ROE-DEER CENSUS AND POPULATION ANALYSIS 75 



ground. A party of three men go round by car and pull the gate wires which 

 all end at a drive, and the deer which have come to the bait are trapped. 

 Trapping has been carried out at all hours but best results are obtained by 

 closing the gates shortly after dark, which is the time when the deer usually 

 come out of the woods to feed in the fields. A total of 14 traps are used, all 

 placed in one wood, Ringelmosen. Two parties of trappers each attend to 

 seven traps. 



Among the deer trapped two age classes are distinguished: fawns bom 

 during the preceding summer, and old animals. The fawns still possess their 

 milk teeth and have a tripartite third premolar in contrast to the bipartite 

 persistent tooth of animals more than one year old. In order to see the third 

 premolar the mouth must be forced open, and an electric torch and a dentist's 

 mirror must be manipulated skilfully. 



A recurrent problem is the method used for marking the deer so that they 

 are recognizable individually at a considerable distance, and remain dis- 

 tinguishable for several years. After a series of studies on captive deer, we 

 have developed a leather collar studded with plastic buttons of different 

 colours and bearing a copper plate giving a serial number and our address. 

 As a special precaution the deer trapped also receive a metal ear-tag from 

 which we can get all the information needed in the — rare — cases when 

 the collar has been lost. 



We have often been asked if the collar is likely to hamper the deer or even 

 expose them to danger. The answer must be that during the years we have 

 used the method we have not noticed any sign of inconvenience to the more 

 than 200 deer which have been marked: they behave and reproduce normally 

 and seem not to differ in any way from unmarked individuals. 



Trapping takes place in January and February and the trapped animals are 

 released immediately after marking. Many enter the traps again, sometimes 

 on the next day, in which case the collars are read and the animals released. 



During the subsequent months, March, April, and possibly May, one man 

 has the job of combing the woods and their immediate surroundings with 

 binoculars, and noting all the individuals observed. This work also has its 

 problems, since all doubtful records must be excluded. Recording is not 

 equally easy at all times: light colours for example show up better during 

 dusk hours or in dense woodland. If the observer sees a group of, say, five 

 de-er together he must be able to 'read' all five; if that is not possible they 

 should all be disregarded. 



For the observer's use a number of observation posts have been made at 

 strategic points; in addition he stalks the deer creating the least possible 

 amount of disturbance; he takes special precautions to cover the entire 

 woodland and to vary the time of his visit to different parts of the wood; 



