Archive by Author | packer2012

The Night Belongs to the Lions

Lions are a different species at night.  During the day, they must remain hidden from their prey.  But there is nothing secretive about a lion’s behavior on a moonless night. There is no skulking, no need to hide.  The lions own the darkness.

The Kalahari Bushmen still live the traditional hunter-gatherer lifestyle of our ancestors, and they frequently hunt at night – but only when the moon is above the horizon and bright enough for human eyes to detect shapes and movements.   Without the light of the moon, say the Bushmen, the night belongs to the lions.  So they divide the night with the lions according to the phase of the moon.

And if there is a lunar eclipse? That is just a hungry lion, placing her paw in front of the full moon, stealing a little extra darkness.

The Serengeti lions don’t feed well on moonlit nights. Lions have fuller bellies around the new moon; they are thinnest at the full moon.  To compensate, they scavenge or hunt more during daylight hours. Wild herbivores are available to lions throughout the night, no matter what the moon is doing. However, humans universally stay up until around 10:00 pm or so and sleep until sunrise.  If we’re going to be out and about at night, we’re out in the evening not before dawn.

By the full moon, the hours after sunset are so bright that you can read a newspaper.  But the next night, the moon doesn’t rise until an hour after sunset; by the fourth night, the darkness persists for over three hours before the moon finally rises.

Outbreaks of man-eating lions have killed hundreds of people in southern Tanzania over the past twenty years.  These are agricultural areas where lions mostly survive on bush pigs – agricultural pests that cause people to sleep in their fields to protect their harvests.  Thus pigs provide the link between lions and vulnerable humans.

Former graduate students Hadas Kushnir and Dennis Ikanda visited survivors and victims’ families and recorded the precise time and date of 450 attacks on humans.  Most occurred between sunset and 10:00 pm, and while the last few nights before the full moon were the safest, the first few nights after the full moon were three-and-a-half times more dangerous.  After enduring the bright evenings prior to the full moon, the lions were hungry, and they mostly attacked people upon the return of evening darkness.

The full moon can feel spooky, and humans have constructed moon-related myths about werewolves and lunacy and Halloween.  But there is no linkage between moon phase and suicide or admission to psychiatric institutions.

So what if the full moon doesn’t make you crazy but just makes you nervous?  What if it keeps you safely indoors for a couple of nights?

The full moon isn’t dangerous in itself, but after a few million years of dividing our nights with lions, it would be surprising if we didn’t somehow sense the monthly dividing line between our time and lion time.

Here you can read the original research article about lions and the full moon.


Lions: Lazy or just very, very patient?

Lions have a reputation for being profoundly lazy. To the list of inert elements of neon, krypton and argon, it is tempting to add lion. But while lions do sleep for most of the day, they are not idle slackers; they are profoundly patient.

Lions are ambush predators: they lie in wait. There is no need to be antsy during those long hours between hunting opportunities. If a group of lions has caught something recently or failed in a chase, they’ve given away their location, which all the prey in the vicinity will avoid for the rest of the day. But the Serengeti is a moveable feast, and any prey animals that slowly drift in to the area will have little idea of the precise location of danger, if the lions are hiding quietly in tall grass.

 females in the grass
On the other hand, lions do tend to wait around near river courses and rocky outcrops, and herbivores will avoid these spots as much as possible. But if there is only one waterhole in the vicinity, the wildebeest, zebra, warthog and buffalo will have to weigh their thirst against the risks of being eaten, should there be lions hiding in those bushes over there. And if nothing stumbles blindly towards them, hungry lions will eventually have to emerge and actively search for their prey – but not until after dark.

Either way, it’s a game that predators and prey must play every day of their lives, but since lions can easily wait 3-4 days between meals, they have a fundamentally different perspective on the passage of time than the rest of us.

And that’s what makes the camera-trap data so incredibly exciting for me. In the mid-1980’s, I took turns with one of my former graduate students, David Scheel, watching lions 96 consecutive hours twice a month for several years – we were out with the lions for four days in a row just before and after each full moon, squinting through night-vision goggles whenever the moon was above the horizon. I nearly went out of my mind waiting for the lions to catch their next meal. We wanted to find out why lions live in social groups – and we were able to dispense with the myth that lions evolved to become social because of advantages from cooperative hunting: individual females in foraging groups didn’t feed any better than solitary females.

But there were so many more questions that we couldn’t hope to address without a better idea how lions and their prey play that spatial game of cat and mouse around the waterholes. And maybe the prey take advantage of the lions’ territorial behavior by finding refuge in the no-man’s land between pride ranges, or maybe the prey somehow move randomly from nowhere in particular to nowhere else in particular just to keep the lions guessing. A few years ago, Ali Swanson and I found that the Serengeti lions consistently fed better during the dark phase of the moon – what extra steps do the prey take to try to keep safe on those dark, dark nights?

We will finally be able to tackle these ideas with the camera-trap data. In the coming months and years, we will overlay the camera-trap grid on to maps of high-risk features in the landscape and of lion-telemetry sightings, and then we will finally see how the Serengeti herbivores cope with the uncertainties of living with the hidden dangers of those not-so-lazy lions.

From lions to everything…

The Serengeti lion project was established by George Schaller in 1966; his book, The Serengeti Lion, is a classic.  When I arrived in 1978, it was hard to imagine there was much left to discover about lions, and I only expected to stay in the Serengeti for a few years.   I just planned to answer a few specific questions about lion behavior before moving on to the next species.  My prior research had been on baboons and Japanese macaques, animals that move around a lot and interact with each other throughout the day. Lions sleep in tall grass and are mostly active at night.  Watching lions is a test of patience.

I took it for granted that lions live in complex social groups (“prides” consisting of about six related females, their dependent offspring, and a coalition of 2-3 males that have joined the females from elsewhere).   I wanted to know why pride females raised their cubs together in a creche; how coalition partners competed with each other for mating opportunities; how the whole crowd managed to feed together at kills.

But whereas a lot of the Serengeti lions were mating and feeding those first few years, there were very few cubs in the population, so I decided to continue the study a bit longer.  But as time went by, I became ever more intrigued about the fundamental ecology of these animals. The Serengeti was changing: trees were spreading in the woodlands, the lion population grew by about 50%, but lions were getting harder to find.   The study area contained a dozen prides in a thousand square kilometers; but some of the prides might not be seen for months on end.  I would go out into the field for four days at time, sleeping in the Land Rover, listening for roars, hoping to see an upright lion in the early morning light.

It wasn’t until we started using radio collars in 1984 that we could find our study animals on a daily basis.   The project then grew in previously unimaginable ways.  We could follow lions through the night; we could see where they went when they didn’t want to be seen. And my graduate students and field assistants could hit the ground running, finding lions for themselves their very first day on the job.

We started asking harder questions: Why did lions live in those complex groups? Why did the males have manes? Who fathered the cubs within the pride? What sort of diseases did they catch – and why were some outbreaks more deadly than others?

By then we tracked close to two-dozen prides, and our focus remained primarily on the lions – on their social behavior, their genetics and epidemiology.  It has only been in the past few years that I’ve felt comfortable about expanding our research program into a broader perspective.  Although there are several other long-term studies in the Serengeti, none of them are able to measure their species’ movements in the same degree of detail as the lions.  Cheetah biologists drive around looking for cheetah with patient optimism; hyena biologists watch hyenas at den sites then accept that their nocturnal subjects will wander off to points unknown during the night.  And no one keeps track of individual topi, hartebeest, waterbuck, bushbuck, impala or dikdik – let alone knows the daily life of a specific wildebeest, zebra or gazelle…  There’s not enough research funding in the world to attach enough radio collars on all those species, and it probably wouldn’t be a good idea to tag any of the herbivores who might then stand out a mile in a lion’s territory.

Then we realized that we didn’t have to touch a thing.  We just needed to set up enough camera-traps to get a composite snapshot of the Serengeti.  We received generous funding from the National Science Foundation, which allowed us to set out 225 camera-traps in our study area, but then we faced the problem of how to process the resultant flood of over a million photos a year…