凉水自然保护区松鼠的越冬行为策略

Behaviour tactics in overwintering Eurasian red squirrel in Liangshui Nature Reserve,China

在2006年冬季预观察的基础上,于2007年10月31日至2008年3月25日在40hm2范围内使用无线电颈圈和彩色塑料颈圈标记8只松鼠。结合无线电追踪技术和雪地痕迹技术,采用目标取样法对凉水自然保护区冬季松鼠行为进行了连续21周的定位观察,以研究松鼠行为节律、空间行为和重取行为对冬季低温条件的响应。结果表明,松鼠冬季的活动节律为单峰型,随着气温的下降显著延后出巢时间(Kendallτtest;n=21,r=-0.92,τ=-0.86,P<0.0001),缩短活动时长(Kendallτtest;n=21,r=0.80,τ=0.68,P<0.0001)。松鼠冬季家域近似椭圆形(面积2.46±0.09hm2),未见个体间家域重叠。秋季松鼠将红松种子分散贮藏于整个家域范围内,但重取行为相对集中于几个主要区域(重取区)。依据巢和重取区的位置特征及其利用率可将家域划分为3个部分:主区位于家域的中段,辅区靠近红松母树林,次辅区位于家域远离红松母树林一侧。贮藏的红松种子是松鼠冬季唯一的食物来源。在冬季的不同阶段,松鼠对不同重取区的利用率显著不同(初冬,Kruskal-Wallistest;df=2,x2=5.65,P=0.0594;隆冬,Kruskal-Wallistest;df=2,x2=14.24,P=0.0008;晚冬,One-WayANOVATest,df=2,18,F=7.00,P=0.0056),位于主区(初冬利用率37.8±7.7%,隆冬利用率80.5±9.2%,晚冬利用率40.5±2.7%)和辅区(初冬利用率41.8±5.9%,隆冬利用率14.8±9.2%,晚冬利用率37.8±4.9%)的重取区是松鼠的主要重取区。随着时间推移空取率显著提高(Kruskal-Wallistest;df=2,x2=16.60,P=0.0002)的现象提示松鼠很可能依靠空间记忆取回贮藏的食物。轮换利用多个巢(6±1)有助于降低松鼠被天敌捕食的风险。这些巢都分布在重取区附近,巢的利用与重取区的利用显著相关(Kendallτtest;主区:n=217,r=0.79,τ=0.6256,P=0.0003;辅区:n=171,r=0.67,τ=0.6186,P=0.0006;次辅区:n=88,r=0.74,τ=0.6565,P=0.0006),松鼠通常取食后即直接进入就近的巢过夜,有助于松鼠减少能量损耗。多域集中重取及相应的巢轮换策略是松鼠对冬季低温环境及天敌捕食压力的综合响应。

Low temperature is the main limiting factor affecting the overwintering of animals. Present behavior research of red squirrels （Sciurus vulgaris） in winter lacks direct observations. We made a focal observation on red squirrels in broadleaved Korean pine forests in Liangshui nature reserve of China, since October 31st, 2007 to March 25th, 2008. Technology of radio telemetry and snow trace was used to detect the overwintering behaviors of red squirrels responded to the low tem- perature. Eight red squirrels were captured then marked by radio collar and colored plastic collar. The activity rhythm of red squirrels was a unimodal pattern in winter. The delay of outgo time （ Kendall test; n = 21, r = - 0. 92, τ = - 0. 86, P 〈 0. 0001 ） and decrease of activity while （ Kendall τ test; n = 21, r =0. 80, τ =0. 68, P 〈0. 0001 ） was notable accompa- nied with the temperature decline. The home range of red squirrels was clearly elliptical （2.46 ±0. 09 ha） without overlaps. Red squirrels hoarded the pine seeds all over the home rage as the only food in winter. The retrieving behavior occurred in three retrieved-cache areas in the home range. The home range can be divided into three parts according to the position and use rate of the nests and retrieved-cache areas, i. e. the major area, in mid-segment of the home range ; the mi- nor area, near to the original broad-leaved Korean pine forests and the third area, far from the original broad-leaved Korean pine forests in the home range. The use ratesamong retrieved-caches areas were significantly different during winter （early winter, Kruskal-Wallis test; df= 2, χ2 = 5.65, P = 0. 0594, mid winter, Kruskal-Wallis test; df= 2, χ2 = 14. 24, P = 0. 0008 ; late winter, One-Way ANOVA Test, df= 2, 18, F = 7.00, P = 0. 0056）. The retrieving-caches areas in the major area （use rate in early winter, 37.8 ±7.7% ; use rate in mid winter 80.5±9. 2% ; use rate in late winter 40. 5 ±2. 7% ） and minor area （use rate in early winter, 41.8 ±5.9% ; use rate in mid winter 14. 8 ±9. 2% ; use rate in late winter 37. 8 ± 4.9% ） were the main retrieving-caches areas. The rate of empty retrieve significantly increased （ Kruskal-Wallis test; df = 2; χ2 = 16. 60; P = 0. 0002） as time went deep into winter. We supposed that the retrieving behavior reminded red squirrels of the cached-seeds by spatial memory. Red squirrels used nests （6 ± 1 ） dispersed near to the retrieved-cashes areas by turns to avoid capture of predators. More nests （6 ±1 ） near the caches-areas were alternatively used by squirrels. The use of nests remarkably related with the use of retrieving-caches areas （ Kendall τ test; the major area n =217, r = 0. 79, τ =0. 6256, P= 0.0003; minor area n =171, r = 0.67,τ =0.6186, P = 0.0006; thirdarean=88, r = 0.74, τ =0.6565, P= 0. 0006）. Red squirrels usually stayed over in the nearest nest after retrieving. Our research suggested that multi-dense area retrieving and the relevant tactics of nests alternation were integrated response to low temperature and predators in winter.