Arachnids also cooperate in a rare way for spiders – ScienceDaily

Birds do. Bees do. Even spiders in their webs do this: cooperate for more peaceful colonies.

This is one of the surprising findings of a new study by UCLA undergraduates on orb-weaving spiders in Peru.

The study also revealed that if there were more females than males in orb-weaving spider colonies, males fought less with each other and fought less in female-dominated colonies than in male-dominated colonies, resulting in colonies. a little more peaceful. Spiders also showed little hostility to individuals from different colonies, a discovery that has not been previously documented for colonial spiders.

The research was published in the journal. Journal of Arachnology.

“We’re used to thinking about communal animals like honeybees and elephants,” said the paper’s senior author Gregory Grether, a professor of ecology and evolutionary biology at UCLA. “But spiders often live alone, so we were excited to study these colonial spiders and learn how they interact with their colony mates and individuals from other colonies.”

Globe-weaving spiders weave interlocking webs in large webs that are fixed to the surrounding vegetation. In colonies, individuals protect their nets from intruders and often fight each other for food and mates. When threatened, they withdraw to communal areas for protection, and some species defend communal areas.

Four student writers – Catherine Wu, Chaiti Bhagawat, Modan Goldman and Nihal Punjabi – were attending a field course that Grether led at the Cocha Cashu Biological Station in southeastern Peru. Their four-day journey to reach the field research station included a long, winding bus ride through the Andes and a boat trip down the Madre de Dios River and into one of its tributaries.

For 18 days, students studied 34 colonies of a species called Philoponella republicana to find out whether the location of the web, the ratio of male and female spiders, or the web or the spiders themselves affect the animals. aggression level. Alongside Grether, their work was overseen by UCLA assistant professor Debra Shier and social insect and spider researcher Roxana Arauco-Aliaga, who was then Cocha Cashu research coordinator and associate director.

They observed that although spiders do not share their food, they cooperate to build their webs and wrap their prey in silk – only one spider ate a particular prey item.

Students staged attacks by relocating spiders in different locations and relocating spiders from other colonies. Some spiders defended their orb webs against all intruders, but the spiders did not cooperate to repel the intruders.

When there were more females than males in colonies, males fought with other males and females fought less with males than in male-dominated groups, resulting in somewhat more peaceful colonies.

However, if colonies had many large and medium-sized females, those females snatched the most prey and formed slightly more aggressive colonies by fighting off the most captured insects.

After returning from the field, the students learned from previous research that group life in spiders is extremely rare — occurring in less than 0.1% of species. Despite this, several types of sociability are recognized by arachnologists. Collaborating in prey catching, web building, and brood maintenance, extraterritorial spiders are most similar to true social animals, such as ants, honeybees, and naked mole rats.

Territorial colonial spiders, which cooperate in building webs but also compete aggressively with other inhabitants of their colonies for food and mates, seem to have evolved from solitary species multiple times, possibly when ecological conditions favor group life. They occupy a position on a continuum of sociability similar to group-dwelling primates, including humans.

The student researchers all graduated from UCLA. Wu is currently studying outdoor education at UCLA Recreation, MA at Bhagawat Ghent University, and Goldman and Punjabi are medical students at Carle Illinois School of Medicine and Case Western Reserve University, respectively.

Since 2001, Grether has been taking groups of UCLA undergraduates to the tropical rainforest for field research training. He plans to return with a new group of students in January 2023 to reveal more of Cocha Cashu’s secrets.

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