A recent investigation highlights the amicable relationships that tarantulas have with certain amphibians, reptiles, and even army ants, which are typically known for preying on spiders. Researchers propose that the thick hair on tarantulas has likely developed as a protective feature against these hungry ants.
A newly published study looks at the synergetic ecological interactions and evolutionary traits of tarantulas. It shows that these well-known spiders often get along with amphibians, reptiles, and even army ants, despite the latter being known to consume spiders. The researchers believe that the thick covering of hair on tarantulas may have actually evolved as a protective mechanism against these predatory ants.
An international team of scientists conducted an in-depth literature review to explore how tarantulas engage with various species.
For the first time, the study reported a connection between tarantulas and species such as snakes, whip spiders, and harvestmen, highlighting over 60 new instances of partnerships with amphibians from ten different countries.
The findings suggest that the interactions—sometimes even cohabitation—between tarantulas and other species often provide mutual benefits.
“Frogs and toads that reside within the tarantula’s burrows gain shelter and protection from their predators. In return, they consume insects that could pose a threat to the spider, its eggs, and its young ones. It seems tarantulas may not be as intimidating as they’re thought to be,” explains Alireza Zamani, the lead researcher from the University of Turku, Finland.
Among the key discoveries is a new hypothesis concerning the reason behind the hairiness of tarantulas. Researchers suspect that the presence of dense hair may have emerged as a defense against predatory ants.
“It has been noted that army ants generally overlook both adult tarantulas and spiderlings. This is particularly noteworthy, given that army ants usually attack a wide range of arthropods,” adds Zamani.
During their encounters with tarantulas, the ants were seen entering the spider’s burrow, collecting food scraps, and cleaning the area, which is advantageous for the tarantula. Few ants made attempts to assault the spider, and these efforts were unsuccessful as the spider’s legs were shielded by stiff hairs.
“The abundant hair on a tarantula’s body hinders the ants’ ability to bite or sting it. Thus, we hypothesize that this hairy attribute may have evolved as a protective adaptation. This theory is further supported by observations that many burrowing New World tarantulas use urticating hairs to cover their egg sacs. These barbed hairs serve as a defense, deterring and sometimes killing attackers. Additionally, this strategy effectively prevents small harmful arthropods, like ants, from reaching their eggs,” explains Zamani.
Nevertheless, the researchers propose that the hairy trait might be an evolving characteristic exclusive to specific tarantula species, with those possessing less body hair being more exposed to predatory ant attacks.
The study also documented a distinctive escape tactic employed by New World tree-dwelling tarantulas when faced with army ants.
“In a field study conducted in Peru, a female Avicularia hirschii was seen vacating its silk-made retreat and dangling from a leaf’s edge using its front legs after sensing the presence of army ants in search of prey,” says Zamani.
The authors indicate that tarantulas might possess another protective strategy through a potentially unidentified chemical mechanism. They hypothesize that these spiders might have specialized epidermal glands that could secrete substances to repel predators.
“This idea is bolstered by the observation that cats and dogs, which have a well-developed sense of smell, tend to recoil and flee after sniffing a tarantula. Notably, tarantulas have slit-like openings of unknown function within epidermal glands that may generate defensive secretions responsible for this reaction,” Zamani elaborates.
While more evidence is necessary to validate the chemical defense mechanism hypothesis, this research represents a notable advancement in unraveling the behaviors and evolutionary strategies of tarantulas.
