An ownerless dog is left under a sign which says, 'We will take care of your dog,' and 'Please call the number below,' posted outside a shelter at Koryama in Fukushima prefecture on March 21, 2011. (Go Takayama/AFP/Getty Images)

Dogs that went through the Fukushima Daiichi nuclear disaster, triggered by the massive 9.0-magnitude earthquake in Japan last year, tended to have symptoms similar to post-traumatic stress disorder (PTSD), according to a new study.

The paper, published Thursday in Nature’s Scientific Reports, said that many dogs were abandoned in Fukushima Prefecture following the plant’s meltdown, caused by a tsunami on March 11, 2011.

Numerous dogs were left to roam around and some were living in a semi-feral state in the 12-mile exclusion zone around the Fukushima plant. People living in the zone were forced to evacuate due to elevated levels of radiation being emitted from the stricken facility, and thousands had to leave their dogs behind.

Researchers with Azabu University in Japan compared other dogs from Kanagawa, another part of Japan, that were abandoned in 2009 and 2010, with 17 Fukushima dogs that were left by themselves after the disaster.

The dogs were all placed into a special rescue program, giving them training and care so they could be sent to adoptive families.

After several weeks, the researchers found that cortisol levels in the Fukushima dogs were higher than in the others.

“The dogs from Fukushima showed significantly lower aggression toward unfamiliar people, trainability, and attachment to their caretakers; also, urine cortisol levels in the dogs from Fukushima were 5–10-fold higher than those in abandoned dogs from another area of Japan,” the researchers noted in their study.

“These results suggested that the dogs from Fukushima suffered through an extremely stressful crisis.”

Although the people affected by the disaster are recovering and slowly returning to normal life, the psychosomatic impact on their pet dogs need to be considered due to the effects on behavior, such as attachment and learning ability.

“Long-term care and concern regarding the psychological impact of disasters appears necessary in humans and companion animals,” the scientists concluded.

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