First Neural Scans of Extinct Tasmanian Tiger Reveal It Was a Predator
Brain imaging of the dog-sized, carnivorous marsupial confirms it had complex thought processes associated with hunting behavior.
Scientists have mapped 100-year-old brains of two extinct thylacines - better known as the Tasmanian tiger - to reveal how the carnivore was wired to be a predator.
Sophisticated imaging shows the thylacine had a larger brain than some other Australian carnivores, with more cortex allocated to decision-making and planning behaviors.
Professor Ken Ashwell, an anatomist at the University of New South Wales and co-author of the research, said no-one had ever studied the thylacine brain in such detail before and that the findings opened the door for use on other extinct and endangered animals.
"What's quite exciting about it for comparative neuroscience and brain evolution is that there are many brains sitting in museums of rare animals, extinct animals," he said.
"[This] opens up the possibility of analyzing the internal structure of those brains in ways that were never possible before."
He said the research, published today in PLOS ONE, will help scientists understand how and why animals evolved to behave the way they do.
The last Tasmanian tiger, a carnivorous marsupial about the size of a medium-to-large size dog, died in Hobart Zoo in 1936.
Scientific evidence of the natural behavior of the thylacine is limited, so researchers turned to the well-preserved brains of two thylacines housed in Smithsonian Institution in the US and the Australian Museum to gain an insight into the iconic animal.
Using a technique called diffusion tensor imaging (which looks at how water diffuses inside parts of the brain) alongside traditional magnetic resonance imaging (MRI), the researchers mapped how molecules moved through the brain of the thylacine while it was alive to reveal the neural wiring of different brain regions.
They then compared this to two brains from Tasmanian devils - one of which was a similar age to the thylacine brains, the other from a recently deceased animal - to see what they could infer about the behavior of each animal from the architecture of its brain."When you look at the cerebral cortex of any mammal there's areas to do with decision making and planning, there's areas to do with motor function, there's areas to do with sense of touch, vision," Professor Ashwell said.
"Depending on the relative size of those you can draw conclusions about behavioral repertoire."
The study found thylacines had more of their cortex devoted to "complex cognition" activities associated with being a hunting animal - like planning actions and making decisions.
That accords with observations made of Tasmanian tigers before they became extinct and features of their anatomy.
Meanwhile, the smaller frontal area of the brains of the Tasmanian devils suggested less of their brain is committed to complex decision making - which was broadly in line with what is known about the carnivorous devil as a scavenger.
The research was also consistent with theories of brain evolution that suggest that brains became more modularized as they became larger, wrote the researchers. Professor Ashwell said the key to the research was demonstrating that their brain imaging techniques could be applied to extinct animals.
He said the combination of MRI and diffusion tensor imaging means that scanning animal brains years after they have died is possible if they are properly preserved.
Professor Ashwell said that could help scientists better understand how the brains of mammals and marsupials evolved.
"We can determine how their cerebral cortex is organised, how their connection to deeper brain structure is organised," he said.
The data from the research will be added to digital archive of animal brains called Brain Ark founded by the study's co-author Dr Gregory Berns, a neuroscientist at Emory University.
Article first appeared on ABC Science.
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