Excerpt from "Ngorongoro"

The same wanderlust must have driven the first hippos of Ngorongoro up and over the crater wall. Whatever the tempting circumstances were that might have encouraged the first hippos to climb the slopes of the extinct volcano--perhaps the lush vegetation of a long pluvial--one day, or more likely, one night, the animals set off on their long trek to the top. It must have been quite a sight when a procession of these rotund grass-eaters left their watery retreats and puffed their way up to an altitude which would have taken them to the peaks of many mountains in Switzerland, only to waltz over steep and slippery trails down into the crater.

The conditions they found were ideal, and they remain so to this day. The swamps, with their extensive papyrus fields, offer them all the privacy they need in the daytime, while the plains provide well-stored grazing where they can crop their green diet at night.

Watching the well-fed occupants of the hippo pool--a small bay at the edge of the Mandusi Swamp--one can't help feeling that the exhausting trek rewarded those first hippos with their own version of the Garden of Eden. Except, perhaps, for the high density of predators they must share it with.

One evening Lala and I were watching the hippos leaving the safety of the swamp to the east of Lerai Forest when, suddenly, the roar of a lion resounded through the silence of dusk. Earlier we had seen a pride resting near the swamp. It must have been one of the pride-males which now unmistakably announced its position with a mighty roar to any stranger who might be in the area. Another lion joined in. The roar sounded too close for comfort for the hippos. We could see their dark figures running back toward the water. The sound of splashing told us that feeding had been postponed for a while.

But there was another problem too. One day while I was watching the animals at the hippo pool dozing through the morning, one adult suddenly rolled over, its legs sticking up in the air and its pink underside exposed. But only briefly, then its head and back surfaced again. Black mud trickled from its back. This was the first time I had noticed this unusual behaviour. A few minutes later I was surprised again, this time by another hippo. And again a third one did it. In the course of the morning I saw nearly every member of the school sticking its feet in the air while wallowing in the mud. Youngsters showed their bellies too, as did calves. Besides these rolling exercises, every animal in the community, from time to time, wagged its tail to shower a fan of water over its back, which made me think that possibly the hippos were simply trying to save their skins from sunburn. The added intensity of sunrays at this high altitude might have necessitated the extra protection.

Lala also noted this unusual hippo behaviour, but in a different context. She found a hippo resting in a bay of its own. Some sacred ibises had taken up position on the shore. Suddenly one of them took to the air and alighted on the hippo's back. The submerged herbivore tolerated its rider as the bird walked around on its back and even on its head. For a moment the ibis even stood between the hippo's eyes. A short while later it became apparent what the bird was looking for. Without warning, the hippo started to roll and the ibis found itself balancing on a revolving drum. With wings spread, it ran over the hippo's broad flank and on to its massive belly where somebody else had been surprised by its host turning upside down. Sticking firmly to the soft skin of the hippo's underbelly, leeches found themselves suddenly exposed to the air, and to the eyes of the ibis. They hadn't been able to detach themselves quickly enough from the nutritious tissues they had found in the muddy darkness of the swamp, and now tried to wiggle back to safety. The ibis plucked off as many as possible before the drum began rolling again. This process repeated itself at regular intervals. Every time the hippo turned belly up it was feeding time for the ibis, which caught several dozens of the fat little suckers bursting with hippo blood.