Vangmethodes en verzamelen van echolocatiegeluid van Microchiroptera in tropisch regenwoud
Lieshout, S. van
Hogeschool InHolland Delft / Adviesbureau E.C.O. Logisch
Inventorying Microchiroptera (bats) by means of ultrasonic sounds is a commonly accepted method in Europe and America. Microchiroptera use these ultrasonic sounds for hunting and to orient itself in obscurity. By means of a bat detector, the ultrasonic sounds which bats expel become reduced to audible tones for people. By analyzing the consonance, the tempo and the frequency (KHz) one can stipulate which species it concerns and (in some cases) which behavior this individual shows. For most of the Central-African species these variables are not known. The overall objective of the project is making Central-African bats identifiable by their ultrasonic sounds. The method which used for this is included two important components. First of all one must catch bats and determine the individuals at species level. Moreover, sound prerecordings of the ultrasonic sounds during undisturbed natural behavior must be made.
This component of the project includes mainly the methods for catching Microchiroptera and collecting the ultrasonic calls. The possible and suitable methods of capture have been joined and described from a large number of scientific publications. The aptitude of the methods has been reviewed on the surroundings of the capturing stage and the different habitats in which one will catch. The most used methods to capture bats are mist nets and harp falls. Mist nets are nets with a very thin wire and thereby badly visible. These are stretched between some piles concerning a suitable location such as a bunch path, over a small stream or in front of the opening of a cave. They are very useful, especially for surveying large surfaces. Harp falls can be established at the same places, but cover however a generally smaller surface. These methods have been selected with certainty to be used in Central-Africa. Beside these general methods for catching bats, alternative manners have been selected. One method has in particular a good potential, the tunneltrap. The tunnel trap exists from several netparts which together forms a closable space. The opportunities of a closable space lies in the fact that the bat notices to late that he is included, as a result of which one is nearly certain of capture when a bat enters the fall. This trap is however not commercially available and must be made by one himself.
This offers, however, the possibility of optimalisation of the fall. Beside these standing traps one will try to catch bats on mobile wise as well. For example with hand nets and capture at the roost, which are being searched for during the day. The measurings of ultrasonic sounds for these roost captures will take place elsewhere under controled circumstances, for example a closed space. Eventually, a first step towards non invasive inventories of Central-African bats is made.