Behaviour tactics in overwintering Eurasian red squirrel in Liangshui Nature Reserve,China
RONG Ke,ZONG Cheng,MA Jianzhang
2009, 29(2):
142-151.
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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 temperature. 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 τ 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 accompanied 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 minor 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,x2 = 5.65,P = 0. 0594,mid winter,Kruskal-Wallis test;df = 2,x2 = 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;x2 = 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; third area n = 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.
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