527.

Small Japanese Field Mouse

Apodemus argenteus

French: Mulot geisha / German: Kleine Japan-Waldmaus / Spanish: Ratén de campo pequeno de Japon

Taxonomy. Mus argenteus Temminck, 1844,

Japan .

Apodemus argenteus is very distinct from others in its genus, and its taxonomic classification is not yet fully understood. G. G. Musser and colleagues in 1996 could not place it in any of the subgenera proposed, and molecular study by K. Serizawa and team in 2000 found it to be distinct and a valid species. Phylogeographic study by H. Suzuki and coworkers in 2004 found

very low genetic variability among differentJapanese populations. In 2003, Suzuki and team had found it to be also very distant from other members of Apodemus, and it has been placed assister taxon of A. gurkha or in its own basal clade by some mammalo-gists, such as Liu Xiaoming and colleagues in 2004 and Suzuki and colleagues in 2008. Re-examination of type series allowed C. Smeenk and coworkers in 1982 to clarify some points of the species’ taxonomy and define a new lectotype. Various subspecies have been named but, as no genetic structure was found, they are not considered here. Monotypic.

Distribution. Japan, including Hokkaido, Honshu, Shikoku, Kyushu, and adjacent islands of Kinkasan, Awashima, Sado, Oki Is (Dogo and Nishino), Awaji, Shodo, Miyajima, Tsushima, Gotd Is (Fukuejima and Nakadorijima), Amakusa-shimoshima, and OsumiIs (Yakushima and Tanegashima).

Descriptive notes. Head-body 65-100 mm, tail 70-110 mm, ear 11-15 mm, hindfoot 17-21 mm; weight 10-20 g. The Small Japanese Field Mouse is a small rodent with a soft and fine fur is pale reddish-brown dorsally and white ventrally. It has a relatively long tail, slightly longer (average 106%) than head-body length. Females bear four pairs of mammae. Chromosomal complement has 2n = 46, FN = 48-52.

Habitat. From lowlands to alpine areas. The Small Japanese Field Mouse prefers mature forests, with a thick leaf layer, from sea level up to more than 2500 m.

Food and Feeding. Like all other Japanese Apodemus, the Small Japanese Field Mouse is primarily granivorous, with variable quantity of insects in its diet.

Breeding. Populations fluctuate during year but maximum density corresponds to summer times, implying that reproduction occurs mostly during spring and summer, and pregnant females were recorded only during May—October. Litter size in the wild was 2-6 (average 3—4), varying regionally and with season. At birth, young are blind and hairless; eyes open at 12-14 days, and they are weaned at days 18-21. Males reach sexual maturity between days 30 and 35.

Activity patterns. The Small Japanese Field Mouse is semi-arboreal. It occupies a more arboreal niche than the Large Japanese Field Mouse ( A. speciosus) and tends to use a horizontally different type of microhabitat, resulting in decreased competition.

Movements, Home range and Social organization. No information.

Status and Conservation. Classified as Least Concern on The IUCN Red Lust.

Bibliography. Abe et al. (2005), Fujimaki (1978), Liu Xiaoming et al. (2004), Matsubara et al. (2004), Musser et al. (1996), Nakata (1986), Ohdachi et al. (2015), Sekijima (2004), Serizawa et al. (2000), Shioya et al. (1990, 1992), Smeenk et al. (1982), Suzuki, Filipucci et al. (2008), Suzuki, Sato et al. (2003), Suzuki, Yasuda et al. (2004).