The wombats didn’t start getting sick until after Australian ranchers moved their livestock off the plot of land that the livestock and wombats had shared, after the foul-tasting weeds took over, pushing aside the tasty native grasses. The older wombats knew that something had changed, but the younger generation ate whatever was available, and they paid for it with liver damage, hair loss, and sun-blistered skin.
Lucy Woolford and Wayne Boardman of the University of Adelaide and Mary Fletcher of the University of Queensland reported recently on their study of ten southern hairy-nosed wombats that lived on a plot of land in the Murraylands near Blanchetown, South Australia, about 130 km (80 miles) northeast of Adelaide. Park rangers had shot five of them to end their suffering, two of them died in an animal rehabilitation center, and three were still alive at the rehab center. All ten wombats were female, five adults and five weaned juveniles.
Wombats, large, burrowing marsupials that live in the southern part of Australia, have had a hard time with it. They have had to contend with agriculture, imported livestock, drought, and disease.
The southern hairy-nosed wombats in the Murraylands have had an especially tough time. Drought and sarcoptic mange (also called scabies, a disease caused by mite infestation) have reduced their population by about 70% since 2002, down to about 10,000 to 15,000 individuals.
Heavy summer rainfall and flooding in 2010 and 2011 damaged feeding areas, and large numbers of emaciated wombats, missing patches of hair, have been sighted since then. Wombats usually feed by night, but after the floods, they have been seen grazing during the day and returning to their burrows before dusk.
The research team examined blood, tissue, and feces from their ten wombats, and they did veterinary examinations on the three that were still alive. The juvenile wombats showed the worst symptoms. Their livers had shrunk, and their gallbladders were inflamed. They were jaundiced, emaciated, and were missing patches of hair on their backs, sides, and heads — areas that were most exposed to the sun. Something had made the wombats more sensitive to sunlight, and their switch to daytime grazing only made things worse.
The team recognized the symptoms as similar to those they had seen in cows, sheep, horses, and red kangaroos that had eaten certain kinds of poisonous plants. They collected samples of plants from the feeding area for identification and comparison with the stomach contents from the sick wombats.
Native grasses were scarce in the area where the ten wombats had lived. The area was overgrown with onionweed. Other plants were present as well, but what caught the researchers’ attention was the heliotrope growing close to the wombats’ warrens. Heliotrope has a pretty flower, but it also contains a class of bitter-tasting chemical compounds called pyrrolizidine alkaloids, which cause liver damage.
There was ample evidence that the wombats had eaten the heliotrope plants, despite the bitter taste. The researchers speculated that juvenile wombats had eaten more of the heliotrope because it was close to their warrens, and they had not eaten enough native grasses to develop a strong preference for them — they just didn’t know any better.
This is one case where letting the land go back to the wild wasn’t good for the wildlife.
Source: Woolford, L., Fletcher, M.T., and Boardman, S.J. Journal of Agricultural and Food Chemistry, 2014, ASAP, dx.doi.org/10.1021/jf405811n.