The serotine bat (Cnephaeus serotinus), also known as the common serotine bat, big brown bat, or silky bat, is a fairly large Eurasian bat with quite large ears. It has a wingspan of around and often hunts in woodland. It sometimes roosts in buildings, hanging upside down, in small groups or individually. The name serotine is derived from the Latin serotinus, which means 'evening', while the generic name derives from Greek ἔπιεν and οίκος, which means 'house flyer'.
Taxonomy
The following subspecies have been recognised.
- Eptesicus serotinus boscai: southern Iberia and Morocco
- Eptesicus serotinus pashtonus: Pakistan and Afghanistan
- Cnephaeus serotinus serotinus: northern and eastern Europe and western Asia
- Eptesicus serotinus turcomanus: central Asia and Xinjiang
Description
The serotine bat has long fur which on the back is smoky-brown in colour, while the underparts are a paler yellowish-brown, the nose and triangular shaped ears are black, and the membranes of the wings are dark black or brown. The juveniles are darker than the adults. Serotine bats are easy to identify in flight, because its broad wings combined with its slow, highly manoeuvrable, flapping flight interspersed with brief glides is distinctive. The tragus has a relatively thin and pointed shape and is not kidney shaped as in Nyctalus.
Distribution
The serotine bat has a Palaearctic distribution lying between about 58 degrees and 30 degrees from southern Great Britain and Spain in the west, east to along the Himalayas to northeastern India and along the Tian Shan to southern Mongolia and northern China, and south to Turkey and Iran. It has been recorded as a vagrant on Lanzarote in the Canary Islands.
The female bats normally give birth to a single young in late summer, and the baby is occasionally carried by its mother for the first few days. The young bats usually make their first flights at around three weeks old, and at six weeks they can forage for themselves. Breeding colonies usually disperse by early September, although a few bats may use the colony site as a roost until early October. The male bats probably remain solitary or in small groups but are occasionally found with females in spring or autumn. Mating seems to take place in the autumn, but very little is known about the mating behaviour. Both sexes reach sexual maturity at one year old.
Reproduction
In 2023 it was reported that Serotine bat is the first known instance of non-penetrative reproductive sex in mammals, a reason seems to be that the male has a rather large penis which spans about a 22% of his entire body length making penetration difficult so the penis is just held firmly against the vulva. Their form of copulation is unique among mammals, but is more analogous to the cloacal kissing found among birds.
Echolocation
The frequencies used by this bat species for echolocation lie between 25–55 kHz, have most energy at 31 kHz and have an average duration of 8.8 ms.
Conservation
The serotine bat has declined in many areas in its European range. Loss of feeding habitat is thought to have played a part in the decline. In addition, as this bat almost exclusively roosts in buildings, it is highly vulnerable to disturbance from construction work and toxic timber treatments. In the United Kingdom serotine bats benefit from a very comprehensive level of legal protection, as is the case across much of Europe.