Photo of the Day #30: Hippo


Today's photo, like yesterday's, was taken at the Philadelphia Zoo, and I was fortunate enough to be able to catch the Hippos (Hippopotamus amphibius) as they were entering the water. I'm sure everyone has heard of their aggressiveness via television documentaries and other sources, but few have heard of the fact that hippos sometimes consume flesh. While hippos occasionally nibble on or play with carcasses in African waterways, in severe drought conditions they sometimes kill prey (as in one account of an impala running into the water to avoid Wild Dogs, only to be killed and consumed by hippos) and may even resort to cannibalism. This can be a problem as cannibalism can assist the spread of disease in stressed populations, and in 2004 that's precisely what happened with an anthrax outbreak in Uganda.

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I am fascinated by the idea of cannibalistic hippos. I was aware of their aggressiveness, but not that they had been known to eat one another under certain circumstances. I am not, however, surprised to find that such behaviour would encourage the spread of infectious diseases such as anthrax. As anthrax is caused by the bacterium Bacillus anthracis, logically consumption of infected animals would also involve consumption of the infecting bacterium.

Anthrax is one of only a few bacteria that can form long lived spores. When the bacterias life cycle is threatened by factors such as lack of food caused by their host dying or by a change of temperature, the bacteria turn themselves into more or less dormant spores to wait for another host to continue their life cycle. On breathing, ingesting or getting anthrax spores in a cut in the skin these spores reactivate themselves and multiply in their new host very rapidly.

Cannibal hippos... That's scary...

My GF told me they're mean-spirited animals, so I'll try to avoid them when/if later this year will be meeting them in the Rwandese rivers... Not that I plan to swim on parasite-ridden (and possibly crocodile-ridden ) rivers...