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.
We’ll simplify things here, but the basic concept of energy flow should be familiar to anyone who did school biology.
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.
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.
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…