Age Determination of Goitred Gazelle (Gazella subgutturosa)

Goitred Gazelle (Gazella subgutturosa) is one of precious ungulate of China.Fewer study were reported on its resource and biology.This paper presents that the methods of two sides grinding-segmenting and etching were used to determine the relation between the growth layers and convex ridges of horn sheath of Goitred Gazelle.There were seven samples of skull of Goitred Gazelle which were obtained in 1990s from Inner Mongolia Autonomous Region.The method was tested and verified by the cementum annulation appeared in the section of the first lower incisor (I1).The sample (No.90001) showed that all growth layers related to the rings which encircling the horn sheath.No rings appeared in the horn sheath of the first growth layer.The first ring was formed in its second winter,and one ring was formed in every winter afterwards.No convex ridge appeared on horn within its first age.From its 2 to 3 years old,there were 4-5 convex ridges within every one year.After 4 years old,there were 2-3 convex ridges within every one year.The true age annulations were the deeper rings with rough edges appeared on horn sheath,differed from the convex ridges obviously.There were 5 age rings can be seen (Fig.1).On the other hand,these age annulations appeared in the vertical sections of tooth (Fig.2).On the vertical sections of tooth,a brown thin line was formed in its first year old;a wide line that pigment granule becomes deeper,appeared in its second year old;the third and the fifth year old was the same as the second year old;the fourth year old was the same as the first year old.This sample was obtained in its fifth winter.According the above,it can be drown that the numbers of convex ridges of horn did not indicate the age,the true age rings was that there was an unobvious rough ring behind the convex ridge.This result can be used in the field research of ecology and the investigation of the social structure.