单选题 .  ①The 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 a decrease in the number of gray squirrels, whose population is sensitive to forest fragmentation. ②Red squirrels tend to hoard food in a central location, while gray squirrels are scatter hoarders. ③Burial of nuts by scatter hoarders is highly beneficial for the regeneration of nut-producing trees. ④Red 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. ⑤If red squirrels successfully colonize the fragmented landscapes of Indiana in response to decreasing numbers of gray squirrels, they may not compensate completely for the loss of gray squirrels as seed dispersers.11.  The passage implies that compared with gray squirrels red squirrels ______