解析库 > 阅读经典300篇
The North American red squirrel has expanded its range into Indiana in conjunction with an increase in the fragmentation of forests due to agriculture and with d crease in the number of gray squirrels, whose population is sensitive to forest fragmentation. Red squirrels tend to hoard food in a central location, while gray squirrels are scatter hoarders. Burial of nuts by scatter hoarders is highly beneficial for the regeneration of nut-producing trees. Red squirrels would have to collect 1,000 walnuts to achieve the same germination success that results from the handling of 150 walnuts by gray squirrels. If red squirrels successfully colonize the fragmented landscapes of Indian in response to decreasing numbers of gray squirrels, they may not compensate completely for the loss of gray squirrels as seed dispersers.