Ants display a curious behavior when one of their own perishes. Their disappearance after death raises questions about how these tiny insects manage their deceased. This behavior points to a sophisticated communication system, which plays a significant role in the daily operations of an ant colony.
The Scent of Death
Ants emit a specific chemical signal upon death, acting as a “smell of death” to their nestmates. The primary chemical responsible is oleic acid, a fatty acid released as an ant’s body begins to decompose, typically within about two days. This chemical is not a “smell” in the human sense, but a chemical cue ants detect with their antennae. The presence of oleic acid signals to other ants that it is deceased.
Ants also identify death by the absence of “life signals,” such as compounds like dolichodial and iridomyrmecin, which are present on living ants but disappear within an hour after death. This dual detection mechanism, involving both the appearance of death chemicals and the disappearance of life chemicals, allows ants to accurately identify and respond to deceased colony members.
Why Ants Smell Dead
The emission of oleic acid serves a crucial purpose for colony hygiene and survival. This chemical signal indicates death, preventing disease or parasite spread within the densely populated colony. Decomposing bodies can harbor harmful bacteria and fungi, which could infect other ants and compromise colony health.
Maintaining a clean environment is paramount for ant colonies, which contain thousands of individuals. Prompt removal of dead ants limits infection risk and prevents pathogens from disseminating throughout the nest. This chemical cue is a vital part of the colony’s overall sanitation strategy.
Colony Response to the Scent
Living ants exhibit a specific behavioral response to oleic acid, known as necrophoresis. This involves worker ants identifying and removing their dead nestmates from the colony. Worker ants detect the chemical signal with their antennae, then pick up the deceased ant with their mandibles and carry it away.
Dead ants are typically transported to designated “graveyard” piles or refuse areas, often some distance from the main nest. This systematic removal of corpses is a sophisticated survival strategy that helps prevent pathogen proliferation and maintains nest health. Some ant species have specialized “undertaker ants” more prone to this task, though any worker ant can engage in necrophoresis.
Beyond Death: Chemical Signals in the Colony
The “death smell” is one example of the complex chemical communication system used by ants. Ants rely on a variety of chemical signals, known as pheromones, for many aspects of their social lives. These chemical substances are produced and released by ants to trigger specific behaviors in other colony members.
Pheromones are used for tasks such as laying trails to food sources, alerting the colony to danger through alarm signals, and recognizing nestmates. This chemical language allows ants to coordinate activities, maintain social structure, and respond to threats effectively. The death signal is just one sophisticated component of how their chemical communication maintains the organization and health of the entire colony.