The truth behind the bump: impala, rain, and the old bush tale

Out here in the south-eastern corner of Kruger, as winter finally loosens its dry grip, something quiet but remarkable is taking place among the impala herds. The change is subtle at first, a bit more fullness in the flanks, a heaviness to the gait, ewes standing a little longer in the shade. But soon, it’s unmistakable: our impala ewes are showing! Their bellies are beginning to swell, and with each passing week, it becomes more obvious, the next generation of lambs is well on its way. Every guide here at Singita has started pointing it out to guests on morning drives: “See how round she’s getting? She’ll be a mother by the start of the rains.” And that’s usually when someone asks the question, the same one I asked years ago when I was still learning the rhythms of this place:

“Is it true impalas can delay giving birth until after the first rains?”

It’s a story that’s floated around bush camps and guide circles for decades. The idea that impala ewes can somehow hold onto their pregnancies a little longer, waiting until the first drops of summer rain before releasing their lambs into a greener, safer world. It’s a romantic notion. Clever little impala moms, in tune with the weather, delaying labour until conditions are just right. I’ve heard it repeated confidently around many a campfire.

But here’s the thing: it’s not true. Biologically, it’s impossible. Impalas, like most antelope, have a fairly fixed gestation period, roughly six and a half months. Once fertilisation occurs (typically during the May rut), the clock starts ticking. There’s no pause button, no way for the ewe to hold the foetus in stasis while she waits for thunderclouds to roll in. So where did the story come from? It likely started with observations — many calves do seem to appear right after the first rains. The veld goes from dust to green almost overnight, and soon after, the bush is alive with wobbly-legged lambs. To early observers, it looked like the impalas were timing birth with the weather. But the truth lies not in delayed birth — it lies in synchronised conception. Impala rams go into full rut during late autumn (usually May), and after a chaotic few weeks of roaring, chasing, and posturing, mating occurs across a short window. Ewes come into oestrus in waves, often within days of one another. This means most of them conceive around the same time — and thus, most of them give birth around the same time, about 200 days later.

Do the rains align with that birthing window? Sometimes, yes. Sometimes, they don’t. But the lambs come anyway. This tight lambing period is one of nature’s oldest tricks. By dropping dozens or even hundreds of calves within days of each other, impalas create a predator swamping effect — more babies than predators can eat. Lions, leopards, hyenas, wild dogs, jackals — they can only take so many. It gives more calves a chance to survive their first, most vulnerable weeks. And yes, it helps if there’s food around — which is why the rut is cleverly timed for the dry season, anticipating that births will occur as the first rains green the landscape in November or early December. That’s what we’re seeing now. In mid-September, those ewes are well into their third trimester. The baby bumps are showing. We’re seeing them graze more selectively, lie down more often in the heat, and stay closer to thicker cover.

I often find myself quietly rooting for them — these elegant, underestimated antelope who must be mothers, sentinels, and survivors all at once. If all goes well, in just under two months, the lambs will come — sometimes awkward and teetering, sometimes born during a downpour, other times in a dusty clearing before the rains even arrive.

There’s something valuable in letting go of these old bush myths — even the charming ones. Because when we do, we’re left with something even more impressive than magic: biology, evolution, and timing so finely tunedthat it can look like magic. The impala does not need to delay birth. She simply relies on thousands of generations of perfectly calibrated instinct to bring her lamb into the world right when it's most likely to survive. As guides, we have the privilege, and responsibility, to share those truths. Because the real story, the honest one, is still filled with wonder.

So next time you're out here with us, and we point out a pregnant impala, now you’ll know the real story. No weather-based wizardry, just nature, doing exactly what it was always meant to do.