Habitat Selection (L10) T2

Question 1

Habitat selection

Answer 1

adequate resources, such as food and shelter, must be available. Species-specific differences occur.

Question 2

Competitive exclusion principle

Answer 2

No two species can occupy the same niche in the same place at the same time.

Question 3

Heredity vs. Experience

Answer 3

A genetic basis for habitat selection has been demonstrated in a variety of invertebrates and vertebrates.

Look at Coal Tit and Blue Tit on pg 58.

Question 4

Habitat imprinting

Answer 4

A genetic predisposition for habitat selection can be altered by early experience.

pg. 58

Question 5

Individual variation

Answer 5

Within a species, individual variation occurs in habitat preferences. These choices affect reproductive success.

Question 6

Poplar aphids on cottonwood trees

Answer 6

Female chooses a leaf and induces formation of a gall (tumor on leaf) and female lives inside of gall and produces eggs that hatch parthenogenetically (without fertilization). The young mature and disperse from the gall.

Question 7

What factors increase the number of offspring produced per female?

Answer 7

Larger leaf and basal position of gall on leaf.

Females that choose bigger leaves have more offspring.

Females that choose a leaf that is already occupied must produce a gall farther from the base of the
leaf and produce fewer young.

Females avoided the smallest leaves (33% of tree)

Question 8

3 Major costs of dispersal

Answer 8

1. Expenditure of energy.
2. Exposure to predation.
3. Reduced fitness in new habitat.

Question 9

2 Major benefits of dispersal

Answer 9

1. Inbreeding avoidance hypothesis: inbreeding increases risk of deleterious homozygous (usually recessive) alleles.
2. mate competition hypothesis: males compete with each other over females, therefore losers cannot mate and should disperse in search of other females.

Question 10

Why are inbreeding costs higher for females than for males?

Answer 10

Energetic costs of nurturing defective offspring.

Question 11

Belding’s Ground Squirrel

Answer 11

Males compete for mates and male dispersal occurs during first year, before reaching sexual maturity. Dispersal cannot be related to mate competition.

Question 12

Lion

Answer 12

Lions live in prides and females stay together and males go to new prides. Dominant males evict younger males of a pride, even if not evicted, subordinate males often leave on their own, suggesting mate competition.

Question 13

Why do dominant males eventually leave the group in both Belding’s Ground Squirrels and Lions?

Answer 13

Prevents them from mating with their own daughters, which is more compatible with the inbreeding avoidance hypothesis.

Conclusion: inbreeding avoidance is the major benefit of dispersal.

Question 14

Philopatry

Answer 14

Faithfulness to a particular site. Often occurs in migratory birds in both their breeding and wintering ranges.

Some birds breed in the same area during successive years. E.g. Bobolink - males that returned to the same territory had higher reproductive success the previous year than those that failed to return to the same breeding territory.

Question 15

Migration

Answer 15

Annual, relatively long-distance dispersal. Many animals migrate to some degree in different ways.

Question 16

Types of Migration

Answer 16

1. Altitudinal migration: up and down mountains (ex: elk)
2. Latitudinal migration: toward temperate areas in spring, toward tropics in fall (e.g. temperate birds).
3. to breeding ground (e.g. salmon)
4. to seasonal food or water sources (e.g. waterbirds, parrot)

Question 17

3 Major costs of Migration

Answer 17

1. Energetically expensive: depletes fat reserves, risk of exhaustion, requires increased foraging.
2. Physical hazards of weather, getting lost, drowning
3. Increased risk of predation.

Question 18

4 Major benefits of Migration

Answer 18

1. Ephemeral (temporary success e.g. food supply during temperate summers)
2. Protected breeding grounds (e.g. salmon, sea turtles, elephant seals)
3. Vacant breeding ground (opportunity to obtain a vacant or better territory than that of the previous year).
4. Reduced interspecific competition (fewer species competing for resources).

Question 19

What happens when two individuals of two migratory populations are hybridized?

Answer 19

The migration orientation of offspring is intermediate. This indicates that migratory orientation is genetic, not learned. Multiple genes likely code for migratory behavior.

Question 20

Dominance

Answer 20

The assertion of one member of a group over another in acquiring access to resources that add to the genetic fitness of the dominant individual. Occurs both intra and interspecifically.

Question 21

Hierarchy of Territory Size

Answer 21

1. Total Range: Entire area covered by an individual in its lifetime
2. Home Range: area that an animal learns and thoroughly and habitually patrols.
3. Territory: area occupied more or less exclusively by an animal or group of animals by means of repulsion through defense or advertisement.
4. Core Area: area of the heaviest regular use within the territory, often centered around sleeping.

Question 22

Individual Distance

Answer 22

Minimum distance that an animal routinely keeps between itself and other members of the same species when NOT on the territory.

Question 23

Size and function of territories

Answer 23

1. Large defended area w/in which sheltering and courtship occur.
2. Large defended area for breeding activities, not the primary source of food.
3. small defended area around nest.
4. pairing or mating territories
5. roosting positions and shelters.
6. absolute feeding territory

Question 24

Where is territoriality most common?

Answer 24

Where resources occur in small, economically defensible patches. Possession of a territory and size of territory is a tradeoff between benefits and costs.

Question 25

Is FORAGING and REPRODUCTIVE success higher in individuals lacking or defending a territory?

Answer 25

Individuals defending a territory! Also, territory quality is positively correlated with reproductive success.

Question 26

Is territory size positively or negatively correlated with territory quality and with a species density?

Answer 26

Usually negatively correlated.

Increasing density results in decreasing territory size.

Question 27

Territoriality regulating a population

Answer 27

1. Low density: territories defended with little competition among individuals.
2. Medium density: more fit individuals obtain best territories.
3. High density: more fit individuals obatin best territories and less fit individuals have no territory, thus becom floaters and adopt alternative mating strategies.