The first and most obvious argument is that other predators are dangerous to hunt, and it would be illogical for a lion or leopard to see a conspecific as a potential food source. When one also considers that predators themselves are of far inferior nutritional value than the herbivores that are usually on the menu, one begins to understand that it would generally be counterproductive for the predators to hunt each other.
We ran a post a few weeks ago on whether or not lions are lazy. The answer of “No” revolved around an argument based on energy conservation, and the fact that lions – and indeed most things in nature – are unlikely to do something if the energy to be gained from the action will probably not outweigh the energy lost in the performing of it.
Energy is key in nature, and an understanding of its flow and uses can go a long way towards helping understand basic ethology, which is the science of animal behaviour.
Lions eat wildebeest and so get energy. Lions eating lions would get nowhere near as much energy.
We’ll simplify things here, but the basic concept of energy flow should be familiar to anyone who did school biology.
How energy is lost as it moves through successive trophic levels.
One of the first terms to understand is Trophic Level:
A Trophic level is each of several hierarchical levels in an ecosystem, consisting of organisms sharing the same function in the food chain and the same nutritional relationship to the primary sources of energy.
The basic breakdown is as follows:
The primary source of energy is the sun. Grass and other plants (Trophic Level 1) absorb energy from the sun, which is assimilated into their structures.
When herbivores (Trophic Level 2) eat the plants, they absorb some of this energy, but far less than the original amount, as the plants will have used some of the energy for their own processes.
On average only about 10% of energy flows into the next trophic level.
When a herbivore is eaten by a carnivore (Trophic Level 3), again only around 10% of the herbivore’s energy passes to the carnivore. Much has been lost through heat production, faecal waste and the fuelling of the herbivore’s own internal processes. We are now left with only 1% of the original energy that the plants absorbed from the sun. This is not a lot.
The grass this Ntsevu lioness is eating contains a lot of nutrients, but the lioness’ digestive system unfortunately isn’t geared to extract it properly. Instead, large carnivores mainly eat grass as roughage to aid digestion and stimulate peristalsis.
So when, say, a male lion kills another male, the male he has just killed will only have roughly 10% of the nutritional value of a similar sized herbivore. This is a rather oversimplified explanation, but it’s the gist of it. Why, therefore, as a predator, would you waste your time eating something that isn’t going to benefit you that much anyway, especially when actively trying to kill it may be incredibly dangerous?
Yet carnivores do kill and eat other carnivores. A lot of the time the consumption of a rival is an act of dominance, particularly among lions.
The Mapogo known as Kinky Tail was killed and eaten by the Majingilane coalition in 2010 when they took over the territory.
Yet more recently the Tsalala sub-adult lioness that was killed by the Birmingham males in early December was not eaten by them; her carcass was left abandoned in the rain, and the Birmingham males simply walked away. She was consumed by hyenas that night, but hyena digestive systems are so efficient they are able to extract the maximum amount of nutrients out of almost any meat they eat. Quite possibly no display of dominance was required by the Birminghams in this case, so small a lioness was she.
The last remaining Tsalala sub-adult looks back towards where her sister had been killed by the Birmingham males only a few minutes before.
Ultimately there are no set rules in ethology, only guidelines. There was a case in the Kruger National Park not so long ago in which a leopard killed a cheetah that had been feeding on an impala. The leopard subsequently hoisted and ate both carcasses, obviously loath to let sustenance in any form go to waste.
In the wild where nothing is certain, a dead carcass, whatever it is, still represents food. Without knowing where the next meal might come from, a hungry predator would far rather go against our preconceived notions and eat a fellow carnivore than remain without food…
And so it goes that thanks to the brilliance of Mother Nature . . . all works as it is supposed to, as long as it is not too messed up by humans.
Very interesting post, James! Thanks for educating me about ‘trophic levels’.
Hi James: I love all your posts, but have to point out something that seemed illogical to me in this one. You asserted that “when, say, a male lion kills another male, the male he has just killed will only have roughly 10% of the nutritional value of a similar sized herbivore.” This I assume was based on your trophic analysis that only 10 percent of the energy at one trophic level is available to consumers at the next trophic level up. But saying that 10 percent of the energy consumed by, say, a 500 pound antelope is available to the 500-pound lion that eats that antelope is NOT the same as saying that the lion itself, were it to be eaten, would provide only 10 percent of the energy gained by eating the antelope. I would wager a 500 pound antelope and a 500 pound lion would provide roughly the same amount of energy, although maybe less tasty energy. Ten times as much raw energy is needed to power a lion compared to an antelope but that has no bearing on how much energy the lion has to offer to a predator, if there were one.
Hi Charles,
A good analogy, and I’ll readily admit I was simply going on the 10% loss rule to simplify things. I’ll do a little more digging here, as I agree about the energy that’s needed to power a lion.
One factor that might make a difference is the respective metabolic rates of predators vs prey and the ability they have to store energy in their tissues. Lions can be scrawny again within a few days of a really good meal, whereas it takes considerably longer for a large herbivore to lose condition. Contradicting my own point here, that probably also has to do with the fact that herbivores are constantly feeding, so it takes a drop in their food source or the environment as a whole to deteriorate for them to start getting skinnier.
Either way, I imagine that the form in which the energy is stored, and we’re talking a variety of sources here – ATP, fat, wherever it might be – may well determine how much is available to the next trophic level.
I’ll do some research and get back to you.
Thanks for the comments!
Best regards,
James
Great post as usual. Although I was going to make a similar comment as Charles…I also very much doubt that a lion has only 10% of the nutritional value of a herbivore of the same weight. Although based on the points in your comment above I think it may be less (Ill hazard a guess of ~80% just so I can regret it later when I am proven wrong haha). The loss in energy at each tropic level doesn’t necessarily mean the individual animals themselves have less nutritional value pound for pound, just that there is less energy available to be passed on from each level to the next…so in its simplest form there can be less animals at each level you go up (although as you mention even that is a simplification. There are even some examples of reverse tropic biomass pyramids e.g. Mourier et al. 2016 DOI: 10.1016/j.cub.2016.05.058 is an interesting one). I will be interesting to see if you can dig up some figures on how the energy is stored and how much of a difference that does make. I suspect we are dragging you away from the simple explanation here but I guess its one of the ‘perks’ of your job ;).
Hi Lachlan,
Great argument re. less animals in total. I think you are right here and I have it wrong. Looking back at it now, its far more about biomass at each trophic level, rather than energy availability per organism.
Thanks for the comments. I enjoy the discussions!
Best
James
This is an interesting blog James. Well researched. The biology lesson just threw me a bit. (Too long ago since I wrote matric.) ?
I’ve read a few studies on predators in the Kalahari, and there predators can’t afford to be picky about what they eat. For example, leopards there regulary prey on jackals, bat-eared and Cape foxes, wild cats and even honey badgers and cheetahs. I’ve also heard of lions there investing considerable energy in catching bat-eared foxes and brown hyenas. But this is defintely the exception rather than the norm.
It’s an interesting one, as the smaller predators here are taken by leopards as well. I think particularly leopards, being solitary hunters, are that much more opportunistic.
And in Mumbai leopards regularly prey on domestic dogs. Would you say that in all of these place leopards are just being opportunistic, going for whatever is readily available, or do they have specific preferences and know that those smaller predators (from dogs to wild cats) have much less nutritional value than an impala, bushbuck or warthog (or a chital deer in the case of the Indian leopards)?
James
Thank you for the refresher course of the eco system as related to the feeding chain. Interesting to note that most predators do not eat their own, but rather stalk members of the vegetarian group. I really appreciate your taking the time to write these educational/interesting articles. Bon weekend!
Hi Denise,
Thanks for the comments. We’re trying to do a number of posts like this as an understanding of the basic processes of the ecosystem can help us understand the intricate dynamics of the wildlife that much better…
Best regards
Very interesting blog James. I always just assumed that carnivores didn’t eat each other out of respect, but that of course would be applying human emotions that might not be accurate. Do you know why the Birmingham males killed the young Tsalala Lioness, and is it not unusual for males to kill a female, especially a sub adult, even though she was not their daughter?
Hi Jill,
I’m sure that they killed her because she was still young enough to be dependent on the resident lionesses. Also, to flee is to invite pursuit, and I imagine a young lioness like that would have immediately run from a big male/s.
I think below a certain age it won’t matter too much if sub-adult is male or female…
Best
James, Thanks for the biology lesson and reminding us of the amazing system that exists. It’s hard to watch sometimes, but understanding the bigger picture helps it all make sense!
Absolutely, things fit into place far easier when you understand some of the basic processes!
James, one of the most odd scene that I know and saw about this theme was when the majingis eated Kinky Tail right after they put up a fight. Some say that they have eated Kinky Tail while he was still breathing.
Hi Thiago,
I believe it was quite a disturbing scene. This would most likely have been a dominance display.
Yeah, I think so too James. I loved the Mapogos, but I like the Majingis too. I plan to go to Londolozi next year in may, I hope they are still alive, I would love to see Dark Mane, Golden Mane and Scar Noose.
Excellent article on predators and the production/consumption of energy in the food chain.
Thank you Eugene.
I had to smile as I read your post since it reminded me of my medical school days. Articles like this are necessary if one wants to truly understand the technical interworkings of the animals living within the bush. I look forward to more of your insightful articles.
Pretty sure the basis of your nutritional value hypothesis is wrong. The energy amount you have is kcal/m2/yr so its relative to ground area, not mass of the animal. Which is right, because there are a higher number of herbivores than predators. Pretty sure the nutritional value of the meat would be the same. Its probably more about going after animals that can’t defend themselves as well, like you said at the top. Good artical otherwise
Hi Andrew, thanks for the feedback!
On one hand I’ll say great article, great research, but on the other hand I have to say few lame arguments such as carnivore will only have 10% energy of a herbivore of the same size clearly shows you are not from science background. 10% rule is a great theory. But it means carnivores get only 10% energy from herbivores of the energy herbivores consumes. It doesn’t mean carnivores only consume one herbivore in their lifetime and it certainly doesn’t mean carnivores have only 10% energy of herbivores of same size. In fact, in a lot of cases carnivores have much higher percentage of protein rich flesh compared to herbivores of same size.
Your diet determines your place on the food chain, not your size. The majority of a leopard’s or lion’s diet is large herbivores/omnivores. Leopards don’t actively hunt other cats or predators. People see a leopard kill another predator then claim leopards are hunting cheetahs. Animals, like humans, are individuals, not machines. Some individuals do bad things. It’s not like nature is controlling their every move. Top biologists and ecologists all say the main cause of predator predator conflict is habitat loss.