6. Evolution & Behavioral Ecology

Behavioral Ecology def.

the study of ecological & evolutionary basis of animal behavior

Evolution def. 

• process of change through time in the genetically determined characteristics of organisms being passed on to successive generations

• change in allele frequencies in a population over successive generations, ultimately involves changes in the frequency of heritable traits

Natural selection def.

Nonrandom process by which individuals with certain genotypes-phenotypes are favored to survive & reproduce over other phenotypes in a particular environment

Variation in the populations def.

Individuals are not exactly alike (different genotypes and phenotypes)

• different allele combinations can represent advantages or disadvantages in a given environment

The environment def.

Conditions and resources show variation, some become limiting factors

Differences in survival and reproductive success

only individuals with advantageous characteristics survive and then reproduce 

Heredity def. 

parents able to pass on some of their distinctive characteristics

Fitness def.

a measure of the genetic information contributed by an organism’s descendants to future generations 

Behaviors influence fitness therefore….

Behavioral traits are often shaped by natural selection

Two main causes of behaviors

Proximate and ultimate

Proximate def.

An immediate underlying cause based on the operation of internal mechanisms possessed by an individual

ex. an increase in testosterone secretion in the male will cause vigorous displays toward females

Ultimate def.

The evolutionary, historical reason why something is the way it is

ex. females prefer males who vigorously display, leading to selection of those males and their traits

Adaptations def. 

A hereditary trait that has spread or is spreading by natural selection and has replaced or is replacing any alternative traits in the species

Foraging behavior

Animals make behavioral choices that enhance their energy gain and reduce their risk of becoming prey

Optimal foraging theory def.

Animals will maximize the amount of energy gained per unit of feeding time, and minimize the risks involved

Foraging Behavior 

Profitability (P) of a food item depends on how much energy (E) the animal gets from the food relative to amount of time (t) it depends obtaining the food:

P = E / t

Infanticide in lions

Male lions killing male cubs to increase chance of mating with females and decrease number of males

Stotting behavior

Jumping high in gazelles, deers to avoid being prey, looking out for survival, traveling, survival

• anti ambush hypothesis

• alarm signal hypothesis

• social cohesion hypothesis

• confusion effect hypothesis

• Purist deterrence hypothesis

stotting gazaelles = antipredator behavior

pursuit deterrence: predator breaks off pursuit

Elaborate traits exhibited by male birds

These traits are costly, detertimenetal to survival?

• energy

• time

• visibility

• developmental tradeoffs 

Sexual Selection

Darwin proposed that extravagant features of some males resulted from sexual selection 

Long-tailed widowbird

the longer the tale of the male the more nests it had

Mating behavior

In some species, male provide females with a direct benefit for mating; gifts of food, help in rearing young, access to a territory with good nesting sites, food, etc

in others, males provide nothing, instead females may receive indirect genetic benefits 

The handicap hypothesis:

a male that can support a costly ornament is likely to be a vigorous individual and whose overall genetic quality is high

The sexy son hypothesis

the female receives indirect genetic benefits through her sons, who will themselves be attractive to females and produce many offspring 

Male ornaments signal…

good genes

Extra-pair copulation def.

an individual that has a social bond with a mate also breeds with other individuals

superior genotypes produce offspring with better genetics? 

Mate guarding by males

is costly