Mating system and territorial behaviour Aglais io employs a
monogamous mating system, which means that they only mate with one partner for a period of time. This is due to their life cycle in which females are receptive only during an
eclosion period, after
overwintering. The pairs only mate once after overwintering, as it is very difficult to find a receptive female after that period. In species where the range of the females is not defensible by a male, the males must defend a single desirable area that females will come through, such as dense food areas, watering holes, or favourable nesting sites. The males then attempt to mate with the females as they are passing through. Holding a desirable territory increases the male's likelihood of finding a mate and therefore increases his reproductive success. However, each individual needs to weigh the benefits of mating with the costs of defending a territory.
Aglais io exhibits this type of territorial behaviour, and must defend a desirable territory from other males. If only one of the males knows the territory well, he will successfully chase off any intruders. On the other hand, if both males are familiar with the territory, there will be a contest between the two to determine which of them stays in the territory. The most desirable sites are those that will increase the male's quota of females. These sites are generally feeding and oviposition sites, which are sought after by females. This territorial behaviour is reinforced by the fact that these sites are all concentrated. If the valuable resources were dispersed, there would be less observable territorial behaviour. To find mates and defend their territory,
Aglais io exhibits perching behaviour. The male butterflies will perch on an object at a specific height where they can observe passing flying objects. Every time they see a passing object of their own species or of a relevant species, they will fly straight towards the object until they are approximately 10 cm away. If they encounter a male, the resident male will chase him off his territory. If the resident male encounters a female, he will pursue her until she lands and mating will occur. The courtship is extended in this species. The male goes through a long chase before the female allows him to mate. He must demonstrate high performance flight. The monandrous mating system has caused the evolution of a shorter life span in males of this species. In
polygynous butterflies, the male's reproductive success is largely dependent on life span. Therefore, the longer a male lives, the more he can reproduce, so he has a higher fitness. Therefore, males tend to live as long as the females. In
A. io the synchronous eclosion at the end of winter cause males to only mate once. Their reproductive success is therefore not linked to how long they live, and there is no selective pressure to live longer. Therefore, the life span of males is shorter than the lifespan of the females. The eyespots are brilliantly coloured concentric circles. Avian predators of the butterfly include
blue tits,
pied flycatchers and other small
passerine birds. The first line of defence against these predators for many hibernating butterflies is
crypsis, a process in which the butterflies blend into their environment by mimicking a leaf and staying immobile. While the main targets of these anti-predation measures are small passerine birds, even larger birds such as chickens have been shown to react to the stimuli and avoid the butterfly when exposed to eyespots.
Avian predators Research has shown that avian predators attempting to attack a butterfly hesitate for a much longer time if they encounter butterflies that display their eyespots than if they encounter butterflies whose eyespots are covered. In addition, the predators delay their return to the butterfly if it displays eyespots and some predators even flee before attacking the butterfly. In one experiment, observed responses of the avian predators to the eyespots included increased vigilance, a delay in their return to the peacock butterfly, and the production of
alarm calls associated with ground-based predators.
Rodent predators While hibernating in dark wintering areas, the peacock butterfly frequently encounters
rodent predators such as small
mice. Against these predators, however, the visual display of eyespots is ineffective due to the darkness of the environment. Instead, these rodent predators show a much stronger adverse reaction to the butterfly when it produces its auditory hissing signal. This indicates that for rodent predators, it is the auditory signal produced by the butterfly that serves as a deterrent. ==Taxonomy==