Animal Behavior ch 16-17

Amotz Zahavi

hypothesized that reliable signals will be favored in a population when the signal is costly to the sender.

Ritualization

phenomenon where incipient signals become more stereotyped and unambiguous in a population over evolutionary time

• approach of Ethologists

Reciever Biased Mechanism

focuses on the characteristics of receiver of the message

• approach of Comparative Psychologists

Sources of Ritualization Signals

1. intention movement

2. displacement activities

3. autonomic respones

Intention movement

often possible to judge what an animal intends to do based on their locomotion

ex: Gray Heron male uses a ritualized hunting behavior as part of his courtship display.

Displacement Activities

occur when an animal experiences high motivation for two or more conflicting behavior

• often involve actions that bring comfort to the animal such as scratching, drinking or feeding.

ex: various primates perform self-directed activities such as grooming and scratching in situations likely to involve anxiety and uncertainty.

Autonomic responses

involuntary nervous system and regulates many of the body’s visceral activities.

ex: blushing

Emancipation

process by which a ritualized signal has become freed from the external or internal factors that originally led to it

• over evolutionary time a behavior has lost its original function and now serves only for communication.

Sensory Exploitation

when a receiver has a pre-existing bias for a particular stimulus and the sender’s signal will evolve to exploit this bias

• receiver’s nervous system is wired to make it more responsive to a particular form of the stimulus.

Sensory drive

hypothesis suggests that the receiver ‘s characteristics are shaped by the environment and that will affect signal evolution.

ex: surfperches have evolved visual systems that will help them to obtain prey in their visual environment.

Aggression

defined as a behavior that is intended to inflict noxious stimulation or destruction on another organism

Testosterone

steroid linked to the prenatal and postnatal development of the male gender and physique, which in turn has been linked on average to more physical aggression in many species

Challenge Hypothesis

outlines the dynamic relationship between plasma testosterone levels and aggression in mating contexts in many species.

• predicts that seasonal patterns in testosterone levels in a species are a function of mating system, paternal care, and male-male aggression in seasonal breeders.

Dehydroepiandrosterone (DHEA)

most abundant circulating androgen hormone and can be rapidly metabolized into potent androgens and estrogens.

• non-gonadal steroids may regulate aggression during the non-breeding season.

Glucocorticoid

hormones also have an important role in regulating aggressive behavior.

• affect development of aggression and establishment of social hierarchies.

Agnostic behavior

any social behavior related to fighting

• includes threat, fighting, and submission

• only apply to intraspecific aggression

Threat Behavior

any behavior that signifies hostility or intent to attack another animal. meant to cause the opponent to back down and leave.

Agnostic fighting

form of aggression that escalates from an indecisive threat display.

• rare because of the risk of injury.

Submissive behavior

individual indicating by an act or posture that it will not challenge a dominant individual in a social group.

Factors affecting whether or not animal will engage in conflict:

1. Relative fighting ability

2. relative experience

3. relative value of disputed resource

home range

area in which an animal carries out most of its normal activities.

• may or may not be shared with conspecifics

core area

Within a home range will be a central area where the animal spends most of its time

territory

refers to any sociographical area that an animal of a particular species consistently defends against conspecifics

• defend areas that contain a nest, den or mating site and sufficient food resources for themselves and their young

• Territory size will be determined by how the fitness benefits from holding a territory outweigh the costs

Resource Abundance

Territoriality will be favored when the resource is moderately abundant.

• If the resource is very abundant then there is not a point in expending energy guarding it.

Resource Distribution

Territoriality will be favored when the resource is moderately aggregated in its distribution.

• If the resource is spread out over a large area then the cost of defending it would be high.

intruder Pressure

the number of other individuals willing to compete for a resource will help to determine if it is beneficial to hold a territory.

• The greater the number of competitors the greater the cost of defense.