Dominance and Hormones

Question 1

What are hormones and what organs are they produced in?

Answer 1

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

Question 2

What are the 2 effects of hormones?

Answer 2

1) Organizational = during development; irreversible structural change
2) Activational = in mature individuals; temporary effects on the body and brain

Question 3

What is an example of organizational (long-term) hormone effects?

Answer 3

Testosterone during development results in masculine genitals

Question 4

What is an example of activational (short-term) hormone effects?

Answer 4

Surges of testosterone correlate to muscle building, aggression (responses to dominance), and libido

Question 5

What are the 2 types of hormones?

Answer 5

1) Steroid hormones (sex hormones and glucocorticoids)
2) Peptide hormones (insulin)

Question 6

What are some examples of sex hormones?

Answer 6

Estrogens (estradiol) and androgens (testosterone)

Question 7

What is an example of a glucocorticoid?

Answer 7

Cortisol (stress hormone)

Question 8

What is the difference between the 2nd and 4th digit of primates?

Answer 8

The 4th digit has more steroid receptors than the 2nd digit

Question 9

What does high testosterone result in?

Answer 9

Males, as they have higher testosterone, they have a low 2D:4D ratio (4D is longer)

Question 10

What does low testosterone result in?

Answer 10

Females, as they have higher estrogen than testosterone, have 2D >= 4D

Question 11

What does a longer 4th digit relative to the 2nd digit (low 4D:2D) indicate?

Answer 11

Higher prenatal androgen exposure (PAE)

Question 12

What does having equal-length 2nd and 4th digits (or a bigger 2nd digit) indicate?

Answer 12

Lower prenatal androgen exposure (PAE)

Question 13

What is the relationship between PAE and mating systems?

Answer 13

In more monogamous societies, where male aggression is less frequent (less intrasexual selection), the 2D:4D ratio is ~1 (equal length)

Question 14

What is the 2D:4D ratio in species with high intrasexual selection?

Answer 14

The 2D:4D ratio is lower (i.e., the 4D is longer than 2D - higher PAE)

Question 15

What are some examples of monogamous species?

Answer 15

Gibbons, siamang, humans

Question 16

How do chimpanzees compare to humans and bonobos in terms of 2D:4D ratio?

Answer 16

Chimpanzees have higher PAE (lower 2D:4D ratio) than humans or bonobos = they are more aggressive

Question 17

What are 4 measures of RS?

Answer 17

1) Earlier age of first reproduction
2) Shorter IBI
3) High infant survival
4) Better survival during mortality crisis

Question 18

What are C-peptide measurements used for?

Answer 18

As an index of energy condition

Question 19

What is C-peptide correlated with?

Answer 19

1) Body weight, where higher body weight = increased C-peptide levels in urine
2) Diet, where increased food intake = increased C-peptide

Question 20

Compare C-peptide levels in captive vs wild chimpanzees

Answer 20

C-peptide levels are higher in captive vs wild animals

Question 21

Compare C-peptide levels during fruit-abundant vs fruit-scarce periods

Answer 21

C-peptide levels are higher during fruit-abundant periods

Question 22

Compare C-peptide levels in richer vs poorer habitats

Answer 22

C-peptide levels are higher in richer habitats

Question 23

What is the relationship between C-peptide/cortisol levels and rank in chimpanzee males?

Answer 23

High-ranking males have lower C-peptides and higher levels of cortisol, indicating they are more energetically stressed

Question 24

What is cortisol a measure of?

Answer 24

Cortisol is a measure of both energetic and social stress

Question 25

What is the relationship between cortisol levels and rank in females?

Answer 25

High-ranking females have lower cortisol levels than low-ranking females, indicating they are less energetically stressed

Question 26

What are 3 features in terms of energy use and hormones of high-ranking male chimpanzees?

Answer 26

1) Lower C-peptide 2) Higher cortisol 3) More energy used

Question 27

What could be the reason for male chimpanzees being more energetically stressed?

Answer 27

Not because they travel farther than lower-ranking males, but because they are more aggressive (cost of aggression can deplete males)

Question 28

How does cortisol levels vary in unstable dominance hierarchies vs stable dominance hierarchies in chimpanzees?

Answer 28

Fighting for dominance = more aggression = elevated cortisol levels

Question 29

How do wild male baboon levels of cortisol differ from chimpanzees (4)?

Answer 29

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

Question 30

What accounts for differences in cortisol levels between alpha males and beta males?

Answer 30

Alpha males are involved in more agonistic and sexual encounters = more energy expenditure (executive stress)

Question 31

What is executive stress?

Answer 31

Increased energy expenditure from constantly fighting and mating

Question 32

How do testosterone levels and age correlate?

Answer 32

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

Question 33

What happens to male fertility (genetic paternity) over time?

Answer 33

Depletes rapidly over time

Question 34

What is the relationship between testosterone and male rank?

Answer 34

Higher ranking males exhibit higher levels of testosterone (exhibit more aggression)

Question 35

What is the challenge hypothesis?

Answer 35

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

Question 36

What are the predictions associated with the challenge hypothesis (2)?

Answer 36

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

Question 37

What is the correlation between female rank and testosterone levels?

Answer 37

High-ranking females have higher levels of testosterone = exhibit more aggression as they compete for status

Question 38

What is special about vervet monkeys?

Answer 38

They have blue scrotum, where the more blue = the higher quality/more dominant