Whilst stretching the corners of my brain to think about a new topic to write about in the Snapshot Serengeti blogs it astounds me to realise just how long we have been going for; over 7 years now as Snapshot Serengeti and almost 10 if you include the Serengetilive days.
It is also humbling to know how dedicated our followers are and what support we get from them. Our fun would have been over long ago if the community had not backed us. It has occurred to me that Snapshot Serengeti’s followers do so in differing ways. Those who follow our facebook and twitter pages or WordPress fans who follow us through our blogs may have missed what it is we are up to. So at risk of boring those of you who do know I thought it was about time to reiterate what it is we at Snapshot Serengeti do and how it all works.
Our largest group of followers do so at www.snapshotserengeti.org helping us classify the millions of camera-trap images that are produced by around 225 camera-traps placed in a permanent grid pattern in our study zone in the Serengeti National Park. For continuity’s sake these sites, after an initial bit of trial and error have remained in their fixed spots since they were first chosen by the projects designer, Dr Ali Swanson back in 2010.
Originally the camera-trap grid was set up to answer questions on carnivore interactions specifically if carnivores were avoiding one another spatially and temporally, it soon became apparent that it could be used to pose many more scientific questions amongst them herbivore coexistence and predator prey relationships. The wisdom to leave this permanent window of observance into the lives of the Serengeti animals should lead to many future studies and has spawned many new similar camera-trap projects around the world.
It’s not all about the animals, in fact since teaming with Zooniverse the project has been as much about the advancement of citizen science as anything else. Back in the Serengetilive days there were so few of us taking part that we used to have our names up in a sort of league table of who had classified the most images. Each classified image was labelled by the classifiers name. Now of course there are far too many participants to bother with that kind of thing, besides with multiple people having to agree on each classification it might get messy. The work on developing a robust algorithm that dealt with the uncertainties in each individual classification was so involved it also paved the way for many more projects and several scientific papers.
So what do we ask classifiers to do? Well first you are presented with either a run of 3 images (day time) or 1 image (night time). You are then asked to decide and record what animals are present, numbers of each species, behaviour and whether there are young present or not. It’s pretty straight forward with prompts along the way. If you don’t know what the animal is you simply guess. Yes you read that right, you guess. One thing the developers worked out is that the whole project works better if you cannot skip images. For one thing it avoids all the hard or boring images being left till the end. As each image has to be agreed upon by several classifiers before it is retired this tends to smooth out any miss classifications and research has shown we are around 97% accurate.
If you find something good or something you cannot id and are curious you can add the image to Talk which is the discussion forum. There we have some very dedicated moderators who will help you with your queries.
All in all Snapshot Serengeti is about learning and sharing both for the researchers and for the community of classifiers so if you have been enjoying the facebook posts or reading the blogs but have never had a go classifying get yourself over there to www.snapshotserengeti.org and have a go.
There is one little animal in Europe that is loved by all, immortalised in children’s books, welcomed by gardeners and flagship of the realisation that our mammal populations may be declining due to our very own actions. Over in the States although not native these same creatures are kept as pets (that’s another story and not such a good one). Although it’s hardly a creature to cuddle or pet they are thought of as very cute, something to do with that snuffling around your garden in dry leaves and, getting all snoozy, having to sleep away the winter in a cosy corner. Yes, I write of the hedgehog.
Now, why, I hear you ask is she writing about a European mammal on a blog about the Serengeti? Well it may come as a surprise to some to find out that there are in fact 18 species of spiny hedgehog found across Europe, Asia and Africa. Six species are present in Africa. The North African hedgehog (Atelerix algirus) extends its range across the Mediterranean belt of North Africa and Iberian Peninsula as well as the Balearic and Canary islands. The long-eared hedgehog (Hemiechinus auritus) touches into Libya and Egypt and the desert hedgehog (Paraechinus aethiopicus) a true Saharan specialist. The last two species are also found through Arabia and Asia. The remaining three species are solely found in Africa; the southern African hedgehog (Atelerix frontalis), Somali hedgehog (Atelerix sclateri) and the four-toed hedgehog (Atelerix albiventris).
The four-toed hedgehog is found across West, Central and East Africa as far as the Zambezi River and so is the species that is found in the Serengeti. As far as I know we have never had a capture event from our camera traps of this enigmatic little creature but please let me know if someone has come across one.
In European culture where woodlands are seen as wildlife havens most people would associate the hedgehog with forests or at the very least the edges of forests and hedgerows where indeed this species is well at home but its African cousins are rather different in their habitat preferences. The four-toed prefers the drier regions and is partial to grasslands and according to The Handbook of the Mammals of the World vol 8 it especially likes overgrazed regions with dense ungulate populations. All that trampled grass and dung supports plenty of insects for it to munch. Well that sounds just like the Serengeti to me!
Although insects make up a large part of the diet they are omnivorous and will eat fungi and fruits as well as other plant matter. A little known fact, they will also kill small vertebrates like frogs, lizards and mice and are known to take on even venomous snakes. Their spines are great protection from the bite of an angry snake.
As formidable as those spines are it is the ability to curl up into a ball that is their true defence. Now they don’t just tuck their heads in and hope for the best, the skin that the spines are attached to is very flexible and is edged by a strong band like muscle that is attached to the forehead. When it is contracted it acts like a drawstring on a bag that holds in the body, head and limbs with the spines closing up the seal. It works remarkably well but inevitably certain animals have learned how to unzip the bag, honey badgers and eagle-owls are amongst those experts in the Serengeti.
As a family hedgehogs are known to perform a bizarre act known as self-anointing. The hedgehog will chew and lick a substance until it has a mouth full of saliva and then with acrobatic contortions it will plaster this saliva all over its body, apparently they do this in a frenzied manor and it is quite hard to distract them once in the process. What is unclear is why they do it. There is no obvious reason. Studies have shown every age group performing self-anointing including nestlings whose eyes have not even opened. They only thing that stands out is that strong smells and tastes seem to trigger the behaviour such as dog or fox urine and a whole host of human made items such as leather, polish or nylon stockings. I am not even going to ask what the scientific research question was when they discovered those three!
So from Mrs Tiggy-Winkle (Beatrix Potter) to sonic the hedgehog we may all be very familiar with this loveable creature but perhaps we don’t know all there is to know. Keep your eyes out for the first Snapshot Serengeti camera-trapping.
Image: Author Jkasui, Wikimedia, https://creativecommons.org/licenses/by-sa/3.0/deed.en
When we think of Snapshot Serengeti we think about the massive array of 225 camera-traps that are spread over 1125 km2 in the Serengeti National Park permanently clicking away. Partly this is fostered by the fact that when citizen scientists help out classifying images for the project they are randomly assigned images from a mixture of the 225 camera-traps rather than a sequential set from one camera. This is done so that each member of the community gets the chance to see a good range of different animals rather than, say, getting a camera-trap that was triggered 1000’s of times by grass.
For the most part anyway, people are concentrating so hard on the animals in the image that the scenery in the back ground is almost incidental. Regular contributors though will be aware that there are one or two camera-traps that are in very recognisable locations for example one trained on a group of boulders and one on a log. For some reason these spots seem to produce some really memorable images; the log was the scene of our melanistic serval as well as lion cubs, the boulder gave us some stunning images of spotted eagle-owl.
Recently the most epic capture event ever on Snapshot Serengeti surfaced of a pride of lions hunting a buffalo (if you missed it look here, https://www.facebook.com/SnapshotSerengeti/). That sequence was captured at a special little spot in the Serengeti, Dik-Dik Corner. The view is basically of a lone tree standing at a three-way cross road in animal tracks. There seems to be a pair of dik dik who hold this area central to their territory and they appear regularly, hence the name, but they are certainly not the only ones.
Here is a slide show of the passing wildlife at Dik Dik corner.
Of course these are not the only critters to have passed this way but this selection really shows how the animals follow the trails, something camera-trap researchers have used to their advantage over the years.
Its summer time again and that means the research teams are out in the field collecting data. The Snapshot Safari team have been checking up on all the camera trap projects dotted across Africa and adding more to the list at the same time as clocking up adventure stories from their travels. Snapshot Serengeti’s Dr Michael Anderson and his team are continuing with their resource partitioning research in the Serengeti and using the opportunity to check up on the condition of our camera traps, probably, as they do each year, replacing one or two that have malfunctioned or been damaged beyond repair.
So whilst they are doing their part for science I am stuck here in France behind my computer catching up with report writing. Though being summer and me an ecologist it is so very easy to get distracted by the outside world.
This year has been a bonanza year for invertebrate locally. The spring started with a mass eruption of the invasive box moth (Cydalima perspectalis). Literally every blooming flower was coated, snow like with their white bodies; one lime tree in our garden we estimated at over 100 000 moths. The caterpillars have decimated the local box (Boxus spp) forests but I was beginning to wonder what effect the millions of moths would have on food resources for other insects. I needn’t have worried, the box moths have gone and summer blooms have brought out hundreds of other butterflies and beetles, bees and spiders. It is an entomologist’s heaven out there.
This seems to have had a knock on effect in the birds. Never have I discovered so many active birds’ nests near to my house. Several rounds of blackbirds, chaffinches and black red-starts have fledged already and the hedges have been awash with the calls of nightingales, black caps and wrens. The air positively rings with the sound of begging baby birds.
Just two meters from my balcony there is a chaffinch nest in the hibiscus with four babies ready to fledge. It is so close that I barely need binoculars to watch the goings on. This is always a great delight for an ecologist or naturalist because it gives you just that little bit more insight to the nesting habits of common birds.
At first appearance it seems just the female was caring for the young birds but then I realised that every time she arrived, flying in at the base of an adjacent bush and making her way to the nest in stealth mode there was another chaffinch calling loudly from a high point in a not too distant tree. It didn’t take too long to realise that this was the male acting as decoy to draw the attention of any would be predators away from the real action. Once the female finished stuffing hungry beaks with juicy insects and flew off, the male was right behind her only to reappear in his tree top squawking seconds before she arrived back with another beak-full.
Thanks to this pairs faith in nesting close to my house I have had lots of time to watch the great team effort of these little common birds.
So whilst feeling somewhat jealous of my team colleagues who are out enjoying themselves in the African sun it is worth remembering just how much goes on under our very own noses and just how wonderful nature is.
A few years back the Snapshot Serengeti community classified its first ever zorilla (Ictonyx striatus). It’s not an animal that most people are familiar with and you would probably not expect to even see one on a safari in Africa. It is certainly not on the big five list or even on the little five list but just like its bigger cousin the honey badger it’s a gutsy little creature.
The zorilla, or African striped polecat belongs to the Mustelidae family that includes the well known honey badger, otters and weasels. Although superficially similar looking to skunks they are unrelated.
So how would you recognise one? First of all they are small, only 28 – 38 cm long with a bushy tail of around 25cm. The most striking feature is the black and white stripy coat. The body is overall black with four white stripes running from the head to the tail which is mostly white. There are white patches on the face and head and the small ears are often white rimmed. The fur is quite long lending the zorilla a slightly scruffy appearance.
Zorillas share more than their looks with skunks; they are also able to squirt noxious smelling liquid from their anal glands as a defence mechanism against predators. So if you do ever encounter one, give this little guy the respect it demands and stay well back.
These tough little creatures will eat a wide range of items, invertebrates, reptiles, rodents and birds but they seem to favour rodents and insects. They are known to tackle venomous snakes and large rats by pinning them to the ground and repeatedly biting at the back of the neck to make the kill. Nocturnal, they find most prey by smell and won’t hesitate to follow prey down into burrows or use their strong claws to un-earth something. Its small elongated size is perfectly adapted for this task.
Zorillas are found across sub Saharan Africa in a wide variety of habitats but seem to avoid the wetter rainforest belt through west and central Africa. They are mainly terrestrial but are known to be good climbers and happy to swim if needed. Due to their widespread presence in Africa their conservation status is classed as Least Concern by the IUCN red list.
So why don’t we see more on our camera-traps? Well not much is known about zorillas, their small size and nocturnal habits make them hard to study and in a place like the Serengeti they are just not a high priority species. However we do know they are present because they do show up on the camera-traps from time to time. I suspect that the main reason they are not picked up more frequently is their small size coupled with their fast paced frenetic life. The weasel family is notoriously hard to capture on camera-trap as they tend to shoot through the trigger zone before the camera has got its-self together to trigger. Perhaps we will see more zorillas in the future when the camera trigger speeds increase.
Lately we seem to have had some great buffalo images. These big imposing beasts aren’t exactly pretty but they have an appeal of their own with their imposing bulk.
There are 4 recognised subspecies of the African buffalo (Syncerus caffer), three savannah buffalo and one forest buffalo. Here in the Serengeti we find Cape buffalo (S c caffer) the biggest of the three savannah species also known as southern savanna buffalo. It weighs in at a whopping 500- 900 kg for males or 350-620kg for females. The two other savannah species are West African savanna buffalo (S. c. brachyceros) and Central African savanna buffalo (S. c. aequinoctialis) both slightly smaller than their Cape buffalo cousins.
The forest buffalo (S. c. nanus) appears quite different being redder in colour and quite a bit smaller weighing around 265-320kg but it is thought that this is in fact the ancestral African buffalo from which the others evolved. According to the IUCN Red-List although the three savannah species appear similar they are at least as different from one another as they are from the more distinct forest buffalo. Defining subspecies is always tricky and apparently there is hybridisation where these different subspecies meet, including between savannah and forest subspecies. I witnessed this when working in the Central African Republic where you could see smaller red ‘forest’ type buffalo intermingled with bigger looking dark ‘savannah’ type.
So what makes African buffalo so special? You would imagine that such a large animal would not seek safety in numbers but this animal is highly gregarious. Herds can reach thousands strong but these tend to be temporary and the usual number is dozens to hundreds formed of clans of related females and their offspring and an assortment of males. The rest of the males form small bachelor herds of 5-10 animals or live alone.
Living in these large herds gives buffalo a certain security and they are highly protective. They are known to chase predators as a herd in order to ‘rescue’ a targeted individual. They don’t hesitate to run at lions if they are threatened. This is to be expected when there are young calves about but buffalo herds are known to extend this behaviour towards injured, sick and even blind herd members. It is so effective that it is actually males not living in large groups, particularly the loners that are most often preyed upon by their arch enemy, the lion. When buffalos are on the move dominant females lead the way with mothers and calves in the centre followed by any infirm individuals and older cows with males forming a protective ring around the entire herd.
Formidable indeed but of course the very thing that allows them to be so aggressive, their size, is also the thing that attracts lion the only true threat other than man to an adult African buffalo.
As a species the African buffalo is listed as ‘least concern’ on the IUNC Red-List due to its widespread distribution. That doesn’t mean that there are not conservation issues. Buffalo are often targeted by poachers for the obvious reason that they provide a rich reward in meat, the usual land reduction is a factor and in areas outside game reserves they are often killed as they compete with domestic cattle for food.
Historically buffalo numbers plummeted in the 1890’s due to the rinderpest epidemic that saw the disease spread from domestic cattle to wild ungulates. The disease continues to have small outbreaks. More recently bovine tuberculoses, again spread from domestic cattle to buffalos, in the Kruger National Park has also caused mortality as well as triggering a cascade of health issues in other animals, in particular, lions who eat infected buffalo. A whole industry has grown up with the sole purpose of breeding TB free African buffalo in South Africa. On the whole though African buffalo are well represented with strong populations in protected areas and as long as these remain their status looks to be stable.
The male and female have large horns that are fused at the base forming a boss across their heads, in the male though this becomes thickened and sometimes massive and fighting males will crash bosses together if things become serious and posturing doesn’t work. The impact is so intense that they risk killing themselves or their rivals.
Next time you find a buffalo image, see if you can work out if it is male or female and take sometime to reflect on these formidable beasts.
I promised I would have some news about what the Serengeti team has been up to recently in the field. Our beloved camera-trap grid is still being cared for, cards downloaded, batteries replaced and cameras given the once over. So all is well on that front but what is the latest question being asked by the team.
Well thanks to the spatial occupancy modelling of the Snapshot Serengeti camera-trap grid we have learned a lot about how the animals share the environment. What we can’t derive from the camera trap images is the details of what the different species are doing when they are in those spaces and how so many large herbivores can exist together. It could be that they simply facilitate each others foraging or maybe they are using different resources. Scientists have identified what is known as niche partitioning, a mechanism that sees different species specialising in eating different proportions of grasses verses non-grasses; pure grazers and pure browsers and a sliding scale between the two. A second mechanism sees different species eating different parts of the same plant.
These two mechanisms seem to make perfect sense but it is not understood to what extent these two truly affect coexistence of large herbivores. This is where the Snapshot Serengeti team research comes in.
Under our own Dr Michael Anderson they have teamed up with Dr Rob Pringle and researchers at Princeton University in using a revolutionary new analysis method known as DNA metabarcoding to see what exactly each animal is eating.
Up until recently scientists studying herbivore diet had two choices, they could watch their subjects and try to identify what they were eating or they could use microhistology, whereby plant parts in faeces are visually identified. As you can imagine these methods are fine for differentiating between, say, grasses and trees but don’t allow scientists to classify down to individual plant species. With DNA metabarcoding they now have that ability and it should tell us a whole lot more about how the animals divide their resources in space and time.
So that’s the science but how does the team collect this data. Well as with microhistology it involves dung. Our intrepid scientists are roaming the Serengeti collecting poop from as many different herbivores as they can and then it all has to be shipped back to the labs for analysis.
If you are thinking that our team must be highly skilled detectives able to identify a wide variety of brown pellets in the savannah grasses then think again. That’s not to say they can’t but this work relies on 100% knowing which species produced said dung its sex and age as well as a sample that has not been contaminated in anyway. The method of collection relies then, on stealthy observation waiting for an individual to lift its tail and sprinkle the ground with brown pellets before running in with your sample jar at the ready to collect the freshly deposited “clean” offerings. I have some experience with this work and believe me it does feel slightly odd to be observing animals in this way, willing them on to have a bowel movement so you can move on to the next species. It is also a little risky as you can get so engrossed at watching your target animal that you forget there are predators there watching and waiting. At least in this project it is only herbivores the team are interested in, to do the same with predator’s faeces, that’s a whole lot more smelly.
The study is still in its early stages but the team reports they are already seeing some noteworthy things.
Spoiler alert, early results suggest that there are only two ‘pure’ grazers in Serengeti (zebra and warthog) and lots of variation between wet and dry season.
We will bring you further updates once the team has finished their analysis work and have the full results. It promises to be exciting stuff. In the meantime you can think on the glamorous job a field scientist has whilst you stay clean at home helping with the job of classification.
Those of you who have been with us for some time will probably have noticed that the image quality since we switched to the Snapshot Safari platform has reduced, sometimes dramatically. Before I go any further, we are trying hard to fix this but in the meantime I thought I would try and explain what the issues are in a hope that it may induce a little more patience from you. I am afraid that I really am technically challenged when it comes to computer stuff so I am going to be a little vague here but please, if there is anyone out there with more knowledge who can either help explain more appropriately or better still offer our team help don’t hesitate to get in touch.
So the trouble all started when Snapshot Serengeti joined the bigger Snapshot Safari platform at the start of this year. At this time Zooniverse was having a big overhaul with older projects operating on Ouroboros moving over to the Panoptes format. Essentially Ouroboros and Panoptes are both software packages which enable projects to build their pages and run them.
Of course Snapshot Serengeti being one of the oldest Zooniverse projects was designed using Ouroboros and has had some teething problems with the switch over. One thing to remember is that the teams involved with bringing all the camera trap images to the Snapshot Serengeti platform are for the most part unpaid graduate and undergraduate students studying ecology. They are not experts in computer programming yet have to keep the platforms running and fix all the problems.
In the old days the University of Minnesota based team would upload the batches of images from the camera traps and send them to Zooniverse who would process and upload them to the platforms. That was when there were a dozen or so projects. There are now over 50 active projects. Can you imagine how long it would take for Zooniverse to do all the uploading? To address this problem they have asked individual projects to manage the uploading themselves. To complicate this process a little more they have also placed a 600GB maximum file size on the images.
This all means that the team of ecologists at Minnesota have to engage computer code developers to write custom scripts enabling their super computers to interact with the Zooniverse web platform. The image quality issue then is not because we have started using different camera’s or taking images at a lower resolution it is due to the code that compresses the images from their full size to less than 600GB. Those images that were smaller in the first place have been less effected than the larger ones and hence the mixture of quality that we are seeing.
So as I said earlier we are trying hard to get this problem sorted and bring you back the kind of top rate images you are used to and hope to have things sorted with the next batch of images we upload. In the meantime please spare a thought for the team and remember that like you they are all volunteers, all be t with a slightly more vested interest in the research project. I hope that you will bear with us and keep up the much needed support you have always given us.
After my latest field trip to Namibia I was fortunate enough to spend a few weeks visiting some old haunts in South Africa. Even though I had very little time and no real scientific purpose other than curiosity I could not help but put out my camera traps whilst I was there. It was after all a nature reserve and surprises can happen.
One of the camera traps was located on a well used animal track that lead from the bush down to the river. The rains had not thus far been kind in that part of Africa and the bush was rather dry with little standing water so I was confident the track would offer some interesting images. As expected I had lots of images of vervet monkey, warthog, impala, nyala and waterbuck. Imagine my surprise then when I scrolled through 20 or so images of a small herd of waterbuck does with young to find this fluffy looking white thing that looked more like a sheep!
In fact it was a leucisitic waterbuck. Not to be confused with albinism, which is a condition caused by absence of melanin leading to pale skin, hair, feathers and eyes, leucism is defined as a partial loss of pigmentation that leads to an animal appearing pale or patchy but often with patterns still showing. The eyes in animals with leucism are normally coloured never the red that can occur in albinism. So albinism is a lack of melanin and leucism is a partial lack of melanin.
You can see this little waterbuck still has the distinctive bulls eye target ring around its rump that distinguish the common water buck from the Defassa waterbuck we are used to in the Serengeti proving it is leucistic not albino.
Regardless of which of the two conditions it has the young animal will have a tough time. The pale colour makes it stand out as a target to predators and it is thought that survival rates for leucistic animals are low. That’s not to say it won’t make it to adult hood, in fact the white lions of the Timbavati are a well followed case of leucism in a population that every now and then throws up a white cub or two, they are so well watched that it is known that some do survive into adult hood. From those few individuals stem most of the white lions that can be seen in captivity in zoos all be it showing all kinds of horrible traits of constant inbreeding.
After finding these images I was lucky enough to spot the herd with my own eyes. I watched the little leucistic waterbuck playing and frolicking with a like aged normal waterbuck and for all the world you wouldn’t know what all the fuss was about. The two were identical in every way except the pure chance of a mutated gene governing colour. Good luck to the pair of them.
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.