Observation is a key when on the field in the wild, and our authors bring to us the interesting story they have witnessed on the evolution of the smaller size of the Jungle cat in Southeast Asia due to the competition it faces with the Fishing cat.
In order to find answers they had to compare the conditions under which the Jungle cat existed in two different geographical habitats.The Jungle cat exists with three other cats – the Sand cat, Wild cat and Caracal in Israel and along a narrow band of the river Nile. Sind onwards, as it steps into the Indian sub-continent, the Jungle cat has to share its resources with at least 10 other small felid species. The Jungle cat could have been naturally selected to become smaller in size here so that it could fit in with the other species and share resources. It could have been the other way around, too.
It might have dispersed into the western part of its distribution where competition for resources is much less as compared to the number of potential competitors. Thus, it would have been allowed to use more resources than in the East, which could have caused it to grow bigger over generations.
WHO IS THE CULPRIT?
However, which one of the ten small felids in the East could have posed the best competition for the Jungle cat? Researchers delved deeper into this question and this is when interesting facts began to surface. For instance, Jungle cats are often referred to as ‘reed cats’ or ‘swamp cats’ in Africa, along Nile,Syria, Lebanon, Turkey and in western Iraq. The name‘Jungle cat’ is misleading as instead of the classic rain forest jungle, this wild felid species is strongly tied to open structured habitats with water bodies. Think of reed beds or scrub or grasslands and water bodies as a landscape and that is where your Jungle cat would love to be in.
So, who is the Jungle cat competing against?
Species who share a similar habitat i.e. wetlands,and in such a situation, competing species ideally take different sizes of prey to co-exist. Thus, a competitor who would be just a little bigger in size would essentially take up all the large prey and would push the Jungle cat towards taking smaller prey. As a consequence, only those Jungle cat individuals who took smaller prey could actually survive and over many generations, become smaller in size. It is a simple case of ‘character displacement’ –a particular trait of a species gets displaced due to competition with a superior species. In the Jungle cat’s case the trait was its body size. But who was the superior species? Ecologists were almost close to solving the mystery and ending the suspense.
There is a decrease in the Jungle cat’s size Sind onwards and Sind in Pakistan is also the Fishing cat’s western-most end of distribution. Both of them are also strongly tied to wetlands. Was there a connection?To reach a conclusion, ecologists had to determine whether there was a significant difference in the sizeof prey they were taking.
Breaking down the anatomy fields in general are strictly carnivorous and thus need to be specialized predators. Their usual method of hunting includes preliminary stalking and a final quick rush. Whether the final rush is successful or not depends on the large canines and the long, blade-like carnassial responsible for killing the prey and slicing through the flesh. The jaws are perfect – short and powerful.The whole mechanism was built for delivering an armed, lethal bite. In small fields, seizing the prey is the sole function of its forelimbs whereas biting is specialized for killing. More importantly, the canine with its structure, shape and position in the jaws are well adapted to being wedged between the vertebrae of the prey animal’s neck. The vertebrae are therefore disconnected; the spinal cord is lacerated leading to instant death. The possibility that canines in small cat species were specifically adapted in shape and size for the neck vertebrae of their principal prey species.Thus, individual cats with canines of greater diameter could kill a large prey as their canines were more efficient in pushing apart the larger prey’s vertebrae.However, it would be tough for these cats to kill as mall prey as the tip of their canine would be too thick to pierce easily into the vertebrae of a smaller prey.
Thus to ecologists, canines reflected that the feeding pattern of felids was in correlation between prey size and the size of the canines. The next challenge was to find whether the diameter of a jungle cat’s canine decreased significantly towards the eastern part especially in areas where it overlapped with the fishing cat. Museum specimens collected from around the world proved that there was a significant difference.These discussions, led to a conclusion that fishing cat is a crucial competitor for the Jungle cat.
Now, finding a difference in the prey size while co-inhabiting the same ecosystem was necessary. I had been working in Howrah, West Bengal on small cats for almost five years. Both these cats lived there with human interference all around the protected areas. In order to assess what these cats were eating and was there a difference in their diet, I collected 275 scat samples, including 96 scat samples of fishing cat and 73 scat samples of Jungle cat. While separating the scat contents, I observed that jungle cats were much specialized in their diet, 90% comprising rodents and the remaining one-fourth being bird remains. The fishing cat, though, had a very broad dietary spectrum that included fishes and rodents along with birds; goat hair was also found in three scat samples. There was,thus, a major dietary overlap in both the fishing and jungle cat with respect to taking rodents and rodents of different sizes.
We assessed the rodent size through the rodent dentition that never gets digested and can be found in the scat. The dentition morphology is unique for all species of rodents and by studying them; you can deduce the species of the rodents being consumed by the cats. In this case, the Rattusrattus and Bandicota bengalensis, with the Bandicota being double the size of the Rattus. Both these rodents are agricultural pests. The jungle cat mostly ate Rattus (the smaller rodent) in areas where it co-existed with the fishing cat. However, in the absence of the fishing cat, it ate similar proportions of both rodents.
Our study, thus, helped in finding out the reason for reduction in size of the Jungle cat in India. However,reduction in size acts as a benefit for this species as it helps them in hiding and adapting well to agricultural landscapes, leading to its range expansion in India. On the other hand, the fishing cat was found taking refuge near reed beds and breeding sites.
Marshlands are termed as ‘wastelands’ by Indian land policies, leaving them defence less against rapid degradation. Almost 44% of Howrah’s marshes have disappeared and with its bigger size, the fishing cat finds it increasingly hard to hide amongst dwindling resources. While they do try and attack poultry and goats, in most cases, they get beaten up and killed.We recorded 27 fishing cat killings within a span of 18 months from Howrah district and despite being a superior competitor, the fishing cat is now being unfairly pushed to the edge.
This article was previously published in the March-May 2016 Saevus magazine edition.