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…
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).
Brown Hyena !!! The shout went up so loud I don’t think I really had need to pick up the radio and call head office with the news. The news being I had just got around 30 camera-trap images of a brown hyena polishing off the remnants of a waterbuck carcass followed by several shots of a rather disgruntled looking leopard whose meal I suspect it had originally been. This was news because in the 20 something year history of the reserve no one had ever spotted a brown hyena. The camera-traps had done it again; they had shown us something we didn’t know!
The brown hyena replaces the striped hyena as you move from eastern to southern Africa. Larger than its striped cousin, it rivals the spotted hyena in size and has a rather shaggy appearance, looking more dog-like. It is, like its Serengeti striped counterpart, a tantalisingly elusive creature with few sightings in the surrounds of my study area, South Africa’s Lowveld. In fact, in South Africa’s Kruger National Park, it has been hotly debated for years as to whether they are even present in the park — that is, until a camera trap study finally came up with concrete evidence of their existence there.
This is the beauty of camera traps. They lay there in the bush performing tirelessly capturing image after image, both mundane and exceptional. Admittedly pictures of impala and zebra passing by are not hugely thrilling even though they give us valuable insight into the ecology of these animals and are the mainstay of any research project. Every once in a while though a camera-trap captures something truly remarkable and this is every researcher’s magic moment. The thrill that pulses through you when you click from one repetitive shot to something totally unexpected is addictive. Some of you have probably experienced it when working through the snapshot Serengeti data. Camera-traps are wonderful tools that help researchers gain valuable insight into the animal world with minimal human disturbance and their place in the field will continue to grow.
As for my brown hyena, in two years he passed through the study area on average once every four months turning up in every corner. (It was a tiny study area compared with the Serengeti.) A camera-trap even captured a brown hyena using its anal gland to paste a blade of grass. Unfortunately we never knew how many individuals used the area as it was outside the realms of our study, but this side track from our leopard survey shows what a powerful tool a camera-trap is. You never know what the pictures might tell you about the wildlife in your area, be it your target species or one of the many others that make up the ecosystem.
It’s hard to tell whether the hyenas really love or really hate my cameras.
To be fair, I have seen hyenas absconding with everything from flip-flops to sofa cushions – and there was an unforgettable night where our neighbors were awakened by the crashing about of a hyena who had gotten his head stuck in a mop bucket. The world is their chew toy.
One of our favorite things about camera traps is that they are relatively noninvasive – we think of them as candid cameras, unobtrusively watching the secret lives of Serengeti’s most elusive animals. We don’t bait our cameras to attract animals: we want to capture the natural behaviors of the animals to understand how they are using their landscape – what types of habitat features they prefer, and whether they alter their patterns of use at different times of day, at different times of the year, or in areas where there are lots of competitors or predators.
But it’s a fair question to ask whether the cameras affect animal behavior, and an important one. Stanford graduate student Eric Abelson, is hoping to answer it. If the animals are being attracted to or avoiding areas with cameras, that could change how we interpret our data. In wildlife research, this is known as being trap-happy or trap-shy. For example, say we want to estimate the population size of leopards in Serengeti. Since leopards have unique spot patterns, we can use what is known as Mark-Recapture analysis to calculate the total number of leopards based on the rates that we “re-capture” (or re-photograph) the same individual leopard. Because of the way that the math works out, if animals become trap-shy – avoiding camera traps after an initial encounter — then we would overestimate the total number of individuals in a population.
Fortunately, although researchers in other systems sometimes find trap-shy animals (baby tigers in Nepal, for example), our Serengeti animals don’t seem too bothered – at least not to the point where they avoid an area after encountering a camera trap. Even at night, with the flash firing away, we get photo after photo of the same bunch of playful lion cubs, or repeat visits by the same leopard, cheetah, lion, or hyena week after week.
Also, since the cameras aren’t baited, we don’t think that they’re drawn to the cameras from long distances. Instead, we think that once the animals are close to the camera, they come a little closer to investigate thoroughly.
Hope you enjoy the view!
### I’m traveling to Tanzania currently, about to begin my final field season (which will be Season 6 on Snapshot Serengeti). As usual, I’m running terribly behind getting ready to go – so thought I’d share a blog post I wrote while embarking on Season 2. ###
It Begins Again: Wet Season Survey 2011
As I leave Minnesota, winter seems to be already breaking. Amidst the national mid-winter heatwave, mountains of snow are melting, turning the roads into rivers and the hockey rinks back into lakes. For the third time, I am watching cheesy movies across the atlantic, fast forwarding through day and night, racing the sun eastward across the ocean and winning by 30 lengths like Secretariat in the Belmont Stakes.
Except this doesn’t feel spectacular anymore. I am on my way to Tanzania, once again, with 240 lbs of luggage catapulting around the belly of the plane. My back feels thrown and the plane feels cramped, and the woman sitting next to me snorts and sniffles like some Sesame Street character.
After three weeks of delays, I’m finally heading…home? I’m dreading – just a bit – the madness that awaits me in Serengeti. A solid three weeks behind, I have 200 traps to place in the next 10 days….which happens to be humanly impossible.
See, my research relies primarily on camera traps – remote, automatic cameras that are triggered by heat and motion, attached to trees so that they take pictures of wildlife night and day. On the street they’re known as “hyena bait.” On my street anyway.
Yeah, that’s right. I’ve discovered that hyenas are like big ugly puppies – the world is their chew toy. However, unlike your neighbor’s cute, squirmy blue heeler, hyenas have no responsible owner to say “No! No demolishing the $200 camera trap!” Last year alone, hyenas ate nearly $8,000 in cameras. I would arrive at my excruciatingly selected camera site to find bits and pieces of plastic, the stray LED, a fragment of circuit board…just no camera. Elephants took down about $5,000 in cameras, but with minimal destruction. They typically ripped the offending trap from the tree and flung it out of site. Those cameras usually worked, with some minor case modifications. But the hyena victims? Beyond repair.
Given the abysmal loss rates from the first year of this ambitious (crazy?) camera trapping study, I am now returning to the Serengeti with replacement cameras and heavy duty steel protective cases…which happen to weigh about 1.35 tons apiece. That might be an exaggeration, but the point is that they are very, very heavy. And hopefully hyena-proof.
It is dark outside, though the fancy seat-back TV map says we are smack dab over the Atlantic. I feel like my mind should be racing with plans for my research, or meandering down memory lane – but mostly I am thinking about how good the red wine tastes, and how tired my eyes feel. The night outside seems endless, the world feels far away and frozen in time – like Zach used to do on “Saved by the Bell” – and in my alternate reality I slip guiltlessly into mass-market movies, into staring blankly out the window, the wine wrapping its velvet fingers around my fraying neurons.
I have a million things to do by…yesterday, but my brain is tired and does not want to work. I do not want to think about where on earth I put my hard drive, or the fact that I have not yet filed my taxes despite my imminent disappearance into the bush. I want to fade into the bright, apoplectic flashes of the action movie’s runaway trains or the feel-good underdog story of the horse that could. When I get to Serengeti, it will be a flat-out race against the rains. I want to get my cameras set before the rains keep me hamstrung for days at a time. Today is Feb 19; the rains start at the beginning of March. Can it be done? I guess we’ll see when I get there.
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 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 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.