Imagine this — you love big red apples and you have enough of them to gorge on. However, the apples are not unlimited in number. If one more person comes and wants to gorge on the same apples, the fruit will get over in a matter of days and both of you will suffer. So naturally both of you compete with each other for the apples. The stronger one will definitely outdo the weaker and in this way only one of you can have the fruit. Then what will the other one have? Well, the other one has to vacate the space altogether, battered and bruised — or choose to sustain himself on something else. In this case, the defeated one chooses an alternative and stays in the space.
In ecology, the first scenario is what we call ‘competitive exclusion’ and the second scenario is called ‘co-existence’. There are some amazing things that can happen when one species tries to co-exist with a superior competitor and one of them is ‘character displacement’. Big term, but let me explain it.
Character displacement is the phenomenon by which one characteristic trait of a species get displaced. Take for example the size of a species. In the above example, if a species starts eating smaller apples, then after a number of generations, that species can become much smaller in size! Yes, this really happens and it has happened with the jungle cat.
And thus, the topic of my story this week is how nature made the jungle cat shrink in size in order to co-exist with the fishing cat.
If you look at the jungle cat in the western part of the world, say in Israel, it is much larger in size than in the east, in India. In Israel a male jungle cat weighs up to 12 kg but in India, a jungle cat weighs between 3 and 4 kg. How did that happen? Read on.
In Israel, the jungle cat is found as far south as the northern Negev, mainly around streams and ponds in low-lying areas. In Africa and Central Asia, the cat is found mostly in marshes and swamps and hence the name of the cat in these areas is swamp cat or reed cat.
The cat then started travelling eastwards and after a number of generations it reached what is present day Sindh where it met the much bigger fishing cat. A male fishing cat can weigh upto 15 kg and is known to inhabit swamps and marshes close to rivers and tidal creeks. So the fishing cat had the same type of habitat as the jungle cat had in Israel and Central Asia.
The fishing cat was therefore a competitor for the jungle cat. What could the jungle cat do now? Would the jungle cat wait to get ousted competitively by the larger fishing cat or would it choose to co-exist? Well, nature chose the second path.
To co-exist in the same habitat, they would need to either depend on prey of different sizes or a different species of prey. Despite its name, the fishing cat eats a variety of prey and is thus a generalist in terms of its diet. Not only does it feed on fish, it also goes for small mammals like rodents, birds, small reptiles and even invertebrates like crabs and molluscs.
The jungle cat is more restricted in its diet. It savours the taste of rodents — almost 90 per cent of its diet comes from rodents with birds and insects forming the rest of its diet. Thus both cats are dependent on rodents.
Now, equate the big apples with big rodents. Being a putative inferior competitor, what would the jungle cat have to sacrifice for the fishing cat? Of course the larger sized prey. The jungle cat thus began eating much smaller sized prey and thus, over generations, became much smaller in size in the Sindh area.
Out of all carnivores, cats are the most specialised predators and their usual hunting method consists of preliminary stalking and a decisive final rush. That is why they have long, blade-like carnassials responsible for killing and slicing through flesh.
The canine teeth are perfectly suited for wedging between the vertebrae in the neck of the prey and lacerating the spinal cord. Species with canines of greater diameter would not be able to kill smaller prey so efficiently because the tip of the canine would be too thick to be inserted into the vertebrae.
Thus the difference in size of canines arise due to competition between species and this is exactly what might have happened to jungle cats as well. So there you have the entire story, of how the cat shrank!