Australian researchers have made an odd discovery: Dingoes are getting bigger—but only in areas where long-term poison campaigns against them have been in place. It seems the bait traps have the unintended consequence of making the surviving animals larger, reports Science Daily. "The most likely theory is that dingoes who survive baiting campaigns have less competition for food," says the University of Sydney's Mathew Crowther, co-author of the study in the Biological Journal of the Linnean Society. Another factor is that smaller dingoes are more likely to succumb to the poison, which leaves the bigger dingoes to thrive. A logical conclusion might be to increase the dose of pesticides, but another researcher, Michael Letnic, says that would probably just start another cycle and result in yet larger dingoes.
In the study, the scientists examined the skulls of hundreds of dingoes from three regions where poison bait traps have been laid for decades and compared them to skulls from a poison-free region, reports Australia's ABC News. They found that the skulls in the poison regions have grown roughly 4mm over the last 80 years, which translates to an increase in body mass of between 6% and 9%. Females had the bigger boost. By contrast, the skulls of dingoes in the unbaited region didn't change much at all over that same span. While previous studies have shown that pesticide causes changes in insects' physiology, this is thought to be one of the first studies to show the same concept in vertebrate animals. (Read more dingo stories.)