Mzima Springs is one of the best known places in the world for watching hippos. So let's take a closer view of it.
Mzima means "alive" and it's certainly competent - a 1.5-km-long series of glassclear pools in Tsavo West National Park, Kenya, is home to many animals. And especially hippos.
Not far from the pools Chyulu Hills are situated - these are peaks of volcanic ash that extend to the height of 2,187 metres. The youngest cones were formed about 500 years ago. Every year up to 90 cm of rain fall here and all the water soaks into the ash which drinks like a sponge. The water goes through until it hits impervious bedrock. Then it begins its 40-km underground journey to Mzima Springs. Filtered over many years, the pure water gushes forth at a steady pace of about 200 million litres a day, creating an oasis at the heart of the Kenyan national park.
Cool, shallow and shaded pools offer practically everything that hippos could need; nearby grasslands fill up their stomachs. So the numbers of hippos at Mzima Springs have remained constant for several decades - there are some 60 to 70 animals divided into four groups living in the three main pools.
Hippos are truly of a vital importance here - their dung keeps the whole ecosystem. Having the consistency of chopped hay, it provides a hiding place for predatory insects and food for snails and fish. Insects are then eaten by fish, fish by birds... The whole ecosystem is anchored to the bulky herbivore. Even after death hippos come in handy: they provide food for scavengers like turtles. These lay their eggs on the shore and there, in wet-season puddles, shaggy coats of algae sprout on the shells of juveniles. When the turtles later enter the springs, the coats become food for Garra fish that clean the shells. But hippos provide food even directly - fish feed on them with algae, parasites and dead skin. What is astonishing is the specialization of the fish: certain species clean certain body parts. The ubiquitous Labeo, in the carp family, is the main cleaner, using its wide rasping mouth to scour a hippo's hide and also teeth and palate in the giant mouth. Barbus feeds directly on dung and cleans the cracks in soles and spaces between toes. Small Cichla grazes around the tail bristles and tiny Garra cleans out wounds. But hippos aren't just passive recipients of these services. They deliberately open their mouths or spread their toes and legs to provide easy access or to solicit cleanings. They also visit "cleaning stations" where the fish gather - much like pampered clients going for a massage or manicure at a spa.
Without hippos, there wouldn't be any life in the pools. A spring about 80 km westward from Mzima Springs bears witness to this. Bones of hippos, crocs and turtles were found there in an underwater cave, some of them so old that they crumbled at touch. So it's clear that hippos and their attendants once must have lived here. It's not difficult to find out why they died off. The surrounding landscape, which lies outside the national park, is crowded with small farms. Hippos must have devastated them during their night forays and that's why the farmers probably chased them away or even killed them for meat. Without hippos and their dung the whole spring died off. As for the bones, it could have been that hippos occasionally blundered into the cave, didn't find the way out and drowned. The crocs, attracted by the smell of the carcasses, followed them and met the same fate. But Mzima Springs is safely ensconced in the national park and there's no fear of a similar disaster here.
In most African coffee-coloured rivers and lakes it's not possible to film hippos underwater, where they spend most of their time. That's why when filmmakers Mark Deeble and Victoria Stone found glassclear Mzima Springs they decided to make a film there. They spent two years in Kenya.
In the beginning, however, they had to get over several problems - e.g. how to record hippos behaving naturally underwater while not being seen either by them or the crocs which live in the pools. The original plan was to put on scuba gear and film normally underwater. But that proved too dangerous when a croc attacked Mark within several weeks. Mark stunned him with his camera and escaped with a new plan: to use remote-controlled cameras and to build a series of 12- to 15-metre observing towers along the shore. "We watched where the hippos congregated and positioned our towers in places where we predicted certain things would happen," says Mark Deeble. But a new problem occurred: hippos were very sensitive to the sound of the camera and they also churned up the dung, that densely covers the bottom, every time anything started to happen. It took nine frustrating months to get any pictures. But it paid off.
Mark and Victoria then witnessed many interesting things - such as hippo mothers suckling their calves or protecting them against crocs. But the events weren't always such happy. For several days both filmars watched a new mother periodically helping her offspring to get to the surface to breathe and impatiently waited for the day when she would introduce it to the rest of the herd. But when it happened it was a shock. The following behaviour is rarely documented and what is even more uncommon, the male wasn't the leader but one of the juveniles. He attacked the baby and mauled it to death. He apparently wanted to get rid of his possible future rival because the baby was a male. The extremely agitated mother naturally tried to defend her calf but she just wasn't up to it. The male didn't release it, he repeatedly bit it and dunked it until the baby died. "I'm not one to attach emotions to animals," says Deeble. "But when the mother was finally able to get back to her baby, she reacted as if it was asleep underwater and tried helping it to the surface to breathe. But it was long dead. She hung around for the whole day, retrieving the body when it occasionally floated away, but gradually realized the calf couldn't be saved. The last time it floated off, she left it to the crocs."
The filmed stuff was completed to a documentary called Mzima - Haunt of the Riverhorse (2003). The film is 52 minutes long and was broadcast e.g. by National Geographic. It also got many awards. Read more about it at www.deeblestone.com.
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