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Muntjac deer population in Chiba Pref. surges by 50 times over 14 years

In this Jan. 28, 2017 file photo, a muntjac deer is seen eating foliage in a residential area in the city of Isumi, Chiba Prefecture. (Mainichi)

KATSUURA, Chiba -- This city along with others on the Boso Peninsula are being overrun by staggering numbers of Chinese muntjac deer.

    The Chiba Prefectural Government reported that the estimated number of muntjac deer grew from roughly 1,000 in 2002 to 49,500 in 2016, ballooning by 50 times over 14 years. As a result, the deer are appearing in neighborhoods and on golf courses and wreaking havoc on agriculture. Unable to capture the deer to keep up with their frequent breeding, authorities are left puzzled over how to solve the problem.

    Chinese muntjac deer mainly inhabit China and Taiwan, and are small deer with an average body length of roughly 1 meter, a height of about 40 centimeters and a weight of around 10 kilograms. They are known for their adorable eyes, but the mischievous deer have escaped from zoos such as on Tokyo's Izu Oshima Island, become feral, and begun breeding in the wild. Because of their disruption of the ecosystem and damage to the forestry, agricultural and fishing industries, the deer have been designated as an invasive alien species.

    The deer on the Boso Peninsula in Chiba Prefecture are thought to have escaped from the tourist attraction "Namegawa Island" in the city of Katsuura, which was known for its flamingo and peacock shows before closing in 2001. According to the Chiba Prefectural Government, there have been sightings of wild muntjac deer since the 1980s. Because muntjac deer can become pregnant at 6 months old, and they can give birth any time of year from 1 year old, their numbers can multiply quickly. Their population has spread from Katsuura over a roughly 40 kilometer radius to the nearby cities of Kamogawa and Isumi.

    The farming land and community promotion division of Chiba Prefecture reported that damage by muntjac deer to farms cost roughly 950,000 yen in fiscal 2015, the highest amount since they began calculating the figure in fiscal 2004. The majority of the inflicted damage was made up of the deer eating leafy vegetables and the new buds of fruit trees.

    Apart from farms, private homes are also being paid visits by the wandering deer, causing trouble for residents by eating garden flowers and leaving behind droppings. "At least once every two days the deer come near my house," says a 77-year-old Katsuura man. "They eat everything except narcissus flowers, so I can't plant anything else. You can hear them calling out at night during the summertime. There are so many of them that I don't know what to do."

    Since 2000, the prefectural government has made plans to exterminate the deer, teaming up with local hunting clubs to set traps along with other countermeasures, but the 2,187 deer captured during the 2015 fiscal year did not match the speed at which the deer are breeding.

    An official of the prefectural nature preservation division explained, "Since the deer are an alien species, we don't know their ecology, so it's difficult to catch them. We need to conduct a survey within the prefecture to research their ecology to find the most effective way to capture them. The only thing to do from there is to ask each affected municipal government to capture the deer."

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