Animal Behavior Quiz 5

Default sex in mammals vs. birds

Default sex mammals : females (no Testosterone)

Default sex birds: Male (no Estradiol)

Studying Hormonal Influences

1) Identify correlation btwn hormone and behavior

2) remove hormone → see if behavior changes (or stops)

• excise organ

• use drug that blocks hormone production

• knockout gene for receptor 

  • progesterone knockout in mice

3) Add hormone → see if behavior returns to normal

Activational effects of Testosterone

In Guinea pigs, male sex drive can recover after castration w/ T implants (Male A,B,C)

• Male A has more T receptors

Behavior is directly linked with what

Hormonal activity

Example of activational effects of T

Japanese Quail

• male behavior (staring at female) stops with castration but returns with T implant

Aromatase : enzyme that converts T to estrogen

estrogen is what drives this behavior → aromatase inhibitor will stop estrogen production → no longer take T → E

the testosterone has to be converted into estrogen (via aromatase) in the brain, and that estrogen is what activates the staring/sexual behavior.

Testosterone Tradeoffs (BENEFITS)

Benefits of T:

• increase atractiveness

• increase territory size

• increase sperm production

• increase # of EPC & EFC

  • EPC = extra pair copulation (act of doing sex)

  • EPF = extra pair fertilization (success fertilize)

Testosterone Tradeoffs (COSTS)

Costs of T:

• increase metabolism

• reduced survival

  • risk of injury and or predation with courtship and fights

• suppression of immune system

• reduced parental care

• T has a high cost

  • otherwise animals would always have T, but they do not

McGlothlin et al 2007 study

Male Carolina dark- eyed juncos charged up with T → shitty parents

gave them T → reduced parental and reproductive success

Behavioral tradeoff caused by T

• although males w/T implants carve out large home range → spend less time gathering food for young

White Crowned Sparrow Study

• Alaska: Only 1 brood → single large T peak before breeding.

• Washington: 2 broods → normal T peak before 1st brood, no 2nd T peak.

• Reason: High T = needed for territory defense & courtship, but it suppresses parental care.

• Adaptation:

  • Alaska: maximize reproduction in short season → strong T surge.

  • Washington: males already mated/territories secured → low T for 2nd brood so they can help parent.

Niche

interelationship of a species with all biotic and abotic factors affecting it or way of life of a species

Two types of niches

Fundamental niche

Realized niche

Fundamental Niche

mainly limited by abiotic factors 

• full range of conditions in which a species can maintain viable pop

Realized niche

limited by biotic factors

• space that an animal occupies in presence of competitors, predators, pathogens, and limited food

Outcomes for when species occupy identical niches

1) Competitive exclusion

• eviction 

• extinction 

2) Resource partitioning : evolution to use diff resource

• Differentiation of niches enables similar species to coexist in a community

Habitat

physical manifestation of species’ niche

Despotic defense

Means the strongest individuals can defend the best resources, but they must balance the cost of defense with the benefit of holding territory.

• Strong, dominant individuals take and defend the best resources.

• Weaker ones are excluded and forced into poorer habitats, where their success is lower.

Example of despotic defense

European great tit

• RS better quality in woodland than hedgerows

• “Despots” (dominant individuals who defend territory) : in woodland force others to lower RS habitat (hedgerows) → birds in hedgerows make best of bad situation

Benefits of territorialty

1) greater access to food (also : shelter, hiding places, water, mates, etc)

2) because more resources → breed earlier and have more young in season

Despotic defense comes with cost

• costs of activity, defense, predation

• cost of T

Example: T implants in lizards

• increase patrolling

• lower survival

both groups were giving T but one with food supplement and one without

• one without food can’t compensate energy loss —> less survival

• one with food can compensate energy loss —> better chance of survival

Evidence of balancing cost-benefits : minimizing costs of defense

• side blotched lizards defend territories with basking rocks (also rocks attract females)

  • reduce rocks : territory becomes larger

  • add rocks : territory becomes smaller 

Few rocks → the lizard has to make its territory larger so it can include enough rocks to survive.

Many rocks → the lizard can keep its territory smaller because there are already plenty of rocks nearby, so no need to waste energy defending a huge area

Economics of Defense

Separating benefits and costs

benefits must outweigh cost ( - - - - line)

have the most reproductive success with least cost of defense

Ideal Free Distribution (IFD)

individuals may sometimes settle in sub-prime habitat due to other factors (other than being kicked out by despot)

Example of Ideal Free Distribution (IFD)

Black cap warbler nests are placed in riparian areas (near river) and sub-prime wood lots

we see that RS in two habitats is equal after riparian areas begin to fill up, WHY?

There is a switch point (fitness payoff is the same)

Both despotic defense and IFD

most systems combine despotic defense and IFD 

ex) Gall aphids

• females fight for access to big leaf (bigger leaf yields more RS) (DESPOTIC DEFENSE)

• loser can either be 2nd on big leaf, or choose smaller leaf (CHOICE DUE TO IFD)

within a leaf, the despots monopolize more RS

losing female chooses btwn second place in leaf or being top-aphid on smaller leaf → yield rough equal RS

Evolutionary Stable Strategy (ESS)

behavioral decision rule that everyone plays by, that one in place cannot be replaced by alternative strategies (other strategies have lower RS)