Do fires stop the Serengeti migration?

Dr Kate Parr lighting a controlled fire in the Serengeti Ecosystem

There's been a bit in the East African press recently claiming that Tanzania has been deliberately setting fires in the Serengeti NP to block the migration. The Tanzanian National Park Authority (TANAPA) have, of course, denied this. Reading the articles and press releases there's obviously both some serious ignorance and some seriously bad journalism going on here, and I thought it might be useful to share a few of my observations.

East African Butterfly families and corrupt, singing caterpillars

Citrus Swallowtail, Papilio demodocus, is very common in Tanzania

We're rarely short of butterflies in Tanzania, but they're a sadly overlooked group. Except, perhaps, when they're swarming by the million as earlier this year most people will, at best, only notice a few in passing. For a hugely diverse group (there are over 18,000 described species), they fall into a relatively small number of readily recognisable families. Unfortunately, all the nice identification books are out of print (and wickedly expensive to buy on ebay!) for East Africa, but there are some resources out there that will help once you've figured out the families. The relationships between the families have recently been the subject of some serious work. It turns out that the family relationship were rather difficult to pin down because they all evolved relatively quickly in the Cretaceous (yes, dinosaur time, 100 - 75 Million Year Ago). But our best guess at the moment sorts them into 4 main groups split into a total of 26ish main family groups, only a few of which are at all diverse. So it's not too hard to get to grips with the main families, and the main change to the traditional taxonomy, if you've been into that, is that the big group Papilionoidea is actually two, rather distantly related groups. I'm going to describe some of the common families here (together with some of my favourite stories about them - yes, including corrupt, singing caterpillars) and hopefully will be able to show how the various families fit together at the end. So, here goes...

On cattle in African protected areas

Typical pastoralist scene near Lake Eyasi

Talking about blog topics the other day, a friend asked me about the impact of goats and cattle on wildlife. And then over here someone else started a similar discussion on cattle, which collected a wealth of different ideas, so I thought it would be a good idea to collate all this information for a different audience over here. Increasingly, discussions about cattle come up when people are visiting areas that aren't National Parks - here in Tanzania many people are surprised to see cattle (and their Maasai herders) right in the Ngorongoro crater, as well as around the rest of the NCA. And increasingly (particularly in Kenya where land laws make it much easier, but also here in places like Manyara Ranch) conservancies are being set up where communities set aside land for both wildlife and pastoralist activities. The fact that organisations like the Northern Rangelands Trust are making a real success of this, combined with ongoing concerns about displaced people and human rights issues, has encouraged people to think seriously again about whether the strict 'no people' policy of many national parks in Africa might be relaxed, and recognising this a few years ago the International Conservation Union (IUCN) relaxed their national park category definition to allow management "To take into account the needs of indigenous people and local communities, including subsistence resource use, in so far as these will not adversely affect the primary management objective". So, what are the issues here, and what are the ecological arguments? In this post I'm going to deal with cattle, and leave the goats and sheep for a future occasion.

How do Kopjes form?

It's a question I regularly get asked by guides and also one that seems to bring a lot of google-searching visitors to the site, but I've not actually posted much of an answer yet although we have covered it briefly here, so here goes...

Cross-section through a kopje in the process of formation
from smooth, uninterrupted landscape at the top to
typical kopje at bottom, following millions upon
millions of years of erosion.

We start by remembering that Africa is old - most of the surface rocks are pretty ancient (and consequently washed clean of most nutrients - an issue we've talked about repeatedly). During these millenia, mountains have been formed and then worn down to small hills, whilst the valleys, plains lakes and seas have been buried in the sands and gravels of this erosion process. Over time and with immense pressure these sands and muds too have sometimes been 'recycled' into sandstones and mudstones in someplaces. It's not just been static though: later volcanic events sometimes push magma (un-errupted lava) through the layers of rock towards the surface where it cooled and formed an intrusion of new rock within a mass of older layers. (As shown in the diagram!)

Why do birds sing in the morning?

Ruppell's Robin-chat: an impressive mimic. Lake Duluti

I enjoyed a walk around Lake Duluti yesterday morning and came across a couple of wonderfully singing Ruppell's Robin-chats. These are great birds, with an amazingly varied song hat's gull of mimicry (of you want to hear one, listen here!). For me, one of the best things about camping in the bush is being able to lie in bed and listen to the birds waking up while it's still too dim to see them properly. The dawn chorus is a worldwide phenomenon and I'm often asked about bird song, so I thought it would be worth exploring some of the theories behind bird song, and - particularly - why birds sing in the morning. It's something that's interested me since I was introduced to the question by a friend of mine who did a PhD on the subject some years ago, and I know he reads the blog so I'm hoping he'll make sure I get the answers right!

Lewa Downs wildlife corridor really works!

As regular readers will have realised, I'm something of a sceptic about most things, and one of the things that I've been pretty sceptical about in the past is wildlife corridors. They sound like a great idea: wild spaces are increasingly fragmented (even here in East Africa), and as that process continues populations of plants and animals within these areas will become increasingly isolated from one another. Isolated and small populations are more likely to go extinct than large, well connected populations for a number of reasons ranging from inbreeding - in small populations you're rather more likely to have to mate with a brother or sister than in a large population, which can have serious genetic costs, to simply the risk of extreme events wiping everything out. So connecting those fragments with corridors along which animals can pass seems like a really good idea. Tiny experiments using micro-ecosystems where no-one cares if you isolate populations or connect them seemed to suggest that there might be something in this idea, and all of a sudden conservation corridors were high on the agenda.

Nairobi bugs: WMD or Cancer cure?!

15 times more toxic than cobra venom, you really shouldn't eat a Nairobi beetle!

Nairobi bugs (also known around East Africa as Nairobi Eye, Nairobi Fly, Nairobi beetles, Blister Beetles and a whole range of other names) are not the best loved creatures out here. This year they've come out in greater number than the last few years, presumably thanks to some relatively good rains, and whilst they're not loved, they're certainly fascinating wee beasties. But before we go into the details, let's start with some identification preliminaries.

There are actually at least two species of beetle known as Nairobi bugs around here, but they're so similar that most people won't notice them. Similarly marked relatives of these two are pretty widely distributed across the world, mainly in the tropics, and for now I don't think we need to bother about the precise identification. They're all small (7mm-1cm ish) and well marked with typical warning (aposematic) colours of black and red. In fact, despite the variety of names these are beetles (Coleopterans) of the family Staphylinidae, the rove beetles. If you don't know the Nairobi beetle, you might well know the Devil's Coach-horse and similar species - much larger and all black, but of a similar basic structure. The beetles we're interested in are of the genus Paederus and are carnivorous beetles that live mostly in long grass and anywhere with rotting leaves. And the most interesting things about them, as anyone will tell you, is that whilst they neither bite nor sting, they're still seriously nasty.

Migrant bird population declines, an African perspective

Willow warbler singing in Africa - 10g but probably headed to eastern Siberia...

March is the month when northward migration of songbirds gets underway in East Africa, so this weekend I was excited to be out west of Arusha with friends and to find stacks of migrants already on the move. Driving in I noticed some really smart looking wheatears (both pied, and the very impressive northern wheatear, though many of them have already set off on their mammoth treck - perhaps as far as Alaska). But the highlight for me was the bushes alive with warblers on Saturday morning. I saw flocks of Willow Warblers, Olivaceous Warblers, Common Whitethroats and even little groups of Barred Warblers, usually a very scarce migrant around here. Some of them were even singing, in anticipation of starting breeding in a few more weeks when they get back to Europe! Having a managed a few photos I thought it the ideal opportunity to talk about bird migration.

Barred warblers are always a treat to see: headed to eastern Europe.

All these birds have been rather scarce until now, this season, and many of us have been wondering where they've got to - usually Willow Warblers and Olivaceous Warblers are one of the commonest birds in the bush from November to March, this year there have hardly been any. It's a question that will be familiar to many readers from Europe - where have the migrant birds gone? Research has suggested over the last few years that in Europe at least, migrant birds are declining faster than resident species, a change that has been attributed mainly to climate change. A number of theories have been put forward to explain why migrant birds may fare worse than resident species from the impacts of climate change - from them simply missing the peak spring food availability by arriving to late in Europe as springs get warmer (and therefore earlier), to direct effects of drought or land-use change in Africa. A recent paper (sorry, not free) has attempted to look into some of these likely causes using data on breeding population changes in the UK, and it serves as a nice bit of background to some of the remarkable things that birds do when they set off on their amazing migrations.

The role of termites in the savanna biome

The ground is crawling with termites! Nr. Tarangire, Now 2011.

Termites are hugely important to the ecology of the savanna biome. We've covered some of their roles here before when we talked about termite mounds and when we covered nutrients and nitrogen in the savanna biome. The numbers of termites in savanna habitats can be quite extraordinary: with over 400/m² of soil, their biomass can exceed that of mammals in the ecosystem. Such a huge abundance of animals mean that termites, by weight of numbers alone, must have a massive impact on the ecosystem. We've seen how they are crucial for keeping nutrients cycling rapidly in the savanna, how their excavations can change the texture of the soil and how these impacts change the plants and, ultimately, the behaviour of animals within the savanna. Despite this obvious importance, however, there's surprisingly little research on what they actually get up to and where they really are - I guess researchers are generally too busy tracking lions sleeping under a bush than worrying about termites under their feet... It's important though, as processes that cause spatial variation in patterns of nutrients and such-like are increasingly being perceived as vital to the ecosystem as a whole, and if we don't understand the processes that cause variation, it will be much harder to understand what's going on at larger levels. Still, some work is coming out now, and a paper last year caught my eye.

Commelina, the Maasai Reconciliation Grass

Commelina sp, Mongo wa Mono, March 2011

It's surprisingly easy these days to find information on the medicinal use of plants (there's a great list for the Samuru people here, for example), such as the Commiphora uses we covered last week, but many plants have cultural significance beyond the simple medicinal uses and it's often much harder to find information about these uses. One of the 10 things I like to get people talking about when there are no lions is all to do with people, and talking about cultural uses of plants is often quite interesting. I was seriously impressed when one of the guides on our training course in November said that in 'circumcisim school' he'd had to learn to identify about 200 plant species and know their cultural and medicinal uses, so this knowledge is still very much alive out here - though he did confess to having forgotten many (before going on to hive an example of a rather harrowing use for one of the Euphorbia species that really isn't suitable for polite company...). So it's rather surprising how shy people can be about sharing the information, perhaps thinking it's not interesting, or somehow backward.

Why the hornbill shuts its nest

Von der Decken Hornbill nest cavity - it's tiny!

 This weekend I enjoyed a camping trip out to Simanjiro with some friends, and as well as finding some very cute new-born wildebeest, we found a number of nests. One of these, just near our campsite, was a pair of Von der Decken's Hornbill. All the hornbills of the genus Tockus have two fascinating pieces of nesting behaviour that it's well worth thinking about: firstly, after choosing (and sometimes modifying) a suitable nest cavity, the female climb inside and then plugs the nest hole with mud, faeces and other grot, sealing herself in until there's only a tiny slit through which the male feeds her and, later, her chicks. Secondly, as she's sitting there she carries out a simultaneous moult, meaning she drops all her flight feathers at once and is unable to fly. Nearly all birds moult their feathers once per year (larger birds sometimes take longer), but most do a sequential moult, meaning they drop feathers one after the other and replace them as they go, thus retaining the ability to fly throughout. (There are exceptions, of course - notably ducks and geese who also drop all their flight feathers at once.) In the case of the female hornbill, however, she goes in the nest hole, shuts the door and a little while later drops all her flight feathers. Interestingly, if she doesn't breed, she moults sequentially, just like the male, so there's some suggestion that the simultaneous moult strategy is triggered as a hormonal response to the dark interior of the nest. Now, that's the story that you'll read in all the papers (e.g. here and here), but it can't be the whole story as I was trying to find some pictures to point you to of birds inside nests looking all naked, and I couldn't. In fact, here are a few pictures that show females in the nest - this one is an African Grey Hornbill with smallish chicks, but clearly well feathered mother with fairly worn plumage - she's not just completed a moult. And here's an Asian species also with young chicks who certainly doesn't look in moult to me. I'm sure it happens though, and may be the norm, but there are obviously exceptions that haven't yet made it into the literature.

Climate change and African vertebrates

Last year I spent a very happy evening in Cape Town enjoying some of the local specialities with a colleague and a visiting student. Or at least, that's what I thought - poor Raquel now tells me I was giving her a hard time... Still, good practice for her eventual defence of her thesis I hope. Anyway, she pointed me in the direction of the paper she was writing at the time that's now out and attempts to describe what's going to happen to some 2723 species of African vertebrates as the climate changes over the next several decades. Now, despite climate change being a huge conservation issue and one of my main research interests (and climate/weather being one of my 10 things to talk about), we've not talked much about it here on the blog before, so the chance to discuss what might happen to 2723 species across the continent as a whole is an ideal opportunity to start!

A few things you (probably) didn't know about weaver ants

 Ants aren't usually the first things people look at when on safari, but they are fascinating beasts when looked at up close. We briefly featured siafu here once before, but that's not enough for a really important group of invertebrates, and it's time to rectify that. Finding I had some nice pictures of Weaver Ants Oecophylla longinoda (right) I thought they might make a good start as they're not only fairly common in some areas (particularly near the coast), but they're pretty interesting too. In fact, on starting a bit of research I discovered they're even more interesting than I first thought! There are actually two species in this genus, the African species, and a closely related species that occurs across Asia and into Australia. There being (I suspect) rather more myrmecologists in Australia than Africa, a lot of the relevant research comes from there, but it seems highly likely 'our' species do the same, so here are a few things you might not have known about weaver ants before.

Life spans of tropical birds

Admirng a White-browed Scrub Robin!

Pangani Longclaws are very impressive up close

This morning I took my children with me to go out and do some bird ringing (banding, if you're from the US or Australia!) with some friends just out of town. As is often the case when I'm ringing, I get asked lots of questions about why we ring birds, today's best was why we keep catching immature birds? There are lots of answers to this question and some of them focus on the fact that young birds are just less careful and are generally more stupid than their parents - but this bias aside it is a really good question and had me thinking again about the differences between bird lifestyles here in Africa, and those in higher latitude areas like Europe and North America. It just happened that the question came up after we'd caught two migrant birds (from Europe) and a very new baby White-browed Scrub Robin - all birds hatched within the last year. What I said at the time (and now I can look back over all the birds we caught this morning it's even clearer) was that whilst we often catch more immature than adult migrants, that's not true for the resident African birds we were catching. In fact, we only caught about 25 birds this morning, and only three of them were migrants (we were hoping for more, but this year has been surprisingly poor so far down here, the talk of all the local birds at the moment, as conditions seem good to us!), but all the migrants were young, whilst of the remaining resident African birds, only three were immature. This sample alone, of course, is of limited use: as a scientist I'd want much larger sample sizes - and I'd also want to know it wasn't just a seasonal thing - many of our local birds are only just begining to breed, so there simply aren't many babies around yet. But put our results together with many others, and start to look at the data gathered in more detail and it is indeed clear that African birds do things rather differently to their higher latitude counterparts - as described in a nice paper by Wiersma et al "Tropical birds have a slow pace of life" (get it free here!). Not unlike a lot of people living here either!

Lovebirds can live up to 20 years - they can also bite hard, so be careful extracting!

How colourful are birds?

Lilac-breasted Roller, eveyone's safari favourite! Indigo & Violet

One of the best things about birding in the tropics is the sheer brilliance of many of our bird's plumage. After a day in the field you can easily think you've seen birds of every colour of the rainbow - and you're probably right! In a paper published last year by Mary Stoddard and Richard Prum (available free to all here) they demonstrate nicely that whilst they do cover the whole rainbow (and more besides), they still don't cover even the majority of the potential colours available to them - only about 26-30% of the potential options, it seems.

Red: Scarlet-chested Sunbirds use structural and pigmented colours

To understand how anyone can ever assess exactly how many colours are availalbe to birds, you need to start by understanding that many birds (though not all) actually see more colours than us - a lot can see ultraviolet light, as well as the usual combination or red, green and blue that we humans (and most other primates) see. (By contrast, most other mammals lack even our ability to see red, so they must live in a rather dull-looking world!) So by knowing the entire set of colours that can be generated from red, blue, green and ultraviolet the authors identified the potential range of colours available to birds, and they then sat down and looked at nearly 1000 (965 to be precise) sets of feathers and precicesly measured their colour, then plotted it in the red/green/blue/uv colour space. And they discovered that despite their efforts to find feathers covering as many different colour types as they could, they only found colours in about 1/3rd of the available space. In particular, birds seem to be missing a lot of the different options of green and purple. Now, there certainly are green and purple birds out there, but not all the possible forms of green, and not all the possible sorts of purple. (They're not particularly good at pure UV either - but that might in part reflect the author's inability to identify strongly UV feather groups in their initial search - we can't see it after all!)

More amazing honeyguide discoveries!

Steel-blue Whydah, Seronera, Dec 2011.

We've featured honeyguides on the blog here before, and I wouldn't normally come back to the same species so soon, but another recent paper (available to all for free here) by Claire Spottiswoode and colleagues has grabbed my attention by demonstrating nicely some of the challenges that generalist brood parasites have to overcome. There are, of course, three groups of brood parasites (birds that lay eggs in the nests of other species to let them raise the young) in East Africa: the well known cuckoos and the less well known honeyguides and whydahs.

Greater Honeyguide, Tarangire, Sep 2011

Now most whydahs are extremely host specific - the Eastern Paradise Whydah will only lay in Green-winged Ptylia nests, whilst Broad-tailed Paradise Whydah nests in Orange-winged Ptylia. Similarly, Straw-tailed Whydah is pretty exclusive to Purple Grenadier, Purple Indigobird is perhaps best identified by listening to snatches of it's host, Jameson's Firefinch, etc. Others are slightly less specific - the Steel Blue Whydah lays in the nests of the very closely related Black-cheeked and Black-faced Waxbills and Pin-tailed will parasitise several waxbill species. Cuckoos and Honeyguides too tend to specialise somewhat, but not completely. And this is where it gets interesting. To some degree is obvious that in a species with a single host there are strong evolutionary pressures on the female to lay eggs of a similar size, colour and marking to that of the single host, a relatively simple problem. But it's less easy if you're trying to match several different species all at once as even closely related species often have differently marked eggs (perhaps as a mechanisim to make brood parasite's lives harder?). And so we find that in some of these groups some interesting evolution has taken place - in Cuckoos we've long known that females will (nearly) always lay their eggs in the nests of the same species as they were fostered in. If such differentiation happened over the long term, one might expect a new species to evolve - one that parasitises one species, another on another (which might well be what happened in the whydahs, or even among the other groups too). But the difference here is that males don't care - they'll mate with any female that looks right and is willing, so the species as a whole remains united, despite female 'races' developing. So then you have to ask whether females from one host lay eggs that differ to those of females from another host, and if so, how can they possibly have evolved such specific genes to colour and pattern the eggs in the face of complete mixing from the males? And this is (part of) the question that Claire and colleagues were interested in.

Male Greater Honeyguide, Tarangire, Sep 2011

They show very nicely that Greater Honeyguides have two main groups of host species - birds that nest in tree holes (African Hoopoe, Green Wood-hoopoe, etc.), and those that nest in earth holes (Little Bee-eater, Striped Kingfisher, etc.). The former have larger and longer eggs, the latter smaller, rounder ones. And so two forms of female greater honeyguides seem to have evolved - one specialising in the tree nesters, one in the ground nesters and as expected the females of each group lay appropriately shaped and sized eggs. So how do they do it? Well, one of the important theories that was developed as long ago as 1933 is based on another fundamental difference between birds and mammals that's important to know. In both mammals and birds the sex of a developing embryo is determined by chromosomes, the DNA containing structures that control inheritance. In mammals, everyone has one 'X' chromosome we inherit from our mothers, but from our fathers we can either inherit another 'X' chromosome (which would make us female), or - like our father - we could inherit a 'Y' chromosome, which would make us male. The 'Y' chromosome is therefore inhereted father to son, to grandson, etc., without ever finding itself in a female, and it's this pattern of inheritance that makes us male or female. Now what differs in birds is that instead of the X and Y combination making us male, it would make a bird female. Male birds have two of the same type of chromosomes, females are the ones with the different pair, and to make this distinction easier we don't use the X and Y terminology, but talk of W and Z chromosomes instead. So, unlike in mammals, it's the females of birds who have a unique chromosome that is passed one through mother to daughter to grand-daughter, without ever passing through a male. So if the information for how to colour your egg is stored on this chromosome, no information about it will ever come from a male. A neat solution to how the species as a whole can be unified by the males, but females can differ (possibly substantially) in the genes they have on their unique chromosome.Hope that's clear...

Now, Claire and her group went one step further and decided to look for differences in a special sort of DNA called mitochondrial DNA that is also only inherited from mother to daughter, and compare the degree of difference between the two groups of tree and ground parasitising females in the mitochondrial DNA with the difference in the DNA in the main part of the cell that comes from both male and females. They expected - and rather neatly demonstrated - that there might be substantial differentiation between the females in mitochondrial DNA, but that the males would mean there's little difference in the main 'nuclear' DNA. And the degree of difference in the mitochondrial DNA between the tree and ground nesters was so much that their ancestors started breeding in these two different way millions of years ago! That's pretty remarkable, and rather different from the more recent splits reported for cuckoos, probably brought on by relatively recent host changes. Why this difference? Well, they speculate that it's thanks to the greater staility of the African climate compared to the Northern one where most of the work on other brood parasites has been undertaken, but I'm not yet convinced - if we could compare similar patterns for a few local cuckoos too, that might be very interesting!

Anyway, all very impressive and a great lesson not only in the complexities of brood parasitism that is fascinating to me, but a bit on sex determination too - a subject we're sure to return to in the future...



Reference:

Spottiswoode, C., Stryjewski, K., Quader, S., Colebrook-Robjent, J., & Sorenson, M. (2011). Ancient host specificity within a single species of brood parasitic bird Proceedings of the National Academy of Sciences, 108 (43), 17738-17742 DOI: 10.1073/pnas.1109630108

TAWIRI Conference discussions

I've spent most of this week at the Tanzania Wildlife Research Institute (TAWIRI) conference here in Arusha. This is an event that happens every two years and involves a very high proportion of researchers active across Tanzania, so it's always a good place to hear about interesting things going on in these areas. I thought I'd give a few of my highlights today. The two talks that most exicted me were from two different aspects of ecology - one by Dr. Grant Hopcraft on the Serengeti and how climate change might impact wildlife there, the other also related to Serengeti, but this time by Dr. Dennis Rentsch from Frankfurt Zoological Society on the economics of the bushmeat industry. I know both of these folk fairly well, so was able to press them for lots of extra information about both talks, and what I'm going to descibe here represents both their presentations and some of the other stuff we talked about - I hope they don't mind me putting this information out before it's all polished and published!

Wildebeest and zebra migrating through Grumeti Reserves, Feb 2010

Grant knows rather a lot about Serengeti and, in particular, the herbivores of the system. His work has focussed on how nutrition impacts herbivores and his talk fitted well into the overall theme of the conference on climate change, by asking how climate change will affect the nutrient content of the grasses and how this might impact the animals that feed on them. You might think it's crazy to suggest that climate change impacts grass quality (i.e. nutrient content), but actually it can have some pretty profound impacts indeed. Grass growing in high rainfall areas gets very tall very quickly, but also tends to be poor in nutrients - it might be that the grass can only collect the same amount of nutrient from it's roots, but in wet years it grows faster, so there's less nutrient per leaf than in dry years when the plants can't grow as much and pack all the nurients into a smaller volume. So more rain means lower quality grass, but more of it, less rain would mean less, but higher quality grass. In fact, lots of people showed plots of rainfall in Serengeti and demonstrated that the area is getting wetter (though I also suspect there might be shifts in the dry season length which could be even more significant, but no-one really talked about that), so we should be seeing more, lower quality grass. What is the consequence of this? Well, according to Grant, perhaps it means different things for different species, since all the herbivores prefer slightly different combinations of nutrient quality and grass quantity. In particular, hind-gut fermenters like zebra are happy with lots of relatively low quality food, whilst wildebeest are typically selective ruminants and need higher quality grass. Now, Wildebeest in Serengeti are food limited, not predation limited or anything else, so a decline in food quality might be bad for them - but they are, of course, interested in quantity too, particularly during the dry season when any rain is going to provide grazing which is clearly better than no rain at all. So a wetter Serengeti, if it impacts the dry season too, is probably going to mean more food at this crucial dry-season food shortage period, and we can expect that even in a wetter dry season the rain will still be scarce, so the grass will be relatively nutritious. So on the one hand poorer-quality forage during the wet season might be bad news, but more grass in the dry season is certainly going to be good news - which effect wins out isn't yet clear. My money will be on the dry season effects, but we'll wait to see! On the other hand, it seems pretty unambiguously clear that a wetter Serengeti will be good news for zebra, provided again that the dry season remains at least a bit wet too. So more zebra will always be good - though how that will affect everything else is also tricky to forsee. Does more zebra mean better facilitation for the wildebeest? Or might there be more competition? Who knows, as usual, more research needed (and if you want to fund Grant on his next project, do let him know - he's searching for money right now!).

The migration reaches Seronera, Nov 2010. Don't get eaten!

Spot the snare: many animals are poached in Serengeti. Moru Jan 2011

Meanwhile Dennis has been working on bushmeat trade on the western side of Serengeti for many years now. His approach to studying what is, after all, an illegal activity has been to deal not with the hard end in the park of finding and apprehending poachers and trying to get them to tell him how many animals they hunt (they're very unlikely to give an honest answer in such circumstances!). Instead he's focussed mainly on trying to work out how much bushmeat is being consumed in the villages around the Serengeti by asking them about the various protein sources they eat during the week. Although there might still be some resistance to tell the absolute truth in this context, it's likely his numbers are underestimates of the full impact of the harvest (especially as it doesn't include any of the meat that gets exported from the region commercially). Underestimates they might be, but the numbers are still staggering. In the villages surveyed, the average number of meals of wildebeest eaten per family per week was 2.4. Obviously that goes up during the period when the wildebeest are migrating through the particular village, and down when they're far away, but 2.4 meals per week is the average for the villages immediately around Serengeti NP. And knowing the number of households in each village, plus the number of villages Dennis estimates that somewhere between 90,000 and 100,000 wildebeest are harvested (illegally) from Serengeti each year. To put that into context, it's equivelant to a harvest greater than the entire wildebeest population of South Africa each year!

At between 500 and 1500TSh / kg (depending on seasonal availablity), and assuming a conservative 100kg of meat per animal that gives a a total market value of $2.5 - $8.5 Million per year. Compare that to TANAPA income from Serengeti gate fees 10 years ago (the latest I can find online) at about $5.23 Million, and we're talking the same size economy. (Bear in mind that these TANAPA fees are used throughout the national park system to subsidise less well visited parks, so Serengeti NP actually has an opperating budget of only around $2Million per year.) That's a pretty remarkable figure on it's own, but Dennis went on to talk about how consumption is related to price of other meat in the area - if the price of beef goes up, more wildebeest is eaten. Which suggests that it might be possible to reduce the amount of wildebeest eaten, if you bring the price of beef down. Now unfortunately I wasn't quick enough to get all the figures off Dennis's slide to do the calculation here, but I think I'm right in saying that if you want, say to halve the wildebeest harvest, his figures suggest you need to bring the price of beef down by about 3 times as much - so 50% of 50% of 50%, which is an 87.5% reduction in price. That's probably going to be tricky to achieve, unless you fill Serengeti with cattle, which is hardly going to help! So you're rather stuck there. Instead, the only effective solution is to make the wildebeest more expensive - and Dennis suggested you can do that either by giving poachers alternative employment and dry up the supply of meat, or by even more strictly enforcing the regulations within the park. But bear in mind that this is a sustainable harvest - there's no impact of this level of poaching on the wildebeest population overall. The problem is the bycatch - people want to trap common wildebeest, but instead their snares catch resident game sometimes and have had a missive impact. So instead of strictly enforcing current regulations, perhaps TANAPA should be looking at ways to encourage sustainable use and minimse the negative off-take. Perhaps making a few million $$ in the process. What do you think? Should we go this way? Or how should we feed these people?

Red and Yellow Barbets and duets

Male Red and Yellow Barbet, Manyara, Jan 2011

There's nothing like a Red and Yellow Barbet to brighten up your morning! Even the most casual of observers wants to have a second look at this fairly common species, and well they might. Both males and females are impressively bright, you have to look past the red and yellow to the black on the throat and cap to identify the sex - male with black cap and throat (as on the right here), female just with black speckles on an orange cap (as below). And when you see one, you often find several as they tend to stick about in pairs and family groups most of the time.

Female Red and Yellow Barbet, Manyara NP, Jan 2011

Such strong pair bonds are re-inforced by their other obvious trait - the crazy duetting or even group singing in this species are thought to be mainly designed to build the pair bond, and less advertise territory occupancy to neighbours (though obviously it does that too). (If you've not heard the song, check it out half-way through this recording - crazy! I remember it when confused, because they're saying "RED (and yellow), RED (and yellow)", etc.) Evidence suggests that the calls of the two birds are so closely aligned there simply isn't sufficient reaction time for one bird to be listening and responding to the other when they do this, rather they both have some internal rhythm that they stick to, keeping each other in time together.

Dueting is actually surprisingly common in birds - at least 120 species of some 32 families are known to duet, but we don't really know why. The main features loosly associated with it are (a) it's mostly tropical birds that do it - so many visitors here won't be familiar with the concept except, perhaps, in owls, (b) it's mostly species that show rather little sexual dimorphism (like the barbets here) and (c) most of them live in rather dense habitats - though I think this species is one of the exceptions here. Certainly it's an impressive sight and sound!

Female Red and Yellow Barbet, Manyara NP, Nov 2010

Another thing you might notice about this species andthe closely related D'Arnauld's and Usambiro Barbets are their association with termites. Like so many things, these two ground barbets are rather partial to a snack on termites, given the chance, but they also rather like to nest within termite mounds - they dig a hole in the side and the termites will eventually wall their nest up, within the mound - giving lots of the benefits of termite-controlled air-conditioning to ther barbets too. Very handy. Though it might well make them vulnerable to brood parasitism from Greater Honeyguides - a species known to favour barbets and often searching termite nests for nests to parasitise.

Finally, check the toes on the top picture - classic zygodactyly (two toes forward, two backwards), perhaps an indication of their shared ancestry with woodpeckers? (Woodpeckers, Barbets and Honeyguides are all fairly closely related, within the order Piciformes - together with Toucans, but not hornbills which are more closely related to trogons and rollers, etc...).

Dung Beetles

Continuing the theme of small but rather important pieces of the savannah jigsaw puzzle, I thought I'd write a little about dung beetles. As usual, I'll try and follow my three questions for interpreting wildlife sightings - what is it? What's it doing? And what's it's role in the ecology of the environment?

Scaning for the route?!

So, let me first confess that I've never even identified a single dung beetle to species level. Unless you're a real specialist, I think you can forget it. Our dung beetles are are insects of the order Coleoptera and, as a rather prominent biologist (J.B.S. Haldane) once (may have) said when asked what we can learn about the Creator through studying His works: "He must have an inordinate fondness for beetles". In fact, the latest estimates  - published here in August - of terrestrial biodiversity are around 8.7 million species, of which about 7.8 million are animals (we've only described about 1.7, though). It's estimated that about 80% of all species are insects, and of these about 40% are Coleopteran beetles, which would suggest there are about 2.5 million species of beetles out there. In one tiny corner of the Serengeti plains alone, over 100 species were recorded in a relatively small study. As only a tiny proportion of these are already described I conclude (a) if you want to discover a species new to science, look at beetles, and (b) there are far too many beetles to spend time trying to identify them specifically. Still, most of our dung beetles belong to the Scarabaeidae family, and most people will have heard of Scarabs, especially if they know anything about the ancient Egyptians, who considered them sacred (holy), since it's clear that the world must be kept in motion by a giant dung beetle rolling it about.

So, that's what they are, identified as far as I feel the need. But what are they doing? Well, when we usually notice them they're rolling balls of dung along the track. Why? Because they eat it. Yumm. Most of the ruminants feeding on grass only extact about 50% of the nutrients from their forage, and obviously much less for hind-gut fermenters like elephants, so there's still significant resource left in the dung of these animals. And dung beetles love it for everything - they eat it themselves (some species eat it on site, some under the dung and some roll it off to snack on elsewhere), they roll it off and eat it as part of their courtship procedure (if you find two on the same ball, they might off on honeymoon with a nice snack to keep up their energy...), and they take it away to provision their young. For breeding, often the males dig large holes where they'll store several dung balls, a female laying a single egg on the top of each one (and in some cases coating the balls with a layer of clay that hardens around the dung ball. These broods are, in turn, a favourite food of honey badgers and some mongooses.

Dung beetle nest predated by honeybadger or mongoose, Lake Manyara, July 2010

The really exciting thing about dung beetles (I promise!) is, however, the impact they have on the ecology. First, let's appreciate the task they perform in tidying up dung. Your average zebra produces about 4.1 kg of dung per day, and a Grant's Gazelle about 0.75kg (never let it be said I'm not full of useful facts!), so let's assume about 200,000 zebra and 1.4M wildebeest for Serengeti, and guess that wildebeest, being bigger than Grant's Gazelles do about 2kg per day, and we're looking at a massive 1.3 Million tons of dung per year in Serengeti - nearly 3620 tons per day! It's just as well there's an army of dung beetles out there, just waiting for their meals (as the Australians learnt, when they started cattle ranches and the Australian dung beetles, used to a fine quality product from kangaroos, turned their noses up at the offerings from cows, with a massive fly problem the result - and they had to import African dung beetles to clean the mess up!). And, of course, we all know that dung is a pretty good fertiliser - whilst most of what they bury they also eat, the sheer numbers ensure that huge amounts of nutrient cycling are carried out by these beasts. What's more, they a bt picky about where they dig - it must be moist enough for them to dig, so that's why they're out there rolling balls long distances, looking for somewhere suitable. And as not everywhere is suitable, they tend to concentrate the dung in certain areas, creating a nutrient hotspot. Which, of course, attracts more wildebeest, to produce yet more dung, which is immediately returned locally - a major source of heterogeneity in the Serengeti plains. So, absolutely critical for nutrient cycling in the savannah - in fact, the huge volumes of dung involved alows you to realise that, thanks to dung beetles removal and burying, almost all the soil you walk on in Serengeti must, at one stage not that long ago, have been a dung ball. Lovely thought...

Termite mounds

Bologonja termite mounds, September 2011

Mostly dead termite mounds visible from the air, Northern Serengeti Sep 2011

One of the most impressive things I saw whilst up in northern Serenget a few weeks ago was the incredible density of termite mounds around the Bologonja River. They were extraordinarily dense, with a mound every few metres. More generally the whole of northern Serengeti seemed very well endowed with termite mounds, both old and new. In fact, flying over I was first puzzled by the obvious bare patches visible across many of the mlains up there, and only once I'd been on the ground for a day or so did I finally convince myself that they really were the remains of old termite mounds. So this set me wondering just what determines the densities of mound-building termites, and when I got back I was able to look things up.

Dead termite mound from the ground. I'm sure that's what it was though...

The most interesting paper I found is this one, which is about the Kruger in South Africa, but I'm sure the same processes are at work in Serengeti. Now, as a bit of background it're worth recapping that (a) not all termites are mound building (in fact, most of them aren't), (b) there's a tremendous number of them out there, having a massive impact on nutrient cycling - three genera (Odontotermes, Macrotermes and Trinervitermes) of mound building termites in Serengeti, and total biomass very similar to that of ungulates or mega-herbivores, (c) they really are fascinating, and deserve more attention on this blog! So, massive densities of termite mounds are quite interesting to understand. Termite mounds are shaped by three main, interacting processes: behaviour of the builders (different species build different mounds); soil properties (the soil used is from the below ground resource); and climate (both how much they have to battle with heat, but also the water table and degree to which they might wash away in heavy rain). So to explain the very high densities in northern Serengeti we both need to be aware that there's obviously a lot of food in this very high rainfall savannah area, but also the soil properties might just be perfect.

Interestingly, in both the South African work and this work in Serengeti termite mounds were found to be at their highest density in general on the tops of hills. The South African study explains this very nicely in terms of soil and water - over very long time-frames, rain washed clay out of the soils on the hilltops, and deposits it lower down the slopes. This mean that when it rains, the soils on the hill tops are fairly free draining - which is important to termites as they have underground chambers that mustn't flood. But it also means that where the clay is washed down to, there's a layer around the hills where the clay content suddenly increases, and when it rains the water flows through the upper soil layers, then hits the clay layer and flows horizontally until it reaches the surface as a seep line - we've all seen them (and probably driven into them!) - the point on the hill slopes where there's a line of tiny springs. However, whilst the hill-top is very well drained, it's also rather poor in clay content, which the termites need if they're going to build a good mound - sand doesn't work very well. So although the top of the hills are the best areas, in some place the termite densities increase towards the seep line - but then below the seep line the soil is too wet, so they suddenly disappear. And I guess that these very high hillside densities in Bologonja must be just the ideal location where there's plenty of clay, but just above the seep line - certainly there were seeps very close to some of these mounds a couple of weeks ago.

Bologonja termite mounds, happily functioning.

There's one more interesting thing that struck me when I was reading up on all this though - in South Africa, the highest densities of termite mounds above the seep lines indicate the areas of (broad-leaved) savannah. Below the seep lines lie grasslands. The authors of that paper found a relationship between local rainfall and the relative position of the seep line (more rain had washed the clay further down the slopes and closer to the rivers, which makes sense), and suggested that termite mounds could therefore be used to predict where woodlands might be if rainfally patterns change. Now, the really high densities on the Bologonja slopes are definitely on grasslands - but there's a good chance these were wooded not so long ago. Are they a relict of that time, and can we take their presence to even indicate areas where there were woods not so long ago? Or not? And  if not, is something different happening in Tanzania to South Africa? Also, there seemed to me to be an huge number of dead termite mounds, now visible only as a bare patch in other parts of the Northern Serengeti. Has something happened? Is this, too, an indication of major change in the savannah? Or does it just take so long for a termite mound to be washed away after the colony dies that we'd expect this many dead mounds? Hmmm.... All interesting stuff I think, any ideas?