Population Regulation and Group-Size Regulation Flashcards
Define a group. What are the group terms for canids, primates, lions, and ungulates?
Any social unit in gregarious and social mammals and birds.
Pack; troop/band; pride; herd.
Mated pairs and dependent offspring with parent(s) are not usually considered a “social group”, but rather a _____.
Family.
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?
Two generations, uncles, aunts, etc.
Cooperative breeders.
Define a population.
Group of organisms of the same species in a particular place.
Population growth can be regulated by external factors or internal factors. What are the two intrinsic factors?
Behavioural, physiological.
Reptiles, birds and mammals tend to be K-selected. What are exceptions to this?
Many mouse-like rodents.
True or false: amphibians are generally r-selected.
True.
Are fish r-selected or K-selected? Provide examples.
Span r-K continuum.
K-selected: pipefish, seahorse.
r-selected: killifish, minnows.
Define density-independent and density-dependent factors. Do they mainly affect K-selected or r-selected species?
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.
What are the two suppressive or inhibitory mechanisms in groups (and populations)?
Behavioural, physiological.
List the two temporal variables affecting behavioural and physiological mechanisms. Provide examples for each.
Preconception (e.g., psychological castration in males, psychological contraception in females).
Postconception (e.g., psychological abortion in females).
Increase in competition (intra or inter-specific) and environmental constraints usually equals what?
Increase in deaths, emigrations, decrease in birth rates, etc.
Epideictic displays are what? Provide an example. What is the other type of display?
Behavioural mean to assess population density; voluntary homeostatic mechanism to inhibit reproduction.
E.g., flocking.
Epigamic (for courtship).
Aside from epideictic displays, list three other behavioural mechanisms.
Territory size, dominance hierarchies, overpopulation and social pathology.
Regarding reproduction, dominance hierarchies do what?
Control group size; 1 male and 1 female reproduce, others typically don’t.
The formation of withdrawn groups is known as what?
Behavioural sink.
Describe overpopulation in mice.
Piles, fights, popcorn effect. Social chaos. Hypersexuality, homosexuality, cannibalism.
Overpopulation effects are somewhat similar in humans, but they are dependent on what?
Culture and social class (high density often = poverty).
In hunter-gatherer societies, overpopulation typically results in what?
Delayed onset puberty, prolonged lactation, preferential female infanticide.
Overpopulation triggers _____ inhibition and dysfunctions.
Reproductive.
Selye (1950) and the general adaptation syndrome said what of the HPA axis?
Stress activates hypothalamus, resulting in cortisol or corticosterone.
Regarding the stress response, how are tree shrews unique?
Need high levels of cortisol to reproduce.
Cortisol is mostly released in _____, while corticosterone is mostly released in _____. In general, what do all animals have?
Fish; rodents.
Both.
Activating both cortisol and corticosterone results in what?
Reduction of reproduction hormone in HPG axis.
Christian (1959) proposed what physiological mechanism?
Agonistic interactions → prolonged psychological stress → exhaustion of the adrenal glands → disease → death.
Christian (1978) suggested suppression or inhibition of what six physiological mechanisms? What is important to note about these effects?
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.
Data from which animals support Christian’s regulatory mechanism? Is density the stressor?
Data from deer, rats, mice and woodchucks.
Stressor not density, but level of agonistic behaviours (from competition for limited and limiting resources).
Another factor in physiological mechanisms is pheromones. This is generalizable to which animals?
Macrosmatic mammals.
Bronson (1971, 1979) showed that the urine from stressed mice will produce what?
Adrenocortical response in naive mice.
Females grouped together release a pheromone that delays _____ in other females.
Sexual maturation.
Smell from a _____ accelerates sexual maturation of young females.
Mature male.
List three problems with pheromonal mice studies.
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?
Describe the favour of group selection (interdemic selection) from Wynne-Edwards (1962) among the scientific community.
Not favoured among modern behavioural scientists (behavioural ecologists, sociobiologists).
Kin selection could be a solution. Why?
Animal sacrifices its reproductive output if survival of the group (kin) is ensured.
Most of the evidence suggests that self-regulation of populations or groups did not what?
Evolve for purpose of controlling group or population size.
