This dunnart has competition for food… so it just eats the competition

By AG STAFF 9 May 2018
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A new study may have solved the mystery of why lesser hairy-footed dunnarts prey on wolf spiders.

EXACTLY WHY THE lesser hairy-footed dunnart (Sminthopsis youngsoni), an insectivore native to arid regions of central and Western Australia, preys on wolf spiders has remained a mystery.

That was until University of Sydney biologist Tamara Potter decided to get to the bottom of the bizarre behaviour back in 2017.

Her research, published in the Royal Society earlier this month, found that the dunnarts and wolf spiders eat similar prey, which may suggest that the dunnarts are hunting the spider to lower the competition for food.

Also known as intraguild predation, this behaviour commonly occurs among animals that use the same resoruces but are not necessarily related.

“Because these animals are eating the same things, they can often compete for food. This is where the predation aspect comes in,” Tamara told Australian Geographic.

“One species, often larger than the other, will kill and sometimes eat a competitor species to reduce competition over food.

“A classic examples are wolves killing coyotes, lions killing cheetahs, and an Australian example is dingoes killing foxes to reduce competition over small mammals.”

wolf spider

A Wolf spider, Simpson Desert south-west Queensland. (Image Credit: Tamara Potter)

By following dunnarts throughout the Simpson Desert and observing how much their diets overlapped with the wolf spider’s, Tamara discovered that the two share very similar meals.

Both the animals are nocturnal, which means that it was likely they hunted for food at the same time, within a short distance of each other as well.

This is the first time intraguild predation has been seen between animals as different as a mammal and a spider.

“Most examples are from animals that are both mammals, both fish, insects or even reptiles,” Tamara said.

“There’s only one other study I know that has suggested intraguild predation between different animals and that was between a skink and a wolf spider.

“Now, we have further insight into how complex the dynamics between different animals are, and how little we still know about some species.”

The complex desert food web

According to Tamara, the results from the study is yet another example of the complex interactions between desert animals.

“The dynamics are very complex and we know very little about them. The interaction between the spiders and dunnarts may weaken or strengthen under different conditions depending how much food is available,” she said.

“As my study was only conducted over a year we don’t know how this selective predation might change through time and how his might impact on the dunnart and spider populations.”

Tamara said that the next step will specifically look at how dunnarts selectively eating wolf spiders affect populations of other animals.