These insects can survive being eaten by a bird. An investigation by researchers at Kobe University has revealed that some insect eggs can still hatch after being swallowed by a bird. The eggs of stick insects, for example, are hard enough to pass through a bird without being digested.
Because stick insects cannot travel very far on their own, being eaten by birds may actually facilitate the expansion of their habitats.
In order for insects to use birds as a means of distributing their eggs over long distances, the eggs must be resilient enough to pass through the digestive tract unharmed. In addition, the offspring must be the type that can fend for themselves and the eggs must be viable without fertilization. Stick insects meet all of these requirements.
For the investigation, the researchers fed birds the eggs of three species of stick insects and found that up to 20 percent of the eggs were safely excreted. From one species, eggs retrieved from the bird’s excrement successfully hatched and the insects survived.
The stomachs of adult female stick insects are always filled with eggs, and this may be a way for them to expand their own distribution – considering that the stick insects are frequently eaten by birds.
Plants have developed strategies to distribute their seeds, and the most common is seed dispersal by animals. Some plants produce eye-catching fruit that will appeal to animals, who eat the fruits and excrete the seeds whole.
Stick insects blend into their environments and do not actively seek the attention of predators, but their consumption by birds still assists in their distribution.
“Our next step is analyzing the genetic structure of stick insects,” said study lead author Professor Kenji Suetsugu. “Based on this we’d like to investigate whether similar genetic structure of stick insects can be found along birds’ migration flight paths, and whether there are genetic similarities between stick insects and plants that rely on birds for seed distribution.”
The study is published in the journal Ecology.