Population Regulation and Group-Size Regulation

Question 1

Define a group. What are the group terms for canids, primates, lions, and ungulates?

Answer 1

Any social unit in gregarious and social mammals and birds.

Pack; troop/band; pride; herd.

Question 2

Mated pairs and dependent offspring with parent(s) are not usually considered a “social group”, but rather a _____.

Answer 2

Family.

Question 3

Extended families (wolves, dholes, lycaons, marmosets, tamarins) are considered social groups. They are usually composed of more than what? What are some of these animals usually referred to as?

Answer 3

Two generations, uncles, aunts, etc.

Cooperative breeders.

Question 4

Define a population.

Answer 4

Group of organisms of the same species in a particular place.

Question 5

Population growth can be regulated by external factors or internal factors. What are the two intrinsic factors?

Answer 5

Behavioural, physiological.

Question 6

Reptiles, birds and mammals tend to be K-selected. What are exceptions to this?

Answer 6

Many mouse-like rodents.

Question 7

True or false: amphibians are generally r-selected.

Answer 7

True.

Question 8

Are fish r-selected or K-selected? Provide examples.

Answer 8

Span r-K continuum.

K-selected: pipefish, seahorse.

r-selected: killifish, minnows.

Question 9

Define density-independent and density-dependent factors. Do they mainly affect K-selected or r-selected species?

Answer 9

Density-independent factors: climate, food, fires, floods. Some may be modified by population density, provoke random fluctuations. Affect mainly r-selected (opportunistic) species.

Density-dependent factors: competition (inter or intra), parasitism, disease, predation, shelter availability, food supply. Affect mainly K-selected (sedentary) species.

Question 10

What are the two suppressive or inhibitory mechanisms in groups (and populations)?

Answer 10

Behavioural, physiological.

Question 11

List the two temporal variables affecting behavioural and physiological mechanisms. Provide examples for each.

Answer 11

Preconception (e.g., psychological castration in males, psychological contraception in females).

Postconception (e.g., psychological abortion in females).

Question 12

Increase in competition (intra or inter-specific) and environmental constraints usually equals what?

Answer 12

Increase in deaths, emigrations, decrease in birth rates, etc.

Question 13

Epideictic displays are what? Provide an example. What is the other type of display?

Answer 13

Behavioural mean to assess population density; voluntary homeostatic mechanism to inhibit reproduction.

E.g., flocking.

Epigamic (for courtship).

Question 14

Aside from epideictic displays, list three other behavioural mechanisms.

Answer 14

Territory size, dominance hierarchies, overpopulation and social pathology.

Question 15

Regarding reproduction, dominance hierarchies do what?

Answer 15

Control group size; 1 male and 1 female reproduce, others typically don’t.

Question 16

The formation of withdrawn groups is known as what?

Answer 16

Behavioural sink.

Question 17

Describe overpopulation in mice.

Answer 17

Piles, fights, popcorn effect. Social chaos. Hypersexuality, homosexuality, cannibalism.

Question 18

Overpopulation effects are somewhat similar in humans, but they are dependent on what?

Answer 18

Culture and social class (high density often = poverty).

Question 19

In hunter-gatherer societies, overpopulation typically results in what?

Answer 19

Delayed onset puberty, prolonged lactation, preferential female infanticide.

Question 20

Overpopulation triggers _____ inhibition and dysfunctions.

Answer 20

Reproductive.

Question 21

Selye (1950) and the general adaptation syndrome said what of the HPA axis?

Answer 21

Stress activates hypothalamus, resulting in cortisol or corticosterone.

Question 22

Regarding the stress response, how are tree shrews unique?

Answer 22

Need high levels of cortisol to reproduce.

Question 23

Cortisol is mostly released in _____, while corticosterone is mostly released in _____. In general, what do all animals have?

Answer 23

Fish; rodents.

Both.

Question 24

Activating both cortisol and corticosterone results in what?

Answer 24

Reduction of reproduction hormone in HPG axis.

Question 25

Christian (1959) proposed what physiological mechanism?

Answer 25

Agonistic interactions → prolonged psychological stress → exhaustion of the adrenal glands → disease → death.

Question 26

Christian (1978) suggested suppression or inhibition of what six physiological mechanisms? What is important to note about these effects?

Answer 26

Immune response.

Inflammatory response.

Growth and sexual maturation.

Spermatogenesis.

Ovulation.

Lactation.

Effects persist from one generation to the other despite return to normal population density.

Question 27

Data from which animals support Christian’s regulatory mechanism? Is density the stressor?

Answer 27

Data from deer, rats, mice and woodchucks.

Stressor not density, but level of agonistic behaviours (from competition for limited and limiting resources).

Question 28

Another factor in physiological mechanisms is pheromones. This is generalizable to which animals?

Answer 28

Macrosmatic mammals.

Question 29

Bronson (1971, 1979) showed that the urine from stressed mice will produce what?

Answer 29

Adrenocortical response in naive mice.

Question 30

Females grouped together release a pheromone that delays _____ in other females.

Answer 30

Sexual maturation.

Question 31

Smell from a _____ accelerates sexual maturation of young females.

Answer 31

Mature male.

Question 32

List three problems with pheromonal mice studies.

Answer 32

Laboratory populations prevent ecological validity.

Natural environment studies difficult to control factors in.

Regulatory mechanisms: evolved for population control; is stress adaptive; did it evolve as regulatory mechanism?

Question 33

Describe the favour of group selection (interdemic selection) from Wynne-Edwards (1962) among the scientific community.

Answer 33

Not favoured among modern behavioural scientists (behavioural ecologists, sociobiologists).

Question 34

Kin selection could be a solution. Why?

Answer 34

Animal sacrifices its reproductive output if survival of the group (kin) is ensured.

Question 35

Most of the evidence suggests that self-regulation of populations or groups did not what?

Answer 35

Evolve for purpose of controlling group or population size.