Symbiotic relationships are common in the Serengeti. They fall into two main types, mutualism, whereby both partners benefit from one another and commensalism, whereby one partner benefits from the actions of the other but the other partner is largely unaffected or unharmed. I wrote recently of oxpeckers and large herbivores, large herbivores provide food in the form of ticks for the oxpeckers and oxpeckers provide a cleaning service for the large herbivores, a good example of mutualism. Birds such as cattle egrets that follow buffalo around to catch the invertebrates the buffalo disturb as they graze is an example of commensalism. Of course it is not just animals that have symbiotic relationships; my blog last week on termites and mushrooms was another example of mutualism.
So what about zebras and wildebeests? We see them all the time on Snapshot Serengeti in mixed herds, grazing peaceably with one another. Is this just coincidence or is this a form of symbiosis?
It is actually hard to say and of course that is why labelling things, especially behaviour is often tricky.
Zebra and wildebeest are both grazers meaning they mostly eat grasses but that doesn’t mean they share the same diet. They preferentially eat different parts of the plants that they consume. Zebras are quite content chewing longer tougher grasses where as wildebeest prefer shorter, more tender shoots. This partition of resources means they can quite happily graze side by side with out exerting pressure on each other.
Another good reason to team up is the extra safety that numbers provide. Not only do more ears and eyes provide better early warning systems but the odds of the individual being targeted by a predator are reduced when there are greater numbers to choose from. Apparently zebra have better eyesight but wildebeest have better hearing so the two complement each other.
There could be another reason. Our very own Meredith Palmer just published a paper about interspecies reaction to each other’s alarm calls, you can read it here: https://www.sciencedirect.com/science/article/pii/S0003347217304207
She found that zebra, wildebeest and impala recognise each other’s alarm calls but that they did not always respond in the same manner. When zebra sounded the alarm all three herbivores reacted strongly but when impala gave the alarm zebra where likely to ignore it, or assess the relative danger themselves. It seems that this varied response is down to predator size. Impala are prey to a wide range of smaller predators that would not be able to handle a mammal the size of a zebra, so when impala give the call it doesn’t always signal danger for the zebra. However when a zebra, the largest of the three herbivores sounds the alarm, whatever it has seen will probably be able to take down the wildebeest or the impala too so it’s prudent that all three scarper.
It is an interesting reaction and maybe wildebeest hang out with zebra because they are more trustworthy alarmists. I am not sure that the companionship of zebra and wildebeest can be classed as symbiotic I think it is more of an interaction due to a shared habitat but it seems that on some level they can benefit each other.
Snapshot Serengeti has around 225 camera-traps laid out in a grid in the heart of the Serengeti National Park. They have been there for around 7 years and make up one of the longest running camera-trap monitoring projects in the world. Snapshot was launched on the Zooniverse portal in December 2012 and has inspired many more similar camera-trap projects from around the world. So Happy 5th Birthday to us, may there be many more to come.
There is no doubt that camera-trapping has gripped the hearts and imagination of both scientists and the public. Eight years ago when I first used camera-traps I had to explain them very carefully to friends and family as they had never encountered them, these days references to camera-traps appear in popular press articles and wildlife documentaries and most people have a basic idea of their use in conservation.
It was K. Ullas Karanth, an Indian wildlife zoologist, who is credited with pioneering the use of camera-traps as scientific tools in his study of tigers in the 1990’s. In the last two decades the technique has advanced at a hugely fast pace and has revolutionised the study of elusive and seemingly well known species alike. It is a scientists dream to observe animals without being present yourself to influence their behaviour.
But looking at the history of the discipline I can across many references to much earlier work using camera-traps. Back in 1927 National Geographic published an article by Frank M Chapman titled delightfully “Who Treads Our Trails”. The piece opens with this amazing paragraph
“If there be any sport in which the joys of anticipation are more prolonged, the pleasures of realisation more enduring, than that of camera trapping in the Tropics I have yet to find it!”
This guy would have loved Snapshot Serengeti. This is most likely the very first scientific paper to report on using camera-traps all be it very different cameras. His rig involved a tripwire the animal steps on rigged up to the camera shutter and bowls of magnesium that will explode and create the flash needed to illuminate the animal at night time. It seems incredible now that this would be allowed considering today’s ethically minded ethos but the author himself points out that the alternatives to studying animals could include using dogs or trappers to catch an animal or even poison bait. He decides he wants a census of the living not a record of the dead and so the idea of camera-traps for scientific study are born. He drew heavily from the work of George Shiras who published the first pictures taken by remote camera back in 1906 (also in National Geographic). George Shiras took the pictures for the pictures sake only later becoming involved with conservation but Frank Chapman was a true scientist.
Obviously the technology has changed a lot and the loud noisy explosions that accompanied Franks work have been replaced by covert black IR where even the glow of the infra-red flash is almost invisible. He would marvel at the amount of pictures that can be stored on an average SD card and that camera-traps are being used from the tropics to the snowfields of Antarctica.
You can look for the original article with this reference:
Chapman, F.M., September 1927. “Who Treads Our Trails?“, National Geographic, 52(3), 331-345
Or visit this site to see some of Frank Chapman’s images: http://www.naturespy.org/2014/03/camera-traps-science/
I thought I would write about wildebeest this week, it seems we take them for granted a bit. Certainly on Snapshot Serengeti they generate about the most images and it has been commented in the past “No, not another wildebeest”. The Serengeti is after all world famous for its wildebeest.
But what do you know about them, other than the roam around in large herds and get eaten by lions, leopards, hyenas and crocs?
Well ecologically they have evolved in a fascinating way. They are heavily dependent on water, never straying more than 20km or so from it. However, their square looking lips are designed for nibbling at short grass swards that are found in drier, fire maintained grasslands like that of the Serengeti and they are unsuited to wetter areas of equatorial Africa where grasses become tall and rank. They are bulk grazers that operate in large herds. Wildebeest are not especially fast runners having a body shape that favours their digestive tract, instead they rely on the size of the herd for protection. Unlike their close cousins, the hartebeest who are designed to outpace predators, wildebeest have proportionately shorter legs and males develop sturdy thick necks.
We have all seen footage of the migration with nervous looking wildebeest stampeding along, hell bent on reaching their destination. What you may not know is that this mass getting together stimulates the rutting state in both sexes. In amongst the moving herds males try desperately to mark out and keep a small territory from which he cavorts around noisily evicting other males and trying to impress a few females to mate with. The problem is he has to keep moving with the herd so these territories are very temperal and really only exist in his mind and he has to move on every day or so in order to keep up with the ladies. There are always a few males left in the wake of the procession that get caught up with fighting each other and trying to hold territories without realising the females have all gone. Once the migration has reached its destination everything calms down a bit and things get back to normal, breaking up into smaller groups until it’s time to do it all again.
Wildebeest no longer exist in their historic numbers. They are particularly affected by land use changes, susceptible to domestic live stock diseases and are targeted by poachers. Their dependence on water, quality short grasslands and large herd size means they don’t fare well on marginal land. However it’s not all bad news. Wildebeest are well represented in national parks across their range in Africa.
Well it is that time of year again when the winners of the prestigious wildlife photographer of the year awards are announced.
Having a browse through this year’s winners I notice with a touch of sadness but a good dose of hope just how many of the photos touch on the demise of wildlife and have a conservation message. Brent Stirton’s moving image of a poached black rhino although tragic is a strong weapon in itself in the fight to change the hearts and minds of those people that covet rhino horn.
One of my favourite images is in the bird behaviour category. The much maligned marabou stork is the subject and the shot was taken in the one spot on this planet that Snapshot Serengeti fans know so well, yes the Serengeti.
But the story doesn’t end there. The photographer who was awarded finalist in the bird behaviour category is well known to us. Daniel Rosengren worked for the Serengeti Lion project for 5 years in the field with the most enviable job going. He spent every day following the study lions getting to know them intimately and generally building up the rich source of study data that this 30 year+ project has gained.
Of course when Dr Ali Swanson came up with her wonderful idea of seeding the area with 200 odd camera traps and the Snapshot Serengeti project was born it was Daniel who looked after our precious cameras for several years. So we have a lot to thank him for.
Daniel moved on from the project in 2015 to pursue a career as a professional wildlife photographer and we congratulate him on his achievement this year in the wildlife photographer of the year award. Well done!
If you want to learn more about the story behind his image or just want to see some stunning wildlife images visit his website here http://danielrosengren.se/wpy-awardee/
And to see all the other winners from this year’s wpy 2017 visit
The Snapshot team have written another paper using the Snapshot data we all help to classify. The paper A ‘dynamic’ landscape of fear: prey responses to spatiotemporal variations in predation risk across the lunar cycle can be found at http://onlinelibrary.wiley.com/doi/10.1111/ele.12832/full for those of you interested in reading the original.
Lead by Meredith Palmer the paper explores how four ungulate species, buffalo, gazelle, zebra and wildebeest respond to predation risk during differing stages of the lunar cycle. These four make up the bulk of the African lion’s diet in the Serengeti along with warthog. Of course warthog are strictly diurnal so are not affected by the lunar cycle as they are tucked up nice and snug in a burrow.
For the other four night time can be a stressful time. None of these animals sleep all night, they snatch rest here and there, keep grazing and most importantly of all keep a watchful eye or ear out for possible attack.
It has long been thought that prey species territory is shaped by fear and that animals have safe areas (where they rest, give birth, etc) and risky areas where they instinctively know predators may be lurking. These areas trigger a risk versus reward response as they often contain better forage/water etc.
What Meredith and the team argue is that this landscape of fear is very much dynamic changing not only with seasons and night and day but on a very much finer scale as influenced by light availability through the moon.
Lions find it so much easier to hunt during nights where the moon gives of least light. It gives them a great advantage to stalking close to their prey using the dark as a kind of camouflage. The prey species, on the other hand, are at a distinct disadvantage, they can’t see the stalker and even if they sense its presence they are reluctant to flee as this presents a great risk in itself if they can’t see.
Meredith and her colleagues took the data from Snapshot Serengeti to quantify nocturnal behaviour of the key species using the presence or absence of relaxed behaviour (defined when we classify a species as resting or eating.) They then overlapped this with data collected through Serengeti Lion Project on lion density and hunting success. This data enabled them to work out what areas where high or low risk to the prey species. Using a clever statistical program, R, the data was analysed to see if lunar cycle had any bearing on animal behaviour, in particular, predator avoidance.
They found that moonlight significantly affected the behaviour of all four species but in a variety of ways. As we mentioned before there is often a good reason to venture into the high risk areas and the trade off in increased risk of predation is a really good feed. Buffalo for instance don’t change their use of space so much but were found to form more herds on dark nights. It seems safety in numbers works well for buffalo. Zebra react similarly in their herding activity but are much more erratic when it comes to space use, moving around a lot more randomly keeping potential predators on their toes.
Each species showed an aversion to using high risk areas at night but, particularly wildebeest and zebra, were found to increase their use of these areas when the moons luminosity was higher and safety increased. It was noted that high risk areas where avoided more frequently in the wet season than the dry. The thought being that there is increased hours of moonlight during the dry season that the animals take advantage of. Perhaps too the drive to find enough good food is a factor.
This paper serves to remind us that although what we do at Snapshot Serengeti is fun it is more than just a way for us classifiers to pass the time. It really has a very significant role in science and that role is ever increasing.
World lion day was set up to raise awareness of the conservation issues facing lions today. The African lion, listed by the IUCN as vulnerable, and the Asiatic lion listed as endangered are facing the triumvirate threats of habitat loss, human conflict and poaching.
Most of you who read my blogs will probably be aware of the threats and today there will be some really informative media pieces out there on the web if you are not penned by the world’s leading lion conservation organisations.
I thought instead that I would concentrate on the other side of World Lion Day, which is the celebration of the animal itself.
The first time I saw lion in the flesh was in South Africa’s, Kruger National Park. A car was stopped seemingly watching two tawny eagles perched in a tree. Now being a bird lover I couldn’t pass up this opportunity to get a good close look at these birds so I stopped too. Gazing up admiring the birds I became aware of the occupants of the other car waving at me, trying to get my attention. They were frantically pointing down under the bushes, following their jabbing fingers I found what they wanted me to see, four tawny legs poking out from under the bush, as if she heard me, up came a head, gave my presence a fleeting thought then slumped back down to sleep. My heart ready to burst with joy I grinned back at the car opposite then as I turned my glance back to the sleeping lion I caught a glimpse in my wing mirror that sent my heart racing. Two huge lions filled the mirror walking down the side of the car towards me. For an instant I forgot I was inside and a bolt of primal fear shot through me. But the lion were not interested in me, just the shade of the nice bush.
Lion have long been revered by man. The Eurasian cave lion has been immortalised by Palaeolithic man in cave art such as that found in Frances Lascaux and Chauvet caves. The Chauvet caves are thought to be the oldest rock art in the world dated at over 30 000 years old. Our very own Dr Craig Packer had the privilege to go into the caves to analyse these lion images. Only a handful of people have ever been inside the caves in an effort to preserve them.
Modern lions probably originated in eastern and southern Africa around 120 000 years ago where they then spread across Africa, south -eastern Europe, the Middle East, South Caucasus and into India. Ancient Greek writers suggest they were still present as recently as 100 BC in Greece and the Balkans. Lions survived in parts of Mesopotamia and Syria into the 19th century when the proliferation of guns saw their demise.
Their image, even today, is commonly used in heraldry as a symbol of strength, nobility, bravery or royalty. The ancient Greeks had many myths and stories of lion and their buildings and statues are resplendent with lions. It is easy to see why they are the most commonly used animal in heraldry. Even today in our jaded world lion are loved by many and as the example of Cecil the lion shows can elicit a huge emotional response from people the world over.
Let’s hope that on this World Lion Day that the tide can start to turn on the conservation fight for these glorious animals and we don’t lose that long history we have with the King of Beasts.
This summer in South West France has not been its usual hot balmy self. In fact as I look out the window now the overriding colour is a deep lush green. Normally by July it is turning a straw yellow colour but this year we have had plenty of rain. In contrast, to the south of us, fires have been raging through Portugal, Spain and South Eastern France. Who knows if this is a taste of what’s to come or a one year glitch in the system but one thing is for sure climate change is going to affect life on this planet in both subtle and not so subtle ways.
I wrote about termites last week and their importance in the ecosystem. This week I read a disturbing news article about aardvark, who of course survives on eating termites and ants.
A group of scientists in South Africa were studying aardvarks in the Kalahari. They had inserted biologgers into several aardvarks in order to follow their activity and body temperature. It turned out that the year of their study was an exceptional year of draught and all but one of the study animals along with others in the area died. They unexpectedly recorded a phenomenon not seen before that should be an eye opener to the ways in which future climate could affect not only individual species but whole ecosystems.
The aardvark themselves can withstand high temperatures but the termites on which they rely for food and water cannot. With the information provided by the biologgers the scientific team where able to see that the aardvark were not finding enough termites or ants to keep their energy levels up. Night times can be pretty cold in the Kalahari and the team found that the starving aardvark even swapped their usual night time foraging behaviour to day time in order to conserve body energy. They were even seen sunbathing in a bid to save energy. It seems that none of this adaptive behaviour was enough. There simply was not enough food for their needs and they slowly starved to death. At an average weight of 60 to 80 kg an aardvark is a large animal and needs to eat around 50 000 termites or ants a night.
One or two bad years will always happen but if climate change shifts as it is predicted many areas of Africa will become drier and hotter creating an aridity that most of the native termites and ants cannot tolerate. True, given time, more tolerant species may take over but in the meantime the much loved aardvark may become a creature of the past. But that is not the end of the story. The aardvark is more than just a curiously put together animal, it is the architect of large burrow systems that many other mammals, birds and reptiles are reliant on to escape extremes of hot and cold weather, to bring up their young and escape from predators. Most cannot excavate the hard earth themselves so with the possible demise of aardvark life would get a whole lot tougher for many many more animals.
If you want to read more about the study have a look at this link https://africageographic.com/blog/aardvarks-beating-climate-change/
Here on the Snapshot blogs we seem to concentrate on talking about the animals that populate the Serengeti. Of course these are the subjects of our many camera-trap images (oh, apart from those annoying over grown vegetation ones) and they are loved by us all but for once I thought I would talk about the Serengeti itself. Monitoring the animals that live in the Serengeti is a valuable way to assess the health of the landscape but to get a true idea of the state of play the whole ecosystem needs to be looked at. More and more scientists are realising that a holistic approach is needed to truly understand what makes an ecosystem tick and how to preserve it. Studying lion without looking at their connection to wildebeest and grass is like studying maths by looking at the numbers without the plus or minus signs.
So we have all heard of the Serengeti but what do we really know. It surprises me how many friends don’t actually know what country it is in. The Serengeti National park, where our 225 camera-traps are located is in Northern Tanzania bordering Kenya’s Maasai Mara National park. The two together with the Ngorongoro Conservation Area and other private game reserves make up the Greater Serengeti Ecosystem which protects the area of the great migration. It is easy to see where the confusion comes from.
Everyone has heard of the wildebeest migration but did you know that it is one of the largest animal migrations in the world that has not been drastically altered by humans, there are no barriers to impede the movement of the millions of animals that seek fresh grazing and water. The 1000km circular migration route sees around 500 000 zebra, over 1 million wildebeest followed by hundreds of thousands of other ungulates annually. All this is still able to happen thanks to the protected status of the entire ecosystem.
The Serengeti National Park itself is made up of around 1.5 million hectares of savannah. Flat or undulating plains covered in grasses which are nourished with ashy soils derived from nearby volcanoes dominate the landscape. Rocky out crops known as kopjes punctuate the flatness with infrequent river courses and their riverine habitat easing the monotypic view.
So what triggers the massive ungulate migration and all the inherent predator action? At the onset of the dry season grasses begin to dry out and water becomes scarce, ungulates are forced to follow their nose to find food and water. Luckily nature is well designed and there is a well defined gradient across the migratory path that sees differences in place and time for abiotic factors such as rainfall, temperature and soil type. It is these factors that govern what vegetation grows where and how available water is and of course where the millions of hungry herbivores can move to next to satisfy their needs. Once settled across the Mara River they can last out the dry season in the mixed savannah woodlands where food is not so scarce. But the pull of the plains is always there and with the onset of the rains back they go thundering towards the Serengeti once more in a tradition that has possibly been around for over a million years.
The area is the last remaining example of a large mammal dominated ecosystem that existed across much of Africa during the last 1.8 million years. With its relatively intact biodiversity and sheer size it is easy to see why scientists flock to study both the individual species that occur here and functioning of the ecosystem as a whole. Sadly there are not many places like it left on Earth.
Of all the antelope that we classify on snapshot Serengeti the eland is one of the most distinct. Its massive size, heavy set horns and swinging dewlap lends it a bovine appearance yet it is an antelope – all be it Africa’s largest. A member of the Tragelaphini family or spiral horned antelope the eland is closely related to kudu, nyala and bushbucks.
There are two species, the common eland (Taurotragus oryx) we are familiar with in the Serengeti and the giant eland (Taurotragus derbianus) found sporadically in woodland savannah across Central and West Africa. One thing to get straight is that giant eland are on average less bulky than their common cousins, the ‘giant’ refers to their horns.
At close to a thousand kilograms in weight a fully grown male eland equipped with a fortified neck and viscous hefty horns could prove a lethal adversary. Perhaps it is unsurprising then that most male interactions are highly ritualised and the real fighting only really occurs between males of near equal stature. It is an unusual trait in male eland that the neck, shoulders and dewlap continue to enlarge as the animal ages. They develop tufts of wiry hair on their foreheads and noses and a strange clicking in their knees develops that is audible quite some distance away. I remember once sitting in a clearing in the bush and hearing what sounded like multiple people cracking their knuckles whilst moving closer towards me. I could not even begin to imagine what was fast approaching me and began to get a little nervous, looking around for a tree to climb. I heard nothing else but the odd branch moving until out from the edge of the bush appeared a small group of eland. Much to my relief it was precisely these knee clicks that I had heard.
Although not a particularly fast running antelope eland are noted to be extreme jumpers. They are capable of leaping over three meters high from a standstill which to me puts to bed any lingering doubts that they are antelope not oxen.
As many of our snapshot images attest to they are often found in quite large herds, congregations 100’s strong are not unheard of. But all the same there is no real structure to the group. Herds can comprise all males, all females or mixed sexes and ages. They are highly interchangeable and very few bonds are formed. Even the sacred mother and calf bond is tenuous in eland society. Calves form crèches when they are a few days old and prefer to hang out away from the adults. They only suckle once or so a day and that can be the only time spent with mum. Female eland will band together in defence of their young but as they are often out of sight of the youngsters this doesn’t happen too often. Instead young eland grow fast attaining 450kg in their first year.
Although life seems good in these juvenile gangs and generally eland are long lived, mortality can be high in youngsters. Whilst studying leopard in South Africa we found eland was a common prey item, in fact we discovered three kills within a month of eland less than six months old and those were just the ones we found. Lion and hyena are also known to take their toll. There is no real synchronised birthing in eland herds with young born at anytime. I guess this means there is always a slightly younger, less savvy, youngster in the crèche that is easy prey for predators.
Next time you find an image of an eland herd have a close look to see if you can work out if they are females (smaller with more slender horns), males or if perhaps it is a crèche.
Across the African Savannahs many different birds can be seen strutting around on long legs, a perfect adaptation, often coupled with long necks, to give them a higher vantage point to see over the long grasses. We are talking about ostrich, korhaan, ground hornbill and storks to name a few. All these birds use the same method of steadily walking through the grass picking of preferred prey items; grass itself in the case of the ostrich.
One of the most fascinating to me is the secretarybird (Sagittarius serpentarius). Reportedly named for its resemblance to a medieval scribe with a quill behind his ear other sources suggest the name is a Francophile corruption of the Arab word saqr et-tair which translates to hunter-bird. Whatever the origins of its name the frond of spatulate nape feathers and the elongated central tail feathers easily distinguish this bird.
It is something of an enigma taxonomically speaking, making up its own unique family, Sagittariidae. It seems secretarybirds are related to eagles sharing skull structure and a type of feather lice. Currently aligned to diurnal birds of prey it has previously been thought of as a relative of storks and cranes. Indeed its breeding behaviour is very similar to that of storks, which to make things more complicated are also share a close affinity to birds of prey.
Taxonomic complexities aside secretarybirds do look like elongated hawks, they share that hooked bill and yellow cere common in birds of prey, they also possess a large gape which allows them to open the bill wide enough to swallow large prey whole. But it’s their feet that do all the work.
The modus operandi for a secretary bird is to stalk along quietly and stomp its prey with a torrent of fast powerful kicks to dispatch it. This method is used for a number of prey items such as arthropods, rodents, amphibians, game birds even mongooses. In fact anything, really, that can be subdued and killed by its deadly kicks is fair game. That said it is the secretarybird’s ability to despatch snakes that has endeared it to most Africans.
To sneak up on a snake and then kill it quickly takes a lot of skill and you best not make a mistake otherwise in the African bush you may end up the one dying.
A study led by Dr. Steven Portugal, from Royal Holloway, University of London found that although other birds of prey strike their prey with far more force this is enhanced by the momentum of their entire bodies plunging down from flight. The secretarybird is able to exert a force 5 times greater than its own body weight from standstill and can repeat this accurately with multiple kicks being delivered at a speed of 15 milliseconds each. Fast and furious, that’s how this bird tackles deadly snakes and biting mongoose.
If you are interested you can read the paper here. http://www.sciencedirect.com/science/article/pii/S0960982215014839