habitat selection, territoriality, and aggression - chapter 11

habitat selection

this term is influenced by resource availability and the presence of other individuals; use of habitat out of proportion to its availability

resource abundance

the total amount of the resource

resource availability

what is accessible to the individual organism

ideal free distribution (IFD) model

a model that explains how animals distribute themselves among habitats or food patches

conspecific attraction

a phenomenon in which individuals are attracted to others, particularly during habitat selection

Allee effect

A situation in which the fitness of individuals increases with increased population density

conspecific cueing

a hypothesized mechanism to explain conspecific attraction; a settler uses the presence of another individual as a cue to habitat quality

territory

an area defended to obtain exclusive access to the resources it contains

Brown’s economic defendability of space

suggests that territoriality is advantageous when the benefits of controlling a resource outweigh the costs of defending it.

• an organism might be territorial when resources are abundant and predictable, making defense worthwhile, but should forgo territoriality when resources are scarce, unpredictable, or the defense costs are too high

• the optimal territory size is determined by balancing the gains from resource access with the costs of defense

home range

an area of repeated use by an individual that is not defended from others (or conspecifics)

hormone

chemical messengers secreted by specialized glands into the bloodstream, regulating various bodily functions

• these act on target organs and cells, influencing processes like growth, reproduction, and metabolism

aggression

these levels in these species will vary greatly over the course of a year, w/ high levels at the start of the breeding season and low levels outside the breeding season

• variation in *** is coincident with variation in levels of testosterone

challenge hypothesis

the hypothesis that male–male interactions increase plasma testosterone and thus sustain subsequent aggressive behavior

winner effect

a phenomenon in which winning an aggressive interaction enhances the likelihood of winning a subsequent interaction

winner-challenge effect

a situation in which winning an aggressive interaction increases plasma testosterone levels and so enhances aggressive behavior and the likelihood of winning subsequent interactions

observer effect

the phenomenon where an animal's behavior changes due to the presence of an observer, even if the observer is seemingly unobtrusive

• observing aggressive interactions will increase testosterone (aggressive behavior in the observer)