Motherhood, a heavy load to bear

By Kirstin Brink, EEB.

Mothers make huge sacrifices for their kids. But some mothers, such as those among black-horned tree crickets, really go out on a limb for their young. Laden with a large number of eggs that prevent them from jumping to safety, they face paralysis and certain death at the jaws of predators. A recent study published in PLoS ONE by ecologist Kyla Ercit and colleagues at the University of Toronto made this discovery when they noticed that wasps preferred to hunt female over male crickets.

Sphecid wasps capture their cricket prey, paralyse it, and return to their nests to feed their larvae. Ercit examined the crickets that were brought back to the nests, and found that females carrying a large number of eggs were captured more often than those with only a few. When the team simulated a predator attack, they found that irrespective of body size or leg size, females with a large number of eggs were unable to jump as far as those without eggs. They suspect that this means that egg-laden females are more likely to be eaten.

Their findings highlight the delicate balance between reproduction and survival faced by these cricket mothers. Producing more eggs generally means producing more offspring, but also potentially missing out on future reproduction because they get eaten. The authors suspect that the mothers must use survival strategies, such as camouflage or reducing their movement, to hide from predators when pregnant.