Ants, like all ectotherms, have a body temperature and moisture level that is largely determined by their immediate surroundings. They cannot internally regulate their heat or water balance to the degree mammals can, making their microenvironment critically important for survival. Humidity, the amount of water vapor present in the air, directly impacts the rate at which an ant’s body loses water. For a colony to survive and grow, the environment inside the nest must be carefully managed to prevent desiccation.
Why Humidity is Essential for Ant Survival
The primary reason ants seek a humid environment is to prevent their bodies from drying out, a process known as desiccation. While adult ants have a waxy outer layer, or cuticle, which helps to conserve internal moisture, they still lose water through respiration and their body surface. Maintaining high relative humidity in the nest dramatically slows this water loss, allowing the workers to focus their energy on colony tasks.
Humidity is of even greater importance for the ant brood, which includes the eggs, larvae, and pupae. These developmental stages lack the protective cuticle of adult ants, making them exceptionally vulnerable to drying out in low moisture conditions. Eggs and young larvae, in particular, require a near-saturated atmosphere to grow properly, as they are largely composed of water and may even absorb moisture directly from the air.
A moist environment aids in the overall metabolic and osmotic balance of the colony. This environmental stability allows the entire colony to function more efficiently. Different species have different moisture needs, but a consistent, species-appropriate humidity level is required for all ant colonies.
How Ants Regulate Moisture in Their Nests
Ants actively control the moisture levels within their subterranean or arboreal nests through both behavior and architecture. They build complex nests with multiple chambers and tunnels that allow for the creation of distinct microclimates within the colony structure. This architectural complexity includes specialized chambers designed for ventilation or for retaining moisture.
A primary regulatory strategy is the creation of a “hydration gradient” within the nest, giving the colony a range of moisture options. Worker ants constantly monitor the environment and physically move the vulnerable brood to the chamber that offers the optimal humidity level for that specific developmental stage. Eggs and very young larvae are often placed in the deepest, most humid chambers, while pupae may be moved to slightly drier areas.
The choice of nesting material is another deliberate form of moisture control. Ants often select materials like soil, wood, or carton (chewed wood pulp), which possess natural moisture-retaining properties. These materials act as a buffer, absorbing excess water when available and slowly releasing it to maintain a stable, humid atmosphere inside the nest, even as external conditions fluctuate. Workers also bring water back to the nest to moisten the material itself, actively raising the internal humidity.
The Consequences of Too Much or Too Little Humidity
If ants fail to maintain the correct moisture balance, the consequences for the colony can be severe, often leading to rapid decline or total collapse. If the nest humidity is too low, the immediate threat is widespread desiccation, especially among the brood. Larvae and eggs quickly shrivel and die. Adult worker ants must expend effort to find water, sometimes resorting to eating their own brood for the moisture content.
Excessive humidity poses a different, but serious, threat to the colony’s health and food supply. High moisture levels, particularly when coupled with warmth and poor ventilation, create an ideal environment for the growth of mold and harmful fungi. These pathogens can quickly contaminate stored food and infect the ants, with the soft-bodied brood being particularly susceptible.
Too much moisture can also lead to condensation on the walls and ceiling of the nest chambers. This condensation forms water droplets that can trap and drown smaller worker ants and brood due to surface tension. The ants’ constant regulation of moisture is a balancing act necessary to avoid both desiccation and biological contamination.