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Why are Domestic Cats Smaller Compared to Big Cats?

Domestic cats share about 95 percent of their DNA with big cats like tigers and lions. They also share several similar traits. Both have the same general body structure and demonstrate the same level of physical fitness like agility, fast reflexes, and balance or coordination. They are also obligate carnivores. Domestic cats also exhibit hunting behaviors similar to their bigger relatives. However, despite these resemblances, domestic cats are smaller than big cats.

The Science Behind Why Domestic Cats Are Smaller Than Their Bigger Relatives in the Wild

It is worth noting that domestic cats or Felis catus are not the smallest species from the Felidae family. The title belongs to Prionailurus rubiginosus or the rusty-spotted cat found in the Indian peninsula and Felis nigripes or the black-footed cat that is endemic to Southern Africa. The fact remains that domestic cats are relatively smaller compared to feline species under the Pantherinae subfamily which include jaguars, leopards, lines, and tigers.

General Evolutionary Background

Domestic cats share a common ancestor with all members of the Felidae or the cat family. This family is believed to emerge about 50 to 35 million years ago and later diverged into different subfamilies with the Felinae and Pantherinae remaining the two only existing subfamilies. The two probably diverged into two separate lines about 11.5 million years ago.

The Pantherinae line includes big-sized cats. The Felinae line includes all medium-sized cats like caracals, cheetahs, cougars, lynx, and servals, and smaller-sized cats like domestic cats and wildcats of the Felis genus. Domestic cats specifically emerged from the domestication of the African wildcat in the Fertile Crescent region about 9000 to 10000 years ago.

Note that African wildcats appeared about 2 million years ago in North Africa and the Middle East. Findings from a phylogenic research by M. Y. Mattern and D. A. McLennan revealed that wildcats evolved through sympatric or parapatric speciation and domestic cats evolved through artificial selection after the domestication of the African wildcat.

Thus, from the aforementioned, the Felidae family diverged into two subfamilies consisting of a line that includes all big cats and another line consisting of medium-sized and smaller-sized cats. However, based on the evolutionary timeline, the oldest known cat is the now-extinct Proailurus which appeared about 35 to 28  million years ago in Europe and Asia.

Proailurus was small. It was a little larger than a domestic cat at about 9 kilograms. Nevertheless, because it emerged more than 28 million years ago, and the Pantherinae and Felinae subfamilies only diverged into two separate lines about 11.5 million years ago, it is probable that all living cat species trace their line further to this small cat or other older similar cat species.

Specific Adaptational Explanations

Environmental pressures significantly influence the evolution of animal sizes. A. R. Cuff et al. investigated how phylogeny and prey choice influence body mass evolution in felids by analyzing body mass data from 39 living and 26 extinct felid species. Note that prey choice centered on dividing prey into small, mixed, and large categories or prey groupings.

Results showed that the sizes of species in the Felidae family differ based on their prey groupings. This suggests a strong ecological influence on body size evolution. Additional findings revealed that big-sized and small-sized cats appear repeatedly across the felid evolutionary tree. This indicates independent evolution toward these sizes multiple times.

Big cats also evolved from smaller cats. Findings from the study of T. Harano and N. Katsukake showed evidence for directional selection toward larger body size in cats under the genus Panthera and other medium-sized cats in the Felinae subfamily. It further concluded that the tendency for larger body size appears to be linked to the need to hunt relatively large prey.

Nevertheless, from the aforementioned, the big cat lineage transitioned to larger body sizes over time. The specific Pantherinae subfamily evolved traits for tackling larger prey in more forested or open environments. This resulted in an increase in body size and power. The evolution of big cats also corresponded to the ecosystems changed during the Miocene epoch.

The populations of early Felidae became geographically isolated as the continents shifted and ecosystems changed. This resulted in genetic divergence and environment-specific adaptations. Most species under the Felinae subfamily retained a small body size because it has been advantageous for survival in environments where smaller prey dominated.

Explaining the Evolution of Relatively Smaller Domestic Cats and the Larger Big Cats

The main reason why domestic cats are small and big cats are big is that the two come from two different subfamilies of the greater Felidae family. Domestic cats did not evolve from big cats. They evolved from smaller wildcats. It is also important to underscore the notion that the entire Felidae or cat family probably started rather small. The more acceptable description is that modern big cats evolved from smaller cats that appeared millions of years ago.

It is important to reiterate the fact that the evolution to bigger-sized bodies in selected Felidae species came from environmental pressures that resulted in the emergence of traits suited for hunting in an open environment with larger prey and competition with other larger predators. Several cat species in the Felinae line like the wildcats and domestic cats retained smaller bodies because they were already in environments dominated by small prey.

FURTHER READINGS AND REFERENCES

  • Cuff, A. R., Randau, M., Head, J., Hutchinson, J. R., Pierce, S. E., and Goswami, A. 2015. Big Cat, Small Cat: Reconstructing Body Size Evolution in Living and Extinct Felidae. Journal of Evolutionary Biology. 28(8): 1516-1525. Oxford University Press. DOI: 1111/jeb.12671
  • Harano, T. and Kutsukake, N. 2022. Way to Big Cats: Directional Selection in Body Size Evolution in Living Felids. Journal of Mammalian Evolution. 30(1): 97-108. Springer Science and Business Media LLC. DOI: 1007/s10914-022-09639-z
  • Mattern, M. Y. and McLennan, D. A. 2000. “Phylogeny and Speciation of Felids.” Cladistics. 16(2): 232-253. Wiley. DOI: 1111/j.1096-0031.2000.tb00354.x