Spiders Who Eat Together, Stay Together

August 5, 2008
Social Anelosimus spiders in large colonies will cooperate to capture insects that are much larger than the spiders themselves.

(PhysOrg.com) -- 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.

The findings, published in this week’s edition of the Proceedings of the National Academy of Science, may also explain why social spiders thrive in tropical areas but dwindle with increasing latitude and elevation.

“The size of organisms tends to be constrained by a scaling principle scientists call ‘surface to volume ratio,’” says Leticia Avilés, lead author and associate professor in the UBC Dept. of Zoology. While organisms typically have energetic needs proportional to their volume, they must acquire nutrients through their surface.

“As the organism grows, this surface to volume ratio declines. In a way, this is how nature keeps the sizes of various species in check.”

The same principle may apply to social groups. The surface area of the three-dimensional webs social spiders use to capture prey does not grow as fast as the number of spiders contained in the nests; so number of incoming prey per spider declines with colony size. But Anelosimus eximius, a species of social spider notable for its enormous colony size – some total more than 20,000 individuals – have gained the ability to stretch that law by cooperating and thus capturing increasingly large insects as their colonies grow.

“The average size of the prey captured by the colony increased 20-fold as colony size increased from less than 100 to 10,000 spiders,” says Avilés, who studied the spiders in the wild in Amazonian Ecuador with undergraduate student Eric Yip and graduate student Kimberly Powers.

“So even though the number of prey falls sharply as the colony grows, the biomass that individual spiders acquire actually increases.”

The study also found that large prey, while making up only eight per cent of the colony’s diet, contributed to more than 75 per cent of its nutritional needs.

“But that only works to a certain point,” says Avilés, who adds that the biomass of prey consumed by the colony peaks when the colony reaches between 500 and 1,000 individuals.

As for the scarcity of social Anelosimus species in higher elevations and latitudes, “there simply aren’t enough large insects in those areas to sustain this type of foraging behaviour,” says Avilés.

Provided by University of British Columbia

Explore further: For social spiders, preying together aids younger siblings

Related Stories

For social spiders, preying together aids younger siblings

May 16, 2013

(Phys.org) —The behavior of social spiders may settle debates over the benefits of older siblings. Cornell researchers studying Australian social huntsman spiders have discovered that younger siblings thrive when raised ...

Bold spiders ensure a bright future for the whole colony

June 9, 2014

Stegodyphus dumicola is a social spider. This curious little creature lives in shared nests with more than 2,000 others. They hunt together, act collectively to subdue the prey stuck in their sticky web and share the catch.

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.

Recommended for you

New discovery: Common jellyfish is actually two species

November 21, 2017

University of Delaware professor Patrick Gaffney and alumnus Keith Bayha, a research associate with the Smithsonian's National Museum of Natural History, have determined that a common sea nettle jellyfish is actually two ...

Cassini image mosaic: A farewell to Saturn

November 21, 2017

In a fitting farewell to the planet that had been its home for over 13 years, the Cassini spacecraft took one last, lingering look at Saturn and its splendid rings during the final leg of its journey and snapped a series ...

0 comments

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.