197.

Northern Serotine

Eptesicus nilssonii

French: Sérotine de Nilsson / German: Nordfledermaus / Spanish: Murciélago hortelano nortefo

Other common names: Northern Bat

Taxonomy. Vesperus nilssonii Keyserling & Blasius, 1839,

Sweden.

Eptesicus milssonii appears to be sister to E. serotinus, and they are often paraphyletic in genetic studies using mitochondrial genes due to extensive ancient hybridization. Nevertheless, when using nuclear genes, LE. nmilssonu forms a monophyletic clade not closely related to E. serotinus . Eplesicus nilssonii 1s sometimes considered to include E. japonensis, but they are generally recognized as distinct species based on morphological data. Eptesicus gobiensis has often been included under E. nilssonii, but it is usually considered a distinct species now based on genetic and morphological distinctions. There is also considerably uncertainty as to whether the north Indian endemic E. tate: represents a distinct species or a subspecies of E. nilssonii, although it is geographically well separated from E. nilssonii and is considered a distinct species here. Distribution of E. nilssonii has been reported differently in a number of sources, making actual distribution somewhat uncertain, and distribution here should be considered as tentative. Two subspecies ( nilssonii and parvus) are usually recognized, but genetic data do not support this view because there is low genetic variability between these two taxa. Monotypic.

Distribution. E France to N Europe well above the Arctic Circle in Norway, Sweden, and Finland, Central Europe, Caucasus, NW Iran, and Central Asia (including N Kazakhstan) through Russia and N Mongolia to Russian Far East including Sakhalin I and Kamchatka Peninsula and S through Amur region into NC & NE China (Inner Mongolia [= Nei Mongol], Heilongjiang, Jilin, and Shandong) and Korean Peninsula, including Hokkaido and Okushirito inJapan and Kuril Is (Kunashir and Iturup); there are occasionally vagrant records throughout Europe as far S as Bulgaria and Italy and W into S Britain.

Descriptive notes. Head-body 54-68 mm, tail 35-50 mm, ear 13-17-5 mm, hindfoot 10-12 mm, forearm 37-1-44-2 mm; weight 9-13 g. Fur of the Northern Serotine is long, silky, and shaggy. Dorsal pelage is dark brown to blackish and frosted with goldyellow tips, giving glossy yellowish appearance. Ventral pelage is lighter pale brown to beige. Bare face, ears, and membranes are distinctly dark brown. Ears are short, rounded, and fleshy, with five transverse folds; tragus is short and rounded, curving inward. Wings are broad and long (wingspans of 240-280 mm) and are attached to base of toes. Tail extends a little past uropatagium, and calcaris about halfway to tail; there is no postcalcarial lobe. Baculum is short (1-3-1-5 mm), relatively long for Eptesicus, and Y-shaped, and it has deep basal bifurcation, with either side going outward from shaft. Skull is relatively delicate and tapered; rostrum is laterally rounded; condylobasal lengths are 14-2—-15-6 mm; zygomatic breadths are 9-5-10-5 mm; braincase is low and subspherical; sagittal crest is very low or absent; lambdoidal crests curve slightly toward point of contact at middle; interorbital region is hourglass-shaped; and lacrimal swelling is present. Dentition is robust; I? is bicuspid; I is unicuspid and more than one-half the height of I’; and lower molars are myotodont. Chromosomal complement has 2n = 50 and FNa = 48 (throughout Europe).

Habitat. Boreal habitats and high mountain ecosystems, mostly forests, but also desert regions, lowland, and foothills from sea level up to elevations of ¢. 2920 m. The Northern Serotine is the most northern distributed bat species. Due to its fast flight, it generally needs open areas to hunt such as open woodlands or forest edges, parks and gardens in urban areas,lakes, wetlands, meadows or swamps in high mountains.

Food and Feeding. The Northern Serotine forages along vegetation edges, forest edges or hedgerows in natural landscapes and around streetlamps in urbanized areas. It is adapted to hunt insects at just above freezing temperatures. It has been reported feeding primarily on small Diptera (specifically Nematocera), but it also captures Coleoptera, Lepidoptera, and Heteroptera in smaller quantities. It generally hunts by aerial-hawking, capturing prey in flight at heights of 2-20 m rather than capturing them on vegetation or the ground. Nevertheless, because it is not clutter specialist,it is capable of visually detecting and recognizing large (greater than 50 mm) and brightly colored insects on the ground and capturing them using visual and acoustic senses. In someareas, it tends to select areas with streetlamps. In localities close to the ocean, Northern Serotines and Eurasian Serotines ( E. serotinus) have been observed foraging over the ocean where insects are abundant.

Breeding. Pregnant Northern Serotines give birth to 1-2 young from mid-June to end ofJuly, occurring earlier at lower latitudes. In Germany, births usually occur in mid-June, but in Scandinavia and further north, births occur in late June to early July, or even in midand late July in some regions. This later birth date might be attributed to females entering torpor more often during the day in cooler weather to conserve energy while pregnant, which would delay fetal development. Young startto fly atjust two (Sweden) or three (Germany) weeks of age. Females become sexually active during their first year but do nottypically breed during theirfirst three years. Males disperse more widely than females during theirfirst year, and females do not change maternity colonies very often. The Northern Serotine is one of the few bat species that has been found breeding above the Arctic Circle. Maximum longevity in the wild has been recorded at c.20 years.

Activity patterns. Nightly activity of the Northern Serotine is generally bimodal, with two activity peaks after sunset and around dawn. Pregnant females usually have unimodal or bimodal activity pattern, with peaks always after dusk and sometimes before dusk; non-pregnant females forage intermittently throughout the night. Reproducing females at 57° N left the roost 47 minutes after sunset and spent an average of three hours outside the maternity roost each night. During pregnancy, however, ¢.20% of their time outside the maternity colony was spent roosting in trees, foraging for an average of 150 minutes each night. Lactating females foraged an average of 120-130 minutes/night just after giving birth, 220-260 minutes/night in mid-lactation, and 320 minutes/night at peak lactation, reflecting energetic costs of lactation. Female Northern Serotines tend to emerge increasingly later as pregnancy advances. Due to the cold climate in its distribution, swarming period occurs from mid-July into late autumn. Hibernation tends to occur from November or December until March or April. Northern Serotines typically choose hibernacula that have ambient temperatures of 0-2°C but will occasionally use roosts that get as cold as =5°C, roosting in houses, cellars, and sometimes caves and mines. Maternity colonies in summer are commonly located in buildings but sometimes in hollow trees. In most ofits distribution, nursery colonies are found in roofs of houses, walls, or empty large cavities below metal sheets. Search calls of the Northern Serotine are not well differentiated from the Eurasian Serotine and have broad overlap with some species of Nyctalus . Pulses are up to 20 milliseconds long and typically shaped as an FM/QCF sweep. Peak frequencies are usually 26-32 kHz. On Hokkaido, Japan, start frequencies were 51-8-64-7 kHz, end frequencies were 24-3-27.7 kHz, peak frequencies were 28-3-31-6 kHz, durations were 4-4-8 milliseconds, and interpulse intervals were 95-185 milliseconds. Swedish recordings had an average peak frequency of 32-4 kHz, end frequency of 30-4 kHz, duration of 7 milliseconds, and interpulse interval of 100 milliseconds. Social calls seem to be quite distinct, consisting of long QCF sweep, with duration of up to 60 milliseconds and powerful second and third harmonics.

Movements, Home range and Social organization. In winter, the Northern Serotine tends to move toward its hibernation sites. During hibernation, only single individuals have been found. Although it shifts roosts quite often between seasons, these movements are rather short, and maximum migratory distance is ¢. 450 km in Europe. A few banded and recaptured individuals suggest that it might be a short-distance migratory species, only occasionally flying long distances. During the breeding season, females form maternity colonies. Maternity colonies can contain tens to hundreds of individuals (very large colonies have been reported in Japan). Single individuals, males, or non-reproductive females can be found roosting in a wide variety of different roosts. Males commonly roost alone year-round, rarely in small groups. Northern Serotines can fly up to 70 km each night to reach foraging areas, but they typically commute only 1-10 km, using up to eight different sites. Foraging areas range from 0-2 km? in summer to 66 km? during swarming and are strongly affected by length of the night (0-91-17-2 km?). Females often establish small feeding territories (c. 100 m?) with abundant insects, where they return every night, sometimes for subsequent years. Feeding territories of males and females are vigorously defended against intruders, involving aerial chases and audible vocalizations with maximum amplitudes of 14 kHz. These same territorial behaviors have been observed outside of hibernacula in autumn, suggesting that roosts are also defended. Foraging localities and activity peaks might be partially affected by competition with other bat species that forage in open spaces but do not forage at the same time, e.g. Eurasian Particolored Bats ( Vespertilio murinus), Common Noctules ( Nyctalus noctula), and Eurasian Serotines. Species that used narrow spaces foraged simultaneously with Northern Serotines (e.g. Daubenton’s Myotis, Myotis daubentonii). Population density decreases at higherlatitudes, with densities at 57° N being five times higher than in similar landscapes at 65° N.

Status and Conservation. Classified as Least Concern on The IUCN Red List. The Northern Serotine is quite common, occurs in high densities in several places in its distribution, and is widespread, sometimes considered the most abundant bat species in northern countries. Nevertheless, in some areas, they are very rare and locally endangered (e.g. Germany). Climate change is the most acknowledged threat to the Northern Serotine because much its current distribution is within northern habitats that will be heavily altered by increasing temperatures.

Bibliography. Abe et al. (2005), Ahlén et al. (2009), Artyushin, Bannikova et al. (2009), Artyushin, Kruskop et al. (2018), Artyushin, Lebedev, Bannikova & Kruskop (2012), Benda et al. (2012), Corbet (1978), Coroiu (2016b), Dietz & Kiefer (2016), Duvergé et al. (2000), EkIof et al. (2002), Frafjord (2013), Fukui et al. (2004), Gerell & Rydell (2001), Haupt & Schmidt (2007), Haupt et al. (2006), Hutterer et al. (2005), Jensen et al. (2001), Jére et al. (2018), Jo Yeong-Seok et al. (2018), de Jong (1994), Juste, Benda et al. (2013), Juste, Bilgin et al. (2009), Kawai & Helgen (2011), Keyserling & Blasius, (1839), Lu¢an (2007), Ohdachi et al. (2009), Pacifici et al. (2013), Pavlini¢ & Tvrtkovié (2003), Rydell (1992a, 1993a, 1993b, 1993c, 1998, 1999), Rydell & EkI6f (2003), Rydell et al. (1994), Siivonen & Wermundsen (2008), Simmons (2005), Smith & Xie Yan (2008), Spitzenberger (2002), Tress (1994), Vintulis & Pétersons (2014), Volleth et al. (2001), Yoshiyuki (1989).