Endozoochorous seed dispersal by sympatric mustelids, Martes melampus and Mustela itatsi, in western Tokyo, central Japan

Yamato Tsuji, Takahumi Tatewaki, and Eiji Kanda

　東京郊外に同所的に生息する二種のイタチ科動物、ホンドテン（Martes melampus）とニホンイタチ（Mustela itatsi）による種子散布について調査しました。研究では、両種の食性およびハビタットの違い（テン：雑食性で樹上性が高い、イタチ：肉食性で地上性が高い）が種子散布特性に及ぼす影響にとくに着目しました。2007年から2008年にかけて、東京西部の盆堀林道で収集した、478個（テン：381、イタチ：97）の糞を分析したところ、種子の出現率はテンが81.4%、イタチが55.7%とテンのほうが高く、また種子の出現種類もテンが28とイタチの17種を上回りました。ほぼすべての種子が無傷の状態で排泄されていました。糞一個あたりの出現種数は1-4と二種の動物間で違いはありませんでしたが、テンは糞一個あたりの種子の総数がイタチのそれを大きく上回っていました。テンでは出現種数や種子の総数に季節的な変化が見られたのに対し、イタチではそのような傾向は見られませんでした。われわれの研究は、同所的に生息する二種のイタチ科動物はいずれも種子散布者として機能しているものの、テンのほうが多様な植物の種子をより大量に散布している可能性を示すものです。

Mammalian Biology 76: 628-633

We investigated seed dispersal by two sympatric mustelid species, the Japanese marten (Martes melampus) and Japanese weasel (Mustela itatsi), along an intercity forest path in western Tokyo, central Japan, from Jul 2007 to Jul 2008.We aimed to investigate the effect of food/habitat preference of these mustelids (martens are semi-arboreal frugivores while weasels are terrestrial carnivores) on their seed dispersal characteristics, which determine their efficacy as seed dispersers. In total, we analyzed 478 fecal samples collected from the two mustelids (Nmarten = 381, Nweasel = 97). The proportions of feces containing seeds for martens and weasels were 81.4% and 55.7%, respectively. The number of plant species whose seeds were found within the feces were 28 and 17, respectively. Almost all seeds within feces of both mustelids were intact. The number of plant species whose seeds were found within a single fecal sample ranged from one to four, but no significant difference was detected between the two mustelids. However, marten feces contained a significantly greater number of seeds of most plant species as well as total number of seeds than did weasel feces. The numbers of plant species and seeds represented in marten feces varied seasonally, but those represented in weasel feces did not. Our findings suggest the possibility that both mustelids act in some ways as seed dispersers, although martens seem to disperse a greater diversity and total amount of seeds.

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