Competition: the active demand for a limiting resource shared by two or more individuals or species intraspecific: same species interspecific: different species Competition does NOT occur in just sharing a resource that is not limiting. interference competition: direct sharing, physical contact exploitative competition: indirect sharing, no physical contact scramble competition: effects of competition equal to all contest competition: effects greater in some than others Ultimate effect is decreased reproductive output, lower fitness
Avoiding Intraspecific Competition 1. Dispersal Movement away from natal environment --allows individuals to reach maximum growth potential, little or no intraspecific competition --how a species with growing populations expands its range to new areas
Costs Associated with Dispersal 1. greater risks, higher mortality --naïve --unfamiliar habitat, cover --where to find food 2. low birth rates (fecundity), at first 3. costs balanced with benefits --selection by fitness levels of vs. non-dispersers dispersers
Helping Behavior in Birds • young remain in natal territory for one or more years • become ‘helpers’ at parent’s new nest • gain experience at raising offspring • increase survivorship for breeding • > 220 spp. of birds have helpers
Quiz 1.How would you define interference versus exploitative competition? Scramble versus contest competition? 2.What are two major impacts on a species that can result from intraspecific competition? Give examples. 3.What is asymmetrical competition and give an example? 4.What are two major ways that a species can avoid intraspecific competition? What is helping behavior? 5.How do you define territory and draw a graph that gives the cost and benefits with territories of different sizes?