Isle of Man in Britain is known for its cats that are seemingly like any other, but with one striking difference: these cats have no tails.
Some cats without a tail lost them due to injury, and in rarer cases, due to abuse. But some cats like those in the Isle of Man, are born that way (Figure 1).
But don’t get us wrong: it is not easy to find a cat without a tail in the Isle of Man anymore (maybe there were not many of them, to begin with?). In fact, there are now far more of these tailless cats in North America than on the island where they supposedly originated. Tailless cats in North America and elsewhere are marketed as a cat breed called Manx.
· Where did the tail go?
Cat’s tail has a few important functions. Cats use their tails to keep balance when jumping and running. Because tails are the most expressive body part, tail movements help cats to communicate with other cats (and humans).
But disadvantages of not having a tail do not end up here. Cats without tails are less healthy and apparently have less satisfying lives. They have abnormalities in their spines and difficulties moving their hind legs (1,2,3). Some of these cats are unable to control their bladder and bowels, while other unlucky individuals are born with blocked or missing anus!
So why do these cats exist at all? One of the reasons is a mutation.
Figure 1.Manx cat exhibited in Manx Museum, Douglas, Isle of Man. Photo credit: Joseph McCafferty.
Geneticists discovered that there are four genetic mutations called “T” that can result in a short tail or no tail in a Manx breed and natural cats from Isle of Man (4).
T gene or T-Brachyury (from the Greekbrakhus oura means a short tail) affects the tail length in animals with backbones (vertebrates) like fish, birds and of course, mammals.
There is no reason to think that these mutations occurred in the Isle of Man, it is more likely they were present in founder population that populated the island.
Besides T gene, the mutations in HES7 gene and others were identified as a cause of tail deformities in cats from China (5).
Cats with tailless mutations have varying tail lengths: from absent tail as seen in Manx breed to the tail that looks normal (Figure 2).
Figure 2.Phenotypes of cats with T gene abnormalities: a) absence of a tail b) very short tail c) short tail (bobtail) d) normal tail. Photo credit: K. J. Buckingham et al.: Mutant T alleles cause short tails in Manx cats.
According to geneticist Prof. Leslie A. Lyons, the natural selection clearly does not favor cats with tailless mutations. Cats who inherit two copies of the mutation do not survive and usually die in a womb (6).
“You never see these babies born, or they never develop. That means there is a high selection against this mutation,” says L. A. Lyons (7).
· Manx: from a disabled cat to a commercial cat breed
Why are these mutations still passed down from generation to generation? The answer is humans.
There were many more tailless cats on the Isle of Man in the past probably because humans wanted to see these cats around by feeding and looking after them. But now, this is cat breeders who keep these mutations alive by producing more cats without tails in order to propagate their “Manx” breed.
Silverwing – one of the first cats to represent the Manx cat breed (1902). Biodiversity Heritage Library / University of California Libraries.
Is it ethical continuing a breed whose characteristics are based on such damaging genes? If we think cat welfare and health as a priority, the breeding of Manx and other cat breeds with tail deformities, Japanese Bobtail, Pixie-Bob, American Bobtail and Kurilian Bobtail, should cease.
While debating the ethics of breeding cats without tails, we should not forget the larger picture.
Cat and dog breeding was never about the health or for the benefit of the animal. Human selection has led to the accumulation of many deleterious genes in cat and dog breeds (8, 9).
It appears that a “healthy cat breed” is an oxymoron rather than a reality. The length of the tail or absence of it probably is not going to make much difference here, as long as breeding cats with disabilities continue to be seen as a harmless act of “preserving” breeds that do not need to be preserved.
1. Leipold, H. W., Huston, K., Blauch, B., & Guffy, M. M. (1974). Congenital defects on the caudal vertebral column and spinal cord in Manx cats. Journal of the American Veterinary Medical Association, 164(5), 520-523.
2. James, C. C., Lassman, L. P., & Tomlinson, B. E. (1969). Congenital anomalies of the lower spine and spinal cord in Manx cats. The Journal of pathology, 97(2), 269-276.
3. DeForest, M. E., & Basrur, P. K. (1979). Malformations and the Manx syndrome in cats. The Canadian Veterinary Journal, 20(11), 304.
4. Buckingham, K. J., McMillin, M. J., Brassil, M. M., Shively, K. M., Magnaye, K. M., Cortes, A., … & Bamshad, M. J. (2013). Multiple mutant T alleles cause haploinsufficiency of Brachyury and short tails in Manx cats. Mammalian genome, 24(9-10), 400-408.
5. Xu, X., Sun, X., Hu, X. S., Zhuang, Y., Liu, Y. C., Meng, H., … & Luo, S. J. (2016). Whole genome sequencing identifies a missense mutation in HES7 associated with short tails in Asian domestic cats. Scientific reports, 6, 31583.
6. Robinson, R. (1993). Expressivity of the Manx gene in cats. Journal of Heredity, 84(3), 170-172.
7. Baraniuk C. (2012, 2 Şubat). Why The Cats on one British Island Have Lost Their Tails. BBC.
8. Lyons, L. A. (2015). DNA mutations of the cat: the good, the bad and the ugly. Journal of feline medicine and surgery, 17(3), 203-219.
9. Marsden, C. D., Ortega-Del Vecchyo, D., O’Brien, D. P., Taylor, J. F., Ramirez, O., Vilà, C., … & Lohmueller, K. E. (2016). Bottlenecks and selective sweeps during domestication have increased deleterious genetic variation in dogs. Proceedings of the National Academy of Sciences, 113(1), 152-157.