The average size of a dingo is increasing, but only in areas where poison-baits are used, a collaborative study between the University of Sydney and UNSW shows.
Dingoes have grown around six to nine per cent bigger over the past 80 years, the research shows—but the growth is only happening in areas where poison baiting is used.
The findings, published in the Biological Journal of the Linnean Society, compared the sizes of dingoes that lived in three baited regions (Kalgoorlie, Pilbara and pastoral South Australia), with those from an unbaited region that stretched from the Northern Territory to South Australia.
The scientists measured the skull size—which is a marker of animal size—of nearly 600 dingo specimens originating from the sites. The skulls from the baited regions grew by about four millimetres since poison baiting was introduced. This equates to roughly a kilogram in body mass.
While both male and female dingoes grew, female dingoes had the biggest growth spurt: their skulls increased by 4.5 millimetres, which is almost nine per cent body mass. Male skulls grew by 3.6 millimetres, or six per cent body mass.
The question is: why are dingoes in poison-baited areas growing?
“The most likely theory is that dingoes who survive baiting campaigns have less competition for food,” co-author Associate Professor Mathew Crowther said.
He explains that dingoes’ primary prey, kangaroos, have been shown to increase in numbers when dingo populations are suppressed.
“With more food in abundance, dingoes’ physical growth is less restricted.”