Posts Tagged ‘dingoes’

Did Large Carnivores Influence Dune Formation in Ice Age Georgia?

July 26, 2018

Over 100 years ago Australians built a 3480 mile long fence to keep dingoes away from livestock. For ecologists this provides a grand experiment of how the exclusion of a large predator influences ecosystems. However, there exists a considerable amount of conflicting scientific literature about this. Many studies report overgrazed regions on the dingo-less side of the fence that have poor soils as a result. The fence bisects a national park. One study confined to part of this park counted 85 dingoes and 8 kangaroos on the side of the fence with the dingoes, and 1 dingo and 3200 kangaroos in a comparably sized lot on the side that is supposed to be without dingoes. Tame livestock, feral goats and hogs, and rabbits along with the kangaroos contribute to these overgrazed landscapes. Parma wallabies, the greater bilby, and small rodents thrive on the side of the fence with the dingoes because the large canines suppress populations of smaller predators. Another study that claims to be more comprehensive than any other found no differences between either side of the fence. The authors of this study suggest there are no differences because dingoes have never been completely eliminated on the supposedly dingo-less side of the fence. They say other studies concluding there is a difference are local and anecdotal.

Image result for dingoes and sand dunes

Dingo on a sand dune.

I think the most interesting study is a recent paper that found the presence of dingoes influenced sand dune formation in arid regions. On the dingo-less side of the fence sand dunes were larger and stabilized with shrubby plants growing on top. On the side of the fence with dingoes sand dunes were more shallow, bald, and dispersed by wind because plant growth was sparse. This seems counterintuitive. But this difference in dune formation is caused by the suppression of small carnivore populations. Dingoes reduce populations of foxes and feral cats (neither of which are native to Australia). In turn dusky hopping mice and rabbit populations increase, and they eat the seeds of plants and shrub saplings that keep dunes stabilized.

This last study is most interesting to me because sand dunes rolled across parts of Georgia during the coldest driest stages of Ice Ages, and I wonder if large predators influenced their shape and pattern. The arid climate caused some small rivers in Georgia to run dry. Wind blew the riverine sand into big dunes that are still evident today, though scrubby vegetation has since stabilized them. (See: https://markgelbart.wordpress.com/2012/04/09/the-ohoopee-sand-dunes/ ) I’ve hypothesized overgrazing by megafauna alongside shrinking water holes located in the river bed may have contributed to the erosion leading to sand dune formation. But maybe the presence of large carnivores played a role as well. Dire wolves, jaguars, and cougars suppressed populations of bobcats and foxes; causing an increase in rodent and rabbit numbers. The small herbivores stripped the vegetation bare, allowing sand dunes to roll. On the other hand hawks, owls, and snakes probably always remained abundant, and they likely provided a check on rodent and rabbit populations. Nevertheless, the notion large carnivores may have influenced dune formation in Georgia is an intriguing idea.

References:

Glen, A.; and C. Dietman, M. Soule, and B. Mackey
“Evaluating the Role of the Dingo as a Trophic Regulator in Australian Ecosystems”
Australian Ecology August 2007

Harris, Emma
“Dingoes have Changed the Actual Shape of the Australian Desert”
The Atlantic July 6, 2018

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Dumpster Dingoes

May 9, 2017

Bacteria. Cockroaches. Flies. And even higher organisms. Mice. Rats. Sea gulls. Crows. Bald Eagles. Cats. Dogs. Wolves. Bears.  These are just some of the organisms that benefit from the food waste produced by humans.  We waste up to 40% of the food we produce.  The proliferation of Homo sapiens since the late Pleistocene has been detrimental to many species, but others have adapted to our presence.  Scientists estimate anthropogenic sources, including livestock and garbage, make up 32% of the worldwide gray wolf diet.  The last surviving population of Asiatic lions almost entirely subsists on livestock.  Studies show Australian dingoes and red foxes that live near landfills have smaller home ranges and higher survival rates than other individuals of the same species.  Dingoes living near garbage dumps grow fat and mate with domestic dogs, producing hybrids that could be called dumpster dingoes.  This same study found black bears foraging around dumpsters have shorter lifespans because they come into conflict with people and get shot.

Image result for Animals scavenging a landfill

Landfills are excellent sites for bird watching.  They attract gulls, crows, and vultures.  I have even seen a bald eagle soaring over one.

Image result for animals scavenging landfill

Dogs evolved from wolves that hung around human refuse heaps.

Dingoes are super efficient hunters that prey on almost everything they can kill

Dingo chasing a kangaroo.  Dingoes that hang around landfills get fat and lazy and mate with domestic dogs.

The existence of human refuse heaps likely spurred the evolution of wolf into dog.  The physical characteristics that differentiate dogs from wolves share the same genetic pathway with tameness.  The 2nd and 3rd generations of canids with the least flight response develop the floppy ears and multi-colored coats common in domestic dogs.  Some scientists think it possible some modern day wolves scavenging dumpsters could again evolve into a type of dog.

Genetic studies suggest dogs developed the ability to digest more starch about 4000-7000 years ago–another step in the ongoing evolution of wolf to dog.  This coincides with the development of agriculture when humans began cultivating cereal grains.  Dogs with digestive systems capable of producing more amylase, the enzyme that helps convert starch to sugar, were better able to survive on bread when humans started consuming more cereal grains instead of (or as a supplement to)  meat.

Dingoes descend from dogs brought to Australia about 4000 years ago by people from the subcontinent of India who later assimilated with Australian aborigines.  Dingoes are primitive dogs similar enough to their wolf ancestors that they can revert to the wild and thrive.  Dingoes rapidly became the top non-human predator in Australia.  Most people are unaware dingoes live in America as well. ( See: https://markgelbart.wordpress.com/2013/02/11/the-american-dingo/ ) Native Americans brought primitive dogs with them from Asia, and some of them went wild here just like they did in Australia.  North American dingoes are known as Carolina dogs and were not recognized as a distinct wild canid until a scientist found them running wild during the 1970s on the Savannah River Site in South Carolina.

The observed differences between wolf, dingo, and dog are a good example of recent evolution.  They also show the line between species can be blurry.  All 3 can interbreed and produce fertile offspring.  So some scientists think dogs and dingoes should be classified as subspecies of wolf.  On the other hand the physical and behavioral characteristics of each are quite different, and some scientists still classify them as distinct species.  Domestic dogs are entirely dependent upon humans, dingoes (a transitional form between dog and wolf) can take us or leave us, and wolves avoid us and probably wish humans would become extinct.  I prefer classifying them as separate species based on behavioral differences.

References:

Marshall-Pescini, Sarah; Ingo Besserdick, C. Kratz, F. Rang

“Exploring Differences in Dogs and Wolves’ Preference for Risk in Foraging Trash”

Frontiers in Psychology August 2016

Newsome, Thomas; Gary Ballard, Matthew Crouther, and Chris Dickman

“Dietary Niche Overlap of Free-Roaming Dingoes and Domestic Dogs: The Role of Human-Provided Food”

Journal of Mammalogy April 2014

Oro, Daniel; et. al.

“Ecological and Evolutionary Implications of Food Subsidies from Humans”

Ecology Letters October 2013