Sunday, May 30, 2010

Dog days

Before I could write this post I had to prise a mealworm from the inner workings of my keyboard (NOT a simple task). This adventurous worm is just one of hundreds that are currently secreted in nooks and crannies in unexpected places around my house.

Why am I suffering a plague of feral mealworms? I have a pet dog.

Now there's been lots of research showing that owning a dog is beneficial. Pet owners enjoy better health (visiting doctors less frequently and popping less pills), they have lower blood pressure, better survival rates after a heart attack, increased morale, reduced loneliness and they're emotionally buffered against stressful life events.

But do pet owners suffer MORE stressful life events?
Such as invasion by mealworms?

Three days ago, arriving home from the field, I noticed a couple of mealworms wriggling across my lounge room floor. That's strange, I thought. I do breed mealworms, in big plastic tubs in my spare room. I use them to tempt reluctant mongooses to stand on a set of scales for weighing.
When I looked more closely, there were mealworms trundling all over the place. So it was with some trepidation that I ventured into the spare room. Chaos! All the mealworm tubs were overturned, the foam mattresses were torn from the beds and the floor was heaped - wall to wall - with spilled bran and fist-sized chunks of mattress foam. Sitting in the middle of the mess was Magic, my husky cross. She was nonchalantly crunching up the last member of an imprudent gerbil family who'd taken up residence beneath a mattress.

Now, I have a strong belief that companion animals are wonderful things. And not because of all those listed benefits. Pet dogs and cats are such an integral part of our everyday lives that we just take them for granted. But when you stop to think, it's utterly amazing that we're able to share so intimately in the life of a completely different species. The privilege of this relationship just takes my breath away.

But I must admit, I may not have been feeling that way today.

Today, I arrived home to find my lounge room besmeared with hundreds of little pieces of avocado skin and the broken remains of gnawed avocado stones. Magic had struck again. She'd filched a 2kg bag of avocados off the kitchen bench and happily munched the lot.
On the bright-side, while clearing up the avocado remnants, I was able to recover another half dozen free-range mealworms.

The after effects of consuming eight large, unripe avocados.

Thursday, May 27, 2010

The reign of rain frogs

An unfortunate aspect of growing up is that we lose our early sense of wonder. We quickly learn to name things and pigeon-hole them, and take them for granted. The world loses its sparkle.

But now and again, we encounter something that defies our expectations, and encourages us to marvel again.
A few nights ago I came across just such a something creeping around my cats' food bowls. I don't know if a cat had put it there (contributing toward its upkeep?) or if it trundled in by itself, but I usually only see them after rain.

It was a frog. The moment you read that, a preconception forms in your mind. Frogs hop. Frogs hang out near water. And they start life swimming about as tadpoles.
Forget it! I'm talking rain frogs.

This bushveld rain frog (Breviceps adspersus) is about one inch long, but they can grow to an impressive two inches. There are 14 different species creeping about South Africa.

Rain frogs spend their lives in holes, and they're shaped to fit. Their stumpy little legs preclude even a hope of hopping (a sensible safety precaution in a burrow dweller). At night, rain frogs crouch at their burrow entrances, licking up any bug that wanders past. And when it rains, they'll even come creeping out – slowly and cryptically – to find their own true love.

When agitated, rain frogs puff themselves up until they're almost spherical, and some species ooze a distasteful, milky fluid that deters potential diners. Photo by Jens Reissig and borrowed from here.

Being so portly and short-legged has its draw-backs; it makes reproduction tricky. Normally, a male frog mounts the female and clasps her in his arms (called amplexus) while he fertilises the eggs she's laying. But with rain frogs it's the ole 'corgi-mating-with-a-collie' problem. So how does the male manage? Fortunately, female rain frogs have it sorted. The skin on their backs secretes an adhesive, so the male only has to scrabble into position once, and he's set. Literally. The bond between them is so tenacious that you can't pull them apart without tearing the male's skin. Only after the pair has dug a burrow together, and the female has laid her 20-40 eggs inside, does her skin secrete a solvent that releases the male. Pretty nifty, huh?

Rain fogs dig their burrows while in reverse. They back into the hole-to-be, slowly revolving, and scratch out the soil with a special horny 'tubercle' on the heels of their hind feet.

Along with their other bizarre characteristics, rain frogs have given up on the whole idea of tadpoles. Their eggs consist of a large whitish yolk coated in thick jelly-like goo. The little rain frogs grow up within the safety of the burrow, sustained entirely by their egg yolk and bathed in fluid from the melting jelly. Only when they're fully metamorphosed frogs, do they creep out to face the world.

A bad day? This cape rain frog (Breviceps gibbosus) isn't feeling grouchy (actually I can't vouch for that). Its flattened face and forward facing eyes give it close-up, stereoscopic vision; all the better for nabbing small bugs. Photo borrowed from here.

Monday, May 24, 2010

Triumph of the traumatised tadpoles

Today is a day for celebration.

My LAST tadpole graduated to froghood!

It's been a long time coming. And not everyone made it.
Out of the 200 mud-wrestling tadpoles I invited into my home, only around a quarter hopped off into the sunset. Floods, desiccation, live burial and serial killers all took their toll.

Poor photo of one of my fingernail-sized froglets (that's a chewed or severely clipped nail). Despite hours lying on my stomach peering at them, I'm still not sure of their species.

Firstly, torrential rain washed many an innocent tadpole over the side of their dish, and then there was the porcupine. Yes, I know porcupines don't eat tadpoles (actually, I don't know this – they seem to eat almost anything), but they are powerfully attracted to the scent of rotting fruit. And the edges of my froglet pool are liberally sprinkled with mouldering pears, to attract tiny fruit flies (for the delectation of tiny frogs). My dogs – while hysterically barking at the sniffing porcupine - overturned the tadpole dish. (Guess how long it takes to individually pick up 150 beached tadpoles; in the dark.) Then the porcupine, while diligently excavating a tunnel under the fence, shovelled all the earth into the tadpoles' bowl. I found 100 tadpoles cowering in the last tiny dribble of water.

Of course, the worst losses occurred at the beak of a vicious killer. A hadeda ibis, sprung one morning fishing in the bowl, was shockingly efficient at nabbing tadpoles. Ibises hunt by feel, groping about with their long sensitive bill, and this meant many victims later died from injuries.

A wicked serial tadpole-killer, the hadeda ibis (Bostrychia hagedash) is named for its ear-splitting cry. Admittedly these birds do sometimes holler HA-DE-DA but more often they just scream ARRRRRRRRR (usually from right behind you). The sound's so loud you can feel it thrum in your chest. Photo by Doug Harebottle and borrowed from here.

I have a horrible suspicion that many of my newly fledged frogs promptly ended up as dinner for the local fauna.

This small toad is an ominously regular visitor to my froglet pool.

Friday, May 21, 2010

Meet a mongoose: Snufkin

Today I want to introduce you to Snufkin (or EF021), an adult female in Ecthelion group.

Snufkin is four years old, and she was born while I was still trying to persuade Ecthelion to trust me. This is a painstaking process (it takes about four months) and Snufkin helped speed things along. Like all small pups, she was a little gormless. She'd come tottering out of the burrow and waddle straight over to where I sat. The adults would stare, aghast. Weaving back and forth in agitation, they'd urgently try to call her back. Of course Snufkin totally ignored them, too busy sniffing my binoculars or chewing on my trousers. Finally someone would pluck up enough courage to come crawling, on their belly, toward me. They'd inch forward, bit by bit, before finally snatching up Snufkin and dragging her back to the burrow. This didn't deter Snufkin, of course, and within moments she'd come tottering back over again.

Snufkin retained her friendly, confiding air, and she's one of my favourite mongooses.
But her real forte is unselfishness.
When she was just ten months old, Morrigan (the group's dominant female) produced a new litter of pups. Although Snufkin wasn't yet full grown, she spent hours fussing over the pups, and once they began munching solid food (at about 3.5 weeks) she ran herself ragged finding bugs for them.

Snufkin is named after a character in Tove Jansson's 'Moomintroll' books, who is independent, public spirited and plays songs (e.g. 'All small beasts should have bows in their tails') on the mouth organ.

Now, the first time I saw mongooses feeding their pups I almost went into shock. This was NOT something that mammals did! Sure, birds bring food to their nestlings, but what choice do poor, milk-free birds have? In all my experience, I'd only ever seen mammals letting their ankle-biters share their own meal. And among the marsupial carnivores I'd worked with in the past, even this was done most begrudgingly. So it was with stunned amazement that I watched as an excited mongoose snatched up the spider he'd just found and bounced enthusiastically over to a small pup. He carefully placed the soggy spider on the ground before the pup, and sat watching - totally enraptured – while the inept little creature munched at it. When the spider made a break for freedom, the adult hurriedly recaught it, disabling it with a couple of surreptitious bites before presenting it again. And when the pup's attention began to wander, the adult carefully nudged the item with his paw. Ah, the wonders of altruism.

Like baby birds, mongoose pups beg noisily using special calls, and hungry pups beg more than well fed pups. Experiments have shown that the more racket the pups make, the more likely it is that an adult will part with its hard-won prey. But with a whole litter of pups madly begging, and everyone in the group contributing edibles, how on earth do they divvy up the spoils fairly?
Banded mongooses deal with this problem in a most civilised manner. Each pup hooks up with one specific adult (its 'escort') who provides the pup with all its food. This means that banded pups never have to fight over food, and they benefit from having their siblings nearby (the more begging the adults hear, the more they donate).

 A banded mongoose pup with its one and only 'escort'.
Photo from the BBC's Banded Brothers documentary.

The arrangement in meerkats is much less amicable. Adult meerkats tend to feed whichever pup is nearest to them, so the pups dog the adults' steps, jockeying fiercely with one another for the best position, and changing adults frequently. Fights between spitting, growling pups are common place, as they try to stop each other from getting too close.

Meerkat pups taking a break from their competitive free-for-all.
Photo borrowed from here.

In dwarf mongooses, it's not aggression that pays but speed. Adult dwarf mongooses announce their imminent donation with a special 'come and get it call', so the pups loiter near the centre of the group and then hurtle madly toward anyone who calls. Whichever pup arrives first, gets the food.

Ready, steady, GO! Dwarf mongoose pups waiting to be called for lunch.

Snufkin's enthusiasm for pup-feeding didn't abate over the years, but in March 2008 tragedy struck.
She broke her left foreleg.
Foreleg injuries are bad news for dwarf mongooses because they dig for most of their food. And digging with just one paw is hopelessly inefficient. Snufkin steadily lost weight. But then things got even worse. The injured leg became totally rigid; she had to drag it about stuck out stiffly to the side. It was forever snagging on the vegetation or getting jammed against rocks. Searching for food clearly pained her and she spent much of the time resting. But Snufkin - being the mongoose she is - didn't just recline in the shade, she'd painstakingly climb up to the top of a boulder or into a tree so she could spend her resting time watching for predators and keeping the group safe. This always stressed me out because, when a predator did threaten, Snufkin had great difficulty clambering down to safety. Even when she finally reached a bolt hole, it usually took her two or three tries to get inside, having to manoeuvre her rigid leg to fit. Then the tendons in her leg began to shrink, curling her paw inwards until it withered into a clenched fist. I couldn't see how she would ever survive the coming winter.
But miraculously, after about seven weeks, she began to get some movement back into her leg. Gradually the stiffness lessened until she was walking almost normally. The deformed paw took a lot longer to recover, but today she's entirely healthy; and happily dedicating herself to the group's littlest members.

Snufkin with her little brother Cadellin.

Tuesday, May 18, 2010

Jackal matters

Yesterday, while checking one of Koppiekat's favourite termite mounds, I came upon a jackal.

Yes, jackals eat mongooses.

But not this one. This one had gone to its last great mongoose hunt in the sky.

Given the location of the body, I wondered at first if the mongooses had pulled off some David-and-Goliath type of act; maybe standing on one another's shoulders (like the sheep in Wallace and Gromit's A close shave) to pull down their mighty foe.
But up close, I could see that the newly dead jackal had huge puncture wounds in its throat. These stab wounds were not only massive, they were alarmingly widely spaced, and that - combined with the aforesaid 'newly' - had me glancing nervously over my shoulder. There wasn't much blood about and the jackal looked as if it had been choked to death, in classic big cat style. Presumably it had fallen foul of one of the leopards who live in the koppies. I actually took a (yucky) photo!

This Black-backed jackal (Canis mesomelas) either suffocated to death or, in its death throes, decided to stitch-up its arch enemy by posing that way.

What I don't understand is why the leopard didn't eat it. Richard Estes (author of The Behavior Guide to African Mammals) describes how a leopard visited his camp in the Ngorongoro Crater (Tanzania) almost nightly for several weeks, and during that time it brought back 11 jackals, to consume beside his cabin. Had my inopportune arrival at Koppiekats' mound RK001 disturbed the killer (more hasty over-the-shoulder glances)? It was at this point that I decided to resume my search for my innocent, harmless little mongooses.   

Later in the morning, I returned to find two bateleur eagles happily feasting on the carcass.
Well, it's an ill wind...

Bateleurs (Terathopius ecaudatus) are very common here and, despite what the books say, they don't seem to prey on mongooses (favouring carrion). At least that's what the mongooses believe (they don't alarm at cruising bateleurs), and they should know.
Photo taken by Tollie Botha and borrowed from here.

Sunday, May 16, 2010

Look at this to feel happier

Today I decided to post some flower photos (yes, I did take them) but while I was sorting through the images I realised my mood was markedly improving.

Was this just me, or does everyone feel better after looking at flowers?

A quick trawl of the literature revealed that Jeanette Haviland-Jones, and her colleges from the State University of New Jersey, having been undertaking experiments to find out.
In their first study, the researchers presented 147 women with a gift: either a basket of fruit and sweets, a bouquet of mixed flowers, or a large multi-wicked candle on a stand (all three gifts were of equal monetary value and were considered equally desirable by a test group of 30 women). The researchers recorded the women's immediate reaction to the gift, and interviewed them (about their feelings and activities) both before and (2-4 days) after the gift-giving.
Women who received a bunch of flowers reacted more positively than those getting other gifts; 100% of them responded with a 'true' smile (which involves the muscles around the eyes, not just the facial muscles). The mood of those that received non-floral gifts didn't alter between the first and second interviews, but flower-receivers were significantly more positive, and they also increased their social interactions (e.g. contacting people, talking intimately, etc.).

 In their second experiment, the researchers tested men too. They targeted 122 people who got into a university library elevator alone. They presented them with either a Gerber daisy (a brightly coloured flower about 4'' across) or a pen with a university inscription. They found that - regardless of their sex - people given a flower were more likely to respond with a 'true' smile, stood closer to the gift-giver and were more likely to start up a conversation, than people given a pen.

 In the third experiment, the researchers sent bouquets of flowers to 113 elderly people living in retirement homes. The experiment lasted two weeks with the seniors keeping a log book of their social contacts and undertaking a final memory test. Half the people received one bouquet of flowers, one-quarter got two bouquets (a week apart) and the remainder received nothing (until after the experiment). Predictably, those that were given flowers showed an improvement in mood, with seniors that received two bunches feeling more positive than those that got one. Although none of the seniors changed how often they interacted with other people, those that received flowers did much better on the subsequent memory test.

I particularly liked the comments that the researchers made about their flower research.
"Some participants responded with such unusual (for experimental studies) emotional displays that we were unprepared to measure them...   In many years of studying emotions, we have never [before] received hugs and kisses, thank you notes or photographs, not even for candy, doughnuts, decorated shirts or hats, gift certificates, or direct monetary payment; the flowers are different."

But why do people react like this?
Is it that we've learned to associate flowers with positive social interactions? But if this is the case, why did the men in these experiments react in the same way as the women? Giving flowers to men is not big in North American culture.
It seems more likely that our positive response to flowers arose early in our nomadic hunter-gatherer days. After all, flowers indicate that an area will be rich in food in the not too distant future. However, if our liking for flowers is related to food resources, wouldn't we be attracted more strongly to fruit or nuts (i.e. the actual presence of food) rather than flowers (the promise of food)?
Maybe the traits that flowers have evolved to attract their pollinators (usually insects or birds) are characteristics that humans also find attractive. People are known to find symmetry appealing and to be stimulated by bright colours. And more than 80% of commercially available perfumes contain floral fragrances.
Whatever the reason for our positive response to flowers, one thing is certain: you should get out there and enjoy some!

Haviland-Jones, J., Rosario, H. H., Wilson, P. & McGuire, T. R. 2005. An environmental approach to positive emotions: flowers. Evolutionary Psychology, 5: 104-132.

Thursday, May 13, 2010

Why I don’t take photos

Everywhere on the internet you'll find stunning photographs. There are thousands of photo-streams, galleries and blogs showcasing people's images.
Nature blogs, in particular, are just brimming with breathtaking photos.

Except for mine.

Now don't get me wrong. I enjoy beautiful photos as much as anyone. There was even a time when I took wildlife photos myself (never very good ones, mind you) and - out in my shed – I've a stack of dusty transparencies to prove it.
But I stopped. Why?
Because gradually I came to realise that photography was changing the way I perceived the world.
Instead of thinking, 'Oh what a glorious place!', I'd be wondering, 'Would this make a good photo?'. I started seeing nature in snapshot-sized pieces, framing everything within a view finder in my mind. Photography doesn't prevent you from observing wonderful things (unless, of course, you happen to be fighting to open your camera bag, or changing lenses, or searching for that spare battery). On the whole, you still get to see the cheetah racing after the springbok lamb, or the baby baboons dangling wrong-way-up from their father's tail. But what do you feel?
Awe? Enchantment? Joy?
Who has time for these, while stressing about shutter-speeds, aperture settings, composition and lighting?

This lovely photograph of a leopard was NOT taken by me (even though I found fresh leopard prints on my driveway yesterday). It was, however, taken in Kruger (by Penny Maddocks) and was scrounged - as usual - from the park's public sightings gallery.

For me, the clincher came one day in Kruger National Park. I was driving beneath the fig trees along the Timbavati River when a leopard stepped on to the road in front of me. Now, leopards are truly stunning animals. Apart from the shock value of a large 'professional killer', the leopard has a coat that almost dazzles your eyes, like some sort of iridescent optical illusion.
This leopard sauntered off the road and sat down in the dry grass right next to my car. I couldn't believe it. I was so excited I could barely grab up my camera.
But there was the grass. Try as I might, I just couldn't get a photo that didn't have stalks of grass in front of the cat's face. 'If only he'd sat a meter to the left', I thought in anguish. 'If only he'd turn his head two inches to the right!'
He didn't. After a few minutes, he rose to his feet, stretched languidly and strolled off into the vegetation. For the rest of the morning I felt awful. Angry, frustrated and disappointed, I just couldn't settle back into the tranquillity of watching wildlife. Yet I'd just witnessed something amazing; an unbelievably rare privilege. Why wasn't I elated? Why wasn't I dancing on air?! It was then that I knew. No more photographs.

Ever since then I've left my camera at home. I seem to be the only person in the universe who thinks this way. If you don't believe me, try holidaying in a National Park or tourist destination sans camera, and watch how people react.
Starting this blog has thrown me into a quandary. Blogs need pictures. Reluctantly, I've started carrying a camera again. But when it comes to the crunch, when I have to choose between experiencing a wildlife encounter or taking a photo, I'm afraid I'm going to opt for wonder and joy every time.
I just thought I'd better warn you!

Monday, May 10, 2010

Big, banded and bolshie

Yesterday while walking the dogs, I ran into a group of banded mongooses.

Six times larger than my dwarf mongooses, banded mongooses (Mungos mungo) remind me more of little dogs (dachshunds or terriers) than mongooses. So imagine 28 small dogs milling about excitedly together, and you've got a pretty good picture of what we met yesterday.

Seeing banded mongooses is a real treat. They're rare here, preferring to live in wetter, more densely vegetated areas.
This photo is from the BBC's new four-part series: Banded Brothers.

The group was trotting along with the local troop of baboons and a sounder of warthogs. Like dwarf mongooses, bandeds understand the value of foraging with other species: more eyes to watch for danger and a reduced chance of being chosen if a predator does strike.

But warthogs? Baboons??

Both these species are very partial to fresh meat, and viciously tear apart small, innocent animals whenever the chance arises. You wouldn't catch a dwarf mongoose setting paw anywhere near one of these hardened opportunists. Banded mongooses might be larger, but they're still small enough to wind up as lunch.

A young banded mongoose. Photo taken by Mike Fisher and borrowed from here.

However, banded mongooses have a secret weapon. When threatened, they adopt a special battle formation. Clustering closely together into a phalanx, the mongooses charge at their quarry. Within the tight formation, each individual writhes and rears up and down so that, together, they look like one large and very threatening animal. The whole scary performance is topped off by an array of alarming sound effects: churring, growling, spitting and snapping. And let me tell you, it is VERY intimidating.

Once I was watching a group of banded mongooses foraging with baboons near Lower Sabie in Kruger National Park. It was a beautiful golden morning, and everyone was peacefully going about their own business. The baboons were sitting in pairs and trios grooming one another, while their youngsters romped in play, and the mongooses were trotting about scratching in the leaf litter for bugs. No one was taking the slightest notice of anyone else. The scene was so lovely and tranquil, I started feeling sleepy.
And then an adolescent male baboon sauntered past. He didn't approach the mongooses (many baboons were nearer); he didn't even glance at the mongooses. But he had a certain, 'I'm not the least bit interested in mongooses' look. If he'd been human, he'd have been standing with his hands behind his back, staring at the sky, whistling. The mongooses reacted instantly. In an eye-blink, the dispersed group members converged into a single snarling mass that hurtled toward the young male. The baboons leapt to their feet, screaming and barking in alarm, and fleeing in all directions. And the great undulating 'MONGOOSE' charged off in pursuit of the terrified adolescent. Within seconds I was completely alone. I could just hear distant alarm barks of the widely scattered baboons. But my heart was pounding from the sudden, unexpected violence of it all.

The banded mongooses at Mweya Peninsula in Queen Elizabeth National Park, Uganda, have gone one step further in cultivating intimacy with other species. Here the mongooses have adopted the role of furry ox-peckers, enthusiastically removing ticks from the local warthogs. Click here to see a video clip of this extraordinary behaviour.
I have to admit, I wouldn't trust any mongoose to do this!

Friday, May 7, 2010

What’s the gardener saying?

When I opened my front door this morning I found a massive footprint on my door step.

It was a hippo's.

But this signature print was just the finale in a very weird performance.

Continuously, for about two hours last night, one of the local hippos performed a deafening serenade of growls, grumbles, wails, chortles and elephant-like trumpeting. Now I'm used to the hippos making a noise: their bellows reach 115 decibels (which is the volume recorded 5m from the speakers at a heavy metal rock concert). Nevertheless, it's only once every couple of months that a hippo indulges in these strange soliloquies. I have no idea why.

Local hippos.

After I retired to bed, the illustrious singer visited my garden. Of course, around here, it's not unusual for a hippo to crop your lawn, and I'm the first to admit that the waist-high grass in my front yard needs slashing. But last night's gardening activities were peculiar. The hippo awkwardly clambered down the three steps to my front door (where he left his print) and then chomped away a two metre-wide strip of grass, right along the wall of my house. He totally ignored the self-same grass growing everywhere else in the garden.
Was it just coincidence that my gardener 'performed' before coming to the house? Was he trying to warn me, or vocally intimidate me, to ensure undisturbed grazing? Or was his visit to my house, the final act of bravado in some macho display for a rival or potential mate?

OK, not crop-circles, but this awful photo shows the cropped strip on the left and the untouched grass on the right.

My ignorance of hippo vocalisations is a constant frustration. Unfortunately no-one (except hippos) knows what they're saying. For example, the classic hippo bellow that you'll have heard on wildlife documentaries is thought to be a territorial call because when one animal bellows, other hippos in the distance respond in kind. But after living by the river for two years, I'm sure this call is used to warn of intruders, and that the hippos 'pass it along'. They bellow whenever a human approaches the river (including me walking the dogs) and, for me, it's a fail-safe warning of someone being about.

But hippos have a problem. As you'll have noticed when swimming, the surface of the water blocks sound. When you're swimming underwater, you can't hear someone shouting from the bank, and they can't hear you scream (you can tell I live next to a crocodile-infested river). So if you're a hippo and half your pod is submerged, while the other half is drifting with their ears and eyes above the water, how do you warn them of an intruder?

Hippo facial features are designed so hippos can keep their ears and eyes above water while remaining safely submerged.
Photo by Lloyd Nel and borrowed from here.

Recent research by William Barklow, from Framingham State College in Massachusetts, has found that when hippos bellow, they snort the sound into the air through their nostrils (like an explosive sneeze), yet they simultaneously keep their mouth and lower jaw submerged, so as to call underwater too. Using underwater microphones, Barklow found that hippos are extremely 'talkative', but 80% of their calls are inaudible to us because they're given underwater. Hippos produce a huge range of sounds, including 'clicks' similar to those made by killer whales and, like elephants, they use infrasound (frequencies too low for our hearing) which carry for many kilometres.
Unfortunately, despite all these exciting discoveries, we still have no idea what hippos are actually saying to one another.

Photo by Neil van Asselt and borrowed from here.

Barklow, W. E. 1997. Some underwater sounds of the hippopotamus (Hippopotamus amphibius). Marine and Freshwater Behaviour and Physiology: 29, 237-249.
Barklow, W.E. 2004. Amphibious communication with sound in hippos (Hippopotamus amphibius). Animal Behaviour: 68, 1125-1132.

Wednesday, May 5, 2010

Spitting in the face of adversary

Today a cobra spat in my face.

It was my own fault really.

We met on the back doorstep; the snake was coming into the house as I was going out.
It was only a juvenile (about 0.5m long) and the colour of flour, which left me unsure of its species. Around here, most Mozambique spitting cobras are either muted terracotta or yellowish tan. Foolishly, I stepped between it and the hole it was fleeing toward, in an attempt to get a better look at it. The instant I blocked its retreat, it went on the defensive, rearing up, flattening out its striped hood and spitting venom like a mad thing.

These very young cobras go quite berserk once they start spitting. While keeping their bodies still, they jerkily swivel their heads back and forth in a semi circle, spitting in every direction. Try to imagine an over-excited machine-gun operator firing from a gun turret.

I felt a spray of venom on my cheeks but fortunately it didn't reach my eyes. The venom is harmless unless it enters a cut or sore, or contacts a mucus membrane. While most cobras' venom is neurotoxic (i.e. targets the nervous system), this species' is primarily cytotoxic (it destroys cells at the site). Get it in your eyes (which is where the snake is aiming) and it's excruciatingly painful; it can even cause permanent blindness if not rinsed out immediately. I'm forever having huge fights with the pets, trying to squirt water into their eyes when they're already going crazy from the pain.

The Mozambique spitting cobra (Naja mossambica) produces 200-300mg of venom; 50mg is fatal to humans. Photo by Ben Tupper and borrowed from here.

It was a snake-filled day all round.

Our brief dalliance with winter weather has ended, and temperatures are now back in the 30's (Celsius). Everyone is shucking off their overcoats and becoming active again. I mean this literally. On my walk with the dogs, I came across four newly shed snake skins. And then, when we were almost home, we met yet another African rock python (Python sebae). This one was young and small (1.5m), which was most reassuring.

Bad photo of tonight's python. Pythons are an ancient group; they used to slither about with the dinosaurs. Their bodies still carry the remnants of their long, lost hind limbs, with the bones from their once-upon-a-time pelvis forming small 'pelvic spurs'.

Sunday, May 2, 2010

I’m stuck in a rut

All around, the bush is reverberating with deep snarling roars and growls.

Imagine the rumbling growl of an attacking Rottweiler, only crank up the volume until it's audible 2 km away. Oh yeah, and there's the occasional explosive snort too.

For the uninitiated these bursts of apparent violence are quite intimidating. I've become accustomed to my new volunteer assistants returning prematurely from the field, ashen faced and muttering, "Er... um... I heard this growling...".

Lions?  Wild dogs?  Fighting hyenas?   Impala.

Impala (Aepyceros melampus) are the most numerous antelope in southern Africa, with more than one million living in the region. And right now it sounds like they're all just outside!

Each May (synchronised between the two full moons) the local impalas mate. Now, before you start thinking that impalas have wildly exotic sex lives, the mating itself isn't noisy. It's the males arguing over breeding territories that create the racket. A study of rutting males at Sengwa, in Zimbabwe, noted 180 roaring displays in just one hour, on a romantic moonlit night.

Displacement grooming is frequent in territorial conflicts, as males waver between attacking their rivals and playing it safe (just as humans scratch their heads when making up their minds).

In East Africa, male impalas hold territories all year round, but here in southern Africa, they relax in mixed-sexed herds for most of the year. However, as the short, intense breeding season approaches, their testosterone levels soar and they go into a frenzy of aggressive competition. In a bid to stake out breeding territories (of around 8 – 13 ha), they use macho displays to intimidate rivals, standing very erect while flexing their neck muscles, tossing their heads, roaring, horning vegetation and even flicking their tongues in and out like professional punk-rockers.

Actual horn-clashing fights are rare (occurring in around 7% of conflicts) and males have a 'dermal shield' of thickened skin that protects their head and neck from stab wounds. Photo by Dougie Cunningham and borrowed from here.

Males that fail to gain a territory retreat to bachelor herds, where they spar with one another to establish a pecking order. Only those at the top of this hierarchy go forth to challenge the territory holders.

Territorial males spend up to a quarter of their time tending the females that pass through, chasing them into the territory's core, tasting their urine for signs of oestrus and, of course, mating. They also patrol their boundaries, face down trespassing neighbours and fight off challengers. As a consequence, they rarely get a chance to feed or sleep, and quickly exhaust themselves. Their average tenure, during the peak rut, is only 8 days. Once they're ousted by a rival, males limp back to the bachelor herd (rejoining at the bottom of the hierarchy) to regain weight and recuperate.

Horning vegetation is not only an impressive visual display, it leaves behind a smear of strong-smelling secretion, from the skin on the male's forehead, that indicates his status.

Female impalas show little interest in the males' squabbles, wandering from territory to territory. Although the population is female-biased, with 1.5 to 2 females for every male, most of the mating is monopolised by just a handful of prime territory holders.

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