Intraspecific Competition …is an interaction in population ecology, whereby members of the same species compete for limited resources.

Competition for resources Intraspecific competition more severe than inter- as individuals are competing for the same resource (food, nest sites, mates). Competition is damaging to individuals. It promotes physiological stress – poor health, increased risk of disease, increased mortality, decreased natality, overall reduced fitness.

Living in groups Most animals live in groups, few live solitary lives eg some of the cat family – tigers. Groups are organised and co-operative. Individuals assist one another. Group maintenance and behaviour are behavioural adaptations – have been selected for as they enhance survival and reproductive success. Advantages of group living must outweigh disadvantages for group living to continue.

Advantages of group living Protection from physical environment Greater ability to detect predators Better defence against predators Role specialisation eg social insect colonies Greater ability to find food Mates available Assistance with rearing young Provision of learning opportunities for young Regulation of population through controlled access to mates/resources

Disadvantages of group living Increase intraspecific competition Increased risk of spread of disease/parasites Access to mates may be restricted to only higher-ranked males Increased risk of infant mortality eg infanticide in lions Activity: ‘Altruism’ and ‘Kin selection’ notes. Do questions on Co-operative groups.

Aggressive behaviour Competition for resources may promote aggression between individuals. Especially common between mates during breeding season. If one/both die, genes lost to gene pool and group loses males needed for group management, protection and breeding. The stronger/healthier male wins access to a group/females and is ‘fitter’ so contributes a higher proportion of alleles. Kangaroo boxing

Agonistic behaviour Results in a reduction of aggression within members of a species. Postures, gestures, vocalisations that threaten an animal are understood and the threatened animal backs off or displays submissive behaviour. So…serious encounters are rare. Agonistic behaviour tends to be ritualised – the dominant/submissive postures are recognised by group members. Limits aggression leading to fatalities.

Ritualised postures Dominant postures: Stand erect/large Head/tail erect ‘eye balling’ Hackles up Teeth displayed Vocalisation eg growling

Submissive postures: Stature small/cowering Belly/throat displayed Tail down/between legs Head down/eyes down or averted Teeth not displayed Vocalisations (whimpering, whining) Submissive behaviours are often copies of juvenile behaviours (appease aggressive adults). Activity – Intraspecific competition and aggression questions . BZ pgs 65-67

Territory A territory is occupied by an animal, which it defends against others. A home range is a geographical area that animals seldom leave, which is defended. Animals hold territory through aggressive behaviour.

Adaptive features of territoriality Ensures enough space for each animal Decreases risk of disease/parasites Most successful males hold best territory – offspring get best genes Once territories established, resources are divided. Losers spread out to find food rather than fighting Ensures enough food Ensures safe/protected nest/home for young or place to breed Become familiar with the area. Learns where resources are, and protection from predators

Marking and defending territories Birds – mark territories by singing on boundaries at dawn/dusk Urine/faeces Scent glands Crabs wave claws frantically Howler monkeys – loudest morning chorus Nb. Some animals that range far/wide only guard territory during breeding season eg seabirds

Hierachies ‘Pecking order’ Hierachies are established competitively. Once in place, reduces competition and tension in the group. So who dominates in a group? larger, more mature Offspring or not Knowing the territory/being a stranger Healthy rather than sick The dominant has first food, first choice of mate, responsibilities Dominance is maintained by posture and display. Activity – Complete ‘Hierachy’ worksheet