三谷 曜子74Yoko MITANI斎藤 昌幸75Masayuki SAITO北海道沿岸におけるラッコの再定着は何をもたらすか：生物多様性保全と持続的利用の両立に向けて（2019採択）What happens next after the return of sea otters along the coast of Hokkaido?: Designing coexistence between biodiversity conservation and sustainable usage of fisheries resources (Project 2019)糞は資源か恐怖の対象か？：タヌキのタメ糞に対する在来および外来哺乳類の応答とその相違（2020採択）Is feces a resource or an object of fear? Responses of native and non-native mammals to raccoon dog latrine and their differences(Project 2020)59日本のラッコ Enhydra lutrisは毛皮を目的に乱獲されて姿を消したが，近年，北海道東部沿岸で定期的に目撃されるようになり，再定着したと考えられる．そこで本研究は，ラッコの餌嗜好性およびウニ類と二枚貝類の存在量を明らかにすることを目的とした．その結果，ラッコは主に二枚貝類を食べ，カニ類，ウニ類，ヒザラガイ類などが続いた．また，0.25 m2のコドラートを用い，水深3〜12 mの22地点（1 地点につき4回）で底生生物を採取した．1 m2あたりの平均密度はウニが二枚貝類よりも高かったが，1個あたりの平均エネルギー量は二枚貝類がウニ類の6〜9倍であったことから，ラッコが二枚貝類を多く食べていたのは，餌1個あたりの獲得エネルギーが高いからだと推察された．商業的価値の高い底生生物が生息している地域では，ラッコと漁業との軋轢を緩和する政策が期待される．Sea otters Enhydra lutris in Japan disappeared due to overhunting for their pelts, however, in recent years they have been regularly sighted along the eastern coast of Hokkaido and are thought to have re-established them-selves. In this study, we aimed to clarify the food preferences of sea otters and the abundance of sea urchins and bivalves. The results showed that sea otters fed mainly on bivalves, followed by sea urchins, crabs, and chitons. Benthic invertebrates were sampled at 22 sites (four replicates per site) at depths ranging from 3 to 12 m using 0.25 m2 of quadrats. The average density per square meter for sea urchins was higher than bi-valves, but the average energy per individual of bivalves was 6 to 9 fole of sea urchins. It was inferred that the sea otters ate more bivalves because of their higher energy acquisition. In areas where benthic inverte-brates with high commercial value are inhabited, policies to mitigate conflicts between sea otters and fisher-ies are expected.本研究ではタヌキのタメ糞場が他の哺乳類に影響を与えているのか，また在来哺乳類と外来哺乳類でタメ糞場に対する反応が異なるのかどうか調査した．2020年6月から12月にかけて，14か所でカメラトラップを実施し，相対出現頻度と行動パターンを記録した．解析の結果から，タヌキのタメ糞場の存在は他の哺乳類に対してあまり影響を与えていないことが示唆された．ただし，ニホンアナグマやネズミ類とは，タメ糞場を介した種間関係が存在する可能性が示唆された．また，外来種であるハクビシンについては，タメ糞場に興味を持つ個体が存在していた．今後さらに調査を進めることで，タヌキのタメ糞場における哺乳類の種間関係を明らかになることが期待される．In this study, we surveyed whether the latrine site of raccoon dogs affects other mammals and whether native and non-native mammals respond differently to the latrine. From June to December 2020, we conducted cam-era traps at 14 latrine sites to record the relative frequency of occurrence and behavioral patterns. The results suggested that the presence of raccoon dog latrines does not have much impact on other mammals. However, it was suggested that there may be interspecific relationships with Japanese badgers and rodents through la-trine sites. As for the non-native masked palm civet species, some individuals were interested in the latrines. Further research is expected to clarify the interspecies relationships among mammals in the raccoon dog la-trine sites.
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