Dominance and Hormones Flashcards
What are hormones and what organs are they produced in?
1) Chemical messengers produced by the endocrine system that regulated metabolism and behaviour
2) By hypothalamus, testes/ovaries, pancreas, pituitary gland, thyroid gland, thymus, adrenal glands, pineal gland
What are the 2 effects of hormones?
1) Organizational = during development; irreversible structural change
2) Activational = in mature individuals; temporary effects on the body and brain
What is an example of organizational (long-term) hormone effects?
Testosterone during development results in masculine genitals
What is an example of activational (short-term) hormone effects?
Surges of testosterone correlate to muscle building, aggression (responses to dominance), and libido
What are the 2 types of hormones?
1) Steroid hormones (sex hormones and glucocorticoids)
2) Peptide hormones (insulin)
What are some examples of sex hormones?
Estrogens (estradiol) and androgens (testosterone)
What is an example of a glucocorticoid?
Cortisol (stress hormone)
What is the difference between the 2nd and 4th digit of primates?
The 4th digit has more steroid receptors than the 2nd digit
What does high testosterone result in?
Males, as they have higher testosterone, they have a low 2D:4D ratio (4D is longer)
What does low testosterone result in?
Females, as they have higher estrogen than testosterone, have 2D >= 4D
What does a longer 4th digit relative to the 2nd digit (low 4D:2D) indicate?
Higher prenatal androgen exposure (PAE)
What does having equal-length 2nd and 4th digits (or a bigger 2nd digit) indicate?
Lower prenatal androgen exposure (PAE)
What is the relationship between PAE and mating systems?
In more monogamous societies, where male aggression is less frequent (less intrasexual selection), the 2D:4D ratio is ~1 (equal length)
What is the 2D:4D ratio in species with high intrasexual selection?
The 2D:4D ratio is lower (i.e., the 4D is longer than 2D - higher PAE)
What are some examples of monogamous species?
Gibbons, siamang, humans
How do chimpanzees compare to humans and bonobos in terms of 2D:4D ratio?
Chimpanzees have higher PAE (lower 2D:4D ratio) than humans or bonobos = they are more aggressive
What are 4 measures of RS?
1) Earlier age of first reproduction
2) Shorter IBI
3) High infant survival
4) Better survival during mortality crisis
What are C-peptide measurements used for?
As an index of energy condition
What is C-peptide correlated with?
1) Body weight, where higher body weight = increased C-peptide levels in urine
2) Diet, where increased food intake = increased C-peptide
Compare C-peptide levels in captive vs wild chimpanzees
C-peptide levels are higher in captive vs wild animals
Compare C-peptide levels during fruit-abundant vs fruit-scarce periods
C-peptide levels are higher during fruit-abundant periods
Compare C-peptide levels in richer vs poorer habitats
C-peptide levels are higher in richer habitats
What is the relationship between C-peptide/cortisol levels and rank in chimpanzee males?
High-ranking males have lower C-peptides and higher levels of cortisol, indicating they are more energetically stressed
What is cortisol a measure of?
Cortisol is a measure of both energetic and social stress
What is the relationship between cortisol levels and rank in females?
High-ranking females have lower cortisol levels than low-ranking females, indicating they are less energetically stressed
What are 3 features in terms of energy use and hormones of high-ranking male chimpanzees?
1) Lower C-peptide
2) Higher cortisol
3) More energy used
What could be the reason for male chimpanzees being more energetically stressed?
Not because they travel farther than lower-ranking males, but because they are more aggressive (cost of aggression can deplete males)
How does cortisol levels vary in unstable dominance hierarchies vs stable dominance hierarchies in chimpanzees?
Fighting for dominance = more aggression = elevated cortisol levels
How do wild male baboon levels of cortisol differ from chimpanzees (4)?
1) Cortisol levels are highest for higher-ranking males, comparable to levels of lowest ranking males
2) Cortisol levels increase with lower ranking
3) There is no difference in cortisol levels during times of stability vs instability
4) The beta male is the least stressed
What accounts for differences in cortisol levels between alpha males and beta males?
Alpha males are involved in more agonistic and sexual encounters = more energy expenditure (executive stress)
What is executive stress?
Increased energy expenditure from constantly fighting and mating
How do testosterone levels and age correlate?
1) Entrance to adult hierarchy is when testosterone levels peak - this is soon followed by agonistic interaction with another male
2) After peaking, testosterone tends to deplete over time
What happens to male fertility (genetic paternity) over time?
Depletes rapidly over time
What is the relationship between testosterone and male rank?
Higher ranking males exhibit higher levels of testosterone (exhibit more aggression)
What is the challenge hypothesis?
If maintaining high testosterone is costly, then male testosterone should only increase when it is most advantageous (when reproductive opportunities are present); testosterone should peak when challenged to enable aggressive responses
What are the predictions associated with the challenge hypothesis (2)?
1) Increased testosterone production during the peri-ovulatory period (POP) of parous females
2) Rise in testosterone is related to increased aggression and not simply a rise in copulations
What is the correlation between female rank and testosterone levels?
High-ranking females have higher levels of testosterone = exhibit more aggression as they compete for status
What is special about vervet monkeys?
They have blue scrotum, where the more blue = the higher quality/more dominant
