Survival instinct, not family bonds, weave massive spider colonies together

March 7, 2017, University of British Columbia
The spiders studied for this research build webs that require a lot of silk, making the rainy conditions of the lowland tropical rainforest too adverse for them to live alone. Credit: Leticia Avilés

Spiders will live in groups if environmental conditions make it too difficult for single mothers to go it alone, new research shows.

It is rare for spiders to live in groups. The arachnids studied for this research build webs that require a lot of silk, making the rainy conditions of the lowland tropical rainforest too adverse for them to live alone. The findings dispute a long-held belief that social groups form merely so individuals can help their kin. Instead it suggests difficult may be the reason why some species live in cooperative social groups and others don't.

"In all species, family members are closely related, but only in some do they band together to raise each others' offspring," said Leticia Avilés, a professor of zoology at UBC and senior author of the study. "By living in groups, the spiders can occupy spaces that they wouldn't otherwise be able to, thus helping us understand why animals evolve to be social species."

Avilés pointed to other animals to support this theory including penguins who are only able to survive extreme cold and winter storms by huddling together. She said this theory could also help explain why single-celled organisms merged together to form more complicated multicellular organisms in our evolutionary history.

For this research, Avilés and graduate student Catherine Hoffman spent time in Ecuador to study Anelosimus spiders and the habitats in which they occur. At higher elevations, where conditions are mild, Anelosimus tend to live in small colonies containing a single family, whereas lower down in the rainforest, where rains are strong and predation high, they live in colonies of hundreds to thousands.

The researchers took spiders living in single-family groups from the higher elevation and transplanted them to the rainforest below to measure how predators and rainfall affected how the spiders lived. They protected some groups from ant predators and others from heavy rainfall that damages their webs. They found that it was these environmental conditions that forced spiders to form larger colonies to help one another.

"The spiders make dense webs that require a lot of silk," said Avilés. "When the webs get damaged by strong rains or colonies are attacked by predators, some can protect their offspring while others go and make the repairs."

The paper was recently published in Behavioral Ecology.

Explore further: Spider sharing isn't always caring: Colonies die when arachnids overshare food

More information: Catherine R. Hoffman et al, Rain, predators, and spider sociality: a manipulative experiment, Behavioral Ecology (2017). DOI: 10.1093/beheco/arx010

Related Stories

Spiders Who Eat Together, Stay Together

August 5, 2008

( -- The ability to work together and capture larger prey has allowed social spiders to stretch the laws of nature and reach enormous colony sizes, UBC zoologists have found.

Male Manogea porracea spiders found to care for young

December 6, 2016

(—A trio of Brazilian researchers has found that a species of spider, Manogea porracea, is unique in that the male plays a major role in web upkeep and protection of their young. In their paper published in the ...

Loner spiders prevail as pioneers

October 4, 2016

A spider looking to immigrate to a different environment is three to four times more likely to survive if it goes by itself, as opposed to as part of a group.

Scientists crack the spiders' web code

May 31, 2011

( -- Decorative white silk crosses are an ingenious tactic used by orb-weaving spiders to protect their webs from damage, a new study from the University of Melbourne has revealed.

Recommended for you

Archaeologists discover Incan tomb in Peru

February 16, 2019

Peruvian archaeologists discovered an Incan tomb in the north of the country where an elite member of the pre-Columbian empire was buried, one of the investigators announced Friday.

Where is the universe hiding its missing mass?

February 15, 2019

Astronomers have spent decades looking for something that sounds like it would be hard to miss: about a third of the "normal" matter in the Universe. New results from NASA's Chandra X-ray Observatory may have helped them ...

What rising seas mean for local economies

February 15, 2019

Impacts from climate change are not always easy to see. But for many local businesses in coastal communities across the United States, the evidence is right outside their doors—or in their parking lots.

The friendly extortioner takes it all

February 15, 2019

Cooperating with other people makes many things easier. However, competition is also a characteristic aspect of our society. In their struggle for contracts and positions, people have to be more successful than their competitors ...


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.