Chapter 13

Question 1

Mating Systems

Answer 1

A description of the social associations and number of sexual partners an individual has during one breeding season: monogamy (1F, 1M), polygyny (F+, 1M), polyandry (1F, M+), polygynandry (F+, M+), and promiscuity (F+, M+)

Question 2

What’s the difference between polygynandry and promiscuity?

Answer 2

For polygynandry, mating occurs within social groups but promiscuity mating is not restricted to specific social associations

Question 3

Emlen & Oring’s Model

Answer 3

a) Assumes that for a female, fitness will often be more strongly limited by the resources she can obtain to invest in offspring than by the number of her sexual partners
b) Male fitness is strongly affected by the number of sexual partners he obtains, this difference between males and females sets the stage for sexual conflict
c) MONOGAMY - favoured if the male will provide resources to young, high quality territory, and a great deal of parental care
d) POLYANDRY - favoured if multiple males all provide care to the female’s offspring
c) POLYGYNY - favoured when males that mate with multiple partners have higher fitness than males who mate with one partner
d) MONOGAMY & BI-PARENTAL CARE - favoured when parents raise offspring equally

Question 4

Polygyny

Answer 4

a) Favoured when bi-parental care is not required and parental care is female biased
b) Evolves when environmental conditions lead to the aggregation of females, since aggregations are more easily defended by a male from rivals
x) Aggregations of females may experience lower predation risk than females alone
c) Female Defence Polygyny: a mating system in which a single male monopolizes and mates with two or more females
d) If resources required by females are clumped, males can monopolize females by defending territories with large amounts of such resources
e) Resource Defence Polygyny: a mating system in which a male mates with multiple females that are attracted to resources he defends
f) If it’s too costly for males to defend resources or females successfully, potential mates must seek each other out, which can involve high energetic and predation costs
g) One way to reduce these costs is for males to settle in fixed locations, called leks, and then display to females there
h) Male Dominance Polygyny: a mating system in which a few males on a lek mate with many females, the more dominant males occupy the more preferred central locations
i) They can benefit as a result of reduced predation risk and and such groupings may be more attractive to females than a single male, increasing encounters
j) Females also benefit from leks since their existence reduces time for mate searching, quickly searching through the lek for quality

Question 5

Polyandry

Answer 5

a) One female mates with multiple males
b) Evolves when it’s advantageous to both sexes that females be freed from providing parental care, making parental care male biased
c) Produced if there’s high predation on offspring
d) If many offspring are lost to predators, both sexes can benefit if a female can quickly reproduce again
e) However, since egg production is costly, if a male is providing care, a female can feed more often to quickly replenish energy for reproduction

Question 6

Polygynandry & Promiscuity

Answer 6

a) They both involve multiple mating partners for each sex but differ in regard to social associations
b) Social associations are found in polygynandry but not in promiscuity
c) EXAMPLE of POLYGYNANDRY: Lions live in social groups which facilitates hunting success, a pride consists of two or more adult males which are often relatives and up to nine adult females, the males defend their females and multiple males mate with multiple females
d) PROMISCUITY evolves when the benefits of social living are low, both females and males are solitary and pair bond formation provides no fitness benefit, also when the defence of mates or resources is uneconomical, when population density is high, or when it’s too costly for males to aggregate on leks like in high predation conditions, also when individuals cannot afford to give up feeding to spend time on a lek

Question 7

Summary of Emlen and Oring’s Model

Answer 7

a) Mating system variation can be understood by examining (1) the competing interests of sexes in attempting to maximize their fitness and (2) how environmental conditions affect the benefits and costs of resource defence and of different mating behaviours for each sex
b) Mating systems and parental care have co-evolved

Question 8

Research 13.1: Mating Systems in Reed Warblers

Answer 8

a) The Emlen & Oring Model allows us to predict how variation in resource abundance should affect a mating system
b) All females provide more parental care than males through egg incubation, food delivery to young but male care varies across species
c) Most species are monogamous but several are polygynous and one is promiscuous

Question 9

REED WARBLERS & MATING SYSTEMS: Research Questions

Answer 9

(1) How does habitat quality (amount of food resources) correlate with mating system?
(2) How are habitat quality and mating systems related to the level of male care?

Question 10

REED WARBLERS & MATING SYSTEMS: Methods

Answer 10

a) Estimated habitat quality, categorized as poor (only small prey), medium (larger prey), and good (many large prey) for each species
b) Characterized the relative level of male care as full (equal to female), reduced, or none
c) Created a molecular phylogeny

Question 11

REED WARBLERS & MATING SYSTEMS: Results

Answer 11

a) Strong association between habitat quality and mating system
b) Monogamy and high levels of male care were predominant in poor-quality habitats
c) Polygyny and Promiscuity and reduced levels of male care were associated with medium and good habitats
d) Polygyny appears to have evolved independently at least twice
e) Phylogeny suggest that the ancestral species was monogamous with a high level of male care
f) Male care co-evolved with the mating system and was reduced or absent in habitats of higher quality that contained more abundant resources

Question 12

Research 13.2: California Mouse Monogamy

Answer 12

a) Adults form exclusive pair bonds, the pair defends a territory and males assist with all aspects of parental care except lactation
b) This includes huddling, grooming the young, and carrying them from one location to another

Question 13

CALIFORNIA MICE & MONOGAMY: Research Question

Answer 13

How does male care affect reproductive success in this species?

Question 14

CALIFORNIA MICE & MONOGAMY: Methods

Answer 14

a) Created male-absent families by removing a male from a family within three days of birth of the season’s first litter
b) In the control male-present treatment, males were trapped and handled but then released and allowed to return to their families
c) Estimated that the number of young born to each female

Question 15

CALIFORNIA MICE & MONOGAMY: Results

Answer 15

a) No difference in the number of offspring born to females that had their male removed or not
b) However, the absence of the father and his parental care significantly reduced offspring survival: significantly more young survived from the male-present families
c) They assist with thermoregulation and protection
d) The need for bi-parental care appears to have favoured the evolution of monogamy in this species

Question 16

Research 13.2: Monogamy and Bi-parental Care in Poison Frogs

Answer 16

a) Both species rear their young in a PHYTOTELMA: a small pool of water that collects at the base of leaves or petals
b) Small size of pools reduces predation but also limits the quantity of nutrients
c) One rears tadpoles in very small pools (24mL), the other prefers larger pools (112mL)
d) R. imitator is monogamous with bi-parental care while R. variabilis is promiscuous and raises young with only male care, they provide parental care but only involving defence and offspring are not fed by the female

Question 17

POISON FROGS & BI-PARENTAL CARE: Research Question

Answer 17

Why does R. imitator have a monogamous mating system when R. variabilis is promiscuous?

Question 18

POISON FROGS & BI-PARENTAL CARE: Hypothesis

Answer 18

When resources are limited, monogamy will evolve because bi-parental care is required to successfully raise offspring

Question 19

POISON FROGS & BI-PARENTAL CARE: Methods

Answer 19

a) Manipulated phytotelma pool size
b) Individual tadpoles of each species were placed in either small (17mL) or large (39mL) pools and did not receive female feeding
c) In the control, R. imitator individuals were placed in a small pool and received parental care in the form of female feeding
d) Visited each pool weekly for three weeks to recored growth rate in size and mortality

Question 20

POISON FROGS & BI-PARENTAL CARE: Results

Answer 20

a) For both species, individuals in large pools had high growth rate and high survivorship
b) In small pools with no parental care, individuals of both species had low growth rates and low survivorship
c) R. imitator controls in small pools with bi-parental care had high growth rates and high survivorship

Question 21

POISON FROGS & BI-PARENTAL CARE: Conclusion

Answer 21

The need for bi-parental care in R. imitator likely provides strong selection that favours monogamy in this species

Question 22

Research 13.2: Monogamy without Bi-parental Care in Snapping Shrimp

Answer 22

a) Monogamy without bi-parental care occurs in coral reef fishes, some mammals, and crustaceans
b) Snapping shrimp are small crustaceans that live in burrows in intertidal rubble
c) Most live in male-female pairs within a single burrow
d) Females provide all parental care, brooding eggs and then carrying them, cleaning them, and aerating them
e) Both males and females are territorial and construct/defend a burrow that protects them from predators
f) Females are sexually receptive only for a short period of time after moulting
g) Mate guarding can enhance his fitness, if he can accurately assess time to moulting

Question 23

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Research Question

Answer 23

Why are snapping shrimp monogamous when males provide no care?

Question 24

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Hypotheses

Answer 24

1) Territorial Cooperation Hypothesis states that because two individuals can better defend a critical resource, such as a safe refuge, than a single individual, selection may favour pair formation and shared defence (Assumption: competition for limited territories is intense or predation outside a safe refuge within the territory is high)
2) Mate Guarding Hypothesis states that selection may favour males that guard females by remaining in close association with them over the course of one or more reproductive cycles (Assumption: a male’s encounter rate with females is assumed to be low, perhaps because females are rare)

Question 25

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Methods

Answer 25

Territorial Cooperation Hypothesis
a) Two treatments: (1) resident female alone and (2) resident female with a male
b) Allowed residents to construct a burrow
c) Added a single female intruder
d) The female in the burrow after 24 hours was considered the winner

Mate Guarding Hypothesis
a) Added two females to test chamber; one close to sexual receptivity and one far away
b) Allowed residents to build a burrow
c) Added a single male
d) Recorded location of the male

Question 26

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Results

Answer 26

Territorial Cooperation Hypothesis: paired resident females won more burrow contests than single females
Mate Guarding Hypothesis: males paired with high-value females more than low-value females

Question 27

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Continuation

Answer 27

a) A water source was attached to each arm of a Y-shaped maze
b) One source (treatment) contained a shrimp and the other did not
c) Seven different treatments, varying the sex of the shrimp and its moulting state
d) Pre-molt, inter-molt, and post-molt males and females and a control (untreated water)
e) Recorded behaviour of test males as water flowed through the Y-shaped maze
f) Results: males only moved toward the post-molt female water, indicating they are able to determine and are attracted to females close to sexual receptivity

Question 28

SNAPPING SHRIMP & NO BI-PARENTAL CARE: Conclusion

Answer 28

Both territorial and mate guarding have favoured monogamy in snapping shrimp

Question 29

Research 13.3: Female Defence Polygyny in Horses

Answer 29

a) Horses live year-round in social units called bands
b) Bands consist of one male and up to a dozen adult females
c) If there are multiple males, a single dominant male obtains most or all of the matings within the band
d)

Question 30

HORSES & FEMALE DEFENCE POLYGYNY: Research Question

Answer 30

Do male horses defend females directly or the resources that females seek?

Question 31

HORSES & FEMALE DEFENCE POLYGYNY: Methods

Answer 31

a) Recorded the location of bands
b) Plotted the home range of each band
c) Recorded social behaviours, particularly aggressive interactions between males from different bands

Question 32

HORSES & FEMALE DEFENCE POLYGYNY: Results

Answer 32

a) Males aggressively defended their band from other males whenever two bands met or when bachelor males were nearby
b) Bands overlapped greatly in their home ranges
c) All bands essentially used the same area although at different times and there was no indication of exclusive defence of territories
d) Suggests that males actively defend females and not resources
e) FEMALE DEFENCE POLYGYNY

Question 33

Research 13.3: Resource Defence Polygyny in Blackbirds

Answer 33

a) Polygyny Threshold Model: a model that predicts the occurrence of polygyny based on the amount of resources available to females in male territories (if access to resources affects female reproductive success)
b) Some males will defend territories rich enough in resources to meet requirements of multiple females but others can only defend territories with lower level resources
c) This variability means that females can mate monogamously on a resource-poor territory or can mate polygynously on a resource rich territory

Question 34

BLACKBIRDS & RESOURCE DEFENCE POLYGYNY: Research Question

Answer 34

Why do some blackbirds mate monogamously while others mate polygynously?

Question 35

BLACKBIRDS & RESOURCE DEFENCE POLYGYNY: Hypothesis

Answer 35

The polygyny threshold model explains variation in polygyny

Question 36

BLACKBIRDS & RESOURCE DEFENCE POLYGYNY: Methods

Answer 36

a) Males defend territories in dense vegetation around lakes and ponds
b) Gave females a choice of mating monogamously in a low-quality territory or polygynously in a territory of higher quality
c) Territory quality correlates with nest placement: nests in vegetation over water experience less predation (higher quality) than land
d) At each three marshes, when male blackbirds migrated back to breeding sites and started defending territories, researchers identified similar adjacent territories (dyads)
e) When first females arrived, one territory in each dyad was randomly chosen to be high quality and the other was low quality
f) Used cattail shoots to manipulate territory quality
g) Any female arriving to the high quality territory which already had one female would be choosing to mate polygynously while the other just had a single male (monogamously)

Question 37

BLACKBIRDS & RESOURCE DEFENSE POLYGYNY: Results

Answer 37

a) New arriving females settled on the high-quality territory 12 out of 14 times
b) All these females began building a nest on the platforms and ten eventually laid a clutch of eggs
c) The two that settled on low quality territory also began nest building but one abandoned her nest and the other laid a clutch that was lost to predators
d) Nesting over water had a benefit of reduced predation but also meant less food provisioning by males due to polygyny, reducing number of offspring a female could successfully raise by 0.6
e) The net benefit of mating polygynously on the experimental plots was an extra 0.4 offspring
f) For females, the benefits of polygyny outweighed the costs and the newly arriving females were indeed selecting the better option

Question 38

BLACKBIRDS & RESOURCE DEFENSE POLYGYNY: Conclusion

Answer 38

a) These findings offer support for the polygyny threshold model since only males defending high quality territories mated polygynously
b) One important consequence of polygynous mating systems: there will be more variation in male mating success than in female mating success
c) males that can successfully defend females or resources will obtain many matings but others will only obtain a few
d) In contrast, there should be much less variation in female mating success since most females will mate

Question 39

Research 13.3: Resource Defence Polygyny in Carrion Beetles

Answer 39

a) In this species, resource defended by a a male is evident: a vertebrate carcass
b) They all use small vertebrate carcasses as a food source for their larvae but these are rare and represent a highly clumped resource
c) Females lay eggs on or next to the carcass, and after hatching, the larvae feed on it
d) Difference in aggression between male-male and female-female

Question 40

CARRION BEETLES & RESOURCE DEFENCE POLYGYNY: Research Question

Answer 40

Does this variation in aggression between the sexes indicate that these beetles exhibit resource defence polygyny?

Question 41

CARRION BEETLES & RESOURCE DEFENCE POLYGYNY: Methods & Results

Answer 41

a) Placed four virgins (two male and female) in an arena with a piece of meat
b) Within each sex, individuals differed in size
c) Large males were dominant, won fights, and actively defended the resource
d) Females move throughout the arena, were observed mating with both males, and oviposited eggs on the meat
e) After a few weeks, the developing larvae crawled away from the peat to pupate
f) Subsequently, the researchers used DNA fingerprinting to determine the parent
g) Large males sired three times more offspring than small males and both females had relatively equal success

Question 42

How do low-ranking males within a lek benefit from the lek? Hotspot vs Hotshot

Answer 42

Hotspot Hypothesis asserts that all males should group where they are likely to encounter many females like near a food resource, lower-ranked males settle at a greater distance from the high-ranked males and high-female activity
Hotshot Hypothesis states that high-ranking males settle (and display to females) in a location to minimize the costs of searching for mates, low-ranking males should then group around these hotshots became females are more likely to visit attractive males
In both cases, these low-ranked males can benefit by encountering more females at a lower cost rather than by searching for females on their own.

Question 43

Research 13.3: Lekking Behaviour in the Great Snipe

Answer 43

a) During breeding season, males display on leks for several hours each evening

Question 44

GREAT SNIPES & LEKKING: Research Question

Answer 44

Why do male great snipe aggregate on leks?

Question 45

GREAT SNIPES & LEKKING: Methods & Results

Answer 45

a) Studied three leks that contained up to 20 males
b) On each lek, they first observed male interactions to determine dominance
c) Each lek had one or two dominant individuals
d) Dominant individuals had the highest display rates and mating success on each lek and mated polygynously
e) Removed individuals for one night and recorded behaviour of remaining males
f) When dominant snipes were removed, territory was left unoccupied and neighbours moved away
g) In contrast, when sub-dominant or subordinate males were removed, neighbours quickly added the vacated space to their territory
h) HOTSHOT HYPOTHESIS

Question 46

Research 13.3: Peafowl Leks

Answer 46

a)

Question 47

PEAFOWLS & LEKS: Research Question

Answer 47

Why do male peafowl aggregate on leks?

Question 48

PEAFOWLS & LEKS: Methods

Answer 48

a) Population of the lek was 100
b) 75% of males aggregated and defended sites on the lek while 25% were floaters
c) Recorded male-male interactions, male display rates, female visitation rates, and the mating success of 29 males
d) The lek was situated near a feeding location, where birds were fed twice each day

Question 49

PEAFOWLS & LEKS: Results

Answer 49

a) Males with sites near the feeding location had the highest display rates, attracted the most females and had a high mating success rate, also mating polygynously
b) Males farther from the feeding location did obtain matings but success was lower

Question 50

PEAFOWLS & LEKS: Continuation

Answer 50

a) The team removed each of the 29 males, a few at a time
b) After male removal, floaters quickly settled on the vacated sites and began displaying to females
c) Display rates of newly settled males were similar to prior owners
d) This supports the HOTSPOT hypothesis

Question 51

POLYANDRY & SEX-ROLE REVERSAL

Answer 51

a) Female Jacanas aggressively defend larger territories from other females while two or more males settle and defend smaller territories within the female territory
b) Females mate with each male and lay multiple clutches, for each male who provide parental care
c) In contrast, females exhibit high levels of territorial defence and aggression

Question 52

Andresson’s Hypothesis

Answer 52

a) Start with a species in which parental care is male-biased
b) This behaviour might be favoured in resource-poor habitats, where females need to spend time feeding to replenish energy for egg production for offspring
c) If predation on clutches is high, selection can favour male-biased care
d) Second phase is the evolution of high female fecundity, a female may be able to lay more eggs than a single male can successfully raise
e) Selection will favour females that mate with multiple mates, they become a limiting resource for females
f) Third phase, intense competition among females for mates, this will favour evolution of increased fighting ability and aggression