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Scientists may have solved a mystery about one of nature’s most imposing creepy crawlies: tarantulas. In a new study this week, the researchers have found evidence that the hairy bodies of some tarantulas keep them safe from army ants. These spiders also seem to be generally friendly toward frogs, toads, and other animals as part of a mutually beneficial arrangement.
Scientists in Canada, Finland, and the U.S. conducted the new research, intended as a deep dive into what we know about how tarantulas interact with other animals. Tarantulas are typically large and hairy spiders that belong to the family Theraphosidae, though some similar-looking species outside this group are also called tarantulas. There are about 1,100 known species of tarantula, which can be found throughout the world. The researchers were especially interested in the mutualistic interactions between tarantulas and other animals—relationships in which both parties will scratch each others’ backs.
According to the researchers, these cross-species partnerships have been seen across nine subfamilies of tarantulas. But the scientists were able to identify new associations between tarantulas and a variety of animals, including snakes, whip spiders, harvestmen, and anurans, or frogs and toads (the reports were either documented by the researchers themselves or uploaded by others to social media and public databases like iNaturalist). In particular, the team spotted 63 new cases of tarantula spiders appearing to team up with frogs and toads across ten countries. Often these arrangements involve the frog living close or even inside a tarantula’s home, acting as a sort of a bodyguard for the spiders and their precious cargo. The team’s findings were published last month in the Journal of Natural History.
“Apparently, the frogs and toads that live within the retreats of tarantulas benefit from the shelter and protection against their predators. In turn, they feed on insects that could be harmful to the spider, its eggs, and its juveniles,” said lead researcher Alireza Zamani, an arachnologist from the University of Turku, Finland, in a statement from the university. “It seems that tarantulas might not be as scary and threatening as their reputation suggests.”
Zamani and his team also identified an especially complex relationship between some tarantulas and species of army ants. They found evidence that these tarantulas use ants as sort of a cleaning service for their burrows, with the ants benefiting from having a free source of food. While the ants could potentially devour the tarantulas, though, the researchers found that this rarely happened; if anything, the ants seemed to avoid getting close to the spiders and their young. Based on these observations and others, the researchers hypothesize that the hairy legs and bodies of some tarantulas, particularly those in the New World, make them a poor choice of meal for the ants.
“The dense hair covering the tarantula’s body makes it difficult for the ants to bite or sting the spider. Therefore, we believe that the hairiness may have evolved as a defense mechanism. This hypothesis is supported by findings that many burrowing New World tarantulas cover their egg sacs with urticating [defensive and spiky] hairs. The tarantulas typically release these barbed hairs as a defense mechanism, deterring and sometimes even killing their attackers. Covering their egg sacs with these hairs, however, effectively hinders the movement of small injurious arthropods, such as ants, that might try to attack the eggs,” said Zamani.
More research will be needed to confirm these findings, as well as other fascinating aspects of these arachnids. The researchers have found some early evidence to suggest that tarantulas can emit defensive secretions to ward off predators, for example, which may explain why cats and dogs have been observed making a hasty retreat after sniffing tarantulas. Either way, it just goes to show that there’s still so much to learn about our many-legged neighbors.
