Field Notes – October 2018
Predicting the unpredictable
No rainfall was measured in our focus area during the month of September, and it seems to have been more and more difficult to predict over recent years. Scientific studies based on various rainfall forecast models are somewhat vague and hanging in the balance, as no accurate predictions seem to be available at present.
Most seasonal pans and wallows have now completely dried up and only the larger earth dams hold water at this time of the year. Distribution of game has changed significantly, especially with the larger mammals that are being forced to travel greater distances in search of food and water. Surprisingly, the physical condition of the animals is still at an acceptable level. As one might recall, this time last year and the year before, we had already started recording mortalities of large mammals such as buffalo. We can only hope that the coming rainfall season brings critical relief to the Lowveld.
The impala rutting season during April and May this year should result the birth of new lambs in October. This is a wonderful time to be in the bush. The rut takes place specifically during April and May so that the ewes give synchronous birth to their lambs some weeks after the onset of the rain. Synchronised birthing means that many lambs are born during the same period, and predators will surely benefit, but it also ensures that enough lambs survive to maintain a viable population of this key food-chain species. The first rains usually fall in October in our area, prompting vegetation growth and providing cover for the newborn lambs, as well as the nutrients their mothers need for lactation. Many other species will also give birth at this time of the year taking advantage of this time of abundance. Keep a watch on our Facebook and Instagram accounts for occasional updates from the field.
General rainfall trends in the Greater Kruger Protected Areas
As expected, Kruger’s rainfall patterns are cyclical in nature, varying seasonally from winter to summer and oscillating between wet and dry cycles. Upon inspection of annual rainfall deviations from longterm means for the past 105 years, wet and dry cycles appear to occur about every five years. It appears these high‐ and low‐rainfall periods generally match La Niña and El Niño years for Kruger in relation to ENSO events. With the occurrence of less extreme rainfall events over the last 15 years, inter‐annual rainfall patterns are clearer. However, the power band between 10 and 16 months does appear to be widening slightly, suggesting seasonality may be shifting. A significant 4–5-year cycle persists from 1997/1998 until 2001/2002 along with a 12–15-year cycle from about 1998/1999 until 2005/2006. The 12–15-year cycle appears to be the more acceptable norm over recent years.
In the Kingfisherspruit area of the Kruger National Park, which encompasses the Southern African Wildlife College (SAWC) focus area, with 41 years of meteorological data on file suggests the long-term average rainfall for the area stands at 571,8 mm and an average of 20 mm of rain for the month of September. No rainfall was measured for September 2018 in the area.