Archive | August 2018

Recap on Snapshot

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Snapshot Serengeti camera-trap image: Topi

Whilst stretching the corners of my brain to think about a new topic to write about in the Snapshot Serengeti blogs it astounds me to realise just how long we have been going for; over 7 years now as Snapshot Serengeti and almost 10 if you include the Serengetilive days.

It is also humbling to know how dedicated our followers are and what support we get from them. Our fun would have been over long ago if the community had not backed us. It has occurred to me that Snapshot Serengeti’s followers do so in differing ways. Those who follow our facebook and twitter pages or WordPress fans who follow us through our blogs may have missed what it is we are up to. So at risk of boring those of you who do know I thought it was about time to reiterate what it is we at Snapshot Serengeti do and how it all works.

Our largest group of followers do so at www.snapshotserengeti.org helping us classify the millions of camera-trap images that are produced by around 225 camera-traps placed in a permanent grid pattern in our study zone in the Serengeti National Park. For continuity’s sake these sites, after an initial bit of trial and error have remained in their fixed spots since they were first chosen by the projects designer, Dr Ali Swanson back in 2010.

Originally the camera-trap grid was set up to answer questions on carnivore interactions specifically if carnivores were avoiding one another spatially and temporally, it soon became apparent that it could be used to pose many more scientific questions amongst them herbivore coexistence and predator prey relationships. The wisdom to leave this permanent window of observance into the lives of the Serengeti animals should lead to many future studies and has spawned many new similar camera-trap projects around the world.

It’s not all about the animals, in fact since teaming with Zooniverse the project has been as much about the advancement of citizen science as anything else. Back in the Serengetilive days there were so few of us taking part that we used to have our names up in a sort of league table of who had classified the most images. Each classified image was labelled by the classifiers name. Now of course there are far too many participants to bother with that kind of thing, besides with multiple people having to agree on each classification it might get messy. The work on developing a robust algorithm that dealt with the uncertainties in each individual classification was so involved it also paved the way for many more projects and several scientific papers.

So what do we ask classifiers to do? Well first you are presented with either a run of 3 images (day time) or 1 image (night time). You are then asked to decide and record what animals are present, numbers of each species, behaviour and whether there are young present or not. It’s pretty straight forward with prompts along the way. If you don’t know what the animal is you simply guess. Yes you read that right, you guess. One thing the developers worked out is that the whole project works better if you cannot skip images. For one thing it avoids all the hard or boring images being left till the end. As each image has to be agreed upon by several classifiers before it is retired this tends to smooth out any miss classifications and research has shown we are around 97% accurate.

If you find something good or something you cannot id and are curious you can add the image to Talk which is the discussion forum. There we have some very dedicated moderators who will help you with your queries.

All in all Snapshot Serengeti is about learning and sharing both for the researchers and for the community of classifiers so if you have been enjoying the facebook posts or reading the blogs but have never had a go classifying get yourself over there to www.snapshotserengeti.org and have a go.

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A Spiky Surprise

There is one little animal in Europe that is loved by all, immortalised in children’s books, welcomed by gardeners and flagship of the realisation that our mammal populations may be declining due to our very own actions. Over in the States although not native these same creatures are kept as pets (that’s another story and not such a good one). Although it’s hardly a creature to cuddle or pet they are thought of as very cute, something to do with that snuffling around your garden in dry leaves and, getting all snoozy, having to sleep away the winter in a cosy corner. Yes, I write of the hedgehog.

Now, why, I hear you ask is she writing about a European mammal on a blog about the Serengeti? Well it may come as a surprise to some to find out that there are in fact 18 species of spiny hedgehog found across Europe, Asia and Africa. Six species are present in Africa. The North African hedgehog (Atelerix algirus) extends its range across the Mediterranean belt of North Africa and Iberian Peninsula as well as the Balearic and Canary islands. The long-eared hedgehog (Hemiechinus auritus) touches into Libya and Egypt and the desert hedgehog (Paraechinus aethiopicus) a true Saharan specialist. The last two species are also found through Arabia and Asia. The remaining three species are solely found in Africa; the southern African hedgehog (Atelerix frontalis), Somali hedgehog (Atelerix sclateri) and the four-toed hedgehog (Atelerix albiventris).

The four-toed hedgehog is found across West, Central and East Africa as far as the Zambezi River and so is the species that is found in the Serengeti. As far as I know we have never had a capture event from our camera traps of this enigmatic little creature but please let me know if someone has come across one.

In European culture where woodlands are seen as wildlife havens most people would associate the hedgehog with forests or at the very least the edges of forests and hedgerows where indeed this species is well at home but its African cousins are rather different in their habitat preferences. The four-toed prefers the drier regions and is partial to grasslands and according to The Handbook of the Mammals of the World vol 8 it especially likes overgrazed regions with dense ungulate populations. All that trampled grass and dung supports plenty of insects for it to munch. Well that sounds just like the Serengeti to me!

Although insects make up a large part of the diet they are omnivorous and will eat fungi and fruits as well as other plant matter. A little known fact, they will also kill small vertebrates like frogs, lizards and mice and are known to take on even venomous snakes. Their spines are great protection from the bite of an angry snake.

As formidable as those spines are it is the ability to curl up into a ball that is their true defence. Now they don’t just tuck their heads in and hope for the best, the skin that the spines are attached to is very flexible and is edged by a strong band like muscle that is attached to the forehead. When it is contracted it acts like a drawstring on a bag that holds in the body, head and limbs with the spines closing up the seal. It works remarkably well but inevitably certain animals have learned how to unzip the bag, honey badgers and eagle-owls are amongst those experts in the Serengeti.

As a family hedgehogs are known to perform a bizarre act known as self-anointing. The hedgehog will chew and lick a substance until it has a mouth full of saliva and then with acrobatic contortions it will plaster this saliva all over its body, apparently they do this in a frenzied manor and it is quite hard to distract them once in the process. What is unclear is why they do it. There is no obvious reason. Studies have shown every age group performing self-anointing including nestlings whose eyes have not even opened. They only thing that stands out is that strong smells and tastes seem to trigger the behaviour such as dog or fox urine and a whole host of human made items such as leather, polish or nylon stockings. I am not even going to ask what the scientific research question was when they discovered those three!

So from Mrs Tiggy-Winkle (Beatrix Potter) to sonic the hedgehog we may all be very familiar with this loveable creature but perhaps we don’t know all there is to know. Keep your eyes out for the first Snapshot Serengeti camera-trapping.

 

Atelerix_albiventris

Four-toed hedgehog

Image: Author Jkasui, Wikimedia, https://creativecommons.org/licenses/by-sa/3.0/deed.en

The Other Great Migration

White Stork

 

I am sitting at home in France in a sweltering 40oc listening to golden orioles calling from the tall riverine trees. I could definitely be in Africa, though if I was I would probably be somewhat reluctant to jump in the river to cool off, something I am about to do, what with all the hippo and crocs that the Serengeti is so famous for.

It has got me thinking though about all our shared birds between Africa and Europe. Hearing the orioles today has made me realise that they will be setting off very soon, in the next couple of weeks probably, for their return trip to their wintering grounds in Africa.

Now the Serengeti is justly known for its rather famous herbivore migration but to me it is utterly fascinating that birds, particularly the tiny ones are also taking part in seasonal movements that cover 1000’s of kilometres.

It’s a dangerous journey, they risk predation, starvation and severe weather and if that’s not enough they have to pass over several places where humans think blasting as many of them out of the sky as possible is sport. For the birds migrating from Europe to Africa they have to fly over open sea and a lot have to negotiate the Sahara Desert, an area around the size of the United States. It is estimated that 500 million birds have to cross this unforgiving wilderness and some do it in a long nonstop flight. Just imagine how exhausted they are the when they reach the safety of the green belts that fringe it. My husband used to work in the Sahara and can attest to finding dozens of swallows just lying panting on the ground, being able to pick them up and give them water before launching them onwards.

So why do they do it, well much the same reason as wildebeest and zebra do, resources. Birds have the very special ability to travel very efficiently, it has been said that a small bird can fly the same distance in hours that an elephant would cover in three days. With this ability birds are able to switch geographical areas in order to take advantage of seasonal food supplies and so they enjoy the best of both worlds in terms of food abundance despite the risk involved with moving the great distance between the two. Risk versus reward.

Unlike the Serengeti herbivore migration birds have many different strategies when it comes to undertaking their colossal movements often depending on the species unique design. Many small passerines will migrate in small groups, travelling at night and will try for the shortest, most direct route. A kind of fast and furious approach that relies on having fed up well and being able to feed quickly at the few places they do stop to refuel. Other birds, particularly waders will take a more leisurely approach flying down waterways and coasts, stopping for days or weeks at a time to feed up before moving on. Many raptors and storks cross the Mediterranean Sea over Gibraltar and Tarifa in Spain. It is roughly a 14 kilometre crossing. It is an amazing spectacle to see. Thousands of birds can be seen soaring around in the late morning over land waiting for the thermals to build up which they will use to ride across the sea to Africa. It’s kind of like surfing only on hot air.

Once they get to Africa of course they have a huge choice of where to go and they spread out accordingly, many making it all the way to South Africa. In fact we still don’t know where a lot of them go, something that is vital to understanding the threats facing them today.

So who are the feathered migrants that we may see in the Serengeti? Well across Tanzania there are thought to be around 160 species of Palaearctic/African migrants. The Palaearctic is a large region covering Europe, Russia, North Africa, Arabia and parts of Asia so that’s a lot of movement.

Some of Europe’s smallest birds can be found in the Serengeti amongst them willow warblers, wood warblers and blackcaps. Spotted flycatchers and several shrikes can be easily seen. The common cuckoo is trickier as it is, like many migrants, silent outside of its breeding ground. European bee-eaters and rollers meet up with their African cousins as do barn swallows and common house martins.

Even raptors make it to the famous park; lesser spotted, steppe and imperial eagles all breed in the Palaearctic. Eurasian marsh harrier, black kite and common buzzard all enjoy the warm African conditions before heading back north to breed.

For Snapshot Serengeti followers the most commonly seen migrants on our camera-traps are probably storks, white storks and black storks all take the long journey north for breeding. More surprisingly given it is not noted for its water even European ducks have been spotted in the Serengeti, wigeon, Eurasian teal and garganey amongst them.

This is not an exhaustive list but gives you an idea of the level in which the two continents are connected through their shared avian fauna and reminds us of what a truly global planet we live on.