1. Intraspecific Competition “competition is an interaction between individuals, brought about by a shared requirement for a resource in limited supply, and leading to a reduction in the survivorship, growth and/or reproduction of the competing individuals concerned” Begon, et al. Chapter 6

2. Two types of competition Scramble (exploitative) competition *no direct interaction Contest (direct or interference) competition *some type of confrontation

3. Four characteristics of intraspecific competition The ultimate effect: decreased contribution of individuals to the next generations The resource must be in limited supply. Competing individuals are all essentially equivalent. The effect on any individual increases with increasing number of competitors

4. Density dependent mortality a=density independent; b=undercompensating density dependance; c=overcompensating density dependent

5. Exactly compensating density- dependent mortality

6. Mortality/fecundity equilibrium Reality means there is a broader range in which an equilibrium can be found

7. Results of Intraspecific competition Stress Dispersal Social interactions *dominance *territoriality

8. Territories Type of territory *general - breaks down after breeding season *nesting - (feeding is done elsewhere) *food resource Means of “defending” *Sound *Visual * Scent marking

9. Example: Red Grouse Three social classes *territorial cocks with hens *nonterritorial surplus birds - on periphery *nonterritorial transient birds Fall to Spring - territories defended *By late winter, all surplus birds removed *# & size of territories determined by amount of heather & N content of foliage

10. Red grouse breeding & survival

11. When is defense profitable? When competition exists When enough resources exist When costs do not outweigh benefits

12. Territory size vs. animal size

13. Timing and Size Plants emerging later grow less than predicted by average wt. gain/day Dactylis