The scourge of Daylight Savings Time
As Ali mentioned, we’re working on figuring out timing issues for all the images in Snapshot Serengeti. Each image has a timestamp embedded in it. And that time is Tanzanian time. You might have noticed that sometimes the time associated with an image doesn’t seem to match the time in the photo — especially a night shot with a day time or a day shot with a night time. We initially shrugged that off, saying that some of the times get messed up when the camera gets attacked by an animal.
But it turns out to be more complicated than that. All the times you see on Snapshot Serengeti — either when you click the rightmost icon below the image on the classify screen, or when you look at a capture in Talk — are on West Greenland (or Brazil) time. Why is that? Well, databases like to try to make things “easy” by converting timezones for you. So when the images got loaded up onto the Zooniverse servers, the Snapshot Serengeti database converted all the times from what it thought was Coordinated Universal Time (UTC) to U.S. Central Time, where both Minneapolis and Chicago are. That would mean subtracting six hours. But since the times are really Tanzanian ones, subtracting six hours sticks us in the middle of the Atlantic Ocean (or in Greenland if we go north or Brazil if we go south).
That wouldn’t be so bad, except for Daylight Savings Time. Tanzania, like everywhere close to the equator, doesn’t bother with it. It doesn’t make sense to mess with your times when sunrise and sunset are pretty much as the same time all year round. However, the ever-helpful database located in the U.S. converted the times as if they experience Daylight Savings Time. So on dates during “standard time,” the Snapshot Serengeti times are off by six hours; subtract six hours to find out the actual time the image was taken. But on dates during daylight savings, the times are off by just five hours.
11:35am Tanzanian time. Shown as 4:35pm on Snapshot Serengeti.
And to make things more of a headache for me, those images that got taken during the hour that “disappears” in the spring due to Daylight Savings Time, get tallied as being taken the hour before. This might explain why we get some captures that don’t seem to go together: the images were actually taken an hour apart!
So now I’m focusing on straightening all the timestamps out. And when I do, I’ll ask the Zooniverse developers if we can correct all the times in Snapshot Serengeti so that they’re shown in Tanzanian time. Hopefully we’ll have that all set before Season 7.
By the way, I was able to figure this all out pretty quickly thanks to the awesome blackboard collection that volunteer sisige put together. You can see the actual Tanzanian time on many of the blackboards and confirm that the online time shown below the picture is five or six hours later, depending on the time of year. Many thanks to those of you who tag and comment and put together collections in Talk; what you do is valuable — sometimes in unexpected ways!
Don’t worry!
Deep breath; I promise it will be okay.
By now, many of you have probably seen the one image that haunts your dreams: the backlit photo of the towering acacia that makes the wildebeest in front look tiny, with those two terrible words in big white print across the front — “We’re Done!” Now what are you going to do when you drink your morning coffee?? Need a break from staring at spreadsheets?? Are in desperate need of an African animal fix?? Trust me, I know the feeling.
Deep breath. (And skip to the end if you can’t wait another minute to find out when you can ID Snapshot Serengeti animals again.)
I have to admit that as a scientist using the Snapshot Serengeti data, I’m pretty stoked that Seasons 5 and 6 are done. I’ve been anxiously watching the progress bars inch along, hoping that they’d be done in time for me to incorporate them in my dissertation analyses that I’m finally starting to hash out. Silly me for worrying. You, our Snapshot Serengeti community, have consistently awed us with how quickly you have waded through our mountains of pictures. Remember when we first launched? We put up Seasons 1-3 and thought we’d have a month or so to wait. In three days we were scrambling to put up Season 4. This is not usually the problem that scientists with big datasets have!
Now that Seasons 5 and 6 are done, we’ll download all of the classifications for every single capture event and try to make sense of them using the algorithms that Margaret’s written about here and here. We’ll also need to do a lot of data “cleaning” — fixing errors in the database. Our biggest worry is handling incorrect timestamps — and for whatever reason, when a camera trap gets injured, the time stamps are the first things to malfunction (usually shuttling back to 1970 or into the futuristic 2029). It’s a big data cleaning problem for us. First, one of the things we care about is when animals are at different sites, so knowing the time is important. But also, many of the cameras are rendered non-functional for various reasons – meaning that sometimes a site isn’t taking pictures for days or even weeks. To properly analyze the data, we need to line up the number of animal captures with the record of activity, so we know that a record of 0 lions for the week really means 0 lions, and not just that the camera was face down in the mud.
So, we now have a lot of work in front of us. But what about you? First, Season 7 will be on its way soon, and we hope to have it online in early 2014. But that’s so far away! Yes, so in the meanwhile, the Zooniverse team will be “un-retiring” images like they’ve done in previous seasons. This means that we’ll be collecting more classifications on photos that have already been boxed away as “done.” Especially for the really tricky images, this can help us refine the algorithms that turn your classifications into a “correct answer.”
But there are also a whole bunch of awesome new Zooniverse projects out there that we’d encourage you to try in the meanwhile. For example, this fall, Zooniverse launched Plankton Portal, which takes you on a whole different kind of safari. Instead of identifying different gazelles by the white patches on their bums, you identify different species of plankton by their shapes. Although plankton are small, they have big impacts on the system — as the Plankton Portal scientists point out on their new site, “No plankton = No life in the ocean.”
Wherever you choose to spend your time, know that all of us on the science teams are incredibly grateful for your help. We couldn’t do this without you.
The Little Guys
##### Today’s blog is a guest post from our own Lucy Hughes. ####
We all love the cats don’t we, the majestic lions, the graceful cheetahs and the elusive leopards. There is something about getting one of these cats to ID on Snapshot Serengeti that makes you feel you hit the jackpot. Then there are the elephants, buffalo and giraffe ‘the big guys’. Lions for instance always get the most ‘likes’ on our facebook page. Let’s not even talk about wildlife documentaries; they always manage to star ‘the big guys’, the crowd pleasers, elephants, tigers, lions, whales.
So what about ‘the little guys’? When was the last time you saw a documentary on aardvark or civets?
Aardvark!
It seems that the documentary makers don’t think we want to see a whole hour on these little guys. Most people know that lions live in prides and that when a new comer ousts the dominant male he will kill any young cubs. They also know that thousands of wildebeest migrate through the Serengeti, preyed upon by lions, hyena and crocodiles. Who knows how many offspring aardvark have at one time? Or who knows how far a honey badger will walk in one nights foraging.
They are fascinating to say the least these smaller mammals and they are totally deserving of their own starring roles in documentaries and the media. Luckily for us they do appear regularly on Snapshot Serengeti’s camera-traps. Next time you get a porcupine, serval or aardvark stop and think what you know about them.
Zorrilla — a rare find!
For me one of the most fascinating small mammals is the sociable mongoose. On the camera-traps they are usually banded mongoose or dwarf mongoose. These guys bustle around all day risking ground based and winged predators. They have complex social lives that find them forever challenging each other of reaffirming bonds. To put it simply they are busy animals.
Dwarf mongoose! One of the cutest critters out there…
I once had the pleasure of a very close encounter with a group of wild dwarf mongoose. One super hot day I was ambling in the bush checking out camera trap spots, following game tracks, looking for likely spots when I came across a beautiful shaded clearing, not very big, a few meters in diameter. I decided to sit awhile and cool down so propping my back against a boulder and stretching my legs out I sat quietly listening to the sounds of the African bush. A sudden black flash and a drongo had flown into the opposite side of my refuge. Now these birds are adept at following mammals and catching any insects scared up by them so I was curious to see if anything else would arrive. Sure enough a rustle in the dry grass and here popped a dwarf mongoose into the clearing. The diminutive creature was followed rather noisily by about 10 or so more of its group. They fanned out each their own direction and immediately started searching for anything edible. I kept very still and tried not to breathe too much until one of the younger mongooses was sniffing my boot. A second scrambled right over my leg and I was entranced. Then the wind must have changed or an adult must have realised the strange rock might just be alive because a squeal was uttered and the whole group scarpered in one direction their drongo with them. The whole episode lasted about 6 or 7 minutes but it has endeared me to these ‘little guys’ for ever more.
Winter vacation
In the winter months (northern hemisphere winter, that is), we catch white storks on camera. They’re taking their winter vacation in the Serengeti — and across eastern and southern Africa.
White storks are carnivorous, eating insects, worms, reptiles, and small mammals. A flock of them like this makes me wonder about the diversity of small critters that they eat that we don’t catch on camera. Because they eat small animals, they can sometimes be seen near fires, ready to gobble up those creatures trying to escape flames and smoke.
The white stork has a favorable reputation with people in both Africa and in Europe, because it feeds on crop pests. In the spring, storks leave their wintering grounds and head north to Europe to breed. They build large nests out of sticks and are happy to do so on buildings and other structures with wide, unencumbered supports. And because they are considered useful — and sometime good luck — people allow them to build their nests on buildings. These nests are then frequently re-used year after year.
Several years ago I went to Poland to find my grandmother’s childhood home. This was made a bit challenging because when my grandmother was a child, the area was part of the Austro-Hungarian Empire and the names of everything — towns, streets — were in German. These days, of course, all the names are in Polish. After finding a list of place name translations, I set out to see if I could locate some buildings my grandmother described in her memoirs in a small town in the countryside outside of what is now Wrocław and was then Breslau. One of these was “Grandfather’s [my great-great-grandfather’s] water mill with its stork nest on the roof.” Sure enough, I found a large old building in the middle of town right by the stream. It no longer sported a water wheel, but there on the roof: a stork’s nest, complete with stork.
It’s no Serengeti, but…
Last year, my mom visited me in the Serengeti. We explored the jungle-like Manyara national park, held our breaths as elephants sauntered within reach of the Land Rover, and woke up at 3am to lions roaring next to our campsite in the middle of the Serengeti plains.
This week, I’m visiting my mom in her own little piece of North American grassland. I made a brief escape from the oncoming Minnesota winter to the normally balmy state of Virginia (it’s getting surprisingly cold at night here!) to help my mom with the little piece of paradise she recently purchased. This past spring she sold her home in the DC ‘burbs and moved out to the countryside, somewhere in between fancy horse country and cattle farms. It’s kind of perfect.
Indian grass, broomsedge bluestem and little bluestem, with autumn olive encroaching in the distance.
It might not be as otherworldly as the Serengeti, and there might not be any giraffes browsing by our deck, but my mom is working hard to maintain a piece of native mid-atlantic grassland on her property. Walking the meadow with the state’s conservation officer, we admired at the Indian grass and bluestem and scowled at the thick carpet of green fescue that made the yard inhabitable for the quail we hoped would recolonize. Grassland restoration is currently a major conservation initiative across the United States. Across the country, most native grasslands have been converted for agriculture; the suppression of natural fires has further allowed trees to grow up in meadows and shade out the sun-hungry grass. Ground nesting prairie birds (such as our bobwhite quail) tend to be the biggest losers in this game, because they need just the right amount of cover to be able to thrive. Fescue grass is too thick for baby quail to waddle through; the relentless olive trees grow fast and thick and threaten to turn our meadow into woods. I had no idea that maintaining native prairie was such a battle.
Spending so much time out in the east African bush, I sometimes forget how amazing our own backyards can be. My mom now has foxes, coyotes, bobcats, and black bears, and a fat, happy family of 8 baby wild turkeys that wobbly by at sunset. As much as I miss the Serengeti, the wildlands here are magical in their own way, and I suspect when I leave, I will feel a little homesick.
Pangolin!
A few weeks ago, Snapshot Serengeti volunteers spotted a Pangolin in Season 6. This is the best pangolin shot we’ve ever seen in this project.
Pangolins are rare and nocturnal, so you don’t see them often out in the field. The pangolin species we have in the Serengeti is called the ground pangolin (Manis temmincki), and it ranges from East Africa though much of Southern Africa.
I once went to Kruger National Park in South Africa for a conference and went on a guided tour in my free time; the tour leader asked what we wanted to see, and I shouted out “pangolin!” The tour leader gave me a withering look and we then went out to see the elephants and giraffes and buffalo that the other tourists were eager to see. I really did want to see a pangolin, though. I’ve never seen one in real life.
Pangolins have scales all along their back and curl up into balls like pillbugs when they feel threatened. They hang out in burrows that they either dig themselves or appropriate from other animals. And they have super long tongues that they use to get to ants and termites, their primary food. Pangolins have one baby at a time, and young pangolins travel by clinging to the base of their mother’s tail.
Pangolins don’t have any close living relatives. In fact, they have an order all to themselves (Pholidota). Because of how they look, scientists used to think they were most closely related to anteaters and armadillos. But now with genetic tools they’ve discovered that pangolins are more closely related to the order Carnivora, which includes all cats and dogs. It’s a bit strange to think that pangolins, which are sometimes called “scaly anteaters” have more in common genetically with lions than with actual anteaters, but that’s what the science tells us.
Many thanks to all of you who marked the new pangolin image in the Talk forum. That lets us make sure it gets classified correctly. ‘Pangolin’ was just one of those rare animals that didn’t make it onto the list of animals you can choose from, so our algorithm will classify it as something else, which we will fix by hand.
Who knew?
Just wanted to brighten your morning with a pretty unbelievable video that has nothing to with the Serengeti. Frogs freeze. That’s right. They don’t hibernate, they freeze. I couldn’t embed this video from NOVA’s Science Now site, but just click here to watch!
I hope that rocks your morning as much as it rocked mine.
Closer look: civets and genets
Civets
The African civet Civettictis civetta is the sole terrestrial civet found in Africa, the rest being found in Indian subcontinent. It is a heavy set cat-like animal and is still referred to as a civet-cat by some though it is not a member of the felids. Civets have a white body with black blotchy spots. They have a black face mask and black legs; the tail appears ringed with a thick black line running down the top. They have an erectile dorsal crest which they raise when alarmed or in aggression. This can be seen on a few of our camera-trap images.
The African civet is most famous for its musk that is used in the perfume trade. Don’t get the wrong impression, it smells terrible, but helps fix scent. Its use has mostly been replaced with synthetic fixers these days which is good news for civets. Civet farms are not regulated and animals are usually kept in small cages from which they are ‘milked’ daily. The real use of their perineal gland which is situated near the anus is to paste an object such as a tree to act as territorial sign post.
African civets are omnivorous, eating a wide range of vertebrate and invertebrate prey as well as taking advantage of fallen fruit. They are clumsy killers and often employ a bite and retreat or bite and throw tactic, where prey is bitten and thrown before quickly running away. The prey is hopefully immobilised so the civet can return to inflict the killing bite. Scent and sound are the predominant senses used by civets. They are classified as Least Concern on the IUNC Red List (International Union for Conservation of Nature)
Genets
The Genet family has 15 subspecies in Africa and these are all still hotly debated. The Serengeti is home to at least two of these, the Common Genet Genetta genetta and the Rusty Spotted or Central African Large Spotted Genet Genetta maculate. It is very hard to tell them apart, especially in a fleeting camera-trap picture but the Common Genet usually has a white tipped tail and the Rusty Spotted Genet has a black tipped tail.
They are small agile mammals that resemble a cat with short legs. Their silvery grey coat is marked with black spots in the Common Genet and black to brown spots in the Rusty Spotted Genet. They have dark marks either side of the muzzle below the eyes giving them a slightly racoon-like look. The tail which is banded is almost as long as the body and can appear quite bushy when alarmed.
The Genets are mainly carnivorous and they will eat mammals, birds, insects and reptiles. They hunt in trees and on the ground and are extremely dextrous. They spend their days in holes in trees, thick bushes, rocky crevices and sometimes in ground holes. Like civets they also have a perineal gland that they use for scent marking. To do this they will stand on their forefeet in a handstand posture and rub the raised gland on a tree or bush. Both Common Genet and Rusty Spotted Genet are classed as Least Concern on the IUNC Red List.
Summary of the Experts
Last week, william garner asked me in the comments to my post ‘Better with experience’ how well the experts did on the about 4,000 images that I’ve been using as the expert-identified data set. How do we know that those expert-identifications are correct?
Here’s how I put together that expert data set. I asked a set of experts to classify images on snapshotserengeti.org — just like you do — but I asked them to keep track of how many they had done and any that they found particularly difficult. When I had reports back that we had 4,000 done, I told them that they could stop. Since the experts were reporting back at different times, we actually ended up doing more than 4,000. In fact, we’d done 4,149 sets of images (captures), and we had 4,428 total classifications of those 4,149 captures. This is because some experts got the same capture.
Once I had those expert classifications, I compared them with the majority algorithm. (I hadn’t yet figured out the plurality algorithm.) Then I marked (1) those captures where experts and the algorithm disagreed, and (2) those captures that experts had said were particularly tricky. For these marked captures, I went through to catch any obvious blunders. For example, in one expert-classified capture, the expert classified the otherBirds in the images, but forgot to classify the giraffe the birds were on! The rest of these marked images I sent to Ali to look at. I didn’t tell her what the expert had marked or what the algorithm said. I just asked her to give me a new classification. If Ali’s classification matched with either the algorithm or the expert, I set hers as the official classification. If it didn’t, then she, and Craig, and I examined the capture further together — there were very few of these.
Huh? What giraffe? Where?
And that is how I came up with the expert data set. I went back this week to tally how the experts did on their first attempt versus the final expert data set. Out of the 4,428 classifications, 30 were marked as ‘impossible’ by Ali, 1 was the duiker (which the experts couldn’t get right by using the website), and 101 mistakes were made. That makes for a 97.7% rate of success for the experts. (If you look at last week’s graph, you can see that some of you qualify as experts too!)
Okay, and what did the experts get wrong? About 30% of the mistakes were what I call wildebeest-zebra errors. That is, there are wildebeest and zebra, but someone just marks the wildebeest. Or there are only zebra, and someone marks both wildebeest and zebra. Many of the wildebeest and zebra herd pictures are plain difficult to figure out, especially if animals are in the distance. Another 10% of the mistakes were otherBird errors — either someone marked an otherBird when there wasn’t really one there, or (more commonly) forgot to note an otherBird. About 10% of the time, experts listed an extra animal that wasn’t there. And another 10% of the time, they missed an animal that was there. Some of these were obvious blunders, like missing a giraffe or eland; other times it was more subtle, like a bird or rodent hidden in the grass.
The other 40% of the time were mis-identifications of the species. I didn’t find any obvious patterns to where the mistakes were; here are the species that were mis-identified:
| Species | Mistakes | Mistaken for |
| buffalo | 6 | wildebeest |
| wildebeest | 6 | buffalo, hartebeest, elephant, lionFemale |
| hartebeest | 5 | gazelleThomsons, impala, topi, lionFemale |
| impala | 5 | gazelleThomsons, gazelleGrants |
| gazelleGrants | 4 | impala, gazelleThomsons, hartebeest |
| reedbuck | 3 | dikDik, gazelleThomsons, impala |
| topi | 3 | hartebeest, wildebeest |
| gazelleThomsons | 2 | gazelleGrants |
| cheetah | 1 | hyenaSpotted |
| elephant | 1 | buffalo |
| hare | 1 | rodents |
| jackal | 1 | aardwolf |
| koriBustard | 1 | otherBird |
| otherBird | 1 | wildebeest |
| vervetMonkey | 1 | guineaFowl |
Night of the Lion
Most of you have probably seen this picture:
Kill in action
As well as the ones after it:
Joined by a pridemate.
staring out of view of the camera…
Three minutes later…
Trade-off again…
Where are the leftovers?
This series of photos was taken at site H11 along the Loyangalani river and remains, to me, one of the most amazing accomplishments of our camera trap survey to date.
First, seeing a kill is rare. In the 47 years that the Lion Project has been watching Serengeti’s lions, we’ve only seen lions with about 4,000 carcasses; of those, we’ve only actually seen them in the act of killing 1,100 animals. That might sound like a lot, but with one or two people on the ground, almost every day of the year, racking up nearly 50,000 sightings, that’s not that often.
I don’t love this series simply because this random, stationary, complacently-stuck-to-a-tree camera trap caught this rather rare event – but because it goes on to document the story that follows: A single lioness takes down a zebra much bigger than herself. Within minutes, her sister joins her (free meal!). Note how big their bellies already are though, when they begin to eat. These aren’t particularly hungry lions to begin with. About 45 minutes later, they are staring out of view of the camera, and then comes a group of hyenas. The carcass goes back and forth between them throughout the night, with a jackal darting in to sneak a nibble.
Food stealing, or kleptoparasitism, is a major part of life for Serengeti carnivores. Contrary to long-standing popular belief (reinforced by the Lion King), hyenas are not skulking scavengers living only off others’ leftovers. Hyenas are quite adept predators and scavenge only about 40% of their diet; lions scavenge at least 30% of theirs. And, in fact, lions steal a lot more food from hyenas than is apparent at first glance. More often than not, when we see hyenas lurking anxiously around a pride of lions demolishing a carcass, it’s because hyenas made the kill, and lions stole it away. Research from Kenya suggests lions might actually suppress hyena populations simply by stealing their food.
On the flip side, work from Botswana suggests that hyenas are able to steal food from lions if and only if hyenas outnumber lions by at least 4 to one, and there are no adult male lions present. (Remember, males are half again as big as females: hyenas don’t stand a chance.) But observations that Craig and a former graduate student made from the Ngorongoro Crater further revealed that even when lions do give up a kill, they are so full they can barely move – it’s simply not worth the effort to fend off hyenas any more.
So, kleptoparasitism is a part of life if you are a Serengeti carnivore, but it’s not always as simple as the movies make it out to be. It’s a pretty cool mechanism that might be driving predator dynamics though – I just wish it weren’t so hard to test!!
Snapshot Serengeti 