we’ve encountered one of our Mpala regulars.

Most of these zebra have been ‘captured’ by Hussein Mohamed, our field assistant, during his census loops covering the whole of Mpala. At the moment we have only combed through photographs taken here. However, we are hoping to soon expand the database to include photos taken in other areas, which ought to give us some idea of the larger scale movements of these awesome creatures at a fraction of the cost of a GPS collar.

While we are using this data mostly to investigate zebra movement, habitat preference and demographics, there are some fun consequences of having photographic series spanning multiple years. For example, we have been able to watch this male grow up.  He was first seen on Mpala in 2004 as a fuzzy foal:

He was last seen in November 2009 as a fully grown bachelor. Perhaps we’ll see him acquire his own territory sometime in the near future.


Flower from a morning walk

It’s not just wildlife that sprout up out of nowhere, after it rains!

The other morning I took my camera along on my early morning dog-walk. Here are some of the colorful flowers I saw along the way…

This is the one we callt he "tissue paper flower" because from far away it looks like discarded tissue, but up close it is quite pretty:

A delicate little violet:


Getting monitoring manual

Thanks to everybody who expressed an interest in the monitoring manual! The "ready to use" Version 2 will be available by the end of February. If you want me to send you a PDF copy when that’s ready, send me an e-mail ([email protected]) and I will add you to my list of people to send Version 2 to.

Black and white and red

I happened upon this cartoon the other day, and it seemed appropriate:

Okay, so zebras might not be the Einsteins of the animal world, but they do know how to run away from lions! The last few weeks we’ve been watching a territorial male Grevy’s whom we often see on our drive home. One day he appeared with a huge gash in his belly (caused by a lion?). He was moving pretty slowly and stiffly. The next time we saw him, the wound was dripping pus. We thought he was a goner, but I’ve seen him more recently and he’s looking a lot better. Sometimes it’s amazing how these animals can survive! See this photo I took last year of a female with an old wound – almost definitely from a big predator:

Others, of course, aren’t so lucky. In fact, one theory is that lions are a major cause of Grevy’s decline. Over the last few decades, lion populations have risen in this region. Ranches used to think of lions as a threat to their cattle so they actively hunted them. Now people tend to want lions on their land, since tourists like to see big cats. (Of course the lions still take the odd cow, and ranchers still take the odd lion…). But does the rise in the lion population spell disaster for Grevy’s? I’ll let Siva comment more on that!



Hi everybody,

Apologies for the silence – our internet has been down pretty much the whole week because it’s been snowing in Italy. Yep. When the weather is foul in Turin, something goes wrong with the satellite connection, and we here in rural Kenya lose contact with the outer world!

I’ve had a post ready to put up all week – which I’ll post soon – but meantime, some good news: the river started flowing! This is the Nanyuki River, the one that passes by our house. Earlier in the week it rained on Mount Kenya, the source of the Nanyuki River. Since Wednesday we’ve been hearing rumors that it’s flowing upstream; by Thursday it had reached the adjacent ranch; and by yesterday afternoon a healthy stream of clear, cold water was burbling past the house. Ah, the wonderful sound of rushing water!

Now, we are just waiting for rain. Dark clouds on many afternoons, but still no rain. We wait. It’s something you learn to be good at, here.



These days it’s DRY. It rained once in January, but otherwise it’s been dry since mid-November. The grass is all yellow and gray, the trees have dropped their leaves and, worst of all, the rivers have stopped flowing. The river that passes by us at Mpala is called the Ewaso Ngiro (“brown river”) and this is the first time in living memory that it has stopped flowing.

To get water, cows and other animals have to walk deep into the river bed to drink from remnant pools:

A different river runs by the house where we live; it’s called the Nanyuki River. The Nanyuki stopped flowing weeks ago, and now even the remaining pools are drying out. The river is our main water supply for bathing, washing, toilets, etc. (everything except drinking – we harvest rainwater for drinking). So naturally, we’re starting to worry… anybody know of a good rain dance?

The rains are supposed to start in late March, but here we are, March 26th, and the skies are clear and blue. We can only hope that the clouds will gather soon…

Meantime, Siva has headed off to the US for six weeks of work there. So it’s just me and the critters. The squirrels are totally free these days, but they still spend most of their time near the house. I put out food for them every day, but now I’m having problems with bigger squirrels stealing the food. I’m not sure how to make sure the babies are getting enough to eat. They are still not fully grown and, like a good surrogate mother, I worry about them! I suppose the big squirrels are also feeling hungry, though, since there isn’t much out there for them to eat.

So we all wait for another dry day to go by – hopefully bringing us one day closer to the start of the rainy season.



Hi everybody,

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?


Forensics with feces

Here’s the problem: we still don’t really know why Grevy’s populations aren’t increasing. Hunting – which almost certainly contributed to their decline – has been banned since the 70s. Yes, the occasional zebra is the casualty of illegal hunting, but that alone can’t explain why the population remains so small.

So why aren’t Grevy’s rebounding? One possibility is disease. Very little is known about this in Grevy’s zebra. What parasites do they carry? How are these parasites affecting the zebras? Are some zebras more likely to suffer the effects of parasites than others?

One new project I’m starting will try to answer some of these questions. But how? Dung! It’s not glamorous, but it works. Here’s what you do: you drive around looking for zebras. When you see a group, you watch them intently until the miracle happens and one decides to defecate. Quickly, you photograph that animal and run out of the car looking for the fresh poop. Scoop it up, and you’ve got your sample. What, I wonder, must the zebras think as they watch us running around and picking up what they’ve just dropped?

This is what I’ve been doing in the field the last few days, along with a colleague, Vanessa. Vanessa is an expert on ungulate parasites and we’ll be working together on this project.

What will the dung tell us? Back at the lab, Vanessa and I are looking at the dung samples under a microscope to count and identify the parasites living inside them. Then we’ll send samples to a lab which can tell us whether the zebra has been eating well or not – how much protein it’s getting, how fat it is, etc. Finally, another colleague of ours will extract DNA from the dung.

With this information, we can start asking some deeper questions – like, do animals living in particular areas suffer from higher parasite loads? Do more inbred animals have higher parasite loads? How do parasite loads affect how fat and healthy the zebra is?

It’s definitely not the most fragrant job I do, but hopefully it’s not just a load of… you know….


Life in the menagerie

As if it’s not enough that we’re surrounded by wildlife in our daily work – we have to have a bit of wildlife inside the home, too!

Siva and I had been married for about a week when we brought home our first puppy. He was one of ten pups born to our landlords’ dog (we rent a house here in Laikipia, about 20 minutes’ drive from the Mpala Research Centre, where our work is based). Now, a year and a half old, Arcas is a bit bigger but still nearly as cute (we think) as he was the day he came home. Here’s a picture of me with him:

Keeping a dog is one thing. Raising wild creatures is another. Living out here, you often wind up the clueless but well-intentioned caretaker of some orphaned creature. A couple of months ago, a friend of ours found two baby hedgehogs. Prickly and tightly coiled in their little hedgehog body-sacs, they looked like small sea urchins at the time. Before long they had doubled in size and were ready to see more of the world:

Now we’ve got our latest project: a pair of baby squirrels. Their mother made a nest in a parked car over the holidays, and when the car’s driver returned, momma squirrel didn’t. Siva and I took in the babies – at the time, 15 grams of shivering skinniness. At first they just slept, but it wasn’t very long before they started jumping around, cheeping, chewing everything, and generally being cute with their big, beady eyes. Even the adults of this species – ocher bush squirrels – are pretty darn cute (they are only about the length of your hand), so you can imagine how adorable the palm-sized version is!

For a while I was getting worried about the squirrels. They had lost interest in the milky formula I had been feeding them (a mix of baby formula, baby cereal, and mayonnaise to add more fat). I tried giving them fruits and nuts, various vegetables, peanut butter, even a ball of Acacia sap. Once, they fought over a piece of mango, then lost interest.

I was starting to despair, when, on a whim, I decided to put a dollop of leftover vegetable biryani in their cage. Within minutes, the rice and vegetable mix was gone! I put out another dollop and they devoured it as if they had never seen food before.

Since then I’ve been giving them our typical assortment of leftovers: rice, lentils, mixed vegetables. Never mind all the Indian spices we usually cook with; the squirrels love it! In the last week they have put on more than 10 grams each (now, at 50 grams, they are slightly more than half grown).

Which just goes to show that even the squirrels know it: when there’s curry, it’s time to scurry.