Although they might not be as unique as human personalities, animal personalities possess a fairly large variation in specific traits such as shyness and aggressiveness and scientists have long wondered why these differences exist and how they came to be. Now, a new study from researchers at the University of North Carolina (UNC) at Chapel Hill has discovered a connection between spider personalities and temperature changes, potentially bringing us closer to answering these questions.

Image credit Alex Wild

The team examined the Anelosimus studiosus, also known as the tangle web spider, which inhabits North Carolina as well as numerous regions across North and South America. Among the spiders in this species, there are two distinct personality types: highly aggressive and docile. Typically, these two types share the same living space and co-exist to care for brood and capture prey.

The study looked at the effect of temperatures from -75 to 93 degrees Fahrenheit on the spiders’ ability to survive and reproduce individually within the colony. The results revealed that while aggressive spiders had a harder time surviving and reproducing at higher temperatures, docile spiders showed an opposing pattern: difficulty surviving and reproducing at lower temperatures.

Interestingly, when colony’s possessed a mix of the two spider personalities, these effects disappeared – aggressive spiders didn’t die off at higher temperatures and docile spiders didn’t die off at cooler temperatures

“Some aspect about living in a diverse society shields these aggressive spiders from selective pressures that would otherwise kill them,” said Spencer Ingley, a postdoctoral fellow at UNC College of Arts and Sciences and co-author of the study. “Without these diverse personalities, these spider societies would be more susceptible to extreme fluctuations in temperature – and it is interesting to think if our own society could benefit from diversity in a similar way.”

The results are particularly relevant in today’s times – with the planet’s climate projected to increase by three to 12 degrees Fahrenheit by 2100 and numerous studies linking global warming to the death of coral and megafauna, scientists are continuing to keep their eyes peeled for the many unique effects of our planet’s temperature increase.

“We live in a time of global change,” Ingley said. “Scientists are seeing that these changes can have a huge impact on individual organisms and groups of organisms. But people have rarely looked at personalities and how the personalities of groups can alter their response to these changes, particularly in different temperature environments.”

Could our planet’s continual warming be affecting our personalities in a way that we have yet to realize? It’s definitely possible, but we’ll just have to wait for further research to give us the final answer.

Journal Reference: Thermal effects on survival and reproductive performance vary according to personality type. 21 June 2016. 10.1093/beheco/arw084

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