This April, the full moon fell on the 28th, signifying the peak of the mating season for impala antelope in the Kruger Park. Impala begin rutting with the moon waxing around its First Quarter stage in late April or early May and, as if by clockwork, I heard the first impala males “roaring” in the Sand River area as they chased competing males from their territories on the 21st April, precisely when the moon reached this phase.
Predators don’t hunt as successfully in bright moonlight as they do when it’s darker for the simple reason that their prey are able to detect them easier. So, nature has determined that impala tend to rut by moonlight, making them less vulnerable to predation while they’re otherwise occupied with the ladies. Accordingly, the peak of the rut is when the moon is full, gradually tailing off as it wanes to its Third Quarter phase and beyond. As a recent guest on a walking safari, Dr. Brian Perry, so succinctly put it: “impala do it with the lights on!”
The rut takes place at this time of the year so that the ewes give synchronous birth to their lambs some weeks after the onset of the rain season. Syncronised birthing determines that with all the lambs being born together, predators may have a field day, but enough lambs survive to maintain a viable population of this key food chain antelope. The first rains usually fall in October in the KNP, prompting vegetation growth to provide cover for the newborn lambs, as well as the nutrients their mothers need for lactation. It is a fallacy that impala ewes are able to delay birthing by extending their gestation period in the event of late rains. The impala gestation period varies from 194 to 200 days and the arrival of the newborn lambs is determined purely by the date of mating.
Thus, according to the date of this years First Quarter moon phase on the 21st April, we should start to see the first lambs appearing in the park in the first week of November.