Effects of Food Shortage and Territoriality

overpopulation

leads to food shortage

population has a food shortage - population suffers from

malnutrition

effects of malnutrition

• increased mortality especially for the young

  • need more food for growing

  • unable to fend for themselves

  • dont have as many fat reserves as an adult

• Reduced resistance to disease and parasites

• Reduced Fecundity (potential reproductive capacity of an organism)

• loss of inherent defensive behaviour

how do animals die from predation in severe starvation cases

when animals are severely starving, their immediate need for food becomes so desperate that it overrides their usual safety behaviors.

The drive to avoid starvation forces them to take greater risks - they might venture into open areas they'd normally avoid, forage during dangerous times, or spend more time searching for food instead of staying vigilant for predators

how does food shortage autoregulate the population size

• death rate increases

overpopulation and territorial behavior

overpopulation increases intraspecific competition for space

how is territory marked

• chemically

• visually

• through ritual fights (almost never fatal)

Question!

ritual fights are rarely fatal, however in what cases are they fatal

• when the stakes are very high

  • eg male sea lions fight to the death for exclusive breeding rights over the females

Regulation through Spatial Interaction

• population size is controlled by how organisms physically interact with and compete for space

Only the fittest maintain adequate territories - hence survive and reproduce

• populations become denser, organisms interact more frequently, compete more intensely for territories and resources, and may be forced to move to new areas