Young red kangaroos grow faster when exposed to dingoes

The dingo barrier fence in Australia – the world’s longest environmental barrier (5,614 km) – was built as an exclusionary measure to control predation of sheep by dingoes. Surprisingly though, a new study led by Flinders University has found that young red kangaroos protected from dingoes by this fence take more time to develop than their counterparts on the other side, who quickly outgrow the risks of becoming a prey for the dingoes. 

The experts also discovered that there are more young and female kangaroos inside the dingo-protected fence, suggesting that this fence has significant impacts on different aspects of the red kangaroo’s life cycle.

“Red kangaroos are one of the dingo’s favorite prey species, so we were not surprised to find fewer of the smaller females and younger animals when there are more dingoes around,” said study senior author Vera Weisbecker, an associate professor of Morphological Evolution at Flinders. “However, we did not expect to see that, on average, young animals inside the fence were lighter and smaller than those outside the fence.”

Differences in growth rates

According to the researchers, the faster growth rate of red kangaroos outside of the fence could be a defensive adaptation for survival against dingoes which usually prefer to prey upon smaller red kangaroos. “They certainly appear to escape the dangerous weight range more quickly than their protected cousins inside the fence,” said lead author Rex Mitchell, a research associate in Vertebrate Feeding Biomechanics at Flinders.

To ensure that the difference in growth rate was not simply related to higher food availability outside the fence, the scientists used satellite-based analyses to assess the impact of vegetation cover on these surprising differences.

“Counter-intuitively, we found less vegetation inside than outside the fence in the year of sampling,” reported co-author Frédérik Saltré, a research fellow in Ecology at Flinders. “There might, in fact, have been more food available to the slower-growing kangaroos inside the fence, meaning they were really taking their time to grow up.”

“Slower growth inside the fence could have some advantages for the animals,” added co-author Corey Bradshaw, an expert in Global Ecology at the same university. “Having to put the whole body’s resources into growth, particularly when food is scarce, can mean that other areas of the body are compromised—an animal might be in poorer health or have fewer offspring, for example.”

More research is needed

According to Mitchell, another surprising finding was that the dingo-proof fence could affect kangaroo growth patterns in such a short period of time (about 17 kangaroo generations). Thus, further research is needed to clarify to what extent the dingo-proof fence affects kangaroos and other species that dingoes prey upon.

“We need to know if this pattern is repeated over more years, and whether it is heritable or just a short-term reaction to exposure to dingoes. We also need to fine-tune our understanding of the vegetation, because vegetation cover might not mean that all the vegetation could be eaten by kangaroos,” Weisbecker said.

“The fence is a unique Australian megastructure, and a huge predator-prey experiment. Examining how the fence modifies our native wildlife is important in the continuing debate over the efficiency and merits of the dingo-proof fence, not only relative to the dingo itself, but also to the invasive species such as rabbits that the dingo eats,” she concluded.

The study is published in the Journal of Mammalogy.

More about red kangaroos 

The red kangaroo (Macropus rufus) is the largest of all kangaroo species and the largest terrestrial mammal native to Australia. It is known for its iconic hopping locomotion, large size, powerful hind legs, large feet, and distinctive red fur, from which it gets its name.

Key characteristics and facts

Physical Description

Adult red kangaroos can stand approximately 5-6 feet tall, with a length of 7-10 feet including the tail. Males can weigh as much as 200 pounds, while females are generally smaller. They are characterized by their reddish-brown fur, with the males having more pronounced red coloring compared to the often bluish-grey females.

Habitat and Distribution

Red kangaroos inhabit most of the dry and arid regions of Australia. Their range extends across most of the continent, excluding the coastal areas and northern rainforests.

Diet

They are primarily herbivores, with a diet that consists mainly of grasses and other vegetation. They can survive long periods without water by obtaining moisture from the plants they eat.

Social Behavior

Red kangaroos are generally social animals. They often live and travel in groups known as mobs, which can consist of anywhere from two to 100 individuals. Males often engage in boxing matches to establish dominance and for mating rights.

Reproduction

The reproductive cycle of the red kangaroo is fascinating. Females have the ability to delay the development of their embryo in a process known as embryonic diapause. This allows them to time the birth of their offspring to favorable environmental conditions.

Locomotion

The hopping movement of kangaroos is unique and highly efficient, especially for traveling at high speed over large distances in their arid habitat. They use their muscular tail for balance when hopping, and as a fifth limb when moving slowly.

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By Andrei Ionescu, Earth.com Staff Writer

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