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Ridley’s Myotis

Myotis ridleyi

French: Murin de Ridley / German: Ridley-Langful 3fledermaus / Spanish: Ratonero de Ridley

Other common names: Ridley's Bat

Taxonomy. Pipistrellus ridleyi Thomas, 1898,

“ Selangor, Malay Peninsula [= Peninsular Malaysia].”

Subgenus Myotis; horsfieldii species group (9 species). In a 2013 phylogenetic study, M. ndleyi was related to M. rosseti and M. cf. browni and more distantly to an Oriental region clade of large-footed, “trawling” Myotis (hasselti, macropus, macrotarsus, and horsfieldii). In a 2016 study, M. ridley and M. rosseti appeared as sister species (diverging c.4 million years ago) to a clade of “large-footed” Myotis ( horsfieldii, macrotarsus, macropus, adversus, and hasselti). Monotypic.

Distribution. Malay Peninsula and N Borneo (Sabah, N Kalimantan, and Gunung Gading National Park in SW Sarawak). Data from Sumatra might be erroneous; specimens previously reported from there were identified as the Hairy-faced Myotis ( M. annectans), but both species might not occur there. Data from Sulawesi identified as M. cf. ridleyi requires more detailed studies, and on zoogeographical grounds, they probably represent a different taxon.

Descriptive notes. Head-body 36-41 mm, tail 23-33 mm, ear 8-11 mm, hindfoot 5-1- 7: 5 mm, forearm 27-37 mm; weight 4-6- 5 g. Ridley’s Myotis has short wings butrelatively heavy body and typical Myotis ears and tragus shape albeit the latter is relatively short and wide at its base. Upperparts are uniformly dark brown, with short velvety fur. Underparts are slightly paler, gray brown to dark brown. Face and muzzle are brown. Feet are small and naked, but toes are covered with stiff hairs. Wings are brownish black and attach at bases of toes. Ears are medium-sized and brownish black, with fairly long tragus, pointed tips, and distinct rounded basal lobe, curved forward. Baculum is less than 1 mm long and saddle-shaped. Skull has elevated frontal region. Braincase is relatively high and inflated. Rostrum is short and deep, with medium width. Dentition is reduced with only 34 teeth. P® and P, are lacking. Incisors are short and broad; canines are relatively short, C' barely exceeds P* in height, and C,is equal in height to P,. There are only two upper and lower premolars. P? is in tooth row, in contact with canine, but separated from P* by short diastema. Condylo-canine lengths are 11-12 mm; maxillary tooth row lengths are 4-4— 4-8 mm. Chromosomal complement has 2n = 44 and FN = 50 (Ulu Gombak, Peninsular Malaysia).

Habitat. Dipterocarp and lowland primary forests, near lowland forest streams, and pristine lowland evergreen forest, near peat swamps, at upper elevations of ¢. 1000 m.

Food and Feeding. Ridley’s Myotis forages over small streams in forest understories and might be dependent on water to forage.

Breeding. A pregnant Ridley’s Myotis was caught in April. At Krau Wildlife Reserve (Peninsular Malaysia), lactating females were found in May and August and pregnant females in March and October.

Activity patterns. Ridley’s Myotis is nocturnal and naturally roosts in caves, rock crevices and hollows, fallen logs, and small crevices in road culverts and under human houses/cabins. Some individuals were caught using hand nets near Krau Wildlife Reserve headquarters inside a culvert.

Movements, Home range and Social organization. At Tabin Wildlife Reserve (Sabah), a colony of ¢.30 Ridley’s Myotis has roosted under a visitor cabin on a hill for many years.

Status and Conservation. Classified as Near Threatened on The IUCN Red List. Ridley’s Myotis has probably declined by close to 30% over the last 15 years due to significant loss ofits forest habitat. This rate of decline is predicted to continue for the next 15 years. Habitat loss from logging, agriculture, plantations, and forest fires is a major threat. It occurs in Kayan Mentarang National Park (Borneo) and other protected areas. It is rarely collected and requires additional research.

Bibliography. Amador et al. (2018), Boitani et al. (2006), Bumrungsri et al. (2006), Chasen (1940), Corbet & Hill (1992), Francis (2008a), Heller & Volleth (1989), Hill (1969a), Hill & Harrison (1987), Hill & Topéal (1973), Hutson, Francis, Kingston & Bumrungsri (2008), Khan et al. (2008), Kingston et al. (2006), Koopman (1994), Lim et al. (2017), Medway (1978, 1983), Payne et al. (1985), Phillipps & Phillipps (2016), Puri (1997), Ruedi et al. (2013), Simmons (2005), Tate (1941d), Thomas (1898b), Volleth & Heller (2012), Wiantoro et al. (2017).