Ants are adaptable insects found across diverse global environments. Temperature plays a significant role in their survival, as ants, like all living organisms, have specific temperature thresholds beyond which their physiological functions fail, leading to death. This article explores the high and low temperatures lethal to ant colonies and individual ants.
Lethal High Temperatures for Ants
Ants are ectothermic, meaning their body temperature and metabolic rate are directly influenced by the surrounding environment. While many ant species are active in warm conditions, extreme heat can be lethal. Most ants become stressed and less capable of thermoregulation above 40°C (104°F), impacting their development and reproduction. Prolonged exposure to 46-49°C (115-120°F) is generally lethal for many common ant species.
The duration of exposure to high temperatures is as important as the temperature itself. For instance, some desert ants, like the Saharan silver ant, can briefly tolerate surface temperatures up to 70°C (158°F) for short foraging periods, but must maintain their body temperature below 53.6°C (128.48°F) to survive. This specialized ant reflects sunlight with silver hairs and has long legs to minimize contact with the hot ground, allowing it to forage when predators are less active. Even these highly adapted species would perish with sustained exposure to such extreme heat.
Different ant species exhibit varying heat tolerance based on their evolutionary adaptations and native environments. Temperate ant species, for example, have lower heat tolerance compared to those from arid or desert regions. Heat tolerance is a relatively conserved trait, meaning it evolves slowly, making rapid adaptation to sudden temperature increases challenging for many species. When temperatures become too high, ants may seek cooler areas, such as moving deeper into their nests or into human structures.
Lethal Low Temperatures for Ants
As ectotherms, ants’ internal body temperature directly mirrors their environment, making them highly susceptible to cold. Their metabolic rates decrease significantly as temperatures drop, slowing movement and overall activity. Generally, temperatures at or below freezing, 0°C (32°F), are lethal to ants, especially with prolonged exposure. This is primarily due to ice crystal formation within their cells, which can damage cellular structures and tissues.
Some ant species possess mechanisms to enhance their cold tolerance and survive brief periods below freezing. One such mechanism is “supercooling,” where body fluids remain in a liquid state even below their normal freezing point, preventing ice crystal formation. This can be achieved by removing ice-nucleating agents or by producing natural antifreeze compounds like polyols and sugars. However, this supercooled state is thermodynamically unstable and can break down, leading to sudden freezing.
Despite these adaptations, sustained deep cold will eventually lead to death. For example, some fire ant species die quickly when exposed to temperatures in the teens Fahrenheit (below -7°C). Even species that can enter a state of torpor or dormancy by retreating deep underground will succumb if the soil temperature drops below their lethal threshold. The insulating properties of their nests offer some protection, but if the cold penetrates deep enough or persists for too long, colony mortality can be substantial.