The art of war in animals: spying, patrols, and surprise attacks

A new study published in Trends in Ecology & Evolution reveals that animals exhibit complex behaviors akin to military strategy before conflicts with rival groups. These behaviors include surveillance, patrols, and surprise attacks, suggesting that social animals anticipate and prepare for intergroup confrontations long before direct confrontation occurs. The research, led by scientists Josh Arbon and Andrew Radford from the University of Bristol, explores what they call a “conflict landscape between groups.” This concept draws parallels to the well-known “landscape of fear,” which describes how animals react not just to immediate threats but learn where, when, and with whom such threats are more likely to occur. The findings suggest that animals modify their behavior based on anticipated conflict, altering patterns of movement, communication, and group dynamics. In the case of chimpanzees, evidence shows that prior to territorial disputes, some groups ascend to elevated positions to rest rather than travel or feed, activities that generate noise and attract attention. From these vantage points, they can better monitor their surroundings and assess the proximity of rival groups. Similarly, dwarf mongooses appear to enter a heightened state of alertness, moving more slowly, examining signals more carefully, and increasing the frequency of sentry duties. They also mark their territory more frequently with scent, effectively warning others that the area is claimed without needing physical contact. Not all strategies involve confrontation. Some species, including Japanese macaques, chacma baboons, and certain birds, reduce their presence near borders frequented by neighboring groups. Avoiding known conflict zones can be more advantageous than attempting to defend them, especially when injury risks threaten survival, offspring care, or future food access. In contrast, other animals engage in proactive raids. Male chimpanzee coalitions may silently infiltrate adjacent territories, guided by unfamiliar calls. Dwarf mongooses launch coordinated attacks against rival young, while certain ants raid nests to seize offspring, thereby enhancing their workforce for the future. Within their own groups, animals also prepare for potential conflict. As external threats increase, many species remain closer together, engaging in more frequent grooming and play. These interactions help alleviate anxiety, strengthen social bonds, and encourage collective participation in potentially dangerous actions. Such cohesion appears crucial for successful defense or offense. Group size plays a role in determining outcomes, though it does not fully explain all scenarios. Lions, hyenas, and chimpanzees can estimate the number of adversaries based on vocalizations and decide whether to advance. Numerical advantage diminishes when some members avoid battle, when the opponent knows the terrain better, or when defending a particularly valuable area provides extraordinary motivation. To make these decisions, animals combine recent information with past experiences. A scent indicates passage, but its usefulness wanes over time. A call reveals immediate presence, yet it may not convey the number of rivals. Previous encounters complete this internal map, helping to gauge the threat level accurately. This ability raises intriguing questions about the cognitive capacities of non-human animals and the evolutionary pressures that shape their strategic behaviors. As researchers continue to explore these phenomena, the lines between animal behavior and human warfare blur, revealing a shared complexity in the ways life navigates conflict.