Photo/IllutrationA 74-day-old toy poodle, left, is grown up compared with its 52-day-old companion. (Masahiko Ohta)

  • Photo/Illustraion
  • Photo/Illustraion

Dog owners in Japan like to take pets home as young as possible, but breeders separate puppies from their birthplaces at such early stages that they develop behavioral problems, research has found.

Takefumi Kikusui, professor of ethology at Azabu University, discovered that puppies who departed from their breeders at 50 to 56 days old tend to display more troubled behavior, such as attacking strangers and their owners, than those who left between 57 to 69 days.

“It was verified that there is a significant difference (between the two groups),” said Kikusui.

Large-sized dogs are especially affected, according to the professor. “You can see a bigger difference in behavior being influenced by larger dogs’ age when they departed their birthplaces than smaller dogs,” he said while adding the proviso that the sample size of larger dogs was limited.

The research is based on information from 4,033 valid responses to a survey of those who purchased puppies from pet shops that are members of Zenkoku Pet Kyokai (national pet association).

Statistical analysis of the data was conducted based on the method developed by James Serpell, a professor of animal ethics and welfare at the University of Pennsylvania in the United States.

Kikusui added, “It was statistically discovered that dogs who departed after 57 days or more are less likely to have problematic behavior.

“The degree of difference, however, is small. We need to research to find out whether other factors including the environments where their mother dogs are put during pregnancy and right after the delivery, as well as heredity, strongly impact the puppies’ future problematic behaviors.”

Dan Sasaki, a professor of economics at the University of Tokyo’s Institute of Social Science, who is knowledgeable about statistics, said, “Breeders tend to rush to ship puppies considering the rearing cost and shipping price, while they also tend to keep slow-growing puppies longer and ship them after they have grown to a certain degree. Therefore, the puppies who departed at eight weeks old or above are more likely to be physically weak and mature slowly. The survey results can be influenced by such factors.

“It is very important that (the research) showed the significant difference of behaviors over sample dogs including both who departed when they were 56 and 57 days old (only one day difference). The survey results showed puppies’ problematic behaviors such as attacking people can be reduced through staying where they were born at least a week longer than 49 days, which is the period stipulated by the currently enforced law. That discovery is especially meaningful from the point of view of social policies.”

The animal protection law already prohibits breeders from letting puppies and kittens depart from their birthplaces at 56 days old or younger, but due to a clause in the law, the limit is interpreted as 49 days.

Suprapartisan Diet members are working toward enforcing the 56-day rule in a revision of the law.

Previous research in Europe and the United States demonstrated that dogs who departed their birthplaces at a very young age are more likely to develop problematic behaviors including attacking humans after failing to be appropriately socialized.

Many developed countries including the United States, Britain, France and Germany have introduced rules that ban breeders from letting pets go from their birthplaces at younger than the eighth week (56 to 62 days).