Trip reports
Report on Indoor Meeting 8th September 2009 - Bats in Durham
Daubenton's Bat scienceblogs.com
Tuesday, 17 November 2009
The talk entitled: "What's Your Battitude?" covered all aspect of bat life and their conservation.
There are around 1100 different species of bat in the world, forming one of the largest orders of mammals. The majority live in the tropics and sub-tropics and around 17 live in the British Isles.
Bats are not blind but have poor eyesight. Their radar-like powers of echo-location enable them to catch their prey, mainly insects, in the air and to avoid obstacles. Although bats can be heard squeaking in flight they also make a high-pitched sound which humans cannot hear. This sound is reflected from any object - even an insect in the bat's path - it hears the reflected sound and so locates the object. Humans can detect the presence of bats and identify the species with an echo-detector: for example, Pipistrelles usually echo at 45kHz, while the Soprano Pipistrelle echoes at the higher frequency of 55 kHz. If one has an echo at 38kHz, it is a Nathusius Pipistrelle, which was only identified in 1994.
In the North of England, bats live in buildings, castles, churches, and old houses. Bats are heterothermic - their body temperature is not constant and they are dependant on the temperature of their surroundings. Roosts are chosen with great care so as to ensure adequate warmth and a good food supply. They move depending on the season.
Caves are important too but mainly for hibernation as bats require a cold environment from early November to early April.
Bats hunt mostly at dusk and dawn, living mainly on insects.
The largest bat in the world is the Flying Fox with a wingspan of more than a metre. It is a fruit-eating bat, widespread throughout the Indian and Pacific Oceans, which finds its way to food by sight and smell.
The smallest bat is the Bumblebee Bat which is on the list of endangered species. It roosts inside bamboo in the Philippines and Malaysia.
Noel then showed us slides of various bats found locally, and explained their key features.
We learned that the Pipistrelle is the smallest bat, weighing only 4.5g, and the most commonly seen in woodlands, parks and open spaces - easily recognisable by its rather fast and perky flight. It often flies low over ground, twisting and turning as it searches for flying insects, eating an average of 3000 midges a night. It hibernates in hollow trees and buildings.
Interestingly the Long-eared Bat whispers: its ultrasonic noises are so quiet and sensitive that it can tell the difference between an echo from an insect and what it is sitting on. It eats moths and insects.
The Whiskered Bat, recognisable by its shaggy fur, is special in the Durham County, and one of the best areas to see them is in Middleton in Teesdale.
A fascinating account followed of several more bat species found locally, including the Brown Long-eared Bat, Daubenton's Bat (called the 'water bat' because it lives near water), Natterer's Bat, the Noctule Bat (Britain's largest bat weighing in at 20g and feeding on beetles), the comparatively recently identified Soprano Pipistrelle with its distinct smell, Leisler's Bat (a quite rare version of Noctule Bat with bicoloured fur, the most northerly colony of which has been found near Wakefield),and Brandt's Bat, recognisable by its teeth.
Sadly, bats are becoming scarcer due to loss of habitat, disturbance of roosting and hibernating sites and shortage of food.
The Durham Bat Group has established the criteria for saving bats before a planning application is granted, which is now used all over the country: age and size of the property, and distance from water and woodlands.
Noel finished this amazing fact-filled talk by asking members to tell other people about the facts of life of bats and their importance in the environment.
Marie Ollerenshaw