Habitat and Territory

• Habitat Selection: resource availability and the presence of others can influence habitat selection.
• Ideal Free Distribution model: explains how animals distribute themselves among habitats.

  Assume:

  • individuals attempt to maximize fitness
  • habitat locations differ in resources and individuals know this
  • individuals are free to move at no cost
• Predictions of the Ideal Free Distribution model:

  • individuals will settle in habitats based on the relative fitness payoffs, the number of individuals in each habitat will be proportional to habitat quality.
  • in the end, all individuals will have the same fitness no matter where they settle.
• Red Knots appear to achieve equal food intake by shifting from site to site depending on mollusk availability and red knot distribution.
• Conspecific Attraction

  • The IFD model assumes that competition for resources results in a decline in individual fitness as the number of individuals in a habitat increases.
  • In fact, individuals sometimes exhibit the opposite pattern- instead of avoiding others, they settle near them, in a pattern called conspecific attraction.
• 2 Hypotheses for Conspecific Attraction:

  1. When population size is low, individual fitness may increase as population density increases. (Allee effect)
  2. The presence of another is a cue that the location is high quality. (conspecific cueing)
• In desert clickers, males use the presence of another male as an indicator of patch quality. Males will prefer bushes with more clickers in them. Ten males clicking in the bush will be more successful at attracting females, compared to only one clicking.  (Allee Effect)
• Spiny Lizards: Elevated testosterone makes lizards more territorial. Elevated territoriality that comes from extra testosterone makes lizards less likely to survive.
• Territoriality:

  • Territoriality is expensive and requires time and effort to defend against rivals, so we need to use the cost-benefit approach to think about territoriality. 
• When animals settle in an area, they can establish a territory, an area defended to obtain exclusive use of the resources it contains (food, nesting sites, access to mates).
•  Distinguish between dispersal and migration. 

  Dispersal is a short distance and one-way travel. Migration is a longer distance and a two-way travel.
• Damselflies: Territorial males had higher fat reserves than nonterritorial males. The males with more territories had the availability of more resources. Territorial defense is energetically expensive, so only males with high energy reserves can successfully defend a territory.
• A species is known to exhibit a win-stay-lose-shift breeding dispersal pattern. You observe that individual A of this species raises 6 offspring, while individual B experiences reproductive failure. What can you predict based on these observations? 


  A will likely exhibit site fidelity in breeding site selection next year.
• Why Give Up When Competing for a Territory?

  If winners in competitions gain substantial fitness benefits, why do we often see challengers quickly concede defeat instead of continuing to fight?
• The Hawk Dove Game:

  • Competition is by displays (the “dove” strategy) or fights (the “hawk” strategy).
  • The Hawks always beat doves in competition. Dove vs. dove and hawk vs. hawk have a 50/50 chance of victory distribution.
  • There is, therefore, no best pure strategy because an all-hawk population can be invaded by doves and an all-dove population can be invaded by hawks.
  • “mixed ESS” (Mixed Evolutionary Stable Strategy), where at equilibrium both strategies are present in a population.