It is not typical for zebras to drown young foals that are not their offspring. The incident involving the adult male zebra and the young foal observed by wildlife biologists is believed to be an isolated case and not representative of the typical behavior of zebras.
Zebras are social animals and adult males play a protective role towards the young in their herd. However, there could be various reasons why the male zebra in this particular incident exhibited such aggressive behavior, including feeling threatened by the presence of the young foal, a hormonal imbalance, or other factors.
It is important to note that this is a rare and isolated incident, and that the majority of zebras are known for their gentleness and protective behavior towards the young. Further research is needed to determine the exact reasons behind this unusual behavior.