Regarding Mr. Adam’s column on “cat spray”, especially his note that, “The hippopotamus, for instance, is said to mark jungle trails by excreting a lethal mixture of urine and feces while twirling its tail like a propeller.” I wish to add my personal observation.
I observed this particular behavior of hippopotami myself. No, not in the wild, but, in a zoo (either the one in my home town of Leipzig, Germany, where the eminent biologist Bernhard Grzimek was director then, or in the zoo in Frankfurt/Main, Germany). Either way, this is what I saw: The hippopotami, of course, had a pond to swim in. I saw one of them swim towards a rather large rock at one end of this pond, point its rear end at it, and let loose with a prodigious spray of feces, while “wagging” its tail so fast that it looked as if it were going around like a propeller. The sight was so remarkable and startling that I still remember it quite vividly, all these many years later (I’m now 71 years old). While I did not then connect this action with a marking of territory, it makes eminent sense now. I would not doubt for a moment that that is what hippopotami do in the wild, as well, for reasons stated.