Coming to the end of an amazing day, the sun had sunk below the horizon with yet another magical sunset. We started making our way home after a long and unfortunately unsuccessful tracking effort to find the Tamboti female leopard. Her tracks, along with those of her two youngsters, led towards a burrow in the side of a termite mound. This is where we assumed she had left them for the evening, leaving us no chance of viewing her. Little did we know then that our game drive was very far from over.
Not too far from camp, some rangers were with the Tsalala Pride, who in classic lion fashion had spent the whole day sleeping and recuperating from the previous evening’s activities, but despite the current lack of activity we decided to join the sighting. Nightfall carries many advantages for the predators; it is cooler and less taxing on them to move around, most prey animals are settling down to rest for the evening, and the predators are able to take advantage of their specially enhanced night vision.
We arrived at just the right moment as the pride began moving, and soon they began to spread out, attempting to hunt an unsuspecting herd of impala. Switching off our lights and spotlight so as to give neither side the advantage, we sat there in the darkness. As we sat we waited for our eyes to adjust, hoping to be able to get even just a glimpse of what was about to happen.
Being a moonless evening, we were unable to see at all and so became totally reliant on our sense of hearing. Managing to hear numerous different sounds and rustling in the foliage and grass around us, we were unsure if it was a lion stalking, impala walking, or field mouse crawling. Leaving so much up to the imagination, I kept wondering if each night was petrifying for impalas, who have eyesight slightly better than us at night, but mainly rely on their hearing as well. With so much going on it takes a very well-tuned ear to determine whether it is danger or not.
Lions on the other hand have eyesight up to seven times better than ours at night. This allows them to focus in on an unsuspecting herd, particularly on a dark evening such as the one I refer to. Stalking silently so as to not alert the prey of the impending danger, we sat in anticipation, not knowing when they would get within the ample distance of less than 20m from the herd. As I was about to mention to my guests that the stalk can take hours, we heard the alerting alarm calls of the impala, sounding like a pot of popcorn on the stove, and numerous footfalls through the leaves, bomb shelling in every direction. The impala, unaware of where the danger was, fled in the hopes of not getting caught, whilst dodging the dense Combretum trees they were feeding in.
Luckily for the impala, the commotion and density of the woodland ended up working in their favour and they all got away. Only to now look forward to the whole evening ahead of them with the knowledge that there was a pride of hungry lions nearby.
So how exactly do the lions have the advantage at night?
Most carnivores, particularly lions and leopards, have large forward facing eyes, giving them binocular vision and the benefit of being able to judge distance very well. With these large eyes they have enormous pupils, allowing ample light through onto the retina. The retina is dominated by rod cells, which are long thin cells responsible for detection of light and therefore only account for black and white vision and help determine shapes and movement. This gives them amazing vision at night, where everything appears to be black and white due to the lack of light. Lions have a low concentration of cone cells in their eyes that are responsible for colour vision. They are still believed to be able to see in limited colour vision and only possess two of the three colour pigments found in the cones. Simply put they can see colour but are colour blind, possibly advantageous due to their nocturnal habits. Human eyes are the opposite in that we have a high concentration of cone cells and minimal rod cells, giving us excellent colour vision and poor night vision.
In case lion vision wasn’t good enough already, the presence of the tapetum lucidum, which is a reflective membrane made up of cellular crystals, increases the ability to see in low light conditions. Light passes through the cells of the retina and hits the membrane and is reflected back through the cells, giving the brain two chances to refine the image. This membrane causes animals eyes to shine when a light is shone at them. Animals who have larger pupils such as lions or leopards, reflect a red tinge as light picks up rich blood supply on the retina. Impala also have a tapetum lucidum, aiding their night vision albeit somewhat slightly less so than the lions.
Exposing ourselves to the dealings many animals face on a daily basis forces us to realise just how tough it is out in the wild. Although all these animals have developed strategies to help them get them through each day, it is a never ending evolutionary arms race to survive.