A plant with seeds that look and smell like antelope droppings to attract dung beetles, which then disperse and bury the seeds, is described in a paper published online this week in Nature Plants. The study suggests that since the seeds are hard and offer no reward to the dung beetles, this represents a rare example of deception in plant seed dispersal.
Examples of flowers, especially orchids, that look like other plants or insects in order to attract animals that will pollinate them are numerous, but whether mimicry is used to help disperse seeds is controversial.
Jeremy Midgley and colleagues investigated whether the nut seeds of Ceratocaryum argenteum - which are larger than those of related species and give off a pungent smell reminiscent of antelope droppings - in the De Hoop Nature Reserve of the southern Cape of South Africa, serve as a disguise to aid their dispersal.
The size and texture of the nuts suggest that they could be collected and cached by small mammals, but no such mammals that display this ’scatterhoarding' behaviour are known in the region and camera traps set up by the researchers showed indigenous rodents ignoring the nuts. Instead they saw dung beetles (Epirinus flagellatus) rolling nuts away and burying them.
The authors analysed the volatile chemicals given off by the seeds and found that their concentration and composition were similar to those emitted from eland and bontebok dung. However, the nuts are too hard for the beetles to eat or lay eggs in. By mimicking antelope dung, C. argenteum may be tricking the dung beetles into planting their seeds without reward.