Sunday, September 25, 2011

The past, the poop and palynology

Do you ever imagine how your neighbourhood looked before humans rocked up?
How about back when giant ground sloths pottered in your garden, or a Tyrannosaurus bedded down where your house now stands?

It’s only a blink ago, in geological time.

Of course we tend to forget that hopping and squeaking, right outside our doors, are the direct descendents of those monstrous beasts.
Photo posted on Flickr by kibuyu.

 OK, I know sparrows are a bit of a comedown, but if you're ever up close and personal with an ostrich’s foot, you’ll never again doubt the dinosaurishness of birds.

Living outside my own backdoor (well actually it’s about 0.5 km away) is a seriously anachronistic beast. Small and inconspicuous with a curmudgeonly air, it cunningly hides its connections to an illustrious past.
You see if you pop back 40 million years here, you won’t meet many of Africa’s iconic beasts. There’ll be no antelopes or zebras, buffalos or giraffes; even the hogs hadn’t tromped in yet. (Of course, there were mongooses; but who could imagine a world without them?).

Back in those days, Africa’s principal veggie-eaters came from an entirely different family; creatures whose great grand-pappy also sired the mastodons and mammoths. These herbivores stomped and frolicked in a carnival of diversity, ranging from diminutive mouse-like critters to rhino-sized brutes; some slick and fleet of foot, others dumpy and lumbering.

So who were these creatures?


Yep, that’s right, good ol’ dassies.

Ellies' rellies? Rock hyraxes (Procavia capensis) might look marmot-like but they've more in common with their elephant kin. Both are scrotum-free (their testes are internal), lack a gall bladder, sport impressive tusks, have hoof-like toenails and endure pregnancies that last forever (7-8 months in hyraxes).
Photo posted on Flickr by Koets.

Small human shown for scale.
Photo (taken on the Cape Peninsula) by Danie van der Merwe.

Sadly, the arrival of ruminants put paid to the Golden Age of Hyraxes. Out-competed by these consummate vegans (who would have thought that chewing your food twice could prove so beneficial), hyraxes withdrew to the nooks and crannies of the continent. Today only four species remain.

Possibly because of this fall from grace, rock hyraxes are obstreperous little beasts. Although they live in colonies of up to 35 animals (one macho male with a harem of sisters, daughters and aunts), social relations are strained. Look closely at a mob of hyraxes basking atop a rocky outcrop and you’ll notice that they never sit facing one another; they fan out like iron-filings around a magnet.
When they bounce down off the rocks to graze as a herd (harvesting a different section of their range each day) they also arrange themselves like this. And when a hyrax wants to join a huddle or enter a crevice, it reverses in backwards.
Weapons of dassie destruction.
Fights (mostly between males) can be fatal
due to the hyrax's tusks.
Photo by Brian Burger.


Well in hyrax-speak, eye-to-eye contact is equivalent to a rude hand gesture and, let me tell you, a pissed-off hyrax is scary. It growls, it gnashes its molars, it erects the black fur around its dorsal gland (a smelly, goo-secreting patch in the middle of its back), it curls its lip and slashes with its gruesome tusks.

Oh yes, despite their heart-warming shape, hyraxes are not heart-warming beasts. Unlike my charming mongooses, they will not suckle one another's pups; heck, they won't even groom each other!
And in the breeding season everything gets much worse due to a massive influx of testosterone: the dominant male's testes increase 20-fold in size! 

For the biblical ‘coney’, soaking up the sun isn’t just a leisure activity. Being of ancient origin, the hyrax’s thermostat is faulty so it basks and huddles to stay warm (even ‘stacking’ on chilly nights) and hides in shady crevices when it's hot.
Photo by Steve Krane.

Quite a mouthful. With their top incisors transformed into tusks and their lower ones converted into a grooming comb, rock hyraxes must nip off their veggies with their molars. Their huge gape lets them take bites as large as a sheep’s (as my deformed thumb will testify).
Photo by Damien du Toit.

Baby hyraxes are born in summer (all the girls in a colony give birth syncronously). They immediately clamber up on to Mum's dorsal gland: their favourite hang-out spot for the next five months.
 Photo by Paul Genge

A teat of one's one. Infant hyraxes divy up Mum's nipples, remaining faithful to their chosen teat/s for the entire 3-5 month suckling period.

Thanks to the tenacity of this weird little animal (it's only got three hind toes: i.e. proof of weirdness) we can begin to imagine the bygone fauna of Africa. But it’s actually one of the rock hyraxes more mundane habits that’s proven most helpful to our understanding of the past.

Like all sensible creatures, rock hyraxes deposit their poop in latrines. Their toilet facilities are conveniently located close to the colony’s sleeping quarters (usually beneath a rock overhang) and are used, unswervingly, for centuries. The hyraxes not only poop here, they merrily splash pee over the rocks, and when the calcium carbonate in the urine crystallises, it not only creates tell-tale white stains, it cements the droppings in place. Protected from the weather, these piles of poop provide an amazing, stratified compilation of the past.

A pile of poop or an
invaluable historical record?

Now I didn’t realise this until I researched this post, but hyrax middens are the bee’s knees for palynologists (pollen enthusiasts). You see air-borne pollen grains stick enthusiastically to fresh hyrax poop, so by sifting through the layers of stratified shit and identifying the attendant pollen, these diligent souls can ascertain past climates. Thanks to radio-carbon dating we know that a hyrax midden from the Karoo provided 1130 years of compiled hyrax history, and a Namibian midden yielded 2000 years worth of ongoing shit data! But it doesn’t stop there. In dry climates, hyrax dung readily fossilises, and fossil middens have shed light on 20,000 years of southern Africa’s past.
Go hyraxes!
Reparation. "This picnic is mine!"
Photo by Tim Parkinson.

Monday, September 12, 2011

Canniness, cowardice or flipping fraud?

Yesterday was International Rock-Flipping Day.

All around the world eager naturalists were out there turning over rocks and recording their discoveries.

Now this is such a fun idea, I always want to take part... until the actual day.

Then two niggling little doubts start gnawing at my enthusiasm.

What are these misgivings?
1. I will die.
2. I will kill something.

OK, I realise that plenty of people flip rocks in places where deadly critters slither and scuttle in dim, dank crannies. But heck, I really don’t want to stick my fingers under there!
Last year I managed to avoid the whole finger-fang close-encounter bit by fortuitously stumbling upon a rock monitor snuggled away in a rock crevice. But what were the chances of repeating such a serendipitous find?

I was mulling over the problem when it hit me that this was the same conundrum that I face professionally every day. You see I’m always trying to figure out ways to obtain the data I need without inflicting harm. If the aim of rock-flipping is to document what’s living under the rock, isn't there a less invasive way to get the info? Why not find a rock that’s clearly someone’s domicile and try to coax the resident out?

Now I was secretly very pleased with this solution, because although it was primarily motivated by my aversion to legless beasts, I could sell it as a commitment to animal welfare. Triumph!
Umm... but would it work?

Well yesterday, after visiting the mongooses (who were appropriately hiding underneath rocks to avoid the attentions of a black-breasted snake eagle), I set out on a binge of non-invasive rock-flipping.

Clutching my camera, a Tupperware container of mealworms and a water bottle, I tracked down a suitable rock.

The rock. OK, I know this behemoth is way beyond the provenance of conventional rock-flippers, but someone’s got to hang out under there.

Sloshing some water about, I sat down in front of this rock to wait for the alluring aroma to work its magic.
The first face to appear in the gloom beneath the overhang was that of a lady rainbow skink. She made straight for the puddle.

A female rainbow (or five-striped) skink (Trachylepis quinquetaeniata) enjoying a thirst-quencher. Youngsters and adolescent males also dress in female garb to avoid the aggro of territorial males (who wear orange).


When I tossed this intrepid pioneer a mealworm pupa, I was immediately surrounded by zipping reptiles. Among the many skittering rainbow skinks were some slicker, racier models.
These were lady common flat lizards.

Common flat lizards (Platysaurus imperator) are dorso-ventrally challenged so they can squeeze under rocks. They favour high density living, and although girls such as this one lay only two eggs annually, she and her rock-mates put all their eggs in one basket crevice.

“Too much lippy?” Flat lizards can live to fourteen in captivity.

I’d been divvying out mealworms for quite a while before the reigning monarch of the flat lizard colony deigned to emerge. In keeping with his status, he was a little more reserved than his courtiers, but I guess it must be difficult being the centre of attention all the time.

Flaunting the royal colours. His highness defends the rock face upon which his harem and progeny live.

Why flat lizards are flat.

When the mealworms were almost spent, a large shadowy figure appeared beneath the rock overhang.

This giant plated lizard (Gerrhosaurus validus) gave me the evil eye but wouldn’t emerge any further. She belongs to an ancient group of lizards (which includes the girdled lizards) endemic to Africa.

Giant plated lizards are... well... giant. They grow to a whopping 70cm (2ft 4in) and hang around in family groups. If you startle one when it’s basking it'll toboggan down the rock face on its tummy (not that I enjoy doing this, of course). Although these lizards guzzle berries and flowers, they’re also keen hunters, tracking down bugs and small vertebrates using their flickering tongues. My dwarf mongooses often run into them, and while this is a non-event for most of the year, during the summer breeding season (when both species have bite-sized young) suspicions run high. Exactly who chases whom depends on which species’ nursery is nearest. Mongoose pups, just big enough to look after themselves, find these scraps endlessly exciting.

After failing to coax mum from the shelter of the rock, I was just wondering whether to call it a day when junior appeared.

A non-giant giant plated lizard.

This little juvenile shared none of mum’s reticence and came dashing out into the sunshine in pursuit of mealworms. In fact, much to my surprise, it came zipping straight up to me, even climbing up onto my shoe to plead for further handouts.

“Please, please, just one more...”

So all in all, I feel that my non-invasive rock-flipping went quite well.
And all of us are still alive!

You can discover what other rock-flippers found beneath their rocks at Wanderin' Weeta.

God’s own creatures contributing to my under-rock species count.

Saturday, September 10, 2011

When your stalker has feathers...

The parched colours of the dry season.
Photo by Kim Reijs.

When I venture into the field these days it's like I've somehow slipped into a Disney animated classic.

All I need is a ballooning skirt and a tripping walk to make the illusion complete.

Why am I suffering these weird fantasies?

Well, the moment I set foot in the bush, I'm surrounded by clouds of little blue birds, all atwitter with excitement. And then the little animals come creeping out of the undergrowth to gather at my feet.
Magic?  Charisma?  Sadly no.
You see it's the height of the dry season here. With the bush seared, dusty and leafless, everyone could use a drink.

In an effort to curry favour with my study subjects (essential if I'm to ever find the little brutes), I reward them with a small bowl of water whenever I join a group. And of course it doesn't take long for the other locals to catch on too.

The mongooses crowd around the bowl, some delicately lapping with pink tongues while others dip in their paws and lick the moisture from their toes. Meanwhile a menagerie congregates around us.
Four-footed or two, feathered, scaled or furred, no one can resist the lure of free drink.

Tamarind (HF047) enjoying a tipple.

The tree squirrels (Paraxerus cepapi) aren't backward in coming forward.

Rough-scaled plated lizards (Gerrhosaurus major) disdain rules of etiquette.

Rainbow skinks (Mabuya quinquetaeniata) tentatively seeking that elusive pot of gold water.

"... and then I told that great brute of a mongoose to just clear off..."

The blue waxbills (Uraeginthus angolensis; pictured above) are the most persistent (and impatient). They accompany me as I search for the mongooses, flitting through the bare twiggy undergrowth, peeping vociferously. We collect more and more followers as we go, with everyone complaining loudly about having to wait to wet their whistle. I find this entourage a bit irritating because it drowns out the subtle, tell-tale peeps of my mongooses.

But if the waxbills are annoying, there's one avian devotee that drives me insane. Dressed in humdrum colours, it flutters from branch to branch above my head, ruffling its wings, wriggling its white-edged tail and bobbing about like a creature possessed. It also feels compelled to squawk non-stop. One of my bird books likens its raucous call to the sound of a shaken box of matches, which is pretty accurate if you pump up the volume about 100-fold.

This irksome devotee will dog my steps for hours (OK, for the purposes of scientific accuracy, I'll admit that this is a slight exaggeration). It certainly doesn't retire once I find the mongooses (and they dislike it as much as I do). You see it's not after a mere sip of water. It wants wax.

Yep, you read right: the greater honeyguide is one of only a handful of critters who's able to dine on, and digest, wax (thanks to special microbes in its gut).

But before you start imagining some ghastly Hitchcockian scene, let me make it clear that it isn't after earwax.
This feathered stalker hungers for beeswax.

Its fervent taunting is designed to persuade me to follow it to a likely bee hive. Once there, it expects me to smoke out the bees and heroically retrieve the honeycomb so it can gorge itself on bee larvae and wax (it doesn't eat honey). I've never felt tempted to accept this offer (opening a jar of jam seems safer), but if I'm unwise enough to move or speak in the bird's presence, it gets super excited and zooms off, in a sweeping, undulating flight, toward the nearest hive.

Although greater honeyguides (Indicator indicator) are only about 20 cm (8 in) long, they vex the inhabitants of woodlands and savannahs throughout sub-Saharan Africa. When not guzzling wax or terrorising baby bees, they make do with flying insects.
Photo by Carol Foil.

Now as a zoologist who studies partnerships between species (see an example here), I know I should revere this bird. Collaboration between beasts of feather and fur is rare, and the greater honeyguide is the poster child for such complicity.
But God it's annoying!
And the creature's not easily deterred; honeyguides will invade villages and gardens in search of someone with a sweet tooth, and they even pursue cars and boats.

You see the honeyguide has had the dubious pleasure of sharing its habitat with humans for millions of years, and that's plenty of time to notice a mutual fondness for bee by-products. But what's really impressive about the alliance that's evolved, is how well human and bird communicate.

For example, when the Boran people of northern Kenya decide to do a spot of honey pilfering they inform the birds by whistling piercingly through clasped fists (this doubles their chances of bumping into a honeyguide, who then reduces the time they spend searching for a hive by two-thirds). Of course the bird has reason to come running flying: only 6% of the hives (of Apis mellifira) in its territory are accessible to beak and claw alone.

Upon arrival, the honeyguide gives its annoying come-hither call, zips off for a moment (presumably to identify landmarks along its proposed route) and then leads the honey gathers in a beeline for the closest hive. (A three-year study found that the birds monitored all the hives in their area, routinely stopping by for a minute or so to check they were active).
Intentionally or otherwise, the honeyguide also informs its followers how far they'll have to walk. The further away the hive, the longer the bird is gone on its initial reconnaissance mission, and the nearer the allies gets to the booty, the shorter the bird's perch-to-perch flights become. When the team finally rocks up at the hive, the bird gives a special 'here it is' call, perches close to the nest and then keeps mum.

If you haven't already seen footage of a greater honeyguide doing its thing, you can view one (and David Attenborough imperilled by bees) here (courtesy of the BBC's Trials of Life).

The weirdness of greater honeyguides is not limited to their dietary habits. These birds are territorial and each male has a special 'song post' where he sits from dawn 'til dusk throughout the breeding season vociferously boasting of his macho charms. Interested lady honeyguides simply drop by for a bit of fun every now and again.
But once knocked up, female honeyguides appear to go to pieces, abandoning the fruit of their passion at the earliest opportunity. They cunningly slip their egg into the nest of unsuspecting hole-nesting birds (such as barbets and woodpeckers). When their little darling hatches, it dispatches its nest mates with a wicked billhook designed for the purpose.
Serendipitously, you can see wonderful photos of this villainous behaviour here.

The adoptive parent (a meves starling) of a greater honeyguide chick bringing home the bacon frogs legs.
Photo by Johann du Preev.

But all is not well in the land of honey procurement.
When I first started working on the dwarf mongooses six years ago, I was constantly beset by these irritating birds; now it's a rarity. I hadn't really given this much thought: sure, the resident birds had learnt I was a no-show and had given up on me (sigh of relief). But after researching this post I began to realise how bad this is.

You see in many places greater honeyguides don't indulge in guiding at all. It's believed that this is the result of humans, at some time in the past, welshing on the deal. And increasingly local people are abandoning traditional food gathering techniques (hey, sugar's dirt cheap at the supermarket), leaving the birds high and dry.
Similarly, human activities such as honey gathering are banned in national parks and other protected areas, exacerbating the problem.

So this amazing alliance between bird and mammal - rightly lauded as the world's most impressive example of interspecies mutualism - is rapidly disappearing.

And I'm hastening its loss!

Honeyguides and Honey Gatherers: Interspecific Communication in a Symbiotic Relationship. H. A. Isack & H. U. Reyer. 1989. Science, 243: 1343-1346.

The Fallacy, Fact, and Fate of Guiding Behavior in the Greater Honeyguide. W. R. J. Dean, W. Roy Siegfried & I. A. W. MacDonald. 1990. Conservation Biology, 4: 99-101.
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