In a twist on using animals as biological control, a method that has not always been well understood and in many cases been an absolute disaster for the environment, scientists have successfully given nature a nudge and taught native predators to actively seek out a new food source they’ve never encountered before.

Unlike humans, most other species don’t tend to vary their diets too much if their necessary resources are available. But now scientists from the School of Life and Environmental Sciences at the University of Sydney, Australia, led by professor Peter Banks, have ‘trained’ native bush rats (Rattus fuscipes) to eat the alien speckled cockroach (Nauphoeta cinerea), a species the rodents have no experience in hunting down and feeding on.

“We wanted to know if we could speed up learning by exposing a free-living native predator to the scent of a novel prey species paired with a reward,” the researchers noted.

While native predators will eventually learn to hunt new prey that shows up in their habitat, it takes time. With time comes the risk that the alien species – one that has crossed into a new environment, often by means of accidental human transport – adapt to their fresh digs and potentially wreak havoc as an established invasive population.

“However, native species can only resist against alien species if they can respond appropriately, which they may not do if they’ve never encountered the invaders before,” the scientists added.

The researchers located 24 wild areas that housed bush rats; 12 would be where the training would take place, while the other 12 would be the non-trained control population of rats.

“At the training sites, we placed a metal tea strainer with the cockroach smell, and three dead cockroaches as a reward,” they explained. “The tea strainer and cockroaches were tethered to a tent peg in the ground so rats couldn’t carry them away.”

It was also important to not risk inadvertently introducing the alien species to this new habitat.

After training, triggering the rats’ hunting mechanism by the olfactory cues, a simulated ‘invasion’ was set up across the 24 sites, with more cockroaches without the scent cues.

With the use of remote cameras, the researchers observed that that predation was 46% more prevalent among the trained animals. All but two cockroaches (of 156 taken) were eaten by the bush rats. Those two were taken by a bird and an antechinus, a small marsupial.

Researchers hope this kind of training can better prepare native animals to adapt to any alien species that may find their way into their territory.

An earlier study saw scientists help another small Australian species, the endangered bettong, sharpen their defensive strategies in the face of alien predation, exposing them to four desexed feral cats in a controlled study.

Fortunately, these approaches are far cry from moves such as the introduction of cane toads to Australia, to protect sugarcane crops from beetles, only to have the hardy, poisonous amphibians spell disaster for many native species. Fortunately, scientists now have a much better understanding of the consequences of introducing alien species to habitats.

The study was published in the journal Biological Conservation.

Source: University of Sydney School of Life and Environmental Sciences via The Conversation