I am puzzled by brambles, raspberries and blackberries. They have sweet, juicy fruit, presumably so they will be eaten by animals who will spread their seeds. But they also have prickles. What鈥檚 the good of that?
鈥� There is a simple solution to this conundrum of why brambles evolved to disperse their seeds in this way, yet appear to deter access with a barricade of thorns.
As the objective is to spread the seeds far and wide, the plants offer a mass of fruit of just the right size to be eaten by birds and small mammals such as rodents. The animals will eat as much as they can, and when they defecate elsewhere the seeds remain mostly intact and are still viable.
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Meanwhile, the thorns deter access by larger mammals including humans. Their larger appetites might strip a bush bare, and their grinding molars would destroy most of the seeds before digestion, leaving very few to germinate.
Don Trower, Braintree, Essex, UK
鈥� I have always been surprised at how effortlessly birds can fly into patches of brambles without injury. But then, birds鈥� legs are small enough to fit in the gaps between prickles and the prickles are far enough apart that they can be straddled by their feet. The brambles also do not pose a difficulty for the birds in that the fruit is usually high up and on the outer parts of the foliage.
I live in an urban area and the nearest wild bramble is probably a kilometre away, but every year I dig up four or five small brambles in my garden that were 鈥渟own鈥� by birds the previous autumn. This shows that the plants鈥� reproductive strategy is highly effective.
The seeds always seem to germinate beneath my fence on which birds perch, and even the first shoot is thorny and hard to remove without gloves.
I share my garden with dozens of grey squirrels, a red squirrel, a chipmunk, many rabbits, a family of raccoons and a skunk. Yet every time I pull up a small bramble I am surprised to see that not a leaf has been nibbled. Some may think this is luck; I suspect it is all about 鈥済ood design鈥�.
Andrew Carruthers, Beaconsfield, Quebec, Canada
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