須磨海浜水族園のなかまたち：ラッコ飼育のこれまでとこれから 高齢化と繁殖難しく減少 ／兵庫 - 毎日新聞
Sea otters, adorable creatures floating on their back, might not be seen in Japanese aquariums in near future. Today, Suma Aqualife Park KOBE is home to two sea otters: a 19-year-old female and a 20-year-old male who came as a potential mate from Niigata City Aquarium. The average age of sea otters in Japanese aquariums is 15 years old, which indicates the severe of captive animals who live typically 15 to 20 years. Also, the number of animals in captivity dropped from 122 in 1994 to 10 as of today. Why did this happen?
There may be two prominent reasons.
First, import of sea otters from overseas has ceased. Sea otters range off the North Pacific and divided in three subspecies by the habitat: northern sea otter, southern sea otter and Asian sea otter. Most animals accepted in Japanese aquariums are the northern subspecies. Although wild population has reportedly increased in some areas today, the population was decreased to near extinction from late 18th century to early 20th century due to over hunting for the fine fur and the sea otter has listed as endangered by IUCN. It was in 1982 when Japan first imported sea otters from the United States. Subsequently, trading of sea otters has regulated by CITES, and 1998 was the last year when Japan imported sea otters from the United States.
Second, breeding otters born in captivity has not worked very well. Of 300 sea otters in Japanese aquariums two thirds were born in captivity and most of them did not have parents born in captivity but parents captured in the wild. Wild animals can learn how to nurse their young and how to mate from others, but captive animals have much less opportunities to do so. Mating of sea otters can be very aggressive and a male often holds a female from back and bites her nose. In captivity some males give up to mate once they are denied by females. We have worked to promote the breeding in captivity by making efforts such as showing otters videos of mating behaviors, exchanging animals with other facilities and adjust the hours of daylight to their habitat in the wild; however, it was 2002 when we successfully saw reproduction. Breeding may be difficult in the future, but we can continue to collect data which can help us understand the reproductive physiology by investigating the sex hormones which are found in sea otter feces.
We will continue to study sea otters in captivity so that we can help more people to learn sea otter ecology and their difficult situation in captivity. ( Yuki Kurisu, Suma Aqualife Park, Japan)
Translation by sea otter channel
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