Quokka 'pellets' best determiner of population abundance

June 16, 2014 by Rogini Moorthi
Estimating populations: Miss Bain faecal pellets can best indicate old and new quokka activity in the area. Credit: Drew Bandy

Resesarchers have put a method of estimating animal population size to the test—and found counting a species' faecal matter is the most accurate way to sum up their abundance quickly—at least with quokkas.

The study investigated the accuracy of the Liddelow rapid survey technique, an existing method that has been widely adopted by land managers, to estimate the population of quokkas (Setonix brachyurus) throughout the south-west of WA.

Co-author and UWA PhD student Karlene Bain says quokkas are a threatened species in the southern forests and to manage them effectively, an understanding of their abundance and occupancy is fundamental.

"The Liddlelow rapid survey technique of providing a qualitative measure of relative abundance by assessing indicators of activity such as faecal , runnels, tracks and sightings is very subjective," she says.

"The approach is potentially providing a false picture of the conservation status of the species as it tends to overestimate the abundance of quokkas due to its inability to differentiate between old and new activity."

"As quokkas are quite mobile within the landscape of the southern forests, counting all of the faecal pellet groups including all of the old ones that have accumulated over time could result in an overestimation of the species."

"Furthermore, if the quokkas are moving between habitats, land mangers may end up with an indication that there are a lot more habitats occupied than what there actually are."

Instead, the researchers attempted to refine the Liddlelow rapid survey back to a quantitative method by testing individual components of the technique such as the numbers of runnels, tracks, and faecal pellet groups at 12 sites between Manjimup and Walpole.

Faecal pellet counts correlated very strongly to the population abundance of quokkas and performed better than the composite Liddlelow technique because runnels, tracks and sightings generated unreliable estimates.

Miss Bain says faecal pellets were the only measure that could be used to differentiate between old and new activity.

"In order to adopt the faecal pellet method, it is critical for observers who are undertaking the study to have some training so they can identify fresh from older pellets as well as differentiate faecal pellets of quokka from those of the western brush wallaby."

Miss Bane says other factors could affect the assessment of faecal pellets, such as moisture in the landscape, which tends to make pellets look fresher than they are.

"In order to avoid variation in the detection probability of faecal pellets, surveys should be undertaken at the same time of the year with the same amount of moisture in the landscape," she says.

Explore further: Under the microscope #13

More information: Bain, Karlene, Wayne, Adrian, and Bencini, Roberta (2014) "Overcoming the challenges of measuring the abundance of a cryptic macropod: is a qualitative approach good enough?" Wildlife Research 41, 84–93. dx.doi.org/10.1071/WR14065

Related Stories

Under the microscope #13

March 2, 2012

Matthew Kuo tells us how tiny worm faecal pellets affect how oil pipelines sit on the seabed.

Scientists confirm worms are eating slug bait

May 20, 2014

Nocturnal monitoring by U.S. Department of Agriculture (USDA) scientists has confirmed that voracious worms in the Pacific Northwest are behind the disappearance of field pesticides used to control equally voracious slugs. ...

Recommended for you

How the finch changes its tune

August 3, 2015

Like top musicians, songbirds train from a young age to weed out errors and trim variability from their songs, ultimately becoming consistent and reliable performers. But as with human musicians, even the best are not machines. ...

4 million years at Africa's salad bar

August 3, 2015

As grasses grew more common in Africa, most major mammal groups tried grazing on them at times during the past 4 million years, but some of the animals went extinct or switched back to browsing on trees and shrubs, according ...

A look at living cells down to individual molecules

August 3, 2015

EPFL scientists have been able to produce footage of the evolution of living cells at a nanoscale resolution by combining atomic force microscopy and an a super resolution optical imaging system that follows molecules that ...

New lizard named after Sir David Attenborough

August 3, 2015

A research team led by Dr Martin Whiting from the Department of Biological Sciences recently discovered a beautifully coloured new species of flat lizard, which they have named Platysaurus attenboroughi, after Sir David Attenborough.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.