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Ants Rescue Sibs From Spider Webs and Surprise Us Once Again

Harvester ants join chimpanzees and mountain gorillas in the "rescue club."

A few days ago someone sent me an essay available online by Jake Buehler called "Watch an ant rip apart a spiderweb to rescue a sibling" that really piqued my interest. It's based on a forthcoming essay by Christina L. Kwapich and Bert Hölldobler titled "Destruction of spider webs and rescue of ensnared nestmates by a granivorous desert ant (Veromessor pergandei)” that's in press in the prestigious scientific journal The American Naturalist.

Mr. Buehler begins, "Ants are famous for putting themselves at risk for the wellbeing of their colony, but desert seed harvesting ants (Veromessor pergandei) are especially heroic. New research suggests the insects charge into spider webs to rescue their ensnared nestmates, sometimes ripping the silk apart to free them." They then clean them. It also turns out that around 6.3% of ants who try to rescue their siblings get caught in the web or are caught by other spiders. They also ignore empty webs. It seems like the ants who go on the rescue mission are attracted by distress signals emitted by ants caught in a web. Frozen dummy ants who were marked with the same chemical also were rescued.

What really caught my eye is a video in his piece about how these ants go about rescuing their sisters from spider webs as they call for help. I highly recommend watching it. In a preview to the research we read, "This remarkable and rare behavior appears to be tied into the food these ants eat, namely, seeds. They found that the seeds carried by foraging ants become tangled in undetected webs, reducing the total number of foraging trips individuals can take per day. By accounting for the length of a foraging career and number of trips per day, they estimated that unchecked spider predation could cost colonies 65,000 seeds per year. This is a high price to pay because colonies need to gather enough resources to rear 600 new sisters each day."

There have been very few observations of nonhumans who rescue other animals from traps and it's rarer to see other animals destroy traps. In fact, only chimpanzees and mountain gorillas have been observed to take apart snares which poachers use. (See "Deactivation of snares by wild chimpanzees," "Gorilla Youngsters Seen Dismantling Poachers' Traps—A First," and "Gorillas Dismantle Poacher's Traps: Compassionate Conservation of the Gorilla-kind.") According to an ABC news report, "Staff at the Dian Fossey Gorilla Fund’s Karisoke Research Center in Rwanda recently witnessed two 4-year-olds and a teenage mountain gorilla work together to destroy the types of snares that have killed at least two young gorillas this year. It was also the first time staff members have been able to see up close exactly how gorillas dismantle the snares...Together they jumped on the taught branch attached to a rope noose and removed the rope. They then ran over to another nearby snare and destroyed it the same way."

Insects are amazing beings and I look forward to writing more about their amazing social and cognitive lives. Stay tuned for more surprises about the unexpected things nonhumans do. Just when we think we know it all, it's clear we don't.