Luangwa - Battlefield of Hippo (Part 5)

Although they all but share a kingdom, both the crocodiles and the hippos are prepared to cross boundaries if something is at stake. For the crocodiles it’s a matter of food, for the hippos, possibly a matter of kinship or simply a lack of cognitive understanding of death. Amidst the feeding chaos, the hippo’s own brave the hordes of shiny teeth and flailing tempers for an investigation. Barging through the ranks of crocodiles, biting, pushing…what are the rules?

Recognition is sought by the hippo through licks and sniffs and nudges. The opening of the mouth indicates the use of the vemoronasal organ (commonly called the Organ of Jacobsen) which detects airborne steroid hormones. Typically this organ is used in determining whether an individual is ready to mate but is also used in the recognition of individuals. Maybe the salts on the sun-baked skin are simply a dry season delicacy for those who survive to harvest it? The teeth of a hippo are not exactly designed to nibble meat off spongy carcasses but licking is certainly possible. Hippos are after all the descendents of pigs.

On a particular channel, the Changwa, there are so many hippos packed together in the shallow remaining water of a fast shrinking river that a photograph reveals 100 heads but no light or space between them…it’s an epic tin of sardines! Changwa especially becomes overcrowded as the water level drops, a giant super-pod of thriving bodies and bad tempers. The rerouting of the river here, in its relentless quest to change course and create oxbows, provided an apparently super-attractive spot of hippo real estate. The Changwa Pod is no ordinary pod of hippos, it’s a super-pod and they offer us an exaggerated look at the dynamics of hippo life in the Valley. Fights break out…disease attacks…heat exhaustion takes its toll and hippos die creating a feast of notable proportions for the 100’s of crocs in the river that pile into these carcasses in numbers up to 200 at a time. The crux comes when the lions find such carcasses on the waters edge and fight off the crocs in a unique predator standoff for sole access to the meat.

For most of the year, these species seldom clash. Lions dispatch all decaying finds on land, crocodiles keep the Luangwa’s waters clean. Not so at this time of year. It’s a free for all and a wealth of hippo meat is too good a find for both competitors and sharing is just not an option. Armed with enormous teeth, lightning fast reflexes and claws of steel, the crocodile is a force to be reckoned with. But although the crocodile is obstinate and has craftiness on its side, there is a chink in its armour. Ten times the size of a lions’ jaws perhaps, the crocodile’s jaws do not provide an enormous amount of crushing power. Success is in the surprise of the attack and thereafter the ability to latch, drown and twist to feed off their prey. If matched against the lions and hippo, the crocs are up against high odds when out of their own domain.

Moving straight in, the lioness drags the carcass inch at a time up the beach, gaining ground for the lions before the carcass is lightened enough to be fleet-footed into the water. The water means victory for the crocodiles and here the lions do fear to tread! The crocodiles crawl up the beach after their escaping meal. The lions have speed and muscular power on land but the crocs have overpowering numbers on their side.

The Luangwa Valley’s top predators come face to face in the ultimate showdown. Lions and crocodiles clash over the final rights to this ultimate dry season prize – a prize defended valiantly by its own kind!

Luangwa: Battlefield of Hippo (Part 4)

Nature’s abundance of sausage trees provides for Luangwa’s abundance of hippo and in turn this supports another abundance…

In the Luangwa, a profusion of Nile crocodiles infests the waters, feeding stealthily on fish, thirsty antelope compelled into the murky shallows and even the occasional unsuspecting fisherman – crocodiles are notoriously indiscriminate in their choice of victim. But it is the giants of the river, the hippos that sustain and replenish the hordes through the dry season. With so many hippo conflicting, large mounds of decaying meat are a common sight along the river during the dry months. The heat rots the flesh quickly and it doesn’t take long for the crocodiles to sense the feast. So acute are their smelling senses for navigating through the murky water that no free meal goes unnoticed. Poking top-mounted beady eyes above the surface of the water, the sight of the mound of decaying flesh confirms what the nostrils already detect and draws the crocodiles in their hordes...in their hundreds.

Sometimes boundaries must be crossed to access the meat…the crocodiles must move onto the land. Disarmed of their usual feeding format, the characteristic grip, spin and rip, the crocodiles can only enter the carcass where it is soft. The exceptional heat quickly loosens the flesh however and with some spectacular land-bound spins, the meat comes free - enough to lighten the load sufficiently after a day or two that they can drag the bulk into the water and there feast more comfortably in their own medium. Until then they pile upon one another, crudely slithering over each other like maggots.

Luangwa: Battlefield of Hippo (Part 3)

The buck doesn’t stop at space and territory issues, there’s more than just lack of water for the hippos to be concerned about during the dry season in Luangwa. Their food supply literally withers away too. Most of the dry, caked earth in the dry months in Luangwa has little to no ground cover. Black cotton soils expand and contract in the heat pruning roots and rendering little edible life. So how do 30000 hippos survive? A magic, albeit little recognised, life source afforded by nature– the sausage tree! It is true in many wildlife areas that most creatures stay away from the enormous sausage-like fruit that lie under the tree (thanks to gravity) until they shrivel. But in Luangwa, the sausage tree means life to many but especially the hippos!

Huge, majestic, sausage-laden Kigelia Africana dominate the valley along the river course and adjacent floodplains. With little other cover on the earth, the sausage trees covered in electric green pre-summer flushes and rosy flowers stand out like towering mountains. Although the puku and impala feast on the fallen flowers and yellow baboon snap off the tender shoots, it’s the full grown, massive sausage fruit that the hippo seek. Where one would find the occasional fallen fruit beneath an Okavango based sausage tree, it is a rare occasion to find any such fruit lying about in Luangwa and this is because the hippos devour them with a determined voraciousness. One even spots hippos merely standing beneath the trees waiting for a fortuitous sausage to fall – even during the middle of the day!

Luangwa: Battleground of Hippos (part 2)

With a scarcity of food, an injured hippo is confined to barracks – left to die in the only available moisture he can find, usually the sludge of an abandoned oxbow. Sometimes death only comes days later as predators of all descriptions line up to watch the slow demise, saving their energy for the feast they know is imminent. On one occasion we watched a dying hippo in such a pool for just short of a week. Assuming the lions would move in and “finish him off”, we were surprised to find them lazily watching the scene from the shade of a small tree the following morning and even more surprised to find the geriatric had acquired a companion. This apparently healthy hippo moved into the puddle with the injured bull and during the course of the week and even after the other had died and turned the pond a mucky green, this loner appeared and disappeared.

A number of explanations are possible. Perhaps the second hippo was also a defeated bull with no where else to go and the injured bull was unable to fend him off his turf, or simply too weak to care. A controversial theory proposed in the past is that perhaps hippo, like elephants, endure some kind of kinship bond. The hippo may have been from its own pod, perhaps in a nearby stretch of river or simply recognised a species member in distress. Hippos have been known to behave quite remarkably around dead or dying creatures. Skinner reports a hippo supposedly rescuing an impala…???

The day that heralded the death of the hippo held another surprise. The first at the scene was a lonesome hyena who merely nibbled at the tough skin over the decimated rump. A couple of mouthfuls and he was gone. The next visitors (aside from warthogs, guinea fowl, puku and baboons all who drank from the fowl pond with its dead inhabitant) arrived only during the course of the following night and after a small feed by lion-standards, the male and female duo also departed leaving most of the carcass intact. They seemed to sense the virtue of allowing time to rot and forge away through the thick hide but even once this happened, the putrid carcass was relinquished to the hordes of vultures that patrol Luangwa’s skies. The dry season is vulture-prime time and the feasts are a comic to watch with birds dominating the carcass despite the ton or two of meat, tackling…falling into the mud…!!!

Luangwa - Battlefield of Hippo (Part 1)

The Luangwa Valley stretches like a giant arm along the Eastern part of Zambia. This vast and unforgiving wilderness, partially protected within the confines of the North and South Luangwa National Parks, does not enjoy a brutality-free history but having survived most of the ravages of man’s exploits (all except the rhino!) remains today as one of Africa’s last. A side branch to the renowned Great Rift Valley, the flat-bottomed Luangwa Valley harvests the fertility washed down from her mother feature and with the provision of copious annual summer floods, consequently supports an inordinate abundance and diversity of life. Water gushes down a 200m wide snaking channel, over spilling its meandering banks to replenish numerous oxbow lagoons and watering the adjacent pastures. With so much surface water and the fertility of the Rift’s clay soils, the valley erupts in a summer harvest of incredibly high plant biomass which in turn supports a high biomass of herbivores including 3 endemic species - Crawshay’s zebra, Thornicroft’s giraffe and Cookson’s wildebeest. The valley consequently is alive with predators – lions, leopards, crocodiles.

Uncommon of most African rivers, the Luangwa River respects her political boundaries, rising in the highlands of Zambia’s northern frontier and terminating at the junction with the Zambezi on Zambia’s southern boundary. This spectacular river is home to the largest population of hippos in the world, and the entire ecosystem is dependant on her, the only river in the valley. And this is a vital characteristic of the Luangwa for although it is a fat and snaking river during the summer rains, Luangwa is a place of extreme seasonal contrasts and when the rain ceases, the river shrinks progressively into the dry months, eventually becoming a mere trickle interlinking deeper channels as temperatures soar into October. With the oxbows dried up and all other ephemeral water in the valley gone, creatures journey huge distances to the river for relief from a dementia-inducing time of dust and hardship – now certainly dependent of the only river in the valley. Interestingly, most creatures here exist in a smaller physical form than in the rest of Africa due to the isolated nature of the Valley, hemmed in by escapements formed by ancient tectonic movements and comparatively less fertile tracts of Miombo Woodland that extend beyond the Valley’s limits creating a relative biodiversity vacuum.

For the mega-population of hippos, ancient pig-relatives Hippopotamus amphibious, the Luangwa is patch of real estate extraordinaire! Luangwa houses an estimated 30000 hippos along its 1100km course - the biggest population anywhere in the world and so in the dry months, a shrinking river is not good news! The wide sandy beaches exposed by the retreating water, become a battleground for the hippo. For the top predators – lions and crocodiles - it’s a feast guaranteed!

So spectacular is the size of the Luangwa hippo population that any visitor to the valley can expect to count at least 80-100 individuals at any random point that one should choose to stop and tally. This in itself is remarkable but more so if one considers that the population was almost annihilated before the area was protected. In 1918 a hippo sighting was considered a significant one! But that really is a thing of the past and the numbers are staggeringly obvious when the river is at its lowest in late October into November.

Hippos seem to favour the quiet oxbow refuges and lagoon-flanked stretches of river as it is here that they can easily access the lush grass from the alluvial areas surrounding the floodplains. But after May, these choice habitats are no longer available, shrivelled to chunks of caked-mud in the heat, and with no where else to go, hippos migrate en masse to the deeper pools in the wide river channel. Survival through these times is a severe ordeal. Here they are vulnerable to the scorching sun and to the wrath of the resident bulls, irritated that their turf is being invaded by the competition. The deeper pools amongst exposed sandbanks are prized territories and conflict is the order of the day!

Enormous in size and decked with formidable canine-like tusks and muscular jaws, the hippopotamus is at the best of times a formidable beast, able to snap a 3m crocodile in half given good provocation! Survival instinct sets in among the swollen pods and it’s each to their own - sometimes with brutal consequences like the death of an infant trampled in the crowd! As the water level drops lower and lower, fights erupt in a flurry of water and honking and then fizzle out almost as quickly once dominance is established or space acquired.

But for the bulls, a deep pool in the river is gold to retain females and they have more important work than mediating commotion. For a bull, the fight is for territory and for the females and mating rights that come with that. During the height of the drought, fights spark swiftly between a proprietor of a sought after stretch of river, and any unwary immigrant male, displaced from the dried up lagoons. So fierce are the bull defenders that it’s all or nothing. Most fights are likely to end in the death of one of the combatants or at least the expulsion of the loser. The bizarre and somewhat unnerving honk-roars of hippos in combat ring out through the dry air throughout August, September and October, night and day. Most of the noisy charade seems to be an intimidation tactic – when matters get serious, the noise disappears, the only sounds being the clash and slash of mighty canines locked in confrontation accompanied by spectacular sprays of water and blood streaming from the afflicted combatants’ mouths. Powerful robust jaws supported by abnormally large head and forequarters and sword-like teeth are the fighting weapons of these massive opponents –the rest just tons of stubborn blubber. Characterised by violent head shakes and swift rushes, these scenes are spectacular, the noisy chorus’ indeed intimidating and the results all too often devastating!