Love Thine enemies!
Say Swedish researchers. The ability to tolerate enemies causes a condition that two researchers from Lund University call "coevolution," and it entails situations in which the victim, instead of fighting or fleeing, allows the enemy to remain and, instead, hope to survive with the consequences.

“This is a new way of viewing the evolution of enemy-victim interactions in animals. The role of tolerance in such interactions has previously been discussed primarily in the context of the plant world. We believe that tolerance could be at least as important as resistance in animal coevolution between enemies and their victims,” Erik Svensson, Professor of Animal Ecology at Lund University.

Examples of ‘coevolution’, when the enemy and the victim influence each other’s development, include plant studies of relationships between a parasite (the enemy) and its host plant (the victim).

In an article in Trends in Ecology & Evolution journal, Svensson and his colleague, Lars Råberg, discuss the evolution of enemy-victim relations in animals. For example, the great spotted cuckoo lays its eggs in the nest of the European magpie and lets the magpie pair raise its young. Because there is a risk of rejecting their own offspring, the magpies tolerate the intruders, entailing that the victim tries to live with the presence of the enemy instead of resisting.

Svensson's research on damselflies shows enemy-victim relationships within the same species after mating, when females are subject to attempts and harassment from other males (quite possibly a.k.a. dudeflies???), that would decrease her number of eggs. Lady damselflies have developed a higher tolerance to such mating harassment, and they buffer the negative effects of mating harassment to benefit their potential offspring.

In other experiments in which mice were infected with malaria, Råberg found that some mice did not become ill to the same extent, despite having the same number of parasites. He concluded that tolerance can also reflect itself in how sensitive a victim is to an enemy.