Small but Mighty: The Hidden Power of Wildwood’s Thatching Ants

By Alexander Smith

Yesterday, after a group had left Wildwood, while I packed up, I left my hard-earned sandwich unattended on a mossy log. I returned minutes later to find it completely overrun by Western Thatching Ants (Formica obscuripes), each one methodically dismantling my lunch and vanishing into the forest floor with military precision. I lost my sandwich, but gained a fascination. These ants, though often overlooked beneath the towering Douglas-firs, are some of the most industrious and influential residents of this rare ecosystem on Vancouver Island.

Western thatching ants are best known for their impressive mound nests—conical structures built from a mixture of soil, conifer needles, twigs, and grasses. Scattered throughout Wildwood in sunlit forest clearings, these mounds can reach over a metre tall and serve as bustling hubs for colonies that sometimes number in the hundreds of thousands. The open, dry conditions of Wildwood’s Coastal Douglas-fir ecosystem provide an ideal environment for them. These mounds are more than homes—they're microhabitats, influencing soil chemistry, moisture, and temperature, and supporting a whole suite of forest-floor life.

Formica obscuripes colonies are polygynous, with multiple queens, which allows them to grow rapidly and dominate large areas. Their foraging trails stretch out in all directions, often creating ant highways across Wildwood’s mossy paths. They are fierce defenders of their territory, using not just numbers and coordinated aggression, but also a unique chemical defense: formic acid. When threatened, these ants raise their abdomens and spray this potent acid—a strong irritant with a vinegary sting. The scent alone is enough to keep many predators at bay. More than once, I’ve smelled that sharp tang in the air before realizing I was kneeling far too close to a mound.

Their role in the ecosystem, however, goes far beyond defense. These ants are voracious predators and scavengers, feeding on caterpillars, beetle larvae, termites, and even ticks. By keeping pest populations in check, they contribute to the health of Wildwood’s aging trees and understory plants. Their scavenging also helps recycle organic material, accelerating decomposition and nutrient cycling in the soil.

In addition to being regulators and recyclers, western thatching ants are soil engineers. Their constant movement and mound construction mix and aerate the soil, improve drainage, and enhance microbial activity. Over time, these changes benefit the surrounding plant life, including the Douglas-firs and salal that define the Wildwood landscape.

Their influence even touches plant dynamics. Thatching ants form mutualistic relationships with aphids, protecting them in exchange for sugary honeydew. While this can put pressure on host plants, it also illustrates the ants’ deep integration into the web of forest life.

At Wildwood, where forest management focuses on ecological integrity rather than extraction, the quiet labor of the western thatching ant fits perfectly. They are the uncelebrated caretakers of the understory—builders, defenders, farmers, and recyclers—working tirelessly beneath our feet, thriving thanks to the low-impact, selective practices of ecoforestry that protect their habitat and preserve the complex layers of life within Wildwood.