The predator of my predator is my friend.
If you’re a prey animal, you spend an awful lot of your time trying to not wind up like this:
As we’ve talked about an awful lot on this blog (here, here, and here, for example), the same holds true for a lot of predators. Just because you kill and eat other animals, doesn’t mean you don’t have to worry about being killed yourself (as this hyena so unceremoniously discovered).
But, what we haven’t talked so much about, is that the same holds true for plants. If you’re a plant, you get eaten by these terrifying animals:
But, just like prey animals and mesopredators can change their behaviour to minimise the risk of being killed, plants have a few tricks up their sleeves. They can spend a lot of energy growing big thorns, for example, that makes them less delectable.
Or! They can grow in places that their predators avoid — the places where their predators’ predators hang out. Got that? It’s a trickle-down landscape of fear, which had, until now, only been really well documented in small experimental systems with critters like spiders and grasshoppers. But researcher Dr. Adam Ford and colleagues just published an elegant paper in Science showing that leopards and African wild dogs can make the Kenyan savanna less thorny through this cascade. Basically, leopards and wild dogs eat impala. Impala eat Acacia trees. Impala much prefer to eat acacias with fewer thorns (because really, who doesn’t?) – and, if given the opportunity, impala will can eat these small-thorned acacias so much that they can suppress the acacia population.
But! Leopards and wild dogs seem to be offering these tasty small-thorned acacias a refuge. Leopards and wild dogs spend most of their time in denser thickets, where they have more cover to hunt. Impala avoid these thickets and rarely venture in — when they do, however, they have a much higher probability of being killed. And this creates this spiral – those tasty small-thorned trees survive and grow in these thickets because predators scare impala away.
So it’s a trickle down landscape of fear – a compelling and really exciting story. But, what sets Adam’s paper apart from many other attempts to document this effect in large predators, is the series of elegant experiments in which he and colleagues explicitly tested each step in this cascade. Controlling for habitat use to confirm that impala aren’t getting killed in the woods simply because they spend more time there (and in fact, they get killed more even though the spend less time there). Adding and removing thorns to acacias to see if it was really the thorns that mattered. Creating herbivore exclosures to measure whether impala could really suppress acacia density. I spent my entire time reading the article alternating between saying “This is so cool!” and “I am so jealous!” It’s an amazing story. Read more about it here (or here, or or here)!
Space and time
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.
Hard to find a better place to nap…
All in the name of science
Today’s guest blogger is Lucy Hughes. Lucy lived and worked on a private nature reserve in South Africa for four years, carrying out field research that included a camera-trap study into the reserve’s leopard population and twice monthly bird surveys for Cape Town University’s Birds in Reserves Project (BIRP).
Arrhhh, that really hurts! A three inch thorn had just penetrated my, admittedly inadequate, footwear and was stuck deep in the sole of my foot. Thorns are a serious hazard of camera trap placement in the South African bushveld where plants with thorns or hooks seem to make up about 90% of species.
My colleague Michelle ran back to the landy to get a first aid kit whilst I set about extracting the thorn, there seemed to be an awful lot of blood. I watched the path eagerly for Michelle’s return but as she got near she seemed to slow down and as she opened her mouth to speak I knew exactly what she was going to say. “Luce, if it’s not too painful, what about spreading your blood around a bit?”
Callous as it may seem it wasn’t a bad idea. We had been having trouble with capturing clear night shots of leopards. They always seem to be in a hurry and the shots we had were often blurry making it impossible to id the individuals. We needed a way to get the leopards to pause for a second or two in shot of the camera trap.
We had been advised that scent was the answer and were experimenting with various different ones and now it seemed human blood was to be the next test. I dutifully hobbled out in front of the camera and scraped my bleeding foot around on a nice flat rock Michelle had procured, wondering about the sensibleness of using human blood as bait for a predator. My slight discomfort was all in the name of science.
In the end it didn’t work, It rained a couple of nights later and my efforts where washed away. We never did find the perfect scent. We were told that tinned sardines worked wonders as well as catnip and perfume. We tried them all. It seems our cats where immune to these. The only thing that stopped them in their tracks was the scent of other leopards. I did learn however that the scent of tinned sardines was particularly interesting to giraffe of all animals. My method was to bury a plastic cup up to its rim in sand and put a blob of sardines in the cup. Now you would have thought that giraffe would have walked on by but as the picture below testifies, giraffe just have to take a closer look. You always learn something new!
Big, Mean, & Nasty
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…
Spot that leopard!
Today’s guest blogger is Lucy Hughes. Lucy lived and worked on a private nature reserve in South Africa for four years, carrying out field research that included a camera-trap study into the reserve’s leopard population and twice monthly bird surveys for Cape Town University’s Birds in Reserves Project (BIRP).
Trying to discover how many individual leopards used a reserve in South Africa was challenging work in more ways than one. Unlike the Serengeti Lion Project’s (SLP) 200-odd camera traps, I could count ours on one hand. That said the study area was much smaller at around 2,500 hectares. The technique was also very different. Whereas the SLP is trying to get a snapshot of animal interaction over a vast area I was interested in individual animals, so setting the camera traps up systematically on a grid basis was not the best option. Instead, to make best use of our limited camera traps, I selected sites that I thought a leopard was most likely to pass.
These sites fell into two categories, the survey sites and the random event sites. Based on recent tracks and scats on game trails and roads, the cameras were moved around the reserve on a regular basis in an attempt to survey the whole area. One or two cameras were reserved for the random events: a fresh kill, old carcass, or hunches about certain water holes or koppies (rocky hills).
My job was to trundle around the reserve, mostly on foot, searching for signs of leopard. Looking for tracks and scats on the network of sand roads was easy and for the most part it seemed these big cats do love a nice clear road to walk down. Wandering down a dry river bed following a set of tracks idly wondering if the leopard is asleep in one of the big Marula trees is one thing, but suddenly realizing that the pug marks seem to have doubled in size and that you are hot on the trail of two lions jolts you to a stop. Finding signs off these roads was a little harder, the substrate of the game trails was often tangled with grasses and small thorny bushes and picking up tracks was virtually impossible.
Half an eye was always on the sky watching for vultures. Their activity often led to carcasses but it was the sense of smell that served best. The smell of rotting carcasses is fairly potent and travels far and my nose became super sensitive to the whiffs. Unfortunately not having the skills of a bloodhound I would flounder around in the bush turning this way and that trying to pin down the source of the smell.
Setting up a camera trap on a dead wildebeest
Other than spending just a little too much time around dead things, camera-trapping carcasses lead to some great data. One surprise was just how often kills seemed to be ‘shared’. The following two shots from the same eland kill highlight this. You can see even without comparing spot patterns that these two leopards are different.
Female 1
Male 3
The first is a young female and the second is the reserve’s dominant male so it’s hardly surprising that he has stolen her meal. At other kills, though, we had various combinations of leopard visitors including three different adult males within two nights to the same zebra kill. The fact that the leopards stayed put in front of the cameras, munching, meant we managed to get shots from every angle, which helped a lot in putting together ID charts. At no time did we tie down any of the carcasses so clearly the leopards where not fazed by the cameras.
This following shot shows a jackal at the same eland kill. The leopards on this reserve where under very little pressure from lions, which only passed through occasionally. They hardly ever resorted to stashing kills up trees as leopards in areas of high lion density would.
Jackal at eland kill
This meant that many smaller mammals took advantage of the leftovers. Other than the obvious spotted hyena, we recorded brown hyena, side-striped and black-backed jackal, honey badger, civet, bush pig, and mongoose. This following shot looks harmonious, but the series shows that the honey badger definitely had the upper hand on the jackal.
Honey badger and jackal
The one thing that fellow researcher, Michele, and I were always aware of was that we were spending a lot of time in places that big cats also spent a lot of time. When you are setting up a camera on a fresh kill you can’t help but wonder if the killer is laying somewhere close watching you!
Check out the time stamps on this next set of pics to illustrate this point!
12:35 – Setting camera
15:58 – Leopard
Photos copyright Michele Altenkirk/Lucy Hughes, Lisssataba NR
Looking for Leopards
Today’s guest blogger is Lucy Hughes, an undergraduate working with us since “Serengeti Live” (Snapshot’s predecessor). Lucy lived and worked on a private nature reserve in South Africa for four years, carrying out field research that included a camera-trap study into the reserve’s leopard population and twice monthly bird surveys for Cape Town University’s Birds in Reserves Project (BIRP).
The purpose of my study on this relatively small reserve was to try and identify how many leopards were using it as part of their home range. Leopards were rarely seen on the reserve but signs of their passing – scats and tracks – were plenty. The fact that there was only an occasional lion passing through the reserve lead us to believe that perhaps the leopard density was greater than expected. So a colleague and I set out to try and identify the individuals using camera traps. Part of our strategy was to look for animals killed by leopards and then set up camera traps nearby in the hope that we would get plenty of shots of a leopard with which to start identifying spot patterns. The method worked well except it meant spending a lot of time hanging around decomposing carcasses. It’s amazing to see a leopard usually thought of as picky munching on a rotting carcass that you would think was fit only for spotted hyenas and vultures. In fact we had a wealth of animals recorded at these carcasses. As well as the expected leopard and spotted hyena we recorded brown hyena, jackal, honey-badger, civet, bush-pig, warthog and even a kudu picking at the remains of ruminant. Needless to say the high smells made us super efficient at putting up our cameras quickly.
The leopards on our reserve were not under pressure from lions and so tended to stash their kills under bushes rather than up trees, probably to keep them out of sight of the vultures. This meant it was easier to set the cameras. On a number of occasions we would return to a kill to collect the camera only to find the bare bones strewn far from the original bush and thousands of pictures of squabbling vultures.
Whilst out scouting for leopard signs, I once came across a dead juvenile baboon. It was lying at the bottom of a power pylon that the baboons would sleep in at night time. It had no obvious injury so I presumed it had fallen from the pylon that night. I decided to put up a camera trap at the site as leopard in this area are quite partial to baboon. I left the camera trap for two nights then went back to check. The baboon had gone and I had around 150 shots on the camera. What I found on those shots is why camera traps are so fantastic. Over 80 shots where of the troop of baboons returning to the site at dusk. The troop of 30 or so baboons each spent time with the dead individual, some touching it, some just sitting around it, some sniffing but for over an hour they remained with the dead individual as if saying good bye. The troop seemed more fascinated with the body than distressed. The following evening, the body by now grossly swollen, four juveniles came close to touch again but then ran off. I think the smell must have scared them. After dark, two spotted hyena came and took the body away. The leopard evaded us this time but thanks to the unobtrusiveness of camera traps we where privileged to witness an amazing moment in the life of a baboon troop.
Lions, hyenas, and leopards, oh my.
Craig (my adviser and the Director of the Lion Project) sometimes jokes that I wandered into his office looking to study tigers. It’s actually sort of true. I had been at the University of Minnesota to interview with a tiger researcher – but fell in love with the science that Craig’s team was conducting. Six months later I became the newest addition to the Lion Lab.
As part of the Lion Lab, my dissertation research focuses on how lions coexist with other large carnivores – hyenas, leopards, and cheetahs. Understanding how species coexist is a really big question in ecology. When two species eat the same thing, the species that eats (& reproduces) faster can exclude the slower species from that area. A lot of ecology is devoted to understanding the conditions that allow for coexistence in the face of such competition. The natural world is an incredibly diverse place, and it turns out the plants and animals have all sorts of strategies to survive together – though we’ll have to dive into those details another day.
Carnivores throw a bit of a wrench into our understanding of coexistence – even when they don’t eat exactly the same prey, they harass each other, steal food from each other, and even kill each other – and these aggressive interactions can result in dramatic suppression or even complete exclusion of certain species. For example, there’s a fair bit of evidence that wild dogs have a tough time surviving in areas with lots of lions and hyenas – not because lions and hyenas kill wild dogs, but because they steal food from them. Since wild dogs expend so much energy hunting, they simply can’t afford to lose those calories to scavengers. These patterns aren’t actually unique to large carnivores – a lot of animals, from bugs to birds, interact this way. However, since carnivores range over such large areas, it can be challenging to understand their dynamics.
That’s where the camera traps come in. The long term lion research project provides incredible amounts of detailed data on what lions do, where they are, and how successful they are at reproducing. By adding the camera survey on top of the lion study area, I can collect information about the other carnivore species and integrate it with the detailed lion data to ask bigger questions than could be answered with one dataset alone. Unfortunately, there aren’t any wild dogs left within the study area, but I can still investigate how lions coexist with leopards, cheetahs and hyenas. It’s a bit gruesome when you get down to it — lions tend to dominate all the other species when it comes to one-on-one interactions, stealing their food or even just killing them for no apparent reason. For example, lions kill somewhere between 25-55% of cheetah cubs! And you can see here Stan’s photos of lions just killing…and leaving…a leopard.
Lions chasing…
…and catching…
…and leaving…a leopard
Lions will also kill hyenas, but enough hyenas can be a pretty solid threat to lions – able to steal carcasses or kill their cubs. Leopards sometimes kill and eat lion cubs. We don’t yet know if hyenas and leopards do this at a rate that actually hurts lions in the long-term, but we’re hoping to find out.
One of the key things I’m trying to find out (with a lot of green coffee and evening sessions) is how these species use their habitat with respect to each other. Research in other ecosystems shows that smaller carnivores (those that usually lose a fight) can get pushed out of large areas, existing sort of in the ‘no-man’s land’ between top carnivore territories – and when this happens, their numbers can plummet. However, if the smaller carnivore can just avoid the larger one within its territory, they might be able to coexist. A lot of this depends on the habitat complexity – for example, in open areas, it’s harder for the smaller guy to hide.
The camera traps let me evaluate these different patterns of avoidance to understand how lions, hyenas, leopards, and cheetahs all coexist in Serengeti National Park. Once we understand their dynamics in Serengeti, we can hopefully understand why they do or don’t coexist elsewhere. It’s a pretty cool science question – and it’s also an amazing adventure. I head back to Serengeti this January for my final field season, and am looking forward to sharing the adventure with you on this blog.
Snapshot Serengeti 