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Natterer’s Myotis

Myotis nattereri

French: Murin de Natterer / German: Fransenfledermaus / Spanish: Ratonero de Natterer

Other common names: Natterer's Bat

Taxonomy. Vespertilio natterer: Kuhl, 1817,

Hanau, Hessen, Germany.

Subgenus Myotis; myotis species group. The taxonomy of the nattereri species complex is currently very convoluted. Four cryptic species have currently been recognized as distinct ( M. nattereri, M. crypticus, M. escalerai, and M. zenatius) based on morphometric and genetic data, and a further two more species (hoveli and tschuliensis) may be recognizable from the Levant and Caucasus that appearto be related to M. schaubi . Anothercryptic species may also be found on Corsica based on limited genetic data; the populations on other large Mediterranean islandsare also currently uncertain due to the recent taxonomic changes. Myotis natterer and M. crypticus are sister species whereas M. escalerai and M. zenatiusare sister to one another with M. schaubi being related to either clade based on various genetic studies. The names hoveli and tschuliensis are here included as subspecies pending further studies that may prove their distinctiveness. Three subspecies recognized.

Subspecies and Distribution.

M. n. nattereriKuhl, 1817 — broadly extended in N, C & E Europe until 60° N and W Turkey. M.n.hoveliD.L.Harrison,1964—SCTurkey,WSyria,Lebanon,Israel,andWJordan.

M. n. tschuliensis Kuzyakin, 1935 — Crimea S to Caucasus region.

Isolated populations from W Russia, Crete, Cyprus, and Iraq, Iran, and Turkmenistan are not currently assigned to a subspecies.

Descriptive notes. Head-body 43-48 mm,tail 38-47 mm, ear 15-4—17- 5 mm, hindfoot 7-1-9-3, forearm 38-5—41- 2 mm; weight 7-10 g. Natterer’s Myotis has very distinct color between dorsum (generally brownish to grayish) and venter(pale grayish to whitish). Fur is remarkably long and shaggy. Young tend to be darker than adults, with skin and wings remarkably blackish. It has very broad wings and short wingspans (245-300 mm) that allow very agile and maneuverable flight. Tail membrane has two rows of bristles onits edge, and it is supported by Sshaped calcar. This trait clearly separates Natterer’s Myotis from most other species of Myotis . This line of hairs looks like a brush and is one of the traits used to separate all cryptic species in the Myotis species group. Ears are relatively long and have several folds at outer edges, surpassing muzzle when flattened. Ears are distinctly curved due to multiple folds that allow backward movement. Natterer’s Myotis differs from other similar species such as Bechstein’s Myotis ( M. bechsteinii) by the number of folds and total ear length. Tragus is long and sharp and surpasses one-half the ear length. Hairless face, especially around eyes,is noticeably pink, with narrow and long muzzle. Tibia is completely naked. Skull is small and delicate with high braincase and strongly concave forehead regions; there are no sagittal or occipital crests. P? is more than one-half height and about three-quarters crown area of P? and is within tooth row; lower molars are myotodont. Chromosomal complement has 2n = 44 and FNa = 52 (Germany).

Habitat. Usually forested areas in a wide variety of deciduous and coniferous woodlands, orchards, gardens, parks, tree plantations, and pastures from sea level to up to ¢. 2000 m. Natterer’s Myotis hunts along rivers and in riparian forests and meadows.

Food and Feeding. Natterer’s Myotis foragesflying slowly 1-4 m above the ground and hunts prey on the ground and in vegetation. It can hover perfectly over prey before gleaning it from a surface. It mainly eats spiders (e.g. harvestmen), caterpillars, and flies. It eats beetles, moths, centipedes, and other insects in smaller proportions. It uses echolocation to detect prey far from a substrate and can hunt insects found in vegetation directly in flight or byfirst picking them off vegetation with their tail membrane. Natterer’s Myotis will move up to 4 km each night to foraging areas, covering up to 500 ha. It has been suggested thatits feeding preferences vary from Geoffroy’s Myotis ( M. emarginatus) to avoid competition.

Breeding. Maternity colonies are in tree holes (e.g. hollow trees, rotten branches, abandoned woodpecker nests, etc.), sometimes rock or wall crevices, bat boxes, hollow bricks and even buildings. These colonies usually have 20-50 adult females and young. Colonies in buildings can have more than 120 individuals. Births occur in early summer(from earlyJune to earlyJuly), and young start flying after 20 daysof life, being totally independent c.1 month after birth. Females only have one young per year. Single males often aggregate in colonies up to 25 individuals, but they are also found in maternity colonies. Natterer’s Myotis mate at swarming sites and in hibernacula.

Activity patterns. Single Natterer’s Myotis can be found roosting in various roosts (e.g. tree holes, hollow trees, cliffs, small crevices and cracks, abandoned buildings, bat boxes, tunnels, caves, and mines). Natterer’s Myotis is very flexible relative to emerging from day roosts. They can be found foraging early at night, late at night, and even during the day. They generally emerge more than 30 minutes after the sunset. It has very slow and agile flight, capable of maneuvering in small and cluttered spaces. Echolocation calls are short and highly modulated pulses,starting at 100-150 kHz and ending at 20 kHz or even lower (one of the broadest frequency range of any Myotis;.130 kHz). In general, its pulses are very short, with an average duration of only 3-5 milliseconds. Its echolocation is clearly distinct from the rest of small Myotis species.

Movements, Home range and Social organization. Natterer’s Myotis is considered sedentary, usually not moving more than 40 km between summer, swarming, and hibernation roosts. In extreme cases, it reportedly moved 266-327 km. During the mating period, it swarms mostly in front of swarming sites, especially from Augustto late October. At swarming sites, it can occur with other species of Myotis such as Daubenton’s Myotis ( M. daubentonii) or Bechstein’s Myotis . In winter, individuals form large hibernation coloniesin caves and mines, exceeding 8000 individuals in some cases, or small clusters isolated in mines, tunnels, and other underground roosts.

Status and Conservation. Classified as Least Concern on The IUCN Red List. Natterer’s Myotis is not very common, but populations in Central Europe seem to be stable. Itis sensitive to habitat loss and fragmentation. It is also one of the most affected bat species by sticky flypaper. Disturbance and loss of old buildings and refurbishing of houses used as roosts might reduce available roosts.

Bibliography. Arlettaz (1996b), Coraman et al. (2019), Halczok etal. (2017), Hope & Jones (2012), Hope etal. (2014), Hutson, Aulagnier & Spitzenberger (2008), Juste et al. (2019), Melcén et al. (2007), Mortimer (2006), Parsons & Jones (2003), Puechmaille, Allegrini et al. (2012), Salicini et al. (2012, 2013), Shiel et al. (1991), Siemers & Schnitzler (2000), Siemers & Swift (2006), Smith & Racey (2005), Swift (1997), Swift & Racey (2002), Volleth & Heller (2012), Zeale etal. (2016).