There are times when the hippopotami seek to be invisible; they then
bury themselves in the sand, and not one can be seen. At other times,
miles of country are covered with them.
When the wind is in a particular quarter it causes a remarkable musical
sound in its passage through the hollow rocks, which seems particularly
sympathetic to the hippopotami. If, at the time the "musical sound" is
heard, the sun shines, they with great rapidity place the young ones
together, running round them as round a central point in a succession of
circles. They jump and bound, pass and repass each other, and as it were
dance with joy, in a state of great excitement continuing their
energetic gambols all the time the musical sound is heard, until,
exhausted with their exertions, they lie down and sleep.
It is a grand sight to see large herds of hippopotami so joyfully
excited. They never act thus when stimulated by fear, but stand doggedly
for some time, as though examining the cause of the disturbance, and as
soon as the terror has mastered them they rush away, running at a great
speed.
When they pair, they are generally constant to each other, and the
female usually remains at the side of her mate: but some are capricious,
and go about as if seeking other males of the herd. When the female is
thus inconstant, her partner, after a time, tries to destroy her and her
young, though pains are taken to prevent this result.
To save the female and her young, we have occasionally been obliged to
kill the male with arrows steeped in a poison so powerful, that the
slightest graze will cause instant death.
The mother is generally much attached to her young. She buries it in the
sand, leaving an aperture through which it may breathe, and she lies at
its side. If the temperature changes, or she fancies the calf has not
sufficient heat, she will cover the aperture for a time with her head,
or some part of her body. She gathers nuts, which the young one likes,
and will sometimes wander for miles along the strand of rivers to seek a
small fish, which she kills, and brings back to the spot where the calf
has been left buried in the sand.
When the young one is sickly, and does not respond to the signs of the
mother, she fancies the little creature does not like her, and leaves it
to die.