So, when did the feline population increase on the Sanagishima island?
There is no historical account mentioning cats population on the Sanagishima but a book published in 1984 (*1), in which, the novelist Tomoko Yoshida, who visited the island, wrote;
A tourist who visited the Sanagishima Island in 2017 will write:
This friendly ginger came so close to a tourist's camera that his face got out of focus.
So, where are the shy cats who fled from the tourist in the 1980s? Why are all the cats in the 2010s friendly with every tourist?
There are two probable scenarios. The first one is that there was a group of tame cats who had lived somewhere on the island or came from out of the island began to thrive as tourists began to come to feed them, while shy cats who had lived on fish died out as local fishermen disappeared. The second scenario is that unfriendly cats became friendly in order to adapt themselves to the island circumstances in the 2010s in which cat-loving tourists came to feed them.
The point is, in a nutshell, whether tameness comes from nature or nurture. If the tameness is determined by nature, tame cats may have some peculiarities in genetic traits. If the tameness is determined by nurture, we may see young cats learning how to be friendly with humans.
So, we first begin with looking at natural aspect.
The cats on the Sanagishima today, comparing with the cats on mainlands, have less variety in their coats. On this island, there is no long-haired cat, no diluted color coats like blue or cream, no blotched (classic) tabby. But we cannot say that cats with these traits were shy and had not survived on this island. Cats with long-haired, diluted color, and blotched tabby coats were introduced in Japan after ending its isolation policy in the middle 19th century, and are found, though minor, on the mainlands today. So the paucity of these genetic traits in the cats on the Sanagishima suggests that number of cats immigrated from the mainlands has been possibly small since middle 19th century to the extent that the Sanagishima today still maintains the feline coat variety of 19th century mainland.
If the tameness of the cats on the Sanagishima comes from nature, they may have some peculiarities not only in their behavior but also in their looks due to the existence of some specific genes. According to the studies of domesticated animals, tame foxes and tame rats have white spots on their coats at a high frequency (*2). If it is also the case of cats, the tame cats on the Sanagishima may have distinctively white spotting.
Are you friendly because you have white fur?
So, the first thing we shall do is to survey the color coats of the cats in Honura village, the Sanagishima.
Coat colors and patterns of cats in Honura village, the Sanagishima Island.
It is evident that the majority is brown mackerel tabby and white, which, as well as black and white, calico, red mackerel tabby and white, has white spots.
The white spots appear due to the presence of piebald gene (S), also called white spotting gene (*3). The piebald gene (S) is dominant to its allele, the completely pigmented gene (s). But the S is incompletely dominant to s, so the homozygous piebald (SS) shows wider white spots than the heterozygous (Ss).
So the next step is to classify the extension of white spots. The cats wearing white fur on the Sanagishima are all different in its extension. Some wear predominant white patches, others wear white spots only on their paws and bellies.
She wears predominant white fur with the inverted V pattern at her forehead, which is called van pattern. Van pattern is associated with homozygous (SS) genotype.
This calico has wider pigmented spot than van, but white is still predominant.
This moo is around 70% white.
This beckoning cat is around 50% white.
This calico is around 30% white.
He, having white fur only on his throat, chest and paws, is more likely to have the heterozygous genotype (Ss) than the homozygous genotype (SS).
Extension of white spots of the cats in Honura village, the Sanagishima
On the premise that a cat with the homozygous (SS) genotype has more than 50% white fur, and the heterozygous (Ss) less than 50% (*4), the frequency of piebald gene (S) works out to be 77%. By the calculation in which recessive homozygous (ss) is equivalent to the completely pigmented, the frequency of piebald gene (S) is estimated to be 60% (*5).
According to the zoologist Ken Nozawa, who conducted a comprehensive survey of cat genetics in Japan from 1975 to 1989, the piebald gene (S) frequency in the nearby prefectures were 30 to 40% (*6). If that was also the case on the Sanagishima in that period of time, the S gene frequency is considered to have doubled since then. That may have worked to make cats tame, but it is also possible that the genetic frequency on the island had been different from that on the mainlands already in the 1970s, since, as the biologist Ernst Mayr pointed out, in an isolated area loss of genetic variation possibly takes place. It is called founder effect, in which, a small number of individuals who migrate to a new place determine the genetic variation of their offspring in the place. If the cats first immigrated to the Sanagishima had piebald genes in a high frequency, it is no wonder that majority of their offspring also have piebald genes.
So long as there is no record of cats' color coats on the Sanagishima in the 1970s, we don't know whether the piebald frequency has increased by natural selection or it had been high already at that time due to founder effect.
What is certain, however, is that on this island not all tame cats are piebald. Completely pigmented cats like black cats, gingers, tabbies, also are friendly with tourists. Piebald, therefore, is not sine qua non of tameness.
So much for genetics! Now we move on to the nurture aspect.
While adult cats are all friendly, some kittens are shy and seem not knowing how to interact with tourists.
There was a litter of four kittens who played around their mom who wore completely black coat.
The black queen is friendly while her kittens are shy.
The kittens were near the queen, staying away from the tourists who were gathering around to take photos of them. The queen was not afraid of the tourists. In front of them, she lay on the ground and began to suckle her four kittens.
The queen suckles her kittens in front of the tourists.
It was a peaceful time. The tourists, taking care not to disturb the family, were watching them from a modest distance, while one of the tourists took so many photos that his camera battery eventually ran out. He went back by about five meters to change the camera battery, but that was not enough of a distance. When he opened his backpack to take a new battery, the mom cat, hearing it, probably expecting him to give her food, stood up and approached to him.
The mom rubs against the tourist. Her kittens are watching it.
Watching the mom cat approaching to the tourist, the kittens followed her. The kittens seemed not old enough to eat cat food, but they imitated the way their mom demanding food from the tourist.
The kittens copycat their mom demanding food from the tourist.
This might be the very moment when the kittens learned how to interact with tourists, and perhaps other tame cats may have become tame in such a manner. If so, the reason why the cats on the Sanagishima are all tame is because they while they were young had affluent opportunities to see adult cats interacting with tourists and learned it. The Sanagishima cats' interaction with tourists, therefore, would be a collective animal behavior that might have spread when cat-loving tourists began to appear, and was to be passed down from generation to generation. If so, the tameness may be determined by nurture rather than nature.
Probably tameness of a cat is caused both by genetic and environmental factors, but which is the leading cause? In order to figure it out, admittedly, years of cohort study will be required, but today it is the era of big data which provides us with a new way of analysis. The more cat islands we visit, the more variety we will find in tame cats, when light will be thrown on the origin of tame cat and his history.
(*1)「瀬戸内海の島々」（1984 中央公論社）
(*2) Coat color, temperament and domestication of Norway rats and deermice
(*3) Eurocatfancy - PIEBALD SPOTTING gene S
(*4) Sonja Prohaska, Cat Coat - Color, Pattern and Genetics, 2015
(*5) When the frequency of the recessive allele count is q, the frequency of a homozygous recessive genetic occurrence is q^2 (=r). Then the frequency of the dominant allele count is 1-√r
(*6) 野澤 謙,「ネコの毛並み」 1996
Wandering around for thirty minutes, I saw five people and 50 to 60 cats. ... The cats on the island are not tame. Every cat fled when I approached.
A tourist who visited the Sanagishima Island in 2017 will write:
Wandering around for 140 minutes, I saw three local people, a couple of dozen tourists, and 64 cats. The cats on the island are all tame. Every cat did not flee when I approached, some even approached to me.
This friendly ginger came so close to a tourist's camera that his face got out of focus.
So, where are the shy cats who fled from the tourist in the 1980s? Why are all the cats in the 2010s friendly with every tourist?
There are two probable scenarios. The first one is that there was a group of tame cats who had lived somewhere on the island or came from out of the island began to thrive as tourists began to come to feed them, while shy cats who had lived on fish died out as local fishermen disappeared. The second scenario is that unfriendly cats became friendly in order to adapt themselves to the island circumstances in the 2010s in which cat-loving tourists came to feed them.
The point is, in a nutshell, whether tameness comes from nature or nurture. If the tameness is determined by nature, tame cats may have some peculiarities in genetic traits. If the tameness is determined by nurture, we may see young cats learning how to be friendly with humans.
So, we first begin with looking at natural aspect.
The cats on the Sanagishima today, comparing with the cats on mainlands, have less variety in their coats. On this island, there is no long-haired cat, no diluted color coats like blue or cream, no blotched (classic) tabby. But we cannot say that cats with these traits were shy and had not survived on this island. Cats with long-haired, diluted color, and blotched tabby coats were introduced in Japan after ending its isolation policy in the middle 19th century, and are found, though minor, on the mainlands today. So the paucity of these genetic traits in the cats on the Sanagishima suggests that number of cats immigrated from the mainlands has been possibly small since middle 19th century to the extent that the Sanagishima today still maintains the feline coat variety of 19th century mainland.
If the tameness of the cats on the Sanagishima comes from nature, they may have some peculiarities not only in their behavior but also in their looks due to the existence of some specific genes. According to the studies of domesticated animals, tame foxes and tame rats have white spots on their coats at a high frequency (*2). If it is also the case of cats, the tame cats on the Sanagishima may have distinctively white spotting.
Are you friendly because you have white fur?
So, the first thing we shall do is to survey the color coats of the cats in Honura village, the Sanagishima.
Coat colors and patterns of cats in Honura village, the Sanagishima Island.
It is evident that the majority is brown mackerel tabby and white, which, as well as black and white, calico, red mackerel tabby and white, has white spots.
The white spots appear due to the presence of piebald gene (S), also called white spotting gene (*3). The piebald gene (S) is dominant to its allele, the completely pigmented gene (s). But the S is incompletely dominant to s, so the homozygous piebald (SS) shows wider white spots than the heterozygous (Ss).
So the next step is to classify the extension of white spots. The cats wearing white fur on the Sanagishima are all different in its extension. Some wear predominant white patches, others wear white spots only on their paws and bellies.
She wears predominant white fur with the inverted V pattern at her forehead, which is called van pattern. Van pattern is associated with homozygous (SS) genotype.
This calico has wider pigmented spot than van, but white is still predominant.
This moo is around 70% white.
This beckoning cat is around 50% white.
This calico is around 30% white.
He, having white fur only on his throat, chest and paws, is more likely to have the heterozygous genotype (Ss) than the homozygous genotype (SS).
Extension of white spots of the cats in Honura village, the Sanagishima
On the premise that a cat with the homozygous (SS) genotype has more than 50% white fur, and the heterozygous (Ss) less than 50% (*4), the frequency of piebald gene (S) works out to be 77%. By the calculation in which recessive homozygous (ss) is equivalent to the completely pigmented, the frequency of piebald gene (S) is estimated to be 60% (*5).
According to the zoologist Ken Nozawa, who conducted a comprehensive survey of cat genetics in Japan from 1975 to 1989, the piebald gene (S) frequency in the nearby prefectures were 30 to 40% (*6). If that was also the case on the Sanagishima in that period of time, the S gene frequency is considered to have doubled since then. That may have worked to make cats tame, but it is also possible that the genetic frequency on the island had been different from that on the mainlands already in the 1970s, since, as the biologist Ernst Mayr pointed out, in an isolated area loss of genetic variation possibly takes place. It is called founder effect, in which, a small number of individuals who migrate to a new place determine the genetic variation of their offspring in the place. If the cats first immigrated to the Sanagishima had piebald genes in a high frequency, it is no wonder that majority of their offspring also have piebald genes.
So long as there is no record of cats' color coats on the Sanagishima in the 1970s, we don't know whether the piebald frequency has increased by natural selection or it had been high already at that time due to founder effect.
What is certain, however, is that on this island not all tame cats are piebald. Completely pigmented cats like black cats, gingers, tabbies, also are friendly with tourists. Piebald, therefore, is not sine qua non of tameness.
So much for genetics! Now we move on to the nurture aspect.
While adult cats are all friendly, some kittens are shy and seem not knowing how to interact with tourists.
There was a litter of four kittens who played around their mom who wore completely black coat.
The black queen is friendly while her kittens are shy.
The kittens were near the queen, staying away from the tourists who were gathering around to take photos of them. The queen was not afraid of the tourists. In front of them, she lay on the ground and began to suckle her four kittens.
The queen suckles her kittens in front of the tourists.
It was a peaceful time. The tourists, taking care not to disturb the family, were watching them from a modest distance, while one of the tourists took so many photos that his camera battery eventually ran out. He went back by about five meters to change the camera battery, but that was not enough of a distance. When he opened his backpack to take a new battery, the mom cat, hearing it, probably expecting him to give her food, stood up and approached to him.
The mom rubs against the tourist. Her kittens are watching it.
Watching the mom cat approaching to the tourist, the kittens followed her. The kittens seemed not old enough to eat cat food, but they imitated the way their mom demanding food from the tourist.
The kittens copycat their mom demanding food from the tourist.
This might be the very moment when the kittens learned how to interact with tourists, and perhaps other tame cats may have become tame in such a manner. If so, the reason why the cats on the Sanagishima are all tame is because they while they were young had affluent opportunities to see adult cats interacting with tourists and learned it. The Sanagishima cats' interaction with tourists, therefore, would be a collective animal behavior that might have spread when cat-loving tourists began to appear, and was to be passed down from generation to generation. If so, the tameness may be determined by nurture rather than nature.
Probably tameness of a cat is caused both by genetic and environmental factors, but which is the leading cause? In order to figure it out, admittedly, years of cohort study will be required, but today it is the era of big data which provides us with a new way of analysis. The more cat islands we visit, the more variety we will find in tame cats, when light will be thrown on the origin of tame cat and his history.
(*1)「瀬戸内海の島々」（1984 中央公論社）
(*2) Coat color, temperament and domestication of Norway rats and deermice
(*3) Eurocatfancy - PIEBALD SPOTTING gene S
(*4) Sonja Prohaska, Cat Coat - Color, Pattern and Genetics, 2015
(*5) When the frequency of the recessive allele count is q, the frequency of a homozygous recessive genetic occurrence is q^2 (=r). Then the frequency of the dominant allele count is 1-√r
(*6) 野澤 謙,「ネコの毛並み」 1996
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