Chapter 7: Territoriality and Migration Flashcards
Sometimes animals actually do better in their second choice habitat rather than their preferred habitat. How does Ideal Free Distribution come to play in this?
ideal free distribution: animals are free to move to any habitat. We expect them to distribute themselves so that they maximize their potential fitness.
At equilibrium fitness should be the same in different habitats.
If one habitat is superior to another, we expect animals to move there, INCREASING COMPETITION. Animals will continue to move there until competition makes it unprofitable.
under an ideal free distribution, the distribution of animals reflects the distribution of ___
resources (ex/ food, or safety as a resource (less predators in a certain locatione)
density dependent habitat selection
when animals must make a habitat selection not just based on food, but also on the intensity of competition, as reflected by the density of organisms in a location.
in ideal free distribution theory, as the number of individuals in a patch increases, the ____ of the patch is assumed to decline
QUALITY of the patch location declines. the key prediction is that individuals will settle on sites where their reproductive success is maximized.
explain habitat selection and the ideal free distribution theory in Red Knot birds
red knots feed on molluscs that occur in varying densities in the mud. these birds are not uniformly distributed over territories however ( as in the surface distribution model).
Instead, as predicted by the ideal free distribution theory, individual birds achieved equal food intakes by shifting from site to site depending on the availability of mollusks and the density of their fellow red knots in the ra.
thus, over both large and small spatial scales, animals appear to minimize resource competition in ways that maximize their probable fitness.
cost-benefit appraoch to territoriality
requires that we consider the disadvantages of territorial defense. Defending a territory has costs such as energy and risk of injury.
economic defensibility
the trade-off in costs vs benefits for maintaining the territory
benefit: high quality food, more mates
con: hard to defend, risk of injury.
explain male chimpanzee territory patrolling
territory defense may be expensive, but it may have great value
male chimpanzees patrol their territory and can even kill any trespassers. some bands have killed so many of their neighbors that they could EXPAND THEIR TERRITORY, giving them access to food and more mates.
Explain the link between testosterone and territoriality
the more testosterone, the more hyperterritorial males are. this is seen in lizards. lizard males with more testosterone mate guard, territory guard, and are so preoccupied with doing pushups they exert so much energy and can die.
high testosterone levels which promote territorial defense may actually impair immune function or reduce parental care. these are all costs to territoriality.
Explain the energetic costs of testosterone induced territoriality in Yarrow’s spiny lizard.
- Males of yarrow’s spiny lizard were given an experimental implant of testosterone. These lizards moved about the territory more than the controls increasing their energetic costs.
- Males of Yarrow’s spiny lizard that received an experimental implant of testosterone spent much more time moving about than control males.
- Testosterone-implanted males that did not receive a food supplement (mealworms) disappeared at a faster rate than control males. testosterone implanted males that DID have a food supplement survived as well or better than controls (because they didn’t need to waste time foraging)
therefore: The high mortality of unfed lizards stems from the high energetic costs of experimentally induced territorial behaviour
Because the costs of territoriality can be very high, we predict that coexistance on an undefended living space or home range should evolve when the ____ of owning a valuable space do not outweigh the ____ of monopolization.
Because the costs of territoriality can be very high, we predict that coexistence on an undefended living space or home range should evolve when the BENEFITS of owning a valuable space do not outweigh the COSTS of monopolization.
explain how heron living strattegies change from territorial to social coexistance.
During winter on the coast of British Columbia, individual herons defend feeding territories. But during the breeding season, large feeding flocks of great blue herons often form at the same sites near breeding colonies. Attempting to defend a territory becomes futile, due to the density of other foragers. Territoriality breaks down and is replaced by social foraging.
T/F: Those with superior competitive ability should be found in the highest-quality habitat
True. those with resource-holding potential and higher competitive ability should be more territorial and should be found in higher quality habitats.
Explain habitat quality and migration in redstarts according to resource holding potential.
American redstarts are warblers that COMPETE for territories on their tropical wintering grounds in the Caribbean and Central America.
In Jamaica, DOMINANT males tend to occupy black mangrove forests on the coast while SUBMISSIVE females and males are found in second-growth scrub inland.
Redstarts occupying HIGHER QUALITY territories in mangrove can leave earlier for the breeding grounds than redstarts in low quality second-growth scrub. Also, the ones that are more dominant and territorial have higher numbers of young.
When a territory owner is challenged, who wins?
almost always the owner. the challenger almost always contests.
three hypotheses as to why challengers concede defeat so quickly even though there a fitness benefits to be gained by challenging for a territory
1) arbitrary contest resolution hypothesis
2) resource-holding potential hypothesis
3) payoff asymmetry hypothesis
