Feeding rats a varied diet early in life could help implement effective control programs.

New research suggests that changing rats’ eating habits before introducing food baits could make the baits more effective.

NSW Department of Primary Industries (DPI) Vertebrate Pest Unit leader, Dr Glen Saunders, said rats are notoriously difficult to control and that much research to date emphasised changing the type or dose of poison or food bait, rather than altering the rats’ behaviour.

A study published in the May issue of the journal Applied Animal Behaviour Science examined the effect of rats’ diets on a phenomenon known as conditioned taste aversion.

More commonly known as “bait shyness”, conditioned taste aversion occurs when an animal associates the taste of a food with illness, and then chooses to avoid consuming that food.

Dr Saunders said the study found that bait shyness in rats is linked to an innate trait – a tendency to dislike anything new.

“All rodents are neophobic, which means they have a dread or hatred of novelty,” he said.

Dr Saunders said rats on a single food diet who feel ill after eating a new food appear to develop a more conservative strategy to new food.

“Those rats raised on one food source will, on the basis of one bad experience with a new food, develop a more persistent aversion to that particular food.

“Meanwhile, juvenile wild rats exposed to a variety of novel foods will be less suspicious.”

The study compared rats raised on laboratory animal pellets with rats fed a variety of seven foods including raisins, peanuts, maize, quail eggs and maggots.

Dr Saunders said the study suggested that rats that had a varied diet early in life, and for whom new foods had been a positive experience, appear more willing to associate all novel foods with safety.

He said that the finding may be of particular benefit for environmental control programs, for instance in protecting eggs from rat predation.

“The effectiveness of food baits might be increased if rats are given different types of food before being baited.

“This opens the door to using alternative or perhaps less poisons,” Dr Saunders said.

NSW DPI invests resources into researching practical methods for controlling a range of pest animals and this project was undertaken in collaboration with scientists in the United Kingdom, where a great deal of rodent research is undertaken.

The research was funded by the Invasive Animals CRC (formerly Pest Animal Co-operative Research Centre).

Contact: Glen Saunders, Orange, (02) 6391 3890
glen.saunders@dpi.nsw.gov.au