Red squirrels start planning for their offspring before they are even conceived, Canadian researchers have shown. They do this by creating additional caches of food which are bequeathed to the young when they are born.
Kangaroo rats and ground squirrels are known to give up burrows to their children. But, 鈥渢his study is the first to show that mothers 鈥榯ake up a loan鈥� to donate essential resources to their offspring,鈥� comments zoologist Xavier Lambin of the University of Aberdeen.
Stan Boutin of the University of Alberta in Edmonton and his colleagues studied the behaviour of red squirrels in the pine forests of Central Alberta. They wanted to explain why the animals acquire and defend more resources than they need for their own use.
Advertisement
The researchers studied eight 鈥渆xperienced鈥� females, which had previously produced young, and eight 鈥渋nexperienced鈥� females that had yet to bear offspring.
They found that seven females, only one of which was inexperienced, acquired additional food caches of pine cones called middens. 鈥淭he experienced females know for sure that they will conceive another litter the following year,鈥� says Boutin.
Normally such parental behaviour is linked to hormonal changes, mating benefits or the presence of offspring. 鈥淣one of those exists when these squirrels are acquiring these second middens,鈥� says Boutin. 鈥淭his is a parental behaviour that takes place some four to six months before the youngsters are conceived.鈥�
Boutin鈥檚 team found no evidence that the additional middens benefited the females directly. There was no change in weight among females that acquired a second food cache, no delay in their dates of conception and no change in the size of their litter.
This suggests that the second midden benefits the offspring and not the mothers, he says. In each case where the mother squirrel bequeathed the midden to her young, Boutin鈥檚 team found that one year later one of the litter was still living there.
But, says Boutin, their research with red squirrels suggests that there must be other costs associated with maintaining two middens. 鈥淚t鈥檚 not a free ride to acquire an additional midden. They have to change their territorial boundaries and any boundary change requires a significant amount of jostling with other squirrels.鈥�
Source: Royal Society Proceedings B (vol 267, p 2081)