Abstract: The burrow index (number of voles／number of burrows) is an index of relative density for small burrowing rodents．Using burrow index，it is possible to transfer this relative density to absolute one．But，there were three burrow indexes (K₁=N_v/N_b ；K₂ =N_vc／N_bc；K3=N_v/N_d，where N_v =the number of voles in the sample;N_b =the number of by burrows in the same sample;N_vc= the number of voles in the colony;N_bc= the number of burrows in the same colony ;N_d=the number of opened burrows in the sample)used by different anthers．In orderto compare the validity of these indexes，a field investigation on relation of Brand's Voles (M icrotus brandti) with their burrows and their seasons1 changes had conducted from April to October and December in 1987．It involved the density cf voles，density and spatiaI distribution of burrows andpercentof opened burrows after covering．The burrows were divided into different categories：(1) new dug，disappeared and unchanged burrows, (2)burrows on mound and outside mound．
The results showed that there was a single peak pattern in the density of voles and their burrows from spring to fal1．The seasonal chhanges ofnew dug burrows were positively correlated with the density of voles， so did the burrows onthe mounds． The percent of opened burrows after covering (r)increaed with time (days)．It approached to the maximum on the third day．r′″，the third day's,was 4O～50% in spring，over 80% in summer and 70～80%in fal1．But the number of opened burrows per vole dropped from spring to summer and then went up from summer to fal1．Among three burrow indexes，K₃(max )was the ideal one，but K₁ was the most useful one in practice．K₁ had significantseasonal changes and equaled to 0.05995 in spring，0.2336 in summer and 0.141in fall.

Key words: Microtus brandti, percent of opened burrows, burrow index, seasonal changes

摘要： 布氏田鼠种群和鼠洞数量均呈单峰型季节动态，新洞口和鼠丘上洞口的季节动态与鼠的季节动态存在—种正相关关系。盗洞率随堵洞后记录时间的推延而增加，并于堵洞后3天趋于最大值。盗洞率(r″′ )春季为40～50%；夏季为8O%以上；秋季为70～80% 。但每鼠盗洞数春季最高，夏季下降到最低，秋季又有所回升。样方内鼠只数／真实盗洞率(K_3max )比较理想，鼠只数／堵洞数(K₁ )比较实用。洞口系数K₁具有显著性季节变化，春季为口0.05995，夏季为O.2336，秋季为0.141。

关键词: 布氏田鼠, 盗洞率, 洞口系数, 季节动态