Tuesday, 28 February 2012

Exercise like a lion!

Wildebeest wrestling - the ultimate fitness regime? Selous GR, June 2010.
I came across a paper this last week - I can't remember how, because it's certainly not my usual reading material (though my wife has just pointed out a report on the BBC today) - but it suggested an answer to one of the things that puzzle me about lions. Like most cats, lions like to sleep. A lot, in fact - they're perfectly content sleeping for 21hrs a day, so it's no wonder tourists don't normally see them doing very much. As a consequence, I think lions are rather boring: I'd rather be birding. Still, on the occasions when I've got visitors staying who need to see lions I do go and look at them, sleeping away, and I wonder. How is it that a lion, sleeping 21hrs per day, can still be so fit and healthy? On the rare occasions when they do shift themselves, wild lions are certainly lean, mean killing machines. But how do they remain in such good condition, when they sleep nearly all the time, and even when hunting tend to walk as slowly as possible, or sit motionless in ambush?

Saturday, 25 February 2012

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.

Tuesday, 21 February 2012

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.

Sunday, 19 February 2012

Threats and opportunities of the bushmeat trade

Snared giraffe, Serengeti NP Jan 2011. A major target right now
Following my post a while back about Dennis Rentsch's work on the bushmeat trade around Serengeti, Matt asked me to cover this issue in a bit more depth. (Though if you want to see how it's possible to have a sustainable harvest of around 100,000 wildebeest per year from Serengeti, with a net value of $2.5-$8.5 Million per year check the original post here!) And there've been a number of interesting papers recently that have started to fill in some details. It's not a subject I've much experience of, so I'm skimming the surface a bit, but I think it might at least highlight some of the issues involved.

We'll start with the caveats. Understanding the bushmeat trade is tricky - in most places it's illegal, and people aren't always going to talk freely. And if they do talk, there's a good chance they won't tell you the truth either - they might either say they do less hunting than they really do to play down the impact, or they might go down the macho route and tell you they're excellent hunters and never come back without a pile of buffalo, etc... Dennis's work took an alternative strategy, instead of asking the poachers to tell him what they hunted, asking the villagers to tell him how much bushmeat they consumed and working back to the harvest that way. Others have worked on data using poacher arrests, viewing this as an index of poaching activity - though there's no way to tell what proportion of poachers get away with it (what poacher, when arrested, will really tell you how often they've been poaching before and not been caught?!). The only comparison between these three methods is Dennis' and that suggests that measuring consumption gives a poaching pressure that parallels that from arrest records, but neither of these fit with pressure as assessed by poacher interviews. That suggests to me that Dennis' work is probably the most accurate, but he's not yet published these studies, so for now you can only read about it here. The vast majority of other work is based on poacher surveys, and we also know that when you compare what poachers say the meat is with what the DNA tells you, you get remarkably little agreement too.All of this suggests to me that we need to take the research based on poacher surveys with a large pinch of salt. So, with that in mind,  I'm going to focus more on the declines that are reported to be associated with bushmeat, rather than the more poacher-based surveys.

Thursday, 16 February 2012

Myrrh trees (Commiphora) are useful things...

Most Commiphora have distinctive peeling bark, Eyasi Aug 2011.
Having last week given you the bad news about the biological warfare that plants with thorns are engaging in, I thought it only fair to share some tips that may help you stave off those tropical nasties threatening to kill you... So the good news is that some of those very same thorny trees that are out to get you also hold the cure in their sap. Traditional healers and many folk still living in the country have long known about the beneficial effects of the sap of Commiphora trees. Indeed, the earliest recorded use of Commiphora to treat infections goes back to 1100BC where Sumerians were recorded using myrrh (for that is what Commiphora is) to treat tooth infections and intestinal worms. It's use is also clear in the Bible, as one of the three famous gifts presented to the infant Jesus. Today it's still commonly used in village communities to treat an endless list of infections and maladies, and it's also pretty good as a mosquito repellant if you need emergency cover!

Wednesday, 15 February 2012

The wheatear's remarkable migration: Alaska to East Africa

A great piece of research came my way today, detailing the migration of the individual wheatears from their Alaskan breeding areas to winter territories in East Africa. We've long known this must happen, as pretty much all the world's Northern Wheatears Oenanthe oenanthe spend the winter in Africa, but now technology has allowed us to follow individual birds on their 14,600km long migration from Alaska to East Africa and back. It's a remarkable story, not least that a 20g songbird can repeatedly do this sort of movement, but that we now have devices that can be attached to such small birds and record their journey. Wheatears are also a favourite of mine, and their migration has been the subject of one of my student's research so I almost feel qualified to make a few comments!
Migration routes and wintering grounds of three northern wheatears breeding in Alaskan (AK) and one in the eastern Canadian Arctic (CN; grey dot, breeding area, blue, autumn migration, orange, spring migration, dashed lines indicate uncertainty in migration routes close to equinoxes). Fifty per cent kernel densities of winter fixes (beginning of December 2009-end of February; purple, bird AK-1; green, bird AK-2; orange, bird AK-3; blue, bird CN-1) are given depending on the sun elevation selected (with 228 for most southern and with 24.58 for most northern densities). Pie charts indicate the proportion of individuals (AK: n 1/4 9, CN: n 1/4 4) originating from one of the three pre-defined wintering regions (red, western; orange, central; yellow, eastern) [8] based on stable-hydrogen isotope (dD) values in winter grown feathers and the dD values within each wintering region (mean+s.d. shown); Credit: F. Bairlein et al. 'Global migration of wheatears' (doi:10.1098/rsbl.2011.1223) in Biology Letters

Tuesday, 14 February 2012

Tarangire wildebeest migration

Tarangire wildebeest on the move, Sep 2011.
Following the ATBC / SCB conference in June I mentioned a talk by Thomas Morrison on the movements of the wildebeest in Tarangire. The Tarangire migrations is, of course, tiny in comparison to the better known Serengeti migration and involves a different race of wildebeest (C. t. mearnsi in Serengeti, C. t. albojubatus in Tarangire) , but it's just as interesting to understand, and Tom and his supervisor Doug have recently published some work describing the movement that was covered in the conference talk. Until fairly recently, Tarangire was home to a large wildebeest population, though only around 6000 remain today. It's still one of my favourite places to visit though... These animals move into Tarangire in the main dry season (arriving in June) and then move out to one of two main areas for the wet season either east onto the Simanjiro plains, or north-west towards lake Natron. As with the Serengeti migration, these wet season movements are onto grasslands growing on recent volacanic soils with high nutrient content and just what is needed during late pregnancy, then when lactating after calving in February. One of the mysteries, however, is whether the population that moves to Simanjiro is the same as that moving to Natron - do the animals go one direction one year, and the other the next? And as those moving to Natron pass close to another population in Manyara, do those Manyara animals also join the movement? It's important to know the answers to these questions if we're to try and protect the animals, given that they spend around six months of the year outside the National Park system.

Sunday, 12 February 2012

On introducing elephants to Australia...

Sometimes scientists suggest the most absurd things. In the news last week (with thanks to an Australian friend for tipping me off) was a paper published in the prestigious journal Nature that suggested in the text and headline that Australia should introduce elephants to control an invasive grass that originally came from Africa: Gamba grass, Andropogon guyanus. The author made a number of sound observations: Australia (like too much of the world) is riddled with invasive species, has suffered a massive extinction of it's native mammal population and has had some pretty nasty wildfires in the last few years. But how you get from those observations to suggesting elephants (and even rhinos) should be introduced to the savannas of Australia is a story worth looking into.

Friday, 10 February 2012

Butterflies moving again...

Well, the initial movement seems to have petered out, with nothing major in Arusha and most other northern Tanzania areas since Sunday. But starting last weekend I started hearing word of movement down on the coast, and then in Kenya, around Nairobi and Mt Kenya areas, all of butterflies headed south. The last couple of days I've been hearing about massive movements - at least as impressive as the original movements over the Pare Mts (around 400/min over a 20m line!) and in much of Kenya (but the Kenyan's haven't yet given me anything specific enough to actually map - come on!). These animals now seem to have arrived more widely in Tanzania, with arrivals in northern Serengeti reported for the first time now, as well as continued movement on the coast. And there are even a few trickling over Ilboru again now - though we're clouding up here and I'm not expecting much. But if you've been following the story, please keep your eyes open and keep reporting. Here's the latest map. Please do encourage your friends and contacts to get involved. (And I'd still love to know what happened around Singida to the original movement!)

View Butterfly eruption 2012 in a larger map

Thursday, 9 February 2012

Why is the African Savanna so full of thorns?

Giraffe lick leaves between thorns. Note how obvious the white thorns are.
Spinescence. Now there's a word! It simply means having spines and one of the first things many visitors to the African savannah notice is that everything is covered in thorns. Or, in other words, Africa is spinescent. It's not a wise idea to brush past a bush when you're walking, and you certainly want to keep arms and legs inside a car through narrow tracks. These are thorns that puncture heavy-duty car tyres, let alone delicate skin. But why is the savanna so much thornier than many of the places visitors come from? Or even than other biomes within Africa, such as the forests?

This post I've just written as a guest blog over at "Nothing in Biology Makes Sense". I'm incuding it here too, but do go and check that blog out if you're interested in evolution! You can read the rest here, so skip to the story there if you want...

How the zebra got his stripes?

 Most animals in the savanna come in one shade of brown or another, except for zebra. Zebra, as everyone knows, are stripey. Black with white stripes, at that; or are they white with black stripes? Anyway, why they're stripey has puzzled many people for a very long time: even Wallace and Darwin debated whether zebra stripes make them conspicuous or not! For stripes to have evolved there must be some evolutionary advantage, but what, exactly is it? There are a huge number of theories out there (many reviewed here), from the rather obvious to the some more ingenious ideas too:

Wednesday, 8 February 2012

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!

Sunday, 5 February 2012

Notes on a butterfly eruption: a billion and counting!

 Just a brief post with the latest news, as it's coming in. The bulk of the movement seems to have passed Arusha Moshi now - there are still large numbers going through but (a) they've turned South West in most areas, and (b) they're coming through in groups now, not as a continuous stream. By contrast, I'm hearing of increasing numbers now in and around the Crater, with the first being reported (headed south and south west) from the broader Ndutu area. I've also confirmed that the movement hasn't been noted north of the Pare Mountains, suggesting the idea that they originated in the Maasai Steppe and headed north from there might well fit. The other very interesting observation comes from Tent with a View (I think that's their website!), who report 1000s appearing just recently headed south down the coast in Saadani NP. So, if you're in Dar, do look out over the next day or two. How this fits into the pattern, I'm not sure! But keep the records coming and we'll find out.

Meanwhile, I've been reading more papers on butterfly movements in Africa!

Friday, 3 February 2012

Butterfly migration update

Thanks to all who've given me information so far! Numbers are definitly falling now around here, but some big waves are still coming through and that big wave of movement must be headed somewhere else... If you've been following you'll notice that new points have been appearing on the map, though more would be great, so if you've been hesitant, please do let me know. You can either add points yourself here, email or SMS me (if you know my number of course) or add a comment to the blog and I'll update things. I'm just as keen on negative data as positve ones if you're in the area - I'm getting hints that there's nothing moving in southern Tarangire, for instance, but only because I've been asking folk there and they've all been silent! Similarly, I think it's negative all over Serengeti, but I'm struggling for people to tell me that despite sending lots of messages!

Vachellia and Senegallia species in massed flower near Longido, Jan 2012
Some things I've been wondering about that might help us piece things together include information on average flight speeds for butterflies of other species - around 14kmh for Monarchs, butteflies that like a little tail wind. And between 10kmh and 6kmh for a range of other species in still air (higher speeds usually by migrant species, but not specifically recorded on migration). When our African Monarchs are on the move they seem to travel at about the same speed as the whites and they use a following breeze too, so let's assume a similar flight speed. Now I first noticed movements in Arusha on Tuesday, but it could have started sooner. Most movement has been between 10am and 5pm, giving 7 hrs of movement time. And most of the butterflies haven't been stopping much to feed. So let's say each individual has been moving for 7hrs on three days, they should have covered nearly 300km in that time. My most easterly records of the movement on the map (did I say to help me fill it in?!) are from Korogwe on Wednesday, when a notiable movement was headed NW - not as many as elsewhere at that time, but I don't know what it was like there on Tuesday or Monday. So those eastern butterflies are around 300km from me, if they followed the direction of movement we've been recording. If they flew each day, they'd be passing here about now. It's tempting to think the lower numbers at the moment represent the end of a continouos movement from Korogwe to here, whilst the peak that was here should no be about 300km further along, takingus beyond Eyasi and into uncharted territoriy. Anyone know folk in Singida or out that way who might tell us what they've seen?

Wednesday, 1 February 2012

Mapping the butterfly eruption

OK, I got rather a lot of information thanks to the previous post and thought we'd cash in on it as fast as possible - the butterflies are moving again over Ilboru right now, not in large numbers yet, but it's still cool. I think I've created a google map that anyone can edit with their location and observations. It's not a polished item, but I've put what I've discovered in for far and it's already interesting. (If anyone tech-savvy can make it neater I'd love to have icons that reflected the direction and volume of movement, rather than just pins...) If we get lots of observations on this it will definitely make a note for some lepidoptera publication and we'll have pushed back the frontiers of science, which would be great!

View Butterfly eruption 2012 in a larger map

So, instructions....

Butterfly migration out now!

African Caper White Belenois aurota
Beleonis creona African Common White
If you're anywhere near me at the moment and it's not dark, get off your seat and look outside. There is a phenomenal butterfly migration happening in the Arusha area at the moment - from my garden in Ilboru I'm counting around 100-150 white butterflies headed west over a 20m wide patch of sky every minute. Truly spectacular! I'd love to know how widespread the migration goes, so if your on safari and getting this on your mobile, let me know what's happening where you are too. I first noticed the movement yesterday and expect it will keep going for a while yet. The butterflies involved all seem to be the African Caper White B. aurota, though there could easily be some African Common White, Belenois creona (subspecies severina) in there as well. Look carefully for a while and there are one or two of the African Migrant Catopsilia florella a much larger and yellow tinged butterfly. The main difference between the two Belenois is that the male in the Caper White has a bar on the forwing and the Common White just as a spot - but it's not always easy to decide if it's a spot or a proper bar as there's lots of individual variation, so I might have got a few pics confused here. Let me know if you're better at these butterflies than me!