Plecotus auritus ≠ The Long-eared bat

 

 

            There are numerous different species of bats known throughout the world which can be categorized into two main suborders: megachiroptera (old world bats) and microchiroptera (old world and new world bats). The Long-eared Bat (Plecotus auritus) is a member of the microchiroptera suborder. Plecotus auritus can be further classified by its kingdom (animalia), phylum (chordate), class (mammalia), order (chiroptera), family (Vespertilionidae), and its genus (Plecotus) (Nowak, 1994).

            Long-eared bats are distributed mostly throughout Europe, but can also be found in Japan and the Himalayas. Plecotus auritus is one of the most common bats found in and around Great Britain and Ireland (Vesey-Fitzgerald, 1949). These bats are found most commonly in buildings, bird boxes (Pauza, 1998), and trees during the summer months, while they tend to be found in caves during the winter months (usually mid October to early April) when they hibernate. When the Plecotus auritus hibernates in caves, it tends to stay near the entrance of the cave rather than deep inside like other species because it comes out of the cave from time to time to get water (Karataş, 2003). Long-eared bats group together in relatively small groups (usually about 10-20, but sometimes more than 50, members). Most of the roosts that P. auritas makes are near to forests and woodsy areas because this species primarily feeds on insects that are on and around trees. This method of hunting is called gleaning. Instead of hunting for insects out in the open using its echolocation, the long-eared bat can stop sending out its echolocation signals, hover momentarily, like a butterfly, and listen for insects moving on the branches and leaves of trees. The bat then grabs the insect off the limb and will sometimes carry it back to a favorite perch or roost to eat. It is fairly easy to spot where these bats usually eat their prey because it leaves a pile of inedible parts, such as wings, below it. Plecotus auritus will also occasionally hunt for prey on or near the ground. This presents a danger for the bat because cats and other ground based predators can easily snatch the bats as they near the ground. Another predator of long-eared bats is owls that attack the bats in mid-flight, while hovering, or while perched on a branch out in the open (Nowak, 1994). These bats are also fairly adept at walking on the ground, as compared to other species of bats, and can even walk up walls (Vesey-Fitzgerald, 1949). Because these bats emerge from the roost mostly after sunset and return shortly before sunrise, they are less susceptible to being attacked by a predator because they are hidden by the darkness of night. Also, these bats have extremely quiet echolocation calls and fly very quietly, making it easier to capture prey and fly near predators without being heard (Nowak, 1994).

            Long-eared bats use echolocation to navigate and sometimes hunt for prey in the darkness. This species of bats has a unique type of echolocation because it is unusually quiet with a very low frequency of about 10-20 kHz and its calls have a very short duration (less than 2 milliseconds). This allows the bats to discriminate very fine details and possibly detect target movement. The only problem is that its calls are just as audible to moths (its primary prey) as calls that are more intense (Altringham, 1996). This is most likely the reason that long-eared bats have the ability to ≥turn off≤ their echolocation to listen for the movements of insects. The batsπ exceedingly large ears allow it to have very sensitive hearing which is why it is able to echolocate at such low frequencies and hear the slightest movements of insects near by. Plecotus auritus is most sensitive to sounds around 10-20 kHz, which is the range of its echolocation and sounds made by the rustling of insects. These bats can hear sounds as quiet as ≠20 dB at this frequency (Altringham, 1996).

            Plecotus auritus has a very distinct body type marked by its very large ears (as the common name suggests), which are almost as long as its body. The head and body length is 45-70 mm, tail length is 35-55 mm, forearm length is 35-52 mm, ear length is up to 40 mm, and the weight of an adult can range from 5-20 grams. The wings of these bats are long and highly pointed, with low wing loading, which allow for hovering and great maneuverability at low speed. The tail is almost totally enclosed within the uropatagium with only the tip slightly extending outward. Long-eared bats are brownish colored on the top and in the facial regions, and paler on the under parts. The fur is long, thick, and silky. The juvenile bats are usually a more grayish hue. When long-eared bats are resting they curl their ears back to look similar to rams horns and when they hibernate, they tuck their ears underneath their wings, leaving only the pointed inner lobe visible. The maternity roosts of long-eared bats are usually occupied from early April to October or later (Nowak, 1994). Many males may be present in the maternity roosts, unlike some species that have a small population of males present. Mating usually takes place in autumn, but the female delays fertilization until early spring and gives birth to a single young usually from June to mid-July. The newborn bats are pink and hairless, with disproportionately large feet that are used to grip onto the motherπs fur. The young is fed solely on its motherπs milk for a period of about three weeks, after which it begins to make its first flights. After about six weeks, the young is able to forage for food by itself. Most females breed in their first year and males are sexually mature at about fifteen months. Plecotus auritus can live up to 30 years, but the average lifespan is seven years for males and sixteen for females (Altringham, 1996).

            Plecotus auritus is very closely related to the very rare Plecotus austriacus, or gray long-eared bat. These two species were considered to be the same until fairly recent because they look exceptionally alike and have similar behaviors (Nowak, 1994). The numbers of long-eared bats has decreased dramatically in recent years all over Europe because of environmental disruptions. This decrease in numbers hasnπt put Plecotus auritus on the endangered species list, but has labeled them vulnerable. The biggest threat to their numbers is the use of toxic chemicals to treat wood used in buildings. This is a problem because the bats roost on the wood in the roofs of buildings and, therefore, breathe in these toxic fumes, which kill them. Another problem is modern agricultural practices that result in the loss of suitable feeding habitats and hollow trees to roost in (Pauza, 1998).

Bibliography

Albayrak, Irfan. The Bats of the Eastern Black Sea Region in Turkey (Mammalia: Chiroptera). Turkish Journal of Zoology, 2003, Vol. 27 Issue 4, p269-274.

Altringham, John D. Bats Biology and Behaviour. Oxford: Oxford University Press, 1996.

Burland, T. M., E. M. Barratt, R. A. Nichols, and P. A. Racey. Mating patterns, relatedness and the basis of natal philopatry in the brown long-eared bat, Plecotus auritus. Molecular Ecology, May2001, Vol. 10 Issue 5, p1309-22.

Karataş, Ahmet, Nuri Yigit, and Ercument Colak. On the Distribution, Taxonomy and Karyology of the Genus Plecotus (Chiropetera: Vespertilionidae) in Turkey. Turkish Journal of Zoology, 2003, Vol. 27 Issue 4, p293-301.

McLean, Jennifer A., and John R. Speakman. Effects of Body Mass and Reproduction on the Basal Metabolic Rate of Brown Long-Eared Bats (Plecotus auritus). Physiological & Biochemical Zoology, Jan/Feb2000, Vol. 73 Issue 1, p112-22.

McLean, J. A. and J. R. Speakman. Morphological changes during postnatal growth and reproduction in the brown long-eared bat Plecotus auritus: implications for wing loading and predicted flight performance. Journal of Natural History, May2000, Vol. 34 Issue 5, p773-792.

Nagorsen, David W., and R. Mark Brigham. Bats of British Colombia. Vancouver, BC: UBC Press, 1993.

Nowak, Ronald M. Walkers Bats of the World. Baltimore: The Johns Hopkins University Press, 1994.

Pauza, N. Bats of Lithuania: distribution, status and protection. Mammal Review, 1998, Vol. 28 Issue 2, p53-69.

Vesey-Fitzgerald, Brian. British Bats. London: Methuen & Co. Ltd., 1949.

 

Matt Willey

February 23, 2004

HONR 278C

Species Account