When constructing a hen nest in ant territory, the perfect protection could possibly be an offensive fungus.

Swollen-thorn acacia timber are aggressively defended by a number of species of ants. And but, a number of species of birds throughout Central America and Africa select to nest in these timber. Plainly fungal fibers within the nests deter the ants who encounter them and alter their conduct, making them apparently alarmed and intoxicated, researchers report within the October Animal Behaviour.

“It appeared very unusual to me that the ants didn’t hurt the chicks,” says Rhayza Cortés-Romay, an ecologist on the Universidad Mayor de San Andrés in La Paz, Bolivia. “So I began to assume from the hen’s perspective: How does it obtain this?”

The connection between swollen-thorn acacia timber (Vachellia collinsii) and ants is a symbiotic one. The ants gather nectar from the acacia and shelter in its thorns whereas patrolling the timber like possessive bouncers, biting and stinging invaders and even trimming again or killing encroaching vegetation. The ants might present safety from different predators, however it was unclear to researchers how the birds saved them away from their younger.

All through the tropics and subtropics, many birds use fungal organs often known as rhizomorphs to construct their nests. These cordlike constructions are fashioned from hundreds of thousands of densely woven fungal filaments, which the fungi use to seek for vitamins. In tropical rainforests, rhizomorphs develop within the forest cover, forming advanced networks that catch falling litter from above. Earlier analysis suggests the birds might use rhizomorphs for his or her sturdy assist, antimicrobial options and water repellency.

In Costa Rica’s Palo Verde Nationwide Park, two hen species that reside usually on swollen-thorn acacias construct their nests nearly completely utilizing rhizomorphs of horsehair fungus (Marasmius) — and seem to efficiently hold out ants. So Cortés-Romay and behavioral ecologist Sabrina Amador Vargas of the Smithsonian Tropical Analysis Institute in Balboa, Panama, positioned strands of horsehair fungus onto the branches of 30 acacia timber inhabited by one species of symbiotic ant (Pseudomyrmex spinicola), together with fibers of a nonfungal plant of comparable thickness and kind that birds additionally use to construct nests. Then the researchers filmed the ants to document their reactions to the totally different strands.

Ants who touched the fungus groomed themselves and sped up extra usually than those that touched solely the plant fibers, actions indicating repellence and alarm. The researchers additionally noticed some excessive behaviors seen nearly solely after contact with the fungus, together with biting different ants, spinning and wandering round aimlessly and unpredictably. This “drunkard’s stroll” is paying homage to ant employees contaminated by the zombifying fungus Ophiocordyceps and suggests the ants might have been disoriented or ingested toxins (SN: 2/21/23).

“The primary time we noticed the behaviors, we have been amazed,” Cortés-Romay says. “These ants are very aggressive. To see one thing that affected them actually was a discovery.”    

A few of the outcomes supply compelling assist to the concept that these fungi are noxious to the ants, says Fran Bonier, a behavioral ecologist at Queen’s College in Kingston, Canada. However birds use the identical rhizomorphs on timber which can be freed from ants as effectively, she says, suggesting that they may additionally profit nests in different methods.

At the very least 176 hen species use fungal rhizomorphs of their nests. Provided that frequency, it’s not stunning the researchers discovered proof that the rhizomorphs might present some chemical defenses, says Todd Elliott, a biologist on the College of New England in Armidale, Australia. “This raises many questions on the chemistry of what’s being launched, and whether it is distinctive to this ant and this fungus or whether or not analogous conditions are taking part in out in different ecosystems world wide.”