Autumn 2001
The Effects of History and Habitat on the
Social and Genetic Structure of the
Southern Hairy-nosed Wombat
(Lasiorhinus latifrons)

 

by

Faith Walker

Introduction

 

This article was originally written for The Friends of Brookfield Newsletter and we would like to offer them our acknowledgements and wish good luck in their work.

 

The author, Faith Walker, has kindly allowed it to be included in this issue of “Keeping Marsupials”.   

 

Faith is a young lady from Northern Arizona in the United States taking a few years away from home to study for a Ph.D. in Conservation Genetics at Monash University.    Her work enables her to tiptoe across Australia chasing after the Hairy-nosed Wombat and even though she has also studied the Mojave Desert Tortoise, Mexican Spotted Owl, Gunnison's Prairie Dog and Kenya's de Brazza's monkey, she still finds marsupials to be among the most captivating creatures she has encountered.

 

Please click on thumbnails to enlarge

I had the immense pleasure of meeting the Friends of Brookfield at the Fall (Autumn to Ozzies Ed) 2000 kangaroo count.    For the past year I have been stealing hair of the wombats at Brookfield Conservation Park by suspending double-sided sticky tape across burrow entrances.    As wombats exit or enter their burrows they kindly donate hair, from which I extract DNA and determine unique DNA profiles (including gender) for individuals (this is the same methodology that is now used in forensics).    From these data I get estimates of relatetedness between individuals, measure of dispersal, likelihood of parentage, and patterns of burrow use.

 

There are two sets of warrens I sample at Brookfield.    The largest consists of 20 warrens, for which I tape all burrows for seven days each time, giving the inhabitants 1,190 opportunities for hair donation.    I have sampled four times so far, in September 1999, March and October 2000, and April 2001.   In the largest warren set I found a total of 24 animals; sixteen of these were present during the first two sampling periods.    Eleven are males; eleven are females and two remaining genderless because I did not secure enough DNA.    I scored these individuals for 17 loci, which means that I have great statistical power for relatedness tests and dispersal estimates.    Males have higher assignment and relatedness values than do females, indicating that females are dispersing further than males.    This means that males tend to remain near the place of their birth and are hence more related to one another than they are to females or females are to each other.    This is unusual among mammals, and consistent with findings for their close relative, the Northern Hairy-nosed Wombat (Lasiorhinus krefftii).    Currently I am running parentage analysis and examining patterns of burrow use.
 

I am doing all this because I’m interested in illuminating the social system of the Southern Hairy-nosed Wombat, and determining how ecology and habitat fragmentation affect their genetic and social systems.    Brookfield is the site at which I am first characterising their social system.    I’ll continue to sample at Brookfield Conservation Park throughout my study to determine how processes change with time.    Meanwhile, I have produced GIS (Geographic Information System ) generated map overlays of soil types and warren distribution from data of DEHAA (Department of Heritage and Aboriginal Affairs), PIRSA and Planning SA which allows me to select appropriate study sites across the species’ range for addressing ecological and habitat fragmentation queries.
 

This leads to the larger picture, which is, that we really know very little about the mechanisms that cause extinction.    It’s to shed light on this, that Dr. Andrea Taylor, my supervisor and I, have been funded by the National Geographic Society.    It’s well known that human induced habitat fragmentation causes a decline in both species richness and abundance.    What isn’t clear, and what needs to be elucidated if we are to conserve native wildlife, is precisely how this occurs.    Both demographic and genetic factors are likely to be involved in observed local extinctions, and I hypothesize that this may occur via altered dispersal patterns and social organization resulting from fragmentation of habitat.    Both, however, have always been difficult to measure using traditional ecological tools.    Traditional tools are also quite invasive, often entailing radio tagging or permanent marking system.    With the development of microsatellites, individuals can be identified and their relatedness to each other estimated, an approach that can be much more successful, and less disruptive.    In addition, by sequencing the flanking regions of microsatellites, areas with very slow mutation rates, I’ll be able to look at the longer-term question of how fragmented Southern Hairy-nosed Wombats were prior to European settlement.
 

This is the first study to comprehensively analyse population processes by remote collection of hair.    The technique I’m using will become more common because microsatellite genotyping and statistical programs for analysis have only recently come of age.
 

It’s quite an honour to work on the wombats of Brookfield.    If you are out there and see a red Toyota Forerunner with the word WOMBATMOBILE on the side, that’s me.    Let’s have tea and chat about these amazing creatures called wombats, which incidentally aren’t bald yet!

Faith Walker

Dept of Biological Sciences

Monash University

Clayton Victoria 3800

Email faith.walker@sci.monash.edu.

 

 
 
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