Solitude breeds aggression in spiders (rather than vice versa)

Date:  July 2, 2019

Source:  PLOS

Spiders start out social but later turn aggressive after dispersing and becoming solitary, according to a study publishing July 2 in the open-access journal PLOS Biology by Raphael Jeanson of the National Centre for Scientific Research (CNRS) in France, and colleagues.

Many species display sociality only transiently during their life cycle. For example, spiderlings at their earliest developmental stage show mutual attraction and social tolerance before they disperse. This strongly contrasts with post-dispersal, solitary adult spiders that behave aggressively toward -- and sometimes even cannibalize -- other spiders. The onset of dispersal coincides with a sharp decline in social tolerance in many animals, but the causal relationship still remains poorly understood.

To address this question, Jeanson and his colleagues used a combination of behavioral, chemical and modeling approaches in spiderlings of a solitary species (Agelena labyrinthica, the labyrinth spider) to investigate the mechanisms controlling the developmental switch leading to the decline of social cohesion and the loss of tolerance.

They found that the process of maturation naturally causes an increase in mobility, which is itself sufficient to trigger dispersal without requiring any change in social behaviors. After spending an initial period of about five days in close proximity, spiderlings progressively dispersed without any change in the social context, that is, no aggressive interactions were observed before dispersal. By contrast, the social isolation that inevitably followed dispersal triggered aggressiveness by altering the way that individual spiders perceived others from the same species. For example, spiderlings that experienced social isolation were much more aggressive toward siblings than those reared socially. According to the authors, the findings provide strong evidence that aggression is a consequence, not a cause, of dispersal in spiderlings.

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Turtle study shows gender lifespan differences likely due to aggressive tendencies

APRIL 25, 2019 REPORT

by Bob Yirka , Phys.org

A team of researchers with members from Taiwan, the U.S., China and the U.K. has found evidence that suggests the reason females of most species live longer than males is because of male aggressive tendencies. In their paper published in the journal Science Advances, the group describes their study of a species of turtle where the females are the aggressors and what they found.

Scientists have been theorizing about the reason for females of most species living longer than males for many years. Some have suggested it has something to do with the differences in hormones, others that it has to do with deleterious mutations in mtDNA passed down from mothers. But the strongest argument has been that it comes down to aggression in males—mostly due to competing for a mate. In many species, fighting for a mate results in both injuries and high stress levels.

In this new effort, the researchers came upon an opportunity to test this last theory quite by accident. They were studying kukri snakes living on Orchid Island, which is just off the coast of Taiwan. The snakes live on the beach, and prior research has shown that the females become territorial because of a major food supply—sea turtle eggs. They actually fight one another while trying to protect their turf. Prior research had also shown that the female snakes tended to have shorter lifespans than the males. Logic had suggested the reason for that was their aggressive behavior—males did not fight each other for eggs, or for a mate.

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Bullies' brains wired to seek pleasure from aggression, study suggests

Researchers from Mount Sinai Hospital, New York, found the brains of mouse bullies activated a reward synapse when they showed aggression to weaker mice

Katie Gleeson 

Friday 1 July 2016

Bullies’ brains are wired to get enjoyment from picking on victims, scientists have found.

The research claims that bullying is motivated by a neurological disorder, whereby the brain activates a reward response to aggressive activity.

Behavioural experiments on mice found that those who acted aggressively toward inferior mice developed a preference for bullying over non-aggression, suggesting that they found the ability to subordinate another mouse rewarding.

Dr Scott Russo, from Mount Sinai Hospital, who lead the research said the unique study is the “first to demonstrate that bullying behaviour activates a primary brain reward circuit that makes it pleasurable to a subset of individuals".

The report says that the activation of the brain reward circuit is caused by the projection of a neurotransmitter which reduces activity in the part of the brain that usually creates an aversion to violence.

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Bovine Kampf: Aggressive Nazi cattle sent to slaughterhouse

January 7, 2015

Brett Smith for redOrbit.com – Your Universe Online

The Nazis of Interwar Germany may be mostly dead and gone now. But one thing still remains: their cows – and they are pissed.

In a plan that sounds like it came from a Nazi brain, German scientists in the 1920s and 1930s tried to reverse engineer the ancient wild ancestor of today’s cattle: aurochs. By selectively breeding cattle, the Nazi scientists hoped to develop a bovine that looked and acted like aurochs.

Credit: Thinkstock

The modern by-products of this unsuccessful breeding are Heck cattle. Smaller and beefier, Heck cattle appear to have inherited the aurochs ill temper – so much so that a herd of Heck cattle in the United Kingdom recently had to be culled of all but the most docile animals.

British farmer Derek Gow had brought the Nazi cows to the UK in 2009 to raise and graze them on conservation lands. Unfortunately, the herd of 20 had to be culled down to 6 after it became unmanageable for him.

”The ones we had to get rid of would just attack you any chance they could,” he told The Guardian. “They would try to kill anyone. Dealing with that was not a lot of fun at all. I have worked with a range of different animals from bison to deer and I have never come across anything like these.”

“We made sure no one went near them so there were never any incidents,” he added. “To get them into the trailer to get them off the farm we used a young and very athletic young man to stand on the ramp and they charged at him before he quickly jumped out the way.”

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Fish fail to see reflections as rivals

Not all cichlids react aggressively to their reflections, casting doubt on the use of mirrors in behavioural studies

Daniel Cressey

10 October 2014

Mirrors are often used to elicit aggression in animal behavioural studies, with the assumption being that creatures unable to recognize themselves will react as if encountering a rival. But research suggests that such work may simply reflect what scientists expect to see, and not actual aggression.

For most people, looking in a mirror does not trigger a bout of snarling hostility at the face staring back. But many animals do seem to react aggressively to their mirror image, and for years mirrors have been used to trigger such responses for behavioural research on species ranging from birds to fish.

“There’s been a very long history of using a mirror as it’s just so handy,” says Robert Elwood, an animal-behaviour researcher at Queen’s University in Belfast, UK. Using a mirror radically simplifies aggression experiments, cutting down the number of animals required and providing the animal being observed with an ‘opponent’ perfectly matched in terms of size and weight.

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Pheromones regulate aggression of non-mother female mice toward pups in wild-derived mice

Date:

August 5, 2014

Source:

Weizmann Institute of Science

Summary:

A new mouse model has allowed researchers to explore, for the first time, the biological roots of aggressive behavior in females, both toward each other and the pups of others. Their findings provide the basis for developing additional mouse strains that will enable a better understanding of the neural and genetic basis of behavior relating to reproduction in females, and the differences between males and females.

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Wasps use ancient aggression genes to create social groups

Date:

February 10, 2014

Source:

Penn State

Summary:

Aggression-causing genes appeared early in animal evolution and have maintained their roles for millions of years and across many species, even though animal aggression today varies widely from territorial fighting to setting up social hierarchies, according to researchers.

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Young cricket characters shaped by 'song'

The experiences of youth can change the adult personalities of crickets, a new study has found.

Scientists discovered that juvenile males that did not hear a cricket chorus while young grew into more aggressive adults.

It suggests that the animals can pick up behavioural traits while young which then become fixed in adulthood.

The scientists believe that personality may play a crucial role in ecology and evolution.

The findings of the team from the University of California, Davis, US are published in the journal Animal Behaviour.

In conducting the experiment the team captured juvenile field crickets that had not yet developed a tympanum, the equivalent to an ear, which grows on the cricket's front legs.

"We isolated them all effectively before any of them could hear anything," said lead author Nicholas DiRienzo.

While one group of crickets were reared in silence, another were played a looped recording of five calling males.

"In the sound treatment there was a chorus of five different crickets playing back, calling, to mimic just what you would hear on a summer night, lots of different crickets calling and singing."

The silence was similar to the conditions experienced by juveniles hatching in spring when the cricket population tends to be at a low density, and hence quieter. Any juveniles born later tend to find a denser population of crickets, which is louder.

Continued:  http://www.bbc.co.uk/nature/19248230