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.
Whilst we all love to see lion, cheetah and leopard, the big cats of the Serengeti, their smaller cousins are fairly elusive. I am referring to caracal, serval and wildcat. These three small cats manage to slink around between the large carnivore guild keeping themselves to themselves. Lion cheetah and leopard not to mention hyena will all kill small cats. Despite their diminutive size their larger cousins still see them as competition and threat. All three are solitary cats and to survive in this very competitive world they each have their own niche.
The largest of the small cats, females weigh in at around 10kg and males up to 19kg. They are found across Africa, Arabia and parts of India preferring drier habitats such as savannahs, steppes and dry woodland. The caracal is a magnificent hunter. It is extremely powerful for its size and is able to take down prey as large as small antelope like duiker and bushbuck. The bulk of their diet is made up of hares, rodents, hyraxes and antelope but they are renowned for their ability to leap into the air to catch flushed birds. Their back legs are longer than their front legs and are endowed with powerful muscles that enable them to burst upwards and snag flying birds.
This cat is uniformly coloured the bulk of its body ranging from a tawny grey to a brick red with some spotting restricted to its pale cream underbelly and chin. Its most distinguishing feature is its black tufted ears and black facial markings as well as a short stubby tail that put one in mind of a lynx. It is in fact not related to the lynx family at all.
Probably the most easily recognised of the three and the most commonly encountered of the cats on Snapshot Serengeti. These exquisite little animals are restricted to the African continent south of the Sahara across savannahs, marshes and forest edges particularly near water courses where tall grassy plants grow.
The serval weighs between 6 and 13 kg with males being larger than females. Proportionate to its size it has the longest legs of any cat species and along with its elongated neck and large pointy ears makes this cat unmistakeable. Its tawny coat is spotted black; these spots may run into bars on its neck, shoulders or legs. Melanistic (all black) morphs are known and we have been lucky enough to capture this rarer variation on Snapshot camera-traps.
Food wise these cats are small mammal specialists stalking prey through long grass locating their prey by sound and then using their long legs to leap into the air and strike prey in a fox like manner. They have very flexible toes and will hook fish and amphibians out of water as well as mammals from burrows. The bulk of their diet consists of small rodents under 200g but they will take reptiles, amphibians, birds and small antelope.
These cats are smaller than the other two, heavily resembling a domestic cat it is found throughout Africa, Asia and Europe. They weigh between 2 and 6kg and like the caracal and serval males are heavier than females. Apart from size the appearance of the sexes in all three cats is very similar and show little dimorphism.
Its coat is highly variable in colour and pattern ranging from grey brown to red. Dark spotting tends to appear towards the rump, down the tail and on the legs which often bleed into each other appearing more like dark stripes.
It is perhaps more of a generalist than the other two small cats and takes a wide variety of small prey with rodents making up the bulk of its diet. Birds are less frequently taken but insects have been identified as an important part of the diet. Its method for hunting is more familiar to us than the stalk and pounce of the caracal and serval. It will locate prey by sight or sound and then silently creep towards it by slinking belly to the ground before pouncing at the last minute. We have probably all witnessed a domestic cat stalking like this.
Of course once you are familiar with these three cats it is easy to tell them apart, that is if you are lucky enough to get a good daytime or colour image. Although serval are seen out in the day caracal and wildcat are less frequently active during daylight and all three mostly hunt at night. It can be harder to tell one from the other in a black and white night image but the trick is to concentrate on the shape. Does it have outsized ears, long legs and obvious spots (serval) or a rounded head on powerful shoulders and ears with tufts (caracal) or does it really remind you of the proportions of a domestic cat (wildcat). Like always make your best guess and perhaps post on the descussions page for more help.
The Serengeti is one of the best examples of a fully functioning grazing ecosystem. It is home to the world’s largest body of free roaming herbivores. If you have helped classify snapshot Serengeti’s millions of camera-trap images you will know that wildebeest, zebra, topi, hartebeest, and gazelle to name a few are far more common than lion, cheetah and leopard.
Most people are aware of the millions of antelope that, along with the grasses themselves, shape this environment but they are not the only herbivores out there. There is a micro world down at ground level that is often forgotten about but which plays an enormous role in the functioning ecosystem; herbivorous insects such as grasshoppers, beetles ants and termites.
I want to take a look at termites. When most people imagine an African savannah they think of an endless vista of gently swaying grasses interspersed with the odd umbrella shaped tree and termite mounds. Termites are an integral part of the ecosystem here and it is thought that in terms of biomass they exceed the combined weight of the Serengeti’s mammals. They consume dead plant matter above ground (often during the night) then retreat underground where anaerobic bacteria in their stomach gets to work on breaking it down into a useable form, this is very similar to the process in ruminant herbivores.
Why are termites so important to savannah ecosystems? Well they serve multiple functions such as nutrient cycler’s, habitat architects and as food for other animals.
The daily activity of millions of tiny termites who bring dead vegetation into their underground homes helps to circulate nutrients with in the soil layer as well as aerating the soils themselves. If you ever get to look at a termite mound you will see that the grasses on them are often cropped short were as the surrounding area is full of long grass. This is because the grasses growing on the termite mound are particularly nutrient rich, thanks to the termites having created a nutrient hotspot and wildebeest, topi and zebras all know this and preferentially munch this grass.
Termite mounds shape the plains around them giving a relief to the flatness. Other animals such as topi, hartebeest and cheetah will use these small hills to climb onto to get a better view of their surroundings. In this flatness even a few inches of elevation could give an advantage. Many animals use termite mounds to create their own burrows. Hyena, warthog and jackal will use them as dens but the master creator is the aardvark who does most of the excavating. Snakes, lizards and mongoose readily take to old mounds too.
Termites are nutritious critters themselves and almost any omnivorous animal will make a meal of them when the chance is offered. I remember seeing about twenty large raptors walking around on a dirt road in the Kruger Park looking like a flock of chickens gobbling up termites after an eruption.
Then there are the termite specialists, aardwolf can consume around a kilogram of termites in a night. Another predator is the ant, whispering ants will raid termite mounds grabbing worker termites, carrying two or three each at a time back to their own nests.
All in all termites are a hugely important part of the Serengeti ecosystem playing a vital role in so many lives be it nutrient provider, habitat provider or as food themselves. You will probably never classify a termite on snapshot Serengeti but it’s worth remembering just how important they are.
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.
Here is another pair of antelope that are often muddled up on Snapshot Serengeti; topi and hartebeest. These two share a similar size and body shape and for those of you not familiar with them they can prove a bit tricky.
Topi and hartebeest belong to the same tribe, Alcelaphini, which also includes wildebeest. These antelope typically have an elongated face, long legs, short necks and stocky bodies. Although these antelope have reasonably large bodies their long legs mean they have retained the ability to run fast, a good adaptation for life on the open plains. It is believed that the long face developed in place of a long neck in order to reach the grasses they consume.
There are several species of both topi and hartebeest in Africa, two are found in the Serengeti. Coke’s hartebeest or kongoni (Alcelaphus cokii) are selective grazers with browse making up less than 4% of their diet. Serengeti topi (Damaliscus jimela) are 100% grazers
In both species males are territorial but topi also form leks from which to display to passing females. Males holding territory close to the lek are more desirable to females. Dominant females will actively prevent subordinate females from mating with these males.
So side by side we can see that the topi is much darker coloured than the hartebeest with distinct sandy socks up to its knees and conspicuous black patches on the thighs and shoulders. In contrast the hartebeest has pale legs and underbelly with a darker upper body. The paleness forms a patch on the top of the thigh.
From behind the contrast between leg colour and backside is very obvious with topi sporting dark legs with pale rump and back and hartebeest pale legs and rump with dark back.
Horn shape is also different. A topi’s horns sweep up and back whereas a heartebeest’s sweep out to the side before kinking back. They also sit on a prominent bony ridge on the top of the head.
Hopefully this will help you tackle all the images waiting on season 10.
In my last blog I mentioned Ingela Jansson and the KopeLion project and promised to tell you more.
Ingela spent three years working for the Serengeti Lion project as a research assistant monitoring lions in the Serengeti National Park as well as the Ngorongoro Crater. Although working in the park was an amazing experience it was the work she did in the crater area that was to prove a more urgent calling. The very real conflict she saw between humans and lions persuaded her that if someone didn’t do something the Ngorongoro lions were headed towards extinction. And so KopeLion project was born in 2011.
The Ngorongoro conservation area was gazetted in 1959 and designated a multi use landscape. The pastoralist population were permitted to continue living there alongside the wildlife. Since this time the population has risen 10 fold and the once harmonious coexistence with lions has collapsed. Lions have disappeared from much of the area and the connection to the Serengeti lions is all but extinguished.
Enter KopeLion. The project aims to foster human – lion coexistence through community engagement, science and mentorship. One of the most successful outcomes so far is the recruitment of former lion hunters as lion protectors, we heard Roimen’s story last week.
But just how do you ‘engage with the community’ to try and change their minds about living with a dangerous predator. Well KopeLion do this in many ways. Firstly most of the employees are local which means they already have the community’s ear. To the Maasai their live stock are sacred so KopeLion spend a lot of time trying to reduce lion conflicts. They follow the model developed by Lion Guardians Ltd ( http://lionguardians.org )by helping local herders to build sturdy bomas, searching for missing livestock, treating injured livestock and warning herders when lion are nearby. The lion guardians or Ilchokutis are assigned an area of between 60 and 200km2 where they monitor lions or signs of lions scientifically. They also try to prevent young warriors or Morani from carrying out lion hunts. Part of their role is as mentors to the younger generation.
The Maasai still hold strong traditional beliefs and have strong community ties, recognising and embracing this is one of the reasons for KopeLion’s success so far on its mission to help humans and lions live in peace. The strong local ties mean KopeLion have won trust amongst the local herders and in 2016 they were able to stop more than 20 lion hunts from going ahead and have seen the evidence that their efforts are working in the fact that two of the monitored lion prides now show complete survival.
Ingela and her team at KopeLion are doing such valuable work that I urge you to head over to their incredibly informative website to read more about it.
Over the next few months I would like to bring you a few blogs about the many people that work to make Snapshot Serengeti possible. Without them there would be no data for us to pour over but what exactly do they do and who are they?
Dr Michael Anderson is currently in the Serengeti collecting data and checking up on how the various projects that make up Snapshot Serengeti are getting along. As part of the projects commitment to engaging with the local community Michael has begun a National Geographic funded intern program. Its aim is to give young locals valuable training and research experience in the fields of ecology and conservation.
The first student to be taken up on the program is Roimen Lelya Olekisay. He is a Maasai from the Ngorongoro Conservation Area. His story highlights why the intern program is a vital part of both the scientific and conservation work we do. Many local people see wild animals as a threat to their own domestic stock as well as themselves and retaliatory killings are common. Living alongside wildlife is not easy. Without the good will of the local people it is very hard to change their attitudes to the work we do and the animals themselves.
Roimen grew up on the Western slope of the Ngorongoro crater, his family, like many Maasai are herders. As a young boy he roamed all over the Ngorongoro protected area (NPA) with the family livestock. The Maasai are permitted to live in the NPA where they can graze livestock but are not allowed to cultivate the land. Roimen spent two years away at secondary school before returning to the family to continue herding. This is a familiar story for many Maasai. The importance of livestock is paramount and many boys do not complete schooling.
As a young warrior, like many his age, Roimen speared and killed at least three lion. Tradition dictates that young Maasai warriors must kill a lion to become a man. He would have maybe carried on killing lions whenever he perceived a threat to his family’s livestock but he met up with Ingela Jannsen’s group Kope Lion Project in 2013 who work in the area trying to mitigate lion/human conflict. He helped fit a radio collar to a lion and this interaction with the king of beasts up close transformed him from a lion hunter to a lion protector. He became one of Ingela’s lion scouts (more about Ingela and the Kope Lion Project in next week’s blog) recording predator-livestock attacks in the conservation area and working to prevent lion conflicts and hunts. His enormous enthusiasm for lions and their research makes him a perfect candidate to further his scientific skills. This is someone with a natural ease and interest in the wildlife around him and its preservation.
In his new role as the first intern for the National Geographic-Serengeti National park program Roimen will be tracking lions and setting up a camera-trap network that hopes to dissuade human-lion conflicts and generally learning all the scientific skills associated with this work. He has just started and will be with us for six months, hopefully we can catch up with his progress in a few months.
Photo’s curtsey of Ingela Jannsen and KopeLion project
This is another guest post by Drs. Tom Morrison and Michael Anderson about the Snapshot Serengeti Special Edition and what their research hopes to uncover.
Seeing the forest for the trees
First, a big THANK YOU to everyone who has helped classified images at Snapshot Serengeti, both past and present. Without the continued help of this great online community, our research would come to a grinding halt! So thank you. A number of folks (and at least one giraffe) have asked about the new study currently up on Snapshot Serengeti, so here’s a fuller explanation of this work.
Photos from our newest Snapshot Serengeti Special Season come from a camera trap experiment in Serengeti involving friends and collaborators based at Wake Forest University (US), University of Georgia (US) and University of Glasgow (UK).
One of the exciting things about these new images is that they come from some of the more remote corners of the park, far beyond where past photos (Season 1-9) were (and continue to be) collected. So, keep an eye out for different species than past surveys. For instance in the north, you might see oribi, a small and elegant ungulate with a large dark scent gland below its eye. In the south, our cameras overlap the home ranges of some of the few black rhinoceros still living in the park, and we already know there are at least a few rhino images in our pile, like this:
We set these cameras at a slightly higher height (1.5 meters in most cases), which allows us to see species from new wider angles. Admittedly, this new experimental design makes animal classifications a bit harder because we can often see far into the distance. Our advice is to simply do your best, but don’t sweat it too much if you can’t figure it out. Better to see the forest than the trees.
Back to the research…
Speaking of trees, this new study is trying to unravel the secret lives of trees. We monitor hundreds of individually marked trees around the ecosystem and revisit them each year to measure growth, survival, disease and few other things. You may have noticed little cages in some of the camera trap photos (see giraffe above). These are part of our experiment and enclose four small native tree seedlings which we transplanted to the plots after growing them in a nursery for 6 weeks. In fact we planted over 800 seedlings around the ecosystem to study the relative importance of herbivory, fire and rainfall on seedling growth and survival. So, we need camera traps to monitor things when we’re not there.
For example, check out the following sequence captured on one of our game cameras in southern Serengeti involving one of our marked trees:
What’s amazing about this is that not only does an elephant kill an adult tree, he does it under 60 seconds. This tree is an Acacia tortilis, or the “umbrella acacia,” named for its characteristic flat top. Umbrella acacias are one of the most common trees in Serengeti and one of our main study species. Images like these help inform our study of trees, telling us how they died, or at least how many large herbivores were in the area to potentially kill and eat them. But this begs the question: if a tree falls in the Serengeti, will anyone hear it? At least we know that there’s a small chance that one of our cameras might see it.
As I’m writing up my dissertation (ahh!), I’ve been geeking out with graphs and statistics (and the beloved/hated stats program R). I thought I’d share a cool little tidbit.
Full disclosure: this is just a bit of an expansion on something I posted back in March about how well the camera traps reflect known densities. Basically, as camera traps become more popular, researchers are increasingly looking for simple analytical techniques that can allow them to rapidly process data. Using the raw number of photographs or animals counted is pretty straightforward, but is risky because not all animals are equally “detectable”: some animals behave in ways that make them more likely to be seen than other animals. There are a lot of more complex methods out there to deal with these detectability issues, and they work really well — but they are really complex and take a long time to work out. So there’s a fair amount of ongoing debate about whether or not raw capture rates should ever be used even for quick and dirty rapid assessments of an area.
Since the Serengeti has a lot of other long term monitoring, we were able to compare camera trap capture rates (# of photographs weighted by group size) to actual population sizes for 17 different herbivores. Now, it’s not perfect — the “known” population sizes reflect herbivore numbers in the whole park, and we only cover a small fraction of the park. But from the graph below, you’ll see we did pretty well.
Actual herbivore densities (as estimated from long-term monitoring) are given on the x-axis, and the # photographic captures from our camera survey are on the y-axis. Each species is in a different color (migratory animals are in gray-scale). Some of the species had multiple population estimates produced from different monitoring projects — those are represented by all the smaller dots, and connected by a line for each species. We took the average population estimate for each species (bigger dots).
We see a very strong positive relationship between our photos and actual population sizes: we get more photos for species that are more abundant. Which is good! Really good! The dashed line shows the relationship between our capture rates and actual densities for all species. We wanted to make sure, however, that this relationship wasn’t totally dependent on the huge influx of wildebeest and zebra and gazelle — so we ran the same analysis without them. The black line shows that relationship. It’s still there, it’s still strong, and it’s still statistically significant.
Now, the relationship isn’t perfect. Some species fall above the line, and some below the line. For example, reedbuck and topi fall below the line – meaning that given how many topi really live in Serengeti, we should have gotten more pictures. This might be because topi mostly live in the northern and western parts of Serengeti, so we’re just capturing the edge of their range. And reedbuck? This might be a detectability issue — they tend to hide in thickets and so might not pass in front of cameras as often as animals that wander a little more actively.
Ultimately, however, we see that the cameras do a good overall job of catching more photos of more abundant species. Even though it’s not perfect, it seems that raw capture rates give us a pretty good quick look at a system.