Posts Tagged ‘Rat’

Australian water rats have learned how to kill cane toads, eat their hearts and carve out their organs with “surgical precision”.

In only two years, highly intelligent native rakali in the Kimberly region of Western Australia discovered how to safely destroy the deadly toad – by removing its gallbladder and feasting on the heart.

The rats even targeted the biggest, most poisonous toads they could find, leaving their bodies strewn by the riverside, according to research published in Australian Mammalogy.

Cane toads were first introduced into Queensland in the 1930s and have been marching slowly west ever since, devastating native animals and driving them towards extinction. The toads first arrived in a site monitored by the researchers in WA in 2011.

But to their surprise, the scientists found the native water rat – better known as the rakali – was fighting back. The highly intelligent rodent has extremely sharp claws and teeth, and can grow to up 1kg in weight.

Dr Marissa Parrott, the paper’s co-author, said the scientists began to see dead toads appear, cut open in a “very distinctive” way.

“It was a small area of creek, three to five metres in size, and every day we were finding new dead cane toads,” she said. “Up to five every single morning.

“They were flipping them over, making a very distinctive, almost surgical precision cut down the chest. They would even remove the gallbladder outside the body, which contains toxic bile salts. They knew to remove that bit.”

“In the medium-sized toads, as well as eating the heart and liver, they would strip off the toxic skin from one or both legs and eat the non-toxic thigh muscle.

“They have very strong sharp teeth, very dextrous little hands. They can pick up a fish or a yabby and open them up very quickly and target the areas they like.”

According to the paper, researchers observed 38 toad carcasses, floating in the river or on the creekbank, over 15 days.

“All carcasses had an incision in the chest area, measuring [on average] 10.8mm vertically and 12.2mm horizontally,” it said.

“There was no evidence of bites to the head or body of the partially consumed toads. Rather, the rats appeared to hold the toad on its back and then incise the thoracic cavity to consume organs while the toad was still alive.”

Parrott, a reproductive biologist at Zoos Victoria, said another astonishing finding was the size of the dead toads. While only 2.5% of the toads in the region were classified as large toads, the big toads made up 74% of the bodycount.

This suggested the rats were specifically targeting the biggest toads.

“Water rats are quite large themselves,” Parrott said. “They have the power to subdue a larger toad and get a bigger payload, get that larger heart and larger liver. By killing those larger toads, it may be easier to avoid the toxic organs like the gallbladder.”

This could have a positive effect for other native animals, because the largest toads are more toxic and more dangerous.

Parrott hopes other water rats around the country could develop the same technique, and help halt the march of the toad, but said other measures were needed.

“The water rats could protect small areas and could slow the progression of toads,” she said. “There have been anecdotal reports of water rats killing cane toads, across Queensland and the Northern Territory. But there are so many hundreds of millions of cane toads those areas could get swamped. It’s a major issue for our native predators.”

The researchers hypothesise that the rats either learned from scratch – by figuring out which parts of the toad made them sick – or already had previous experience from eating Australian native toxic frogs.

Either way, Parrott said, it was likely helped by the fact the rats spent a lot of time raising their children.

“The parents have quite a long period of care with their offspring. The baby rats will stay with their mother – and they can learn from their parents. It would make very good sense that their parents are teaching their children how to kill those cane toads and avoid those poisonous areas.

“And it is very possible that those children will spread to other areas and teach their children how to kill and eat those biggest toads.”

Other animals, like crows and kites, have been observed turning cane toads inside out to avoid the toxic skin and only eat non-poisonous organs, the report said.

Parrott said her focus was now on promoting water rat conservation. The rats face threats from pollution of waterways, can be caught in fishing line and discarded balloons, and hunted by stray cats, foxes and dogs.

“[The findings] show the intelligence of our native rodents,” she said. “A lot of people don’t really know we have native rodents in Australia. A story like this has really raised their profile and made people not only realise they are very clever but they are a very beautiful animal we should be protecting.”

https://www.theguardian.com/world/2019/oct/26/australian-water-rats-cut-cane-toads-open-with-surgical-precision-to-feast-on-their-hearts

Thanks to Kebmodee for bringing this to the It’s Interesting community.

Summary: Study reports the anterior cingulate cortex of rats contain mirror neurons that respond to pain experienced by and observations of others.

Source: KNAW

Why is it that we can get sad when we see someone else crying? Why is it that we wince when a friend cuts his finger? Researchers from the Netherlands Institute for Neuroscience have found that the rat brain activates the same cells when they observe the pain of others as when they experience pain themselves. In addition, without the activity of these “mirror neurons”, the animals no longer share the pain of others. As many psychiatric disorders are characterized by a lack of empathy, finding the neural basis for sharing the emotions of others, and being able to modify how much an animal shares the emotions of others, is an exciting step towards understanding empathy and these disorders. The findings will be published in the leading journal Current Biology on April 11th.

Human neuroimaging studies have shown that when we experience pain ourselves, we activate a region of the brain called “the cingulate cortex”. When we see someone else in pain, we reactivate the same region.

On the basis of this, researchers formulated two speculations: (a) the cingulate cortex contains mirror neurons, i.e. neurons that trigger our own feeling of pain and are reactivated when we see the pain of others, and (b) that this is the reason why we wince and feel pain while seeing the pain of others. This intuitively plausible theory of empathy, however, remained untested because it is not possible to record the activity of individual brain cells in humans. Moreover, it is not possible to modulate brain activity in the human cingulate cortex to determine whether this brain region is responsible for empathy.

Rat shares emotions of others

For the first time, researchers at the Netherlands Institute for Neuroscience were able to test the theory of empathy in rats. They had rats look at other rats receiving an unpleasant stimulus (mild shock), and measured what happened with the brain and behavior of the observing rat. When rats are scared, their natural reaction is to freeze to avoid being detected by predators. The researchers found that the rat also froze when it observed another rat exposed to an unpleasant situation.

This finding suggests that the observing rat shared the emotion of the other rat. Corresponding recordings of the cingulate cortex, the very region thought to underpin empathy in humans, showed that the observing rats activated the very neurons in the cingulate cortex that also became active when the rat experienced pain himself in a separate experiment. Subsequently, the researchers suppressed the activity of cells in the cingulate cortex through the injection of a drug. They found that observing rats no longer froze without activity in this brain region.

Same region in rats and humans

This study shows that the brain makes us share the pain of others by activating the same cells that trigger our own pain. So far, this had never been shown for emotions – so-called mirror neurons had only been found in the motor system. In addition, this form of pain empathy can be suppressed by modifying activity in the cingulate cortex.

“What is most amazing”, says Prof. Christian Keysers, the lead author of the study, “is that this all happens in exactly the same brain region in rats as in humans. We had already found in humans, that brain activity of the cingulate cortex increases when we observe the pain of others unless we are talking about psychopathic criminals, who show a remarkable reduction of this activity.” The study thus sheds some light on these mysterious psychopathological disorders. “It also shows us that empathy, the ability to feel with the emotions of others, is deeply rooted in our evolution. We share the fundamental mechanisms of empathy with animals like rats. Rats had so far not always enjoyed the highest moral reputation. So next time, you are tempted to call someone “a rat”, it might be taken as a compliment…”

https://neurosciencenews.com/emotional-mirror-neurons-rats-11066/

Neuroscientists at Indiana University have reported the first evidence that non-human animals can mentally replay past events from memory. The discovery could help advance the development of new drugs to treat Alzheimer’s disease.

The study, led by IU professor Jonathon Crystal, appears today in the journal Current Biology.

“The reason we’re interested in animal memory isn’t only to understand animals, but rather to develop new models of memory that match up with the types of memory impaired in human diseases such as Alzheimer’s disease,” said Crystal, a professor in the IU Bloomington College of Arts and Sciences’ Department of Psychological and Brain Sciences and director of the IU Bloomington Program in Neuroscience.

Under the current paradigm, Crystal said most preclinical studies on potential new Alzheimer’s drugs examine how these compounds affect spatial memory, one of the easiest types of memory to assess in animals. But spatial memory is not the type of memory whose loss causes the most debilitating effects of Alzheimer’s disease.

“If your grandmother is suffering from Alzheimer’s, one of the most heartbreaking aspects of the disease is that she can’t remember what you told her about what’s happening in your life the last time you saw her,” said Danielle Panoz-Brown, an IU Ph.D. student who is the first author on the study. “We’re interested in episodic memory — and episodic memory replay — because it declines in Alzheimer’s disease, and in aging in general.”

Episodic memory is the ability to remember specific events. For example, if a person loses their car keys, they might try to recall every single step — or “episode” — in their trip from the car to their current location. The ability to replay these events in order is known as “episodic memory replay.” People wouldn’t be able to make sense of most scenarios if they couldn’t remember the order in which they occurred, Crystal said.

To assess animals’ ability to replay past events from memory, Crystal’s lab spent nearly a year working with 13 rats, which they trained to memorize a list of up to 12 different odors. The rats were placed inside an “arena” with different odors and rewarded when they identified the second-to-last odor or fourth-to-last odor in the list.

The team changed the number of odors in the list before each test to confirm the odors were identified based upon their position in the list, not by scent alone, proving the animals were relying on their ability to recall the whole list in order. Arenas with different patterns were used to communicate to the rats which of the two options was sought.

After their training, Crystal said, the animals successfully completed their task about 87 percent of the time across all trials. The results are strong evidence the animals were employing episodic memory replay.

Additional experiments confirmed the rats’ memories were long-lasting and resistant to “interference” from other memories, both hallmarks of episodic memory. They also ran tests that temporarily suppressed activity in the hippocampus — the site of episodic memory — to confirm the rats were using this part of their brain to perform their tasks.

Crystal said the need to find reliable ways to test episodic memory replay in rats is urgent since new genetic tools are enabling scientists to create rats with neurological conditions similar to Alzheimer’s disease. Until recently, only mice were available with the genetic modifications needed to study the effect of new drugs on these symptoms.

“We’re really trying push the boundaries of animal models of memory to something that’s increasingly similar to how these memories work in people,” he said. “If we want to eliminate Alzheimer’s disease, we really need to make sure we’re trying to protect the right type of memory.”

https://news.iu.edu/stories/2018/05/iub/releases/10-scientists-find-first-evidence-animals-can-mentally-replay-past-events.html