Archive | September 2013

The sound of silence?

## Today’s guest post is from our moderator and regular contributor Lucy Hughes. ##

African sunset 1

What does silence mean to you? Maybe it’s that moment at the end of the day when the telephones stop ringing and the office hubbub finally stops and you can hear yourself think. Maybe sitting in your garden listening to the insects and aeroplanes pass overhead. Or maybe it’s that first 5 minutes of waking before the baby starts howling. Whatever it means to you the point is silence isn’t really silent. Something is always making a sound even if it’s a leaf rustling in the wind or a cricket singing.

In the African bush night time silence is deafening.  Just before sunset there is a rush of activity. The day shift starts looking for a place to spend the night whilst frantically searching out that last mouthful of food. Young banded mongoose are scolded into their burrows by older siblings. Antelope take a drink before heading to thicker cover. Francolins are calling out their staccato calls whilst sandgrouse flock to drink. As the sun sets and darkness looms everything quietens down, the last to make a noise are the guinea fowl who wait till it is just dark to, one by one, barrel up to adorn their favourite roosting trees like giant Christmas baubles. They finally settle down, and the nearby baboons stop squabbling and there is a moment’s peace before the night shift takes over.

African sunset 2

The Scops owl is first with its ‘poop poop poop’ call sounding almost like an insect.  Then the night-jars join in. A distant rasping bark and the jackal are off calling ownership of their territory. They stop suddenly and a moment later there it is, the slow wo-oop! Woo-ooop! and the hyena clan are declaring they are up for business.

There has been no respite to the constant noise of the African bush during this transition between day and night; a seamless mix between the two sound tracks. As the evening wears on and the night shift are out hunting in earnest it gets quieter.  If you are lucky enough to experience this it is unforgettable. The silence is thick, it hurts your ears and you want to shake your head to clear it. You are straining to hear anything out there in the blackness and your senses have you on high alert, never mind that you are in a vehicle your primal instinct knows this is Africa and beasts roam that want to eat you.

The only sound is a cacophony of insects and it is this that gets in your head, it is a relief when a spotted eagle owl calls breaking the pitch and giving you perspective again. Staring into the blackness you see a shape move , you can’t make out what it is, then comes a noise that goes right through you, a guttural, low sawing sound, a leopard is calling broadcasting its presence using the ground as a sounding board. He walks out in front of you, pauses for a moment, then strides off purposefully into the night.

The silence of the African night is palpable. You could slice it with a knife. It is so full of promises of wonderful animal encounters that I never want to sleep. It’s my favourite sound of silence; what’s yours?

Guinea-fowl flying to roost


The short and happy life of a Serengeti lion

### Last week Craig spoke for Cafe Scientifique about lions and shared the research that Lion Project has been conducting for the last 45 years. Check out the video here. Peter and Faith, UMN undergrads conducting research in the Lion Lab, attended the talk and share their experiences as well. ####

Peter and Faith here! Last week we had the opportunity to attend the Bell Museum’s Cafe Scientifique. Cafe Scientifique allows scientists from all disciplines and specialties to share their research directly with the public in the form of a casual presentation given at the Bryant Lake Bowl in Minneapolis, MN. This past month’s talk was given by Snapshot Serengeti’s own Professor Craig Packer, giving a historic rundown of some of the highlights of the lion research conducted by the University of Minnesota’s Lion Research Center.

As prospective lion researchers ourselves, it was both interesting and valuable to hear the conclusions of past research from the perspective of the researcher. Not to mention having it be told in a casual and humorous way, which is a refreshing break from the stack of scientific papers we are usually reading!  The audience, which was made up of local community members, was also engaged in the talk. Even though Dr. Packer presented complex graphs and maps, he explained the research in a way that was accessible to everyone.  The studies that were discussed during the talk included the lion’s mane study, why lions form prides, and even a bit about lion conservation and the potential use of fences to protect vulnerable populations.  In addition to reviewing past research, Dr. Packer also talked about the lion project’s current research–Snapshot Serengeti. The audience was amazed by how fast volunteers sorted through the millions of images on Snapshot Serengeti. (To all of you that have contributed to the success of “Snapshot”, cheers to you!) By the end of the talk, the entire audience, (including us!) had loads of insightful questions, and left with a piqued interest in the world of lion research.

A Young Grad Student’s Project…

Three weeks into graduate school and I’d have to say that it’s been an overwhelming and exciting time thus far. The coursework is intense, the lectures intriguing, and it’s certainly been interesting getting to know the diverse array of people who populate the Ecology, Evolution, and Behavior department. Accomplishment of the week, however, would have to be rounding up some IT guys to fix the lab printer so that I can finally make copies of all the papers I need to be reading! Score.

Even though I’ve just begun at UMN, I had been developing potential research project to do in the Lion Lab over the last several months. While Ali focuses on interactions between different predator species, I will be diving into the interspecies interactions that compose the Serengeti’s predator-prey dynamics. Specifically, I want to look into how physical predation along with the fear of potential predation influence how and where herbivores move throughout the day. Snapshot Serengeti is essential to my research because the camera traps are collecting data on where herbivores are congregating 24/7. Most other studies have been limited to looking at large-scale distributions during the day, whereas we can pick apart fine-scale distribution patterns even during the hours of darkness.

Now the Serengeti and the creatures in it are not static, but move around and prioritize different activities throughout the day. Herbivores are active during the day (diurnal), whereas the major savanna predators are most active in the twilights (crepuscular) and evenings (nocturnal). To avoid predators and maximize resource intake, herbivores could be strategizing about what they do and when they do it. I want to look at where the prey herbivores are during different times of the day and see if and how this changes throughout the 24-hour cycle in. If it does, we can then move into examining different hypotheses and motivating factors for these particular movement patterns.

One thing I would like to do is use lion behavioral data from the Serengeti Lion Project to construct a map of predator “attack risk” – a diagram showing the areas which include landscape features that are known to increase predator attack success. Another kind of map I can construct is one highlighting areas of prime resources based off of information on different herbivore species’ primary diets. This would reveal where herbivores should be going if they were focused solely on resource acquisition. The camera traps provide yet another layer by showing us where the herbivores ARE actually spending their time, and we can compare this (actual) distribution to those predicted by the two mentioned models.

Studies like this would not be possible without the novel type of information being generated by the camera traps. Being able to pull information from the pictures and add in additional data from the lion behavior projects, I have a good chance of being able to reveal something interesting about the dynamic interactions being hashed out in the Serengeti.

A cheetah made from galaxies

This is what happens when astronomers haven’t gotten enough sleep. From Kyle Willett: a cheetah made out of many, many small galaxy images from Galaxy Zoo. Click it for the awesome full-sized image.


Why does the zebra have stripes?

While procrastinating on this lovely Sunday afternoon, I stumbled across this incredible video of a octopus camouflage in action:

Now, we don’t have anything quite that camouflaged in the Serengeti, but in watching that video my thoughts turned to one of our more strikingly colored species: the zebra. Their starkly contrasting black and white stripes have puzzled researchers and naturalists for a long time.

For starters, the stripes seem like they would be terrible camouflage. I mean, how much more could you stand out from the open plains of waving gold grass? But at dawn and dusk, especially from a distance, the stripes seem to bleed into gray, making them look a surprising lot like elephants (no joke), or rocks, or even nothing at all. Still, up close they still look like bright black-on-white zebras, and it’s hard to imagine that any lion lurking in the thickets nearby would be fooled.

Some researchers have mused that the bold patterns disrupt the perception of predators, and that when the zebras run en masse from an attacking lion, they become a confusing jumble of stripes into which the initial target disappears. Others have pointed out that every zebra has a unique set of stripes, and that these stocky equids  might use these patterns to identify herd members, mates, or even mothers (if you’re a hungry foal).

One of the my favorite explanations has always been that the stripes protect against the savanna’s most fearsome creature: the tsetse fly.  These blood-sucking insects are not only vectors for some nasty diseases (such as sleeping sickness), but also hurt. A lot. (Having spent more time than I care to remember in the woodlands where these terrible, terrible creatures thrive, just the thought of tsetses makes me shudder. I have spent many hours hurling expletives (fruitlessly) at the tiny terrors.) Tsetse flies suck. A lot. And if wearing stripes were a way to fend them off, I’d have gone out in a zebra suit every day. There are in fact stories of one intrepid researcher back in the day dressing up in a stripey suit and attempting to test whether zebra stripes deter tsetses. But there’s only so much that one man in a zebra outfit can do, and field experiments are notoriously difficult…and so this remained a buried rumor until last year.

Last year, Swedish researchers discovered that horseflies (a close cousin to the terrible tsetse) don’t like stripes. And they tested this on an experiment useing  number of fake, plastic zebras painted solid black, solid white, and various things in between. Turns out that the flies really like dark colors over light colors, but still like solid light colors over stripes. And while in the real world, there are things (such as smells) that may attract tsetses to stripey animals despite their off-putting pattern, this study is pretty exciting. And next time I have to venture into the savannah woodlands? You can bet I’m wearing that zebra-striped shirt.

Human, 1, dancing

Seriously, this was too good not to share!


Handling difficult images

From last week’s post, we know that we can identify images that are particularly difficult using information about classification evenness and the fraction of “nothing here” votes cast. However, the algorithm (and really, all of you volunteers) get the right answer even on hard images most of the time. So we don’t necessary want to just throw out those difficult images. But can we?


Let’s think about two classes of species: (1) the common herbivores and (2) carnivores. We want to understand the relationship between the migratory and non-migratory herbivores. And Ali is researching carnivore coexistence. So these are important classes to get right.

First the herbivores. Here’s a table showing the most common herbivores and our algorithm’s results based on the expert-classified data of about 4,000 images. “Total” is the total number of images that our algorithm classified as that species, and “correct” is the number of those that our experts agreed with.

species migratory total correct % correct
wildebeest yes 1548 1519 98.1%
zebra yes 685 684 100%
hartebeest no 252 244 96.8%
buffalo no 219 215 98.2%
gazelleThomsons yes 200 189 94.5%
impala no 171 168 98.3%

We see that we do quite well on the common herbivores. Perhaps we’d wish for Thomsons gazelles to be a bit higher (Grants gazelles are most commonly mis-classified as Thomsons), but these results look pretty good.

If we wanted to be conservative about our estimates of species ranges, we could throw out some of the images with high Pielou scores. Let’s say we threw out the 10% most questionable wildebeest images. Here’s how we would score. (Note that I didn’t do the zebra, since they’d be at 100% again, no matter how many we dropped.) The columns are the same as the above table, except this time, I’ve listed the threshold Pielou score used to throw out 10% of the images of that species.

species Pielou cutoff total correct % correct
wildebeest 0.60 1401 1389 99.1%
hartebeest 0.73 228 223 97.8%
buffalo 0.76 198 198 100%
gazelleThomsons 0.72 180 175 97.2%
impala 0.86 155 153 98.7%

We do quite a bit better with our Thomsons gazelle and increase the accuracy of all the other species at least a little. But do we sacrifice anything throwing out data like that? If wildebeest make up a third of our images and we have a million images, then we’re throwing away 33,000 images(!), but we still have another 300,000 left to do our analyses. One thing we will look at in the future is how much dropping the most questionable images affects estimates of species ranges. I’m guessing that for wildebeest it won’t be much.

What if we did the same thing for Thomsons gazelle or impala? We would expect about 50,000 images of each of those per million images. Throwing out 5,000 images still leaves us with 45,000, which seems like it might be enough for many analyses.

Now let’s look at the carnivore classifications from the expert-validated data set:

species total correct % correct
hyenaSpotted 55 55 100%
lionFemale 18 18 100%
cheetah 6 6 100%
serval 6 6 100%
leopard 3 3 100%
jackal 2 2 100%
lionMale 1 1 100%
aardwolf 1 1 100%
batEaredFox 1 0 0%
hyenaStriped 1 0 0%

Wow! You guys sure know your carnivores. The two wrong answers were the supposed bat-eared fox that was really a jackal and the supposed striped hyena that was really an aardwolf. These two wrong answers had high Pielou scores: 0.77 and 0.83 respectively.

Judging by this data set, about 2.5% of all images are carnivores, which gives us about 25,000 carnivore images for every million we collect. That’s a lot of great data on these relatively rare animals! But it’s not so much that we want to throw any of it away. Fortunately, we won’t have to. We can use the Pielou score to have an expert look at the most difficult images.

Let’s say Ali wants to be very confident of her data. She can choose the 20% most difficult carnivore images — which is only about 5,000 per million images, and she can go through them herself. Five thousand images is nothing to sneeze at, of course, but the work can be done in a single day of intense effort.

In summary, we might be able to throw out some of the more difficult images (based on Pielou score) for the common herbivores without losing much coverage in our data. Further analyses are needed, though, to see if doing so is worthwhile and whether we lose anything by throwing out so many correct answers. For carnivores, the difficult images can be narrowed down sufficiently that an expert can double-check them by hand.

Craig at Bryant Lake Bowl TONIGHT

If you’re in the Twin Cities area, Craig will be giving a Café Scientifique talk (“The Short and Happy Life of a Serengeti Lion”) at the Bryant Lake Bowl at 7pm tonight.

If you’ve never been to one, the Café Scientifique talks are loads of fun. They’re informal presentations by scientists in a bar setting. Eat, drink, laugh, science. Can’t get much better than that.


Elles in the night

## I’m currently on a mini-holiday in the Minnesota wilderness (Boundary Waters Canoe Area). As I’ve lately been missing long mornings on the porch watching Serengeti wildlife, and Margaret wrote a recent post on one of the all-time most-watchable animals out there, I thought I’d share a story of a late-night elephant encounter from my first year in the field. I was in the car with Candida, a Lion Project Field assistant, and Philipp Henschel, a lion researcher for Panthera who has spent years working in west Africa, and the man who taught me how to camera trap, when we came across this…#

As we hurtled along the gutted road, we came face to face with a herd of elephants paying their respects to a fallen buffalo. At first, in the murk of night, we thought they huddled around one of their own, and concerned silence fell upon us. Ellies, for as aggressive as they can sometimes be, have earned our admiration and careful respect. They seem to me intelligent and emotional creatures; where they are not persecuted, they tolerate the roar of our passing engine with a casual glance. But they are supposedly nearsighted to the point of legal blindness*.  In heavily hunted areas we are sometimes charged by a protective female, but as we hold our breaths and brace for impact, they stop their charge short and listen…but give up and turn away. If we remain downwind in silence we are invisible…or so we hope.

The elephants tonight are agitated as they mill around the buffalo. Philipp tells us that ellies often investigate death in the forests where he’s worked. In an eerie display of some sort of cognizance, they seem to recognize that something is not right and come to look at fallen creatures. When they come across the bones of one of their own, he says, they pick them up and carry them away. It is sad and scary and moving and beyond my comprehension, what must be going on in the heads of these big, gray, lumbering beasts.

The two tour vehicles that are blocking the watering hole eventually pull away, and the ellies step forward to drink. They cluster close, pressing together side by side. Hesitant lions slowly creep back to reclaim their half-eaten kill, and the matriarch whirls around, her ears flaring, watching the lions in a silent stand-off. The air is still. It is thick with tension and heavy with the severity of the moment. One ill-timed thud against the car window or a frightened squeal from any of us, and we could incited a rampage. Silence is imperative and we hold our breaths as the ellies file past within inches of our landrover.We can almost feel their fear and my heart twists as I wonder what it must be like to stumble blindly through a blurry world, sensing death and its bearers all around you lurking in the hazy shadows and around every corner. As they disappear into the acacias, we hear a long, lumpy-sounding elephant fart and giggle nervously. We can breathe again.

We drive closer to the buffalo carcass and watch the lions return. In the faint starlight, we see that an adult female has already resumed her demolition; her whole head disappears inside the opened belly to rip solid tracts of muscle from the ribcage. We fumble for our headlamps and cameras; I look around optimitistically for an onslaught of hyenas. I have yet to see them challenge a lion kill, and begin to question the feasibility of my research plans. The subadult males pad around our car, their massive paws falling silently in the sandy soil. They are full, and are now studying us. Our windows are open, as always, and we glance around with slight unease – where did the two subadult males go? Suddenly we hear a loud chomp from the back of our vehicle. Fearing that they’ve gone of one of our tires, and hardly in any position to fix a flat, we frantically turn the car ignition and pull a few meters forward. In the sideview mirror, we see a lion trot into the darkness with our plastic tire cover dangling from his teeth. Candida’s jaw drops. We are not quite sure what inspired them to steal such an inedible adornment, but it is late and we have company coming that night. So we chalk the loss up to a casualty of the field…and as we drive home along the corrugated dirt road, we remind ourselves that at least we are better off than the buffalo.

*Elephants do have pretty bad vision, but it’s not as bad as I believed it was on this ominous night at the buffalo kill.

Introducing Meredith

Please welcome Meredith Palmer, a new graduate student with us here in the Lion Lab at the University of Minnesota. Meredith is joining our Snapshot Serengeti science team, so you’ll be hearing more from her as she gets settled in. In her first blog post here, she gives us a glimpse into the work she’s been doing the past several years. — Margaret

I hear the “ragged jean” look is still cool with young people these days, but when I slip into my black hoodie with the ripped up sleeve, it’s not to make a fashion statement. Rather, it serves to remind me of a time several years ago when I was last in Africa. This particular jacket once fell afoul of a rambunctious pair of orphaned lion cubs, and I must admit that I’m looking forward to the time when I once again will be sacrificing perfectly good clothing during the call of field duty.

Joining the Lion Lab is my opportunity to work with the giant accumulation of behavioral and camera trap data, supplemented by my own work in the Serengeti, which will enable me to elucidate some of the mechanisms involved in savanna predator-prey dynamics. I’m a first-year grad student, freshly back in school after spending the last several years working on science projects in various corners of the globe. I’ve had the good fortune to have spent time in Africa, Central and South America, the Caribbean, and even a brief stint on the island of Borneo! I’ve come straight to the University of Minnesota from the South Pacific, and the disparity between the warm tropical air I’m used to and the cool Twin Cities mornings is almost (almost!) makes me wish that I had a jacket that wasn’t full of holes…

My previous work in Africa has for the most part taken place in the southern portion of the continent. I stepped foot into Namibia five years ago to work for the Cheetah Conservation Fund (CCF). Cheetahs were having a particularly bad time, as they were considered – unjustly, in almost all cases – by local farmers to be a substantial source of livestock losses and were persecuted accordingly. We did a substantial amount of work on education and outreach with the people in the surrounding communities, but I would be lying if I didn’t say the exciting part for me was the work we did out in the bush. Shivering in the cold during 24hr water-hole watches, spitting out dust as we sped along in the back of a Toyota conducting large herbivore surveys, and of course, interacting the with the population of injured and rehabilitating cheetahs maintained on the reserve were the highlights of my experience.

I returned to Africa after I graduated college and helped to manage large herbivore populations at a safari reserve in the Limpopo region of South Africa. This area is right outside of the famous Kruger National Park and abounds with much of the same wildlife. It was here that I drove my first stick-shift, ate my first warthog, and spent many an evening sitting on top of a kopje drinking sundowners and watching the stars come out over the African plains. I had the opportunity to camp out in the Kruger Park and met characters involved in African conservation at all levels. I later migrated to the other side of the country to take a job in the Succulent Karoo. This was a desert landscape, loomed over by weirdly rounded hills and covered, during the springtime, in the most gorgeous blanket of wildflowers that I have ever encountered.

That being said, I simply can’t articulate how much I am looking forward to working again in the savanna ecosystem and getting a chance to glean some good data out of Snapshot Serengeti!