The August edition of National Geographic Magazine has a cover story on the Serengeti lions that Craig has been studying for decades. And because Ali set out the camera trap grid in the same place as Craig’s lion study area, you see the same lions (plus more) on Snapshot Serengeti as those featured in the article. In fact, photographer Michael Nichols was out in the Serengeti during Season 5, so his pictures are contemporaneous with the ones up on Snapshot Serengeti right now.
So if you have a moment, go check out “The Short Happy Life of a Serengeti Lion,” which is entertaining and gives a nice history of the foundational research on which the Snapshot Serengeti science rests. And take a gander at the editor’s note, which accompanies this picture.
Last week, we left off with this crazy biological paradox: lions kill cheetah cubs left and right, yet as the Serengeti lion population tripled over the last 40 years, cheetah numbers remained stable.
As crazy as it sounds, it seems that that even though lions kill cheetah cubs left and right, it doesn’t really matter for cheetah populations. There are a number of reasons this could be. For example, cheetahs are able to have cubs again really quickly after they lose a litter, so it doesn’t take long to “replace” those lost cubs. It’s also possible that lions might only be killing cubs that would probably die from another source – say, cubs that would otherwise have died from starvation, or cubs that might have been killed by hyenas. Whatever the reason, what we’re seeing is that lions killing cheetah cubs doesn’t have an effect on the total number of cheetahs in the area.
I think this might hold true for other animals, not just cheetahs. It’s a bit of a weird concept to wrap your head around – that being killed, which is really bad if you’re that individual cheetah, doesn’t actually matter as much for the larger population – but it’s one that seems to be gaining traction among ecologists who study how different species live together in the natural world. Specifically, ecologists are getting excited about the role that behavior plays in driving population dynamics.
Most scientists have studied this phenomenon in predator-prey systems – say, wolves and elk, or wolf spiders and “leaf bugs”.
What scientists are discovering is that predators can suppress prey populations not by eating lots of prey, but by causing the prey to change their behavior. Unlike many spiders, wolf spiders actively hunt their prey – sometimes lurking in ambush, other times chasing their prey for some distance. To avoid being eaten, leaf bugs may avoid areas where wolf spiders have lots of hiding places from which to stage an ambush, or leaf bugs may avoid entire patches of land that have lots of wolf spiders. If these areas are the same ones that have lots of mirid bug food, then they’ve effectively lost their habitat. Sound familiar?
Back to Africa – what does this mean for wild dogs and cheetahs? Interestingly enough, lions do not displace cheetahs from large areas of the Serengeti. We’ve discovered this in part from historic radio-collar data that was collected simultaneously on both species in the late 1980’s. Below is a map that shows average lion density across the study area. Green indicates areas with higher densities. The black “+” symbols show where cheetah were tracked within the same study area. They are overwhelmingly more likely to be found in areas with lots of lions. This is because that is where the food is – and cheetahs are following their prey, regardless of the risk of encountering a lion. The Snapshot Serengeti data confirm this – cheetahs are way more likely to be caught on cameras inside lion territories.
Unfortunately, we don’t have radio-collar data on the Serengeti wild dogs from the 1980’s. But we do have radio-collar data for the wild dogs that have been living in the larger Serengeti ecosystem for the past 8 years. As you can see in the map below, wild dogs regularly roam within just 30km of the lion study area. But they don’t settle there – instead, wild dogs remain in hills to the east of Serengeti – where there are local people (who kill wild dogs), but very few lions.
Other researchers in east and southern Africa are starting to pick up on the same patterns in their parks. From Tanzania, to Botswana, to South Africa, researchers are finding that wild dogs get kicked out of really large, prime areas by lions…but that cheetahs do not. What they’re finding (since they have all these animals GPS-collared) is that cheetahs are responding to lions at a very immediate scale. Instead of avoiding habitats that have lions, cheetahs maintain a “safe” distance from the lions – allowing them to use their preferred habitats, but still minimize their risk of getting attacked.
Carnivore researchers are only really just beginning to explore the role of behavior in driving population-level suppression, but I think that there’s good reason to believe that large scale displacement, or other behaviors, for that matter, have greater effects on population numbers of cheetahs and wild dogs, as well as other “subordinate” carnivores – not just in African ecosystems but in systems around the world. It’s a new way of thinking about how competing species all live together in one place, but it’s one that might change the way we approach carnivore conservation for threatened species.
By now it’s no secret that lions are kind of mean – and that if you are any other carnivore living in the Serengeti, you’d probably prefer a lion-less world. No tawny, muscle-bound foes to steal your food, kill your cubs, chase you around…life would be easy! You’d have plenty of food, your cubs would grow up strong, and your numbers would increase.
Or would they?
It certainly makes sense that all the nasty things that lions do to other carnivores should add up to limit their numbers. Lions are responsible for nearly 30% of wild dog deaths, and over 50% of cheetah deaths! On top of that, they steal food that cheetahs and wild dogs have worked hard to get – and might not have the energy to get again. Researchers are pretty sure that more lions means fewer wild dogs in two ways: 1) In reserves where there are more lions, there are fewer wild dogs, and 2) When lion numbers increase through time, wild dog populations decline.
The same has generally been believed about cheetahs, and some research from the 1990s suggested that reserves with more lions had fewer cheetahs. But as I started digging into the data from Serengeti, I saw a different, quite unexpected, story.
Lions, cheetahs, and wild dogs were all monitored by long-term projects for a number of years. This graph shows their population sizes since the 1960s. The increase in lions is pretty clear – lions have nearly tripled in the last 40 years, largely due to increases in wildebeest. Wild dogs disappeared from the study area. Now, their final disappearance was due in large part to disease, but it’s possible that lions didn’t help matters. In sharp contrast, the cheetah population has stayed pretty much the same. Sure, there are some ups and downs, but on average, the population has been holding steady over the last 40 years.
Wait a minute, if lions are really bad for cheetahs, then why haven’t cheetah populations declined in the Serengeti? How can they possibly be holding steady when lion numbers have tripled? What is going on???
It’s a good question. Tune in next week for an answer!
If you are a nerd like me, the sheer magnitude of questions that can be addressed with Snapshot Serengeti data is pretty much the coolest thing in the world. Though, admittedly, the jucy lucy is a close second.
The problem with these really cool questions, however, is that they take some rather complicated analyses to answer. And there are a lot of steps along the way. For example, ultimately we hope to understand things like how predator species coexist, how the migration affects resident herbivores, and how complex patterns of predator territoriality coupled with migratory and resident prey drive the stability of the ecosystem… But we first have to be able to turn these snapshots into real information about where different animals are and when they’re there.
That might sound easy. You guys have already done the work of telling us which species are in each picture – and, as Margaret’s data validation analysis shows, you guys are really good at that. So, since we have date, time, and GPS information for each picture, it should be pretty easy to use that, right?
Sort of. On one hand, it’s really easy to create preliminary maps from the raw data. For example, this map shows all the sightings of lions, hyenas, leopards, and cheetahs in the wet and dry seasons. Larger circles mean that more animals were seen there; blank spaces mean that none were.
And it’s pretty easy to map when we’re seeing animals. This graph shows the number of sightings for each hour of the day. On the X-axis, 0 is midnight, 12 is noon, 23 is 11pm.
So we’ve got a good start. But then the question becomes “How well do the cameras reflect actual activity patterns?” And, more importantly, “How do we interpret the camera trap data to understand actual activity patterns?”
For example, take the activity chart above. Let’s look at lions. We know from years and years of watching lions, day and night, that they are a lot more active at night. They hunt, they fight, they play much more at night than during the day. But when we look at this graph, we see a huge number of lion photos taken between hours 10:00 to 12:00. If we didn’t know anything about lions, we might think that lions were really active during that time, when in reality, they’ve simply moved 15 meters over to the nearest tree for shade, and then stayed there. Because we have outside understanding of how these animals move, we’re able to identify sources of bias in the camera trapping data, and account for them so we can get to the answers we’re really looking for.
So far, shade seems to be our biggest obstacle in reconciling how the cameras see the world vs. what is actually going on. I’ve just shown you a bit about how shade affects camera data on when animals are active – next week I’ll talk more about how it affects camera data on where animals are.
A few weeks ago, I wrote about how awful lions are to other large carnivores. Basically, lions harass, steal food from, and even kill hyenas, cheetahs, leopards, and wild dogs. Their aggression usually has no visible justification (e.g. they don’t eat the cheetahs they kill), but can have devastating effects. One of my main research goals is to understand how hyenas, leopards, cheetahs, and wild dogs survive with lions. As I mentioned the other week, I think the secret may lie in how these smaller carnivores use the landscape to avoid interacting with lions.
Top predators (the big ones doing the chasing and killing) can create what we call a “landscape of fear” that essentially reduces the amount of land available to smaller predators. Smaller predators are so afraid of encountering the big guys that they avoid using large chunks of the landscape altogether. One of my favorite illustrations of this pattern is the map below, which shows how swift foxes restrict their territories to the no-man’s land between coyote territories.
The habitat inside the coyote territories is just as good, if not better, for the foxes, but the risk of encountering a coyote is too great. By restricting their habitat use to the areas outside coyote territories, swift foxes have essentially suffered from habitat loss, meaning that they have less land and fewer resources to support their population. There’s growing evidence that this effective habitat loss may be the mechanism driving suppression in smaller predators. In fact, this habitat loss may have larger consequences on a population than direct killing by the top predator!
While some animals are displaced from large areas, others may be able to avoid top predators at a much finer scale. They may still use the same general areas, but use scent or noise to avoid actually running into a lion (or coyote). This is called fine-scale avoidance, and I think animals that can achieve fine-scale avoidance, instead of suffering from large-scale displacement, manage to coexist.
The camera traps are, fingers crossed, going to help me understand at what scale hyenas, leopards, cheetahs, and wild dogs avoid lions. My general hypothesis is that if these species are generally displaced from lion territories, and suffer effective habitat loss, their populations should decline as lion populations grow. If instead they are able to use the land within lion territories, avoiding lions by shifting their patterns of habitat use or changing the time of day they are active, then I expect them to coexist with lions pretty well.
So what have we seen so far? Stay tuned – I’ll share some preliminary results next week!
Map adapted from: Kamler, J.F., Ballard, W.B., Gilliland, R.L., and Mote, K. (2003b). Spatial relationships between swift foxes and coyotes in northwestern Texas. Canadian Journal of Zoology 81, 168–172.
I recently gave a talk at the Arusha-based Interpretive Guide Society – a really cool group of people interested in learning more about the natural history of Tanzania’s places and animals. I’ve taken a few clips from the presentation that describe in a bit more detail how lions bully their competitors.
Looking at the photos above (all nabbed from the internet), how many of you would like to be a wild dog? A leopard? A cheetah? There’s no doubt about it – lions are big, and mean and nasty. If you are any other carnivore species in the Serengeti – or across Africa, lions chase you, steal your food, even kill you. So what do you do? How do you survive? That’s essentially what my dissertation seeks to answer. How smaller “large carnivores” – hyenas, leopards, cheetahs, and wild dogs — live with lions. Under what circumstances do they persist? Under what circumstances do they decline or even disappear?
There are a handful of ways in which these species interact, but what I’m most interested in is aggression and it’s repercussions. As the above pictures suggest, lions tend to dominate aggressive interactions.
The relationship between lions and hyenas is one that has wormed its way into the public psyche through nature documentaries such as “Eternal Enemies.” While such movies play up the frequency of such interactions, they certainly do happen. Lions not only kill a number of hyenas, but steal their hard-won kills. Dispel any notion of lions as some noble hunter — they in fact steal a lot of their food from other carnivores. In fact, research from Kay Holekamp’s group in Masaai Mara indicates that lions can suppress hyena populations just because they steal food from them! It’s actually a similar story for wild dogs – lions kill wild dogs too, but since wild dogs expend so much energy hunting, that if lions steal just a small fraction of the food that wild dogs catch, wild dogs simply cannot recover. They would have to hunt for more hours than there are in a day to make up for this caloric loss.
It doesn’t stop there. We don’t know how much food lions steal from cheetahs or leopards. We also don’t know how often lions kill leopards, but lions kill cheetah cubs left and right. Studies from Serengeti indicate that lions may be responsible for up to 57% of cheetah cub mortality!
So how do hyenas, wild dogs, leopards, and cheetahs survive? Well, that’s what I’m trying to figure out. But what I can tell you is that not all of these smaller carnivores sit back and take their beating quietly. Take hyenas. They’re about 1/3 the size of a lion, but they live in groups. Big groups. Much bigger groups than lions. And if there are no male lions around, if hyenas have strength in numbers, they can steal food from female lions, and even kill their cubs. While leopards don’t live in groups, they can easily kill (and eat!) a lion cub that has been hidden while mom is away hunting.
Unfortunately, what we don’t know is whether this reciprocal aggression by leopards and hyenas has any measurable affect on lion populations, and whether it’s this aggression that allows hyenas and leopards to coexist with lions. The cameras behind Snapshot Serengeti will provide the first-ever map of leopard and hyena distributions within the long-term lion study area – by comparing lion reproductive success (which we know from >45 years of watching individually identified animals) to leopard and hyena distributions, we can see if lions do better or worse in areas with lots of hyenas or leopards – and whether this is due to getting less food or producing fewer cubs.
What about cheetahs and wild dogs? Even though wild dogs, like hyenas, live in groups, there’s no evidence that this helps them defend themselves or their kills against lions. And cheetahs, well, there’s no record of them killing lion cubs, but who knows?
So how do these guys live with lions? To be honest, wild dogs don’t tend to do very well in places with lots of lions. In fact, it’s generally believed that wild dogs have failed to recolonize Serengeti, despite living *just* a few km from the border, because lion populations are so high. For a long time, researchers and conservationists believed that cheetahs also couldn’t survive in places with lots of lions – but that perception is beginning to change, due, in part, to data coming in from Snapshot Serengeti! It seems that cheetahs not only do just fine in reserves with lots of lions, but use the same areas within the park as lions do. I have a sneaking suspicion that how cheetahs use the habitat with respect to lions, how they avoid encountering lions even though they’re in the same places, holds the key to their success. Avoidance, combined with habitat that makes avoidance possible (read: not the short grass Serengeti plains you see below).
I’ll write more about avoidance and habitat another day. In fact, I’m currently revising a paper for a peer-reviewed journal that addresses how cheetahs and wild dogs differ in the ways they avoid lions – if accepted, it will be the first appearance of Snapshot Serengeti data in the scientific literature! I’ll keep you posted…
### Craig, his wife Susan, and lion researcher Daniel and I went camping at Barafu the other night. These are Craig’s thoughts as we all sat on top of Barafu kopjes, watching the wildebeest out on the plains. ###
The rains have been especially good this year. We are camping at Barafu Kopjes, at the eastern edge of the lion study area. The wildebeest have moved very far east, as I type this, I can hear them grunting loudly. The noise will only reach greater volume in the coming weeks as the rut approaches. The grass is green, the sky is full of rain clouds, and this is really the most glorious time to be in the Serengeti.
Back within the camera trap grid, the grass is getting tall, and Ali has to mow it every time she checks the cameras. There is almost nothing for the lions to eat inside the grid; most of the lions have moved very far to the south and east. This is the happiest time of year for the wildebeest, zebra, and gazelle – they are out on the open plains where they can see any danger approaching. They can easily move off away from a hyena, a lion, and still be in the lush green grass –so short it’s like the fairway of a golf course. For the lions, though, having to shift so far outside of their usual territories, this is a time of uncertainty. They may encounter rivals, unwelcoming territory holders, and so they move quietly across the land, always on edge. Further to the east, across the park boundary, into the Ngorongoro Conservation Area, there is also the danger that our study lions may encounter the Masaai warriors. Several years ago we lost three of our study lions in a wet April like this one.
All the grazers are drawn eastwards by the extraordinary richness of the volcanic soils immediately downwind from the Ngorongoro highlands. Without the wildebeest, the grass would be nearly as tall here as anywhere else, but it is so sweet, that it is mowed right down to the ground. The vistas here are breathtaking; every animal looks as though it’s floating in green space. It’s almost like snorkeling – the bright orange of the gazelle from head to toe, the vivid black and white stripes of the zebra, the dull brown of the wildebeest but in such mass it’s like a living train as the herd flows across the landscape. And lions, when we see them, stand out a mile. Usually they look like the bulls-eye – a large green target with a concentric circle of brown wildebeest around them.
This is the wet season.
Craig wrote an op-ed in the Los Angeles Times today. He argues that fencing wildlife reserves in Africa is a cost-effective and necessary step to conserving Africa’s big mammals. The reasons that reserves need fencing now have to do with demographic changes over the half-century since they were established. He points out that fences won’t work for some reserves, especially those that depend on wildlife migration over reserve boundaries, but that for many, it may be an important step towards conservation sustainability. (For what it’s worth, those reserves like Tarangire with in-out migration may be doomed anyway, as human population and agriculture increase around the reserve and effectively block the migration anyway.)
Craig’s opinion piece derives from a study he and many others did comparing the success of Africa’s reserves based on various attributes of those reserves *. The effectiveness of conservation efforts is not usually measured; mostly, people would rather their money to go conservation actions rather than conservation monitoring programs. Lacking specific monitoring data, the approach of Craig’s study is one way to look at what works and what doesn’t when it comes to conservation. And the data say that fences work in (most) African wildlife reserves.
Your gut reaction to fencing wildlife areas might be aversion, or even horror. I know I wince when I consider the idea. Fences are unattractive. But they’re especially unattractive, I want to point out, for those of us with the luxury of living far from major human-wildlife conflict. If there were reasonable chances that a lion or leopard might carry off my child – or kill my livestock – or that elephants would trample my carefully tended crops – I would welcome a fence. North Americans and Europeans have historically come into conflict with wild animals when human needs for land, food, and fuel have increased. They have largely solved this human-wildlife conflict by eliminating the wildlife. Africans have done a better job of retaining their wildlife, but their needs for land, food, and fuel are also increasing. As unaesthetic as they might seem, maybe fences around wildlife reserves can help both Africa’s wildlife and its people.
* “Conserving large carnivores: dollars and fence” in Ecology Letters, 2013 Volume 16, pages 635-641. DOI: 10.1111/ele.12091
Authors: C. Packer A. Loveridge S. Canney T. Caro S.T. Garnett M. Pfeifer K.K. Zander A. Swanson D. MacNulty G. Balme H. Bauer C.M. Begg K.S. Begg S. Bhalla C. Bissett T. Bodasing H. Brink A. Burger A.C. Burton B. Clegg S. Dell A. Delsink T. Dickerson S.M. Dloniak D. Druce L. Frank P. Funston N. Gichohi R. Groom C. Hanekom B. Heath L. Hunter H.H. DeIongh C.J. Joubert S.M. Kasiki B. Kissui W. Knocker B. Leathem P.A. Lindsey S.D. Maclennan J.W. McNutt S.M. Miller S. Naylor P. Nel C. Ng’weno K. Nicholls J.O. Ogutu E. Okot‐Omoya B.D. Patterson A. Plumptre J. Salerno K. Skinner R. Slotow E.A. Sogbohossou K.J. Stratford C. Winterbach H. Winterbach S. Polasky.
Lion hunting is an active sport in Africa, with wealthy foreigners paying thousands of dollars for a chance to kill a lion and take its skin back home to taxidermy. Done right, lion hunting could benefit the species, by helping to pay for land protection and other conservation measures. However, too often it is done poorly.
For many years, Craig has been actively involved in figuring out how to do lion hunting sustainably. In 2009, he, Ali, and I, and a bunch of others wrote a paper (“Sport Hunting, Predator Control and Conservation of Large Carnivores”) about the pressures and dynamics of hunting large carnivores with a focus on lions and wolves. If you’re not a hunter yourself, you may believe that hunting and conservation are diametrically opposed to one another. But that’s not true; most hunters are also conservationists and many of the strongest wildlife protection laws in our country were championed by hunters. In our paper we explore the complexities that arise when you add the third party: not just hunters and conservationists, but also rural citizens, and particularly ranchers. While hunters want to maintain wildlife (to hunt, and often for other reasons as well), ranchers would be most happy if there were no predators around at all; predators like lions and wolves kill livestock and even threaten rural people. Wildlife managers then have the unhappy task of trying to please all three groups, and they often do so by employing hunters to maintain lower than full capacity predator populations.
Late last year, the U.S. Fish and Wildlife Service responded to a petition to list African lions as endangered species, which would prohibit the importation into the U.S. of lion trophies. This week the Tanzanian Ministry of Natural Resources and Tourism wrote an opinion piece in the New York Times about it, saying that doing so would cripple Tanzania’s ability to protect lions and other wildlife. Our intrepid safari reporter Chris Egert followed up with Craig on KSTP to get his take on the controversy. What do you think? Should the U.S. prohibit the importation of lion trophies? What do you think about hunting as a component of conservation? What can be done to reduce the conflict between large carnivores and the people who live (and tend livestock) near them? These are not questions with easy answers, and I’m curious to hear what Snapshot Serengeti fans think.
#### Today’s guest post is from Daniel Rosengren, one of the full-time field researchers on the Serengeti Lion Project. ####
The prettiest lion born in our study area lately got the code name “SPQ”. “SP” because she was born in the Spurs pride and “Q” because that’s the order she was born, starting from A. Fittingly, her more personal name thus became SuPer Qt (Super Cute). One might think that lions all look alike. But SuPer Qt definitely stands out with her striking looks.
The other day I found the still young SuPer Qt together with her mother and another adult female. They were resting in the tall grass, at least the old females were. SuPer Qt sat up scanning the plains around her for anything to eat. Suddenly lightning struck really near. Close enough not to give a thundering sound but a very loud bang. SuPer Qt jumped while the adults didn’t even react.
After the rain passed SuPer Qt spotted two warthogs in the distance and started stalking. She’s young but not too young to participate in hunts. The other females lifted their heads, saw the pigs and followed suit. I drove around in a big semi-circle to get closer without disturbing. The lions were lucky, the hogs walked straight towards them. Then their luck vanished, just like the warthogs down a burrow. At first, the lions seemed confused and looked around widely as they slowly pushed forward. I don’t know what gave the hiding place away but once the lions came within about 15 meters of the burrow they instantly knew the hogs were there.
All lions took turns digging. The two older and more experienced lions dug with more force and determination. SuPer Qt seemed to dig more randomly. Her inexperience showed in more comical ways too. Twice she managed to place herself in a position behind a digging lion, getting her face full of dirt. Another time she circled the burrow and instead of walking around the oldest female she decided to walk under it. Something got SuPer Qt’s attention down the hole and she stood up while still under the old female who got her hind legs air borne. The old female was too busy looking down the burrow to seem to notice. They stood like this for a good while until the old female ungracefully, one leg at the time, managed to get her hind feet on the ground again.
After a long time of digging, the lions finally gave up. They lay down about 20 meters from the hole and rested. Half an hour or so later, the warthogs emerged. They were watched by the lions as they walked away but never had to run for it. The warthogs lived to see another day and must have had a very thrilling time.