How big cats hunt zebras and impalas, and how these prey flee their predators | Hacker News Reader

How big cats hunt zebras and impalas, and how these prey flee their predators

nytimes.com

65 pointsJerry224 comments

I was lucky enough to visit a private game reserve in South Africa for a few days. One of the things I saw was a pregnant ex-Zebra being eaten by lions (including the fetus that was dragged to the shade under a bush by other Lions). The guide explained that what likely happened is that the lions tried to separate the pregnant zebra from the herd and make her go down slope. The added weight of the fetus makes maneuvering down slope harder, especially when trying to make tight turns, giving the lion the edge. It was fascinating (although a bit gruesome) to see animal behavior in action that way.

I always wonder for the herbivores why does "the saving your own kind" instinct not kick in more often. A lion is more powerful than a zebra but there are cases like a herd of bison running away from wolves who are trying to isolate youngsters. If they stay put and don't blink the wolves have no chance. A recent documentary episode I saw (I think in frozen planet or the hunt) had an extreme case of a pack of wolves trying to bring down a juvenile bison and an adult just running through the struggling juvenile, bringing it down and making it easy for the wolves.

r/K selection theory has been subsumed by more advanced theories over the last few decades, but many of its themes are still applicable and it provides a simple way to think about some general reproduction strategies. Herbivores fundamentally have far more energy availability, because they're a level closer to the primary input of the sun (Sun -> plants -> herbivore, energy for useful work lost at every conversion step), and in turn many of them follow a more r-selection strategy where they have lots of offspring with lower investment in each individual one, and huge populations of which significant numbers die young (from predation, accidents, starvation, disease, etc) but enough survive through quantity. Conversely this can actually make healthy adults more valuable then any single young one, since they represent a success that can and will breed many many more times.

In contrast big predators sink a lot more energy and time into each individual juvenile, and have far fewer of them. You'll notice that with many highly mobile herbivores juveniles come out and are ready to walk and begin moving with their parents/the herd in very short order without an extended period of total helplessness.

Herds do have to keep moving to find new food supplies, so staying in place indefinitely is not an option. They generally are much faster in a straight line then most predators too, so they can in fact outrun them (and in turn predators are forced to deploy tactics, go after ones with restricted mobility which takes more function to recognize, and so forth). These various pushes and pulls on selection have resulted in the successful strategies we see each species deploy. The emergent effects of life really is incredible as trite as it may sound to say it. Such incredible complexity driven by basics that are pretty straight forward.

That seems to make a lot of sense. Good write-up, thank you!

There are so many of them that any individual is expendable. Beyond that, they don't need the other for survival (aside from strength through numbers) because they don't hunt.

Lions and wolves hunt in packs, so the individual more directly contributes to the group's survival than in herbivore populations.

Turn away if squeamish ... I saw a very similar thing on safari. The other attraction of hunting pregnant animals, our guide told us, was that the unborn animals are nutritionally dense. We did not witness the kill, thank goodness (I am squeamish!) but did see the aftermath - which was the lions extracting and eating the fetus first, while the mother was still alive. Nature is cruel.

> (I am squeamish!)

Then why'd you go on a safari?

> Nature is cruel.

Nature isn't cruel. Nature is ambivalent.

Multiple definitions of cruel fit nature, with no reference to willfullness:

3. causing or marked by great pain or distress: a cruel remark; a cruel affliction. 4. rigid; stern; strict; unrelentingly severe.

also bonus side dish

If anyone else found that unsatisfying, here is a recent book that does a better job of telling the story of tracking animals:

http://wheretheanimalsgo.com/baboons/

https://www.amazon.co.uk/gp/product/1846148812

More generally when it comes to tracking animals...

What I want to see is facial recognition for animals, so that some one-way hash resolves to a name, so anyone who pointed their phone at a particular bird would reliably get the name determined by the facial recognition hash, so it could be consistently a 'Trevor' for instance. Of course 'Trevor' could be tagged in photos in this bold new future of 'facial recognition for birds' so it might be possible to find him in lots of different social media posts with different people and in different locations.

By default 'Trevor' would have a shadow Facebook profile complete with shadow profile links to his other half, mum and the rest of the flock.

More seriously, I do wonder at applications for this alt-coin circus that has come along and whether a large database of every living creature on the planet could be magically possible using these magic blockchain technologies.

So, very much tongue in cheek, when it comes to implementing 'facial recognition for birds, hamsters and many tens of thousands of species', how would the 'ICO' work out?

I am sure this could all be easily done and coded up by next Friday by a teenager if it was based on blockchain technologies with coins being mined by adding new animals to the distributed database photographically. To lure ICO bitcoin-bores in this magic database would be super fast because it would be modelled on DNA and therefore compact, albeit forked on a per-species basis so fish coins could be traded for apex primate coins but not necessarily vice-versa. All of this blockchain could solve the hard problem of digital rights management, so if 'Trevor' appeared in the back of one of your selfie pictures then the micro-payment for that would pay out with 'Trevor' getting his share of Instagram likes.

You have to watch the SafariLive Channel on Youtube. They are live everyday and they dont shy away from the hunt. amazing stuff.

I think, it would be much better if they provide visualization or even video.

TL; DR:

> Though cheetahs and impalas were universally more athletic than lions and zebras, both cheetahs and lions had a similar advantage over their prey — they were 38 percent faster, 37 percent better at accelerating, 72 percent better at decelerating and their muscles were 20 percent more powerful.

> [...] impalas and zebras were typically moving at only half their maximum speed. [...] The model showed that impalas and zebras have the best chance of making a getaway if they run at moderate speeds, because that leaves more options for maneuvering away at the last second

And how it relates to programming:

> Everyone knows that debugging is twice as hard as writing a program in the first place. So if you're as clever as you can be when you write it, how will you ever debug it?

- Brian Kernighan

> Though cheetahs and impalas were universally more athletic than lions and zebras

Wait, what? Did they mean that cheetahs and lions were more athletic than implalas and zebras?

No, I think they mean they meant exactly what they wrote. Impalas are too fast for lions to hunt (normally). Single cheetahs are too small to take down a zebra (normally).

Impalas and zebras must be more athletic because they have to scape the cheetahs and lions 100% of the time. If you scape only 99% of the time you are dead.

Also, the predator is happy to catch any of the preys, they can pick a tired/old/sick/unlucky one. So if 99% of the prey scape, they are probably happy.

The articles says right there that the hunters are better at acceleration, deacceleration, top speed, and muscle density than their prey. The conclusion of the paper (at least as shared in its abstract) is exactly "the predator needs to be more athletic than its prey to sustain a viable success rate".

You don't need to be faster than the predator, you need to be faster than other members of the herd.

Reminds me of the Billy Connolly joke about the two camera men filming a lion. The lion sees the two camera men and proceeds to chase after them. One camera man stops and puts on a pair of running shoes. His colleague tells him “You will never outrun the lion in those”. He replied, “I don’t need to outrun the lion, I just need to outrun you!!”.

An Impala is basically a deer. 150lbs, can jump over an 8 foot fence...where a Zebra is basically a small horse. 500lbs and can only jump 2 feet in the air.

Translation for SI users:

150 lbs ≈ 70 kg

8 ft ≈ 2.4 m

500 lbs ≈ 230 kg

2 ft ≈ 60 cm

Please use the orignal title.

Thats how i play basketball, i do not go 100% all time as then defence can easy predict my motion, instead i go half speed and burst in speed when needed.

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