Sunday 23 October 2022

The Lion Stalks Tonight

In the jungle, the mighty jungle, the lion probably does not sleep tonight.

The main reason for this is that lions don't really live in the jungle. Their primary habitat is savannah and open grasslands and while they can be found found in dry woodland (especially in India) they aren't found in the tropical rainforests that we typically associate with the word "jungle". Indeed, a map of Africa showing where you can find lions would have a very noticeable gap in the middle where the Congo jungle is - along, of course, with blank spaces over the harsher deserts. The idea of lions living in dense jungle probably owes more to Tarzan than reality.

But another reason that the lion may not be sleeping tonight is that lions are, by and large, nocturnal. (And, by the way, if you've ever wondered about the "wimoweh" part, in the original 1939 version of the song, the phrase is "uyi mbube", which translates as "you are a lion" in Zulu). Now, granted, they are cats, so they spend a lot of their time sleeping, and some of that will certainly be at night. Furthermore, under some circumstances, lions will switch their activities to a more diurnal cycle and, as many nature documentaries will show you, they do sometimes hunt during the day.

But, for preference, they do most of their hunting at night. This, naturally, makes it comparatively difficult to observe exactly how they hunt, in the sense of where they go to look for food and how they respond to a variety of different prey animals being available on the menu. However, this has become easier over the last few decades due to the ease of following animals using GPS - something that also means you will be disturbing them less, at least once you've finished fitting the tracking device.

An example of this sort of study, specifically concentrating on nighttime activities was recently published and, while it's not ground-breaking or anything, serves as an example of what we can learn by this method. It looked at the movements of three lion prides active in and around the Kruger National Park in South Africa. They were followed by having vets fit GPS collars to five of the lionesses and then recording their positions on an hourly basis, 24 hours a day for over a year.

In this part of Africa, there are three main sources of food for lions: buffalo, wildebeest, and zebras. Between them, these comprise around 70% of the lions' diet, although they also attack kudu antelopes and giraffes. Impalas are plentiful as well, but are much less popular as prey, probably because they're individually too small to make much of a meal. These various animals all have slightly different habitat requirements, so that the lions can't simply go to one place and expect to find whatever they want there. Instead, they have to choose areas where they think particular prey will be found, and where there is likely to be sufficient cover, whether from long grass or from shrubs and woodland to conceal themselves while they hunt.

The lion prides in this study were, indeed, more active at night than during the day. On average night, each pride travelled a little over 4 km (2½ miles), but they moved an average of just 1 km (¾ mile) during the hours of daylight. Each of the three prides focussed their movements on open patches of  tall grass. Despite the fact that such "lawns" would have provided the lions relatively little cover from which to stalk prey, they are exactly where you would expect to find wildebeest, especially during the wet season. 

When the wildebeest herds moved elsewhere during the dry season, the lions tended to travel further afield, but still did not entirely abandon the lawns, which are more commonly used by zebras and impala at this time of year. Nonetheless, it seems that these particular lions really did favour wildebeest as prey, and considered them well worth the risk of being spotted.

It's probably not a surprise that the lions also made regular nightly visits to the rivers running through their territory. The annual rainfall in the area is typically 540 mm (21 inches) and 85% of that is during the rainy season between November and March. Lions need to drink as much as anything, but perhaps more importantly, so do their prey. Here, the lions are mostly found hunting where the vegetation is thickest, giving them ample hiding opportunities. This is bad for hunting zebras, which, as grazing animals feeding on grass have the good sense to stay away from thickets that might conceal predators. But it would be perfect for ambushing kudu or even giraffes, which need exactly this sort of vegetation to eat.

On the other hand one would expect, for much the same reason, that lions would also visit more isolated or temporary watering holes, especially during the dry season. This is exactly what they do in the Serengeti, for instance. But the study at the Kruger National Park did not show that. The authors suggest that this might be because water holes are just too common in the area, meaning that prey animals might pick any one of them on a given night, so that any planned ambush at a specific one is more likely to result in the lion going hungry. Nearby, in a much drier National Park in Zimbabwe, the lions behave more as we'd expect, because water holes are so far apart that the herd animals have little choice as to which one to use. Probably for the same reason, lions there also leave a much longer gap - around 25 days - between visits to the same water source, allowing the prey to start relaxing again before the next attack.

When they aren't waiting at riverbanks for kudu or stalking in grassy patches for wildebeest or zebra, the lions were travelling further afield, wandering around the local area in search of whatever they might come across. It was these more opportunistic hunting trips that provided the best chance of feeding on buffalo, which otherwise seem quite good at avoiding lions when they know where they might be located.

The upshot of all this is that it shows lions can adapt their hunting techniques to local prey and conditions. In this particular area, they focus on places where they know wildebeest will be most common, switching to zebras only when wildebeest are less available, and they also spend more time simply patrolling the landscape in the hope of running into buffalo, rather than lying in wait at water holes as they do elsewhere. When the lion stalks at night it is doing so with purpose.

[Photo by Carlos Gonzalez, from Wikimedia Commons.]

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