Part 3 - conflict

Question 1

Sexual conflict is rife in nature, including within families.

Langurs live in … societies with a single reproductive male. There is a turnover of males through time, with males competing to become the dominant male and monopolise reproduction within the group. In one particular study group, four males ‘ruled’ over 5 years and, during this time period, 83% of … …. This is so that females come into … more quickly, to ensure that their short time in reproductive dominance results in the maximum amount of offspring. Obviously this is not very beneficial for a female.

Answer 1

matrilineal, infants died (infanticide), oestrus

Question 2

It used to be thought that infanticide was a … behaviour resulting from males with high testosterone, but we now know that it is adaptive. It not only occurs in males, but also females, for example in … …. This is a … species from central America. These females have two or more males living on their territory. She will mate with them and produce a clutch of eggs for each male to look after. When the females were experimentally taken away from their territories…

Answer 2

wattled jacanas, polyandrous, a new female would claim the territory and kill any original broods and destroy any current breeding attempts. The male would then accept a new clutch of eggs from the new female and raise those.

• adaptive for individuals who have a short reproductive tenure within a group

Question 3

Acorn woodpeckers are co-breeders. These co-breeding groups are usually relatively highly related (~… are first order kin, ~… unrelated). Yet 38% of all eggs laid in joint nests are…

Answer 3

86%, 14%

destroyed by co-breeding females

Question 4

Females destroy eggs that are laid in the nest before they start laying their own eggs (i.e. eggs likely to belong to likely related co-breeders). Eggs laid … in the sequence of laying within a given nest have a higher probability of being destroyed. This is an example of reproductive conflict and suppression by co-breeders (each female trying to maximise her own representation of offspring in a given breeding attempt). This is because there will be … among the offspring for limited resources. Despite the close relatedness of females within a group, this is an adaptive strategy.

Answer 4

earlier, competition

Question 5

Meerkats are co-breeders that live in relatively large groups of …-… individuals. Within each group, there is typically a dominant … and dominant …, who attempt to … reproduction. There are … females (normally relatives of the dominant) and … males (who normally disperse between groups and are … immigrants). The society could be described as ….

Answer 5

3-50, female, male, monopolise, subordinate, subordinate, unrelated (to main breeding pair), matrilineal

Question 6

Dominant females attempt to monopolise reproduction, but subordinate females, especially in large groups, also attempt to have litters. There are plenty of subordinate males around willing to oblige. However, we see marked differences in the result of pregnancies between dominant and subordinate females.

Dominant females have on average … pregnancies per year, with … of these failing and only … of litters failing (all pups dying). Subordinate females only have … pregnancies per year, with … of these failing and … of their litters failing. Clearly, dominants are very effective at monopolising reproduction.

Answer 6

3. 1, 18%, 13%,
4. 2, 33%, 71%

(so almost double pregnancy failure rate and over 5 times higher litter failure rate)

Question 7

This is because the breeding of subordinates is costly to the dominants. Pup … at independence is significantly higher when the dominant breeds alone than when she breeds synchronously with a subordinate. This is a predictor of future reproductive success

Answer 7

weight

• chance of becoming dominant in future greatly affected by weight/size - subordinate breeding compromises (as more pups to share food and care and compete with)

Question 8

How do dominant females protect their monopoly and their offspring’s future reproductive success?

Answer 8

By evicting subordinates (more likely if less related and more likely the closer you get to the dominant’s birth date) and infanticide (which leads to subordinate litter failure) - other subordinates often help with this

Question 9

In other species of mongoose, for example the … mongoose, … breeding (breeding by multiple females synchronously) is routine behaviour. There is still a cost to having multiple litters at the same time, as there is competition among the offspring over care and in the future. In these mongooses, small subordinate females pre-empt future competition via spontaneous … in … groups and under … conditions.

Answer 9

banded, plural, abortion, large, harsh (study looked at lower rainfall and higher number of co-breeding females)

Question 10

When thinking about eusocial insects, it is often assumed that workers are sterile. However, this is not always the case. In some social insects, workers retain functional … and can produce … (i.e. from unfertilised eggs).

Answer 10

ovaries, sons

Question 11

In these (haplodiploid) insects, worker-brother relatedness = …, worker-son relatedness = …, and worker-nephew relatedness = … (as worker-worker relatedness = … and …/2 = …)

So workers should lay eggs to produce sons and allow sisters to produce nephews. (as nephews are more closely related to them than their own brothers - better to help sisters raise sons than it is to raise brothers)

Answer 11

0.25, 0.5, 0.375, 0.75, 0.75, 0.375

Question 12

Queen mating … affects relatedness. If the queen mates with many males, it is likely that most sisters will only be related via their mother (so r = …). This is why … is so important in the evolution of eusociality.

Relatedness between members of a colony rapidly diminishes as the … of a queen increases

Answer 12

frequency, 0.25, monogamy,

promiscuity

Question 13

When a queen mates multiply, she prefers sons (r = 0.5) to grandsons (0.25) - i.e. worker sons

Workers prefer sons (0.5) to brothers (0.25) - i.e. queen sons

Workers prefer brothers (0.25) to nephews (0.25/2 = 0.125)

So workers should…

Answer 13

prevent other workers reproducing, known as worker policing (when queens mate multiply)

Question 14

This was tested by adding honeybee eggs into the hives of study colonies. These eggs could be …-… or …-…. The survival of these eggs was monitored over a number of hours. Workers were observed … the eggs of other workers. This is evidence of worker policing.

Answer 14

queen-laid, worker-laid, removing

Question 15

In Dolichovespula wasps, queens mate a variable number of times (sometimes many, sometimes monogamous). This means there will be a range of worker relatedness across colonies (can be calculated).

Found that, in those colonies where worker relatedness is high (monogamous queens), there was…

However, when worker relatedness was reduced (because queens had mated multiple times)….

This was due to…

Answer 15

a high proportion of males produced by workers

there was a very low proportion of males produced by workers

worker policing (destroying eggs laid by other workers when average relatedness was lower due to queen mating multiple times)

Question 16

Data across species with varying levels of queen promsicuity shows that…

Answer 16

those species with a higher average relatedness among workers have higher reproduction by workers

Question 17

Policing serves to enforce ….

In those species where policing is very effective (workers are good at discriminating the eggs of other workers from those produced by a queen), fewer workers attempt to reproduce.

Answer 17

altruism

Question 18

Another consequence of variation in worker relatedness among colonies is that workers will sometimes…

Answer 18

kill the queen - if the queen mates once, workers are more closely related to their nephews than their brothers. If the queen mates multiply it is the other way around. In Dolichovespula arenaria, when the colony switches from producing workers to producing sexuals (including males), workers kill the queen in monogamous colonies (to protect high worker pedigree relatedness)

(prob listen again - lecture 10 slide 29)

Question 19

Avian e.g. of conflict between breeders and helpers: …-… …-…. These birds live in colonies of extended families and multiple breeding pairs. Each pair has a burrow in a bank of sand and helpers. A lot of harassment occurs within these groups (e.g. chasing and interfering in …, blocking nest access, … removal). The harassers are always paired (so not looking for reproductive partner) and usually closely related. … of victims of harassment became helpers at the nest of the harasser.

Hypothesised that harassment is used to…

Answer 19

34%

courtship, egg

recruit helpers

Question 20

Does harassment to recruit helpers make sense?

Assuming breeders and helpers are close kin (r = 0.5) - typically the case:
A breeding pair alone produce … young. Every helper adds … young (very significant effect on productivity of pair)

From a helper’s perspective, helping has about the same pay-off as breeding (siblings as related as offspring)
From breeders’ perspective, a helper breeding alone produces 0.51/2 = 0.26 young for the breeder

This means that a helper contributes more to a breeder’s inclusive fitness as a helper than if it breeds independently, yet from the helper’s point of view it doesn’t make much difference.

(remember assuming that r = 0.5)

Answer 20

0.51, 0.47

Question 21

Found that recruitment of victims of harassment as helpers varied with ….

Answer 21

relatedness

75% recruited when r = 0.5
35% when r = 0.25
0% when r < 0.125

• degree of conflict and outcome of conflict is a function of relatedness

Question 22

Conflict over inbreeding: acorn woodpeckers. Inbreeding is bad as it exposes deleterious … mutations which may have adverse consequences for the fitness of offspring. Avoidance of incest is adaptive.

In cooperative systems, there is a lot of potential for incest, as there are many related individuals of the opposite sex living in close proximity.

In acorn woodpeckers, there is potential for incest when a breeder … and is replaced by a … who may be related to the remaining breeder. However, just … of 75 cases of potential inbreeding resulted in incest. How is incest avoided?

Answer 22

recessive,

dies, helper, 5%

power struggles between helpers and breeders which generally (50% of the time) are resolved within a month, but can last up to 3 years.

Question 23

If there was a female breeder and helper sons, … of the time the helpers left and … of the time the breeder left.

If there was a male breeder and helper daughters, the helpers left … of the time and the breeder left … of the time

Answer 23

64%, 27%

91%, 2%

(males are more dominant in this species)

Question 24

In red-winged fairy-wrens, inbreeding can be avoided by seeking…

Maternity is typically monopolised by a female within a territory. ~40% of paternity within a group is generally obtained by a dominant male, and a very small amount by helpers. However, … of paternity is also obtained by an extra-group dominant male.

Answer 24

extra-pair paternity (very high rate), ~40%

Question 25

Looking across multiple pairings, extra-pair paternity is higher when…

Answer 25

the relatedness of the social pair (dominant male and dominant female) was higher

Question 26

Trivers’ parent-offspring conflict model:

with increasing parental investment, the benefits show a…

with increasing parental investment, the cost … at an … rate, as the more invested in offspring, the less available to sustain themselves

Answer 26

curve of diminishing returns (offspring can only survive to 100% - plateaus)

increases, accelerating

Question 27

Since the offspring only shares 50% of their parents genes, the cost will be the same as…

Answer 27

the cost to the parent divided by 2 (see phone pic)

Question 28

The optimal parental investment, from the parent’s point of view, is where the…

Answer 28

difference between the benefit and cost curve is highest (maximum benefit to cost ratio)

• same true of offspring curve

Question 29

We find that optimal parental investment for the parent is…

Answer 29

(generally) less than the optimum for offspring - this creates a conflict

Question 30

American coots: chick are very strange looking things with bald heads, bright red beaks, blue patches around their eyes.

Parental care is essential for the survival of these chicks: … of them starve to death. The parents control which of the chicks get food and which do not. They deliberately favour some chicks over others

Answer 30

50%

they basically choose who lives or dies

Question 31

American coots rearing their young brood will sometimes…

Answer 31

tousle disfavoured chicks, picking them up and shaking them. These chicks eventually end up dying

Question 32

Lyon hypothesised that the ornaments (orange feathers and papillae etc.) the young chicks, who are vulnerable to predation (usually young are more cryptic), have are signals to the parents and related to parent-offspring conflict.

He conducted a field experiment where chicks were captured and subjected to 1 of four treatments:

• orange feathers painted … (orange …)
• black feathers painted … (black …)
• black feathers painted …
• orange feathers painted …

He asked how these affected the rate at which chicks are fed and the rate at which they grow

Answer 32

orange, controls

black, controls

orange (orange chick treatment)

black (black chick treatment)

Question 33

He found that there was…

Answer 33

no significant difference between the orange and the black controls, but that orange chicks were fed more and grew at a faster rate than did the black chicks. These chicks survived more frequently than black chicks

Question 34

Sexual conflict can lead to the evolution of sexual signals via female choice, and parental choice can..

Answer 34

lead to the selection for ornaments in their offspring

Question 35

Parent-offspring conflict is also apparent in human pregnancy:

Foetal genes are selected to maximise…

Maternal genes are selected…

So there is … conflict between mother and foetus

Answer 35

transfer of nutrients to the foetus

not to exceed maternal optimum

genetic

Question 36

During implantation, foetal cells modify endometrial arteries into …-…, …-… vessels. This is so:

• the foetus gains direct access to … blood
• blood flow to the placenta isn’t under … control
• the placenta can release … directly into the mother’s blood

Answer 36

low-resistance, non-constricting

maternal,
local,
hormones

(all enable foetus to grow at as optimal a rate as possible)

Question 37

Usually, the foetus and the mother manage the conflict effectively. However, foetal manipulation can result in:

• gestational … - the placenta releases human placental lactogen to maintain blood glucose levels, the mother increases insulin in response, … occurs if the response is inadequate
• …-… - the foetus enhances blood and nutrient flow to the placenta by increasing maternal blood …. If it goes too high, the mother and the baby’s life can be threatened (by a haemorrhage in the uterus).

Answer 37

diabetes, diabetes

pre-eclampsia, pressure

Question 38

European earwigs: one of few good examples of evidence for the parent-offspring conflict model.

The mother gives a lot of care for offspring, tending eggs and young nymphs until their independence. Earwigs typically have 2 clutches in a lifetime (1 year).

Kolliker et al. selected lines of earwigs into two groups - … clutch and … clutch lines - over 6 generations. Importantly, the size of their … clutch was unaffected. Only the … clutch was selected to be either large or small.

Answer 38

small, large

first, second

Question 39

Did selection on future reproductive output have an effect on first clutch offspring in earwigs?

Answer 39

Yes - the fitness traits of the first clutch of offspring were mostly negatively affected by selection for greater future reproduction. These traits included hatching success, egg development rate, nymph survival, body mass gain etc.

Question 40

There is also conflict between … due to limited resources provided by parents.

Answer 40

siblings
- an individual would rather take the most resources for itself as it is only related to siblings by r = 0.5, it is related to itself by r = 1. An asymmetry in relatedness, like in parent-offspring conflict, leads to sibling rivalry

Question 41

In some species, conflict between siblings over resources often results in … or even ….

Answer 41

siblicide, cannibalism (e.g. spadefoot toad tadpoles sometimes become cannibal morph when resources are limited. Sand tiger sharks eat siblings in the mother during gestation - only ever one born)

Question 42

Female hyenas typically give birth to …. These pups are usually placed in a nursery burrow which is generally too small for the parents to enter - therefore when they are born they are initially unsupervised. Unusually for mammals, the pups are born with a full set of …. When in their burrow the pups are often in … involving biting. As a result, often one of them …. The rivalry is usually more intense when the pups are…

Answer 42

twins, teeth, conflict, dies, of the same sex

Question 43

If sex is randomly determined, survival within burrows is random, and rivalry is more intense with same sex twins, we’d expect there to be…

Yet only…

Answer 43

50% same sex twins (1MM : 2MF : 1FF)

15% of those twins that emerge are same sex

Question 44

What is happening here in hyenas?

Answer 44

When there are same sex twins, there is more extreme competition as they will be future reproductive competitors and it is beneficial to eliminate competition ASAP

Question 45

This kind of behaviour is also common in birds, for example in black eagles: 2 eggs hatch 3 days apart, so there is an asymmetry in … early on. In the majority of cases, only one chick survives. Why?

Answer 45

size

The older chick attacks the younger sibling as soon as it hatches. From 199/200 nests in which both eggs hatched, only one survived.

• This siblicide is sometimes referred to as cainism.

Question 46

Great white egret siblicide is conditional upon … …. They typically have 3-4 young which hatch at 1-2 day intervals (producing a hierarchy in size). There are often low levels of aggression within the brood, but if conditions worsen and as chicks become older, this can worsen. In … of all nests, attacks end in siblicide (via eviction from the nest).

Answer 46

food supply, 1/3

Question 47

Common characteristics of siblicide:

1. Resource …
2. Monopolisable resources (if parents provide packages of resources)
3. Spatial confinement (small offspring can’t escape aggression of larger siblings)
4. Weaponry (e.g. hyena dentition, eagle beak) - not essential as sometimes small siblings are simply outcompeted
5. Competitive disparities (prob most important) - often under parental control (e.g. providing first hatched with immediate incubation and therefore a competitive advantage)

Answer 47

competition

Question 48

E.g. of resource competition: white-winged chough (a cooperative breeder) - food provided to one group to reduce resource competition and not provided to another (control).

Outcome: … of broods in groups who were provided with additional food was significantly higher than in control groups, due to reduced sibling … and better survival of chicks.

Answer 48

productivity, rivalry

Question 49

Why does siblicide occur? Why do parents set up their brood for sibling rivalry?

Answer 49

1. insurance - only enough resources for one chick, second is produced as insurance against first not surviving (in which case all resources will end up going to it)
   - in black eagles, in 17/22 nests the first chick fledged. In 5/22 nests the 2nd chick fledged as the sole surviving chick (prevents breeding attempt being wasted)
2. Parental optimism (prob most widespread) - produce large clutch so in good conditions all will survive and in poor conditions sibling rivalry will efficiently reduce the brood size
   (if always produced conservative small clutch, could miss out on opportunity to produce more offspring in resource-rich years)

Question 50

E.g. of parental optimism being tested: cattle egrets. In this species there is a brood … arising from a parental strategy to produce … offspring.

Researchers engineered different degrees of synchrony within the brood by removing eggs and replacing them dummies. In some cases they produced 2 chicks that were entirely synchronised (0 hatching interval), in some cases the hatching interval was normal (control) and in some cases they … the hatching interval.

They monitored the consequences of this on the survivorship of broods and found that…

Answer 50

hierarchy, asynchronous,

doubled

the most productive broods (highest survivorship) were those with the normal hatching interval (1.5 days). If hatching was synchronised, both chicks suffered in competition as neither was able to quickly eliminate the opposition. When the hatching interval was doubled, one chick could dominate the food supply at all times, making the younger chick’s chances of survival very poor, regardless of conditions.

(+ the normal hatching interval allowed both to survive if conditions were good)

Question 51

Sibling rivalry may have effects that are more subtle than siblicide and may operate among siblings from different broods. In humans, … are costlier to produce as they demand more resources in utero and following birth (due to larger size)

Work on pre-industrial Finnish people (Rickard et al. 2007) (from church records) - did producing sons have an effect on later siblings compared to producing daughters?

Answer 51

sons

Probability of surviving to age 15 was not affected by the sex of the elder offspring. However, lifetime reproductive success was significantly higher if the elder offspring was female - due to sibling rivalry and more resources invested in male.

Question 52

This same general pattern has been shown in a study of parental investment and child development in contemporary British families (Lawson and Mace 2011). As family size increases, the … score (amount of investment per child) decreases. This effect is decreased in daughters compared with sons. As family size increases there is a greater chance of … hardship, lower average … … scores, and lower average … (at 10 years).

Sibling rivalry has fitness consequences in humans (across broods/families)

Answer 52

parent, economic, school test, height

Question 53

In summary, families are characterised by conflict and cooperation. This occurs between the male and female partner (sexual conflict/biparental care) but also between the closely related individuals within the family (parent-offspring, sibling rivalry). There is also conflict between breeders and their helpers over opportunities to reproduce.

Answer 53

Nice one man

Question 54

Although males usually provide little or no care, … care does occur quite commonly and is widespread across different taxonomic groups.

It is particularly common among …, but also …, …, burying beetles and some species of ….

This is apparent … between a male and female, yet there is inevitable … between parents over the provision of care.

Answer 54

biparental,

birds, frogs, fish mammals,

cooperation, conflict

Question 55

Why is biparental care a problem?

Answer 55

Parental care is costly. This may be obvious, for example in some species of spider (such as Stegodyphus lineatus), matrophagy is a routine behaviour), or more subtle (such as in blue tits and other species, increased parental care (via adding or taking away offspring in a given year) has been shown to lead to reduced adult survival) - due to working harder

Question 56

The costs of parental care are borne …, yet the benefits of biparental care are …

This is a case of “a … of the …”, in that we might expect that each parent would … from reducing (or even abandoning) their own care if their partner was to compensate by … their care.

Why don’t we see this occurring in instances of biparental care? (next card)

Answer 56

individually, shared (by the mother and father)

tragedy, commons, benefit, increasing

Question 57

This problem was first addressed theoretically by Houston & Davis (1985) and their “… …” model. It imagines that parents’ effort evolves through time, but each player could only invest a fixed effort at any one time.

Answer 57

sealed bid

Question 58

Imagine there are 2 parents feeding a brood of chicks. Each parent has an … response to their partner’s effort. If parent 1 is working very hard, the best response for parent 2 is…

If, on the other hand, parent 1 is contributing relatively little, parent 2 should respond by…

Parent 1 will also have a best effort in response to the care of parent 2

Answer 58

optimal, to not work at all,

working harder

(have a look at graph on phone)

Question 59

If we put the two optimal efforts for either parent on the same figure, we can see how parental care can evolve through time.

Answer 59

(Just watch lecture 12 slides 8 to 20)

• eventually an equilibrium is reach, called the ESS (evolutionarily stable strategy)

Question 60

There are three other possible outcomes…

Answer 60

• best response for female work rate always higher than for male
• vice versa
• Unstable biparental care - ESS always ends up with single sex care if deviation from middle point

Question 61

If we look in nature, we see many examples of uniparental care as the ESS. In the … …, we see sexual conflict over care which results in various ESS’s. In this bird, 50-70% of care is … only, 5-20% is … only, and in …-…% of cases, both parents ….

Answer 61

penduline tit, female, male, 30-40 (brood inevitably fails), desert (the nest)

• in these birds, males build the nests hanging over water and advertise them to females

Question 62

The strategy of males and females seems to be dependent on the … … in the population at the time.

Answer 62

sex ratio

• When there are many females looking after broods there is a male bias in the population, females are more likely desert the nest and find another male partner.
  When more males are providing care in the population, this creates a female bias, so males are more likely to desert and find a new partner, leaving the females to care for the brood. In around 1/3 of cases, both leave thinking they have alternative reproductive opportunities.

Question 63

Houston and Davies’ model (1985) assumes that each parent has a … amount of effort they put in, which has evolved through time. Various researchers have asked whether this was really realistic.

In house sparrows, male parental effort (provisioning rate) is … within and between years.

To some extent, there is consistency in the effort provided by an individual parent across different broods. However, clearly individuals do not always work at precisely the same rate.

Answer 63

fixed

repeatable (females had relatively lower repeatability)

Question 64

We know that in most species, parental effort varies dramatically depending on many different factors, such as:

• nestling …
• brood …
• … supply
• number of …
• the list goes on

So in general, NO, an individual’s parental effort is not fixed. The assumption is likely to be flawed.

Answer 64

age, size, food, carers

• long-tailed tit data

Question 65

McNamara et al. (1999, 2003) proposed an alternative investment game, more inclusive of potential influences on parental effort. This is called the “…” model.

Rather than responding to their partner through evolutionary time, each parent responds in real time to their partner’s efforts.

The basic assumptions are similar to the sealed bid model. Imprtantly, both models predict that stable biparental care evolves only when one parent…

Answer 65

negotiation

compensates incompletely for reduced effort by their partner (e.g. if male reduces effort by x, female responds by increasing their effort by less than x)

Question 66

Is this central prediction of biparental care theory supported in empirical studies?

(as birds are the predominant taxonomic group in terms of biparental care, most studies have been conducted on them)

a) The first approach to this question is conducting … experiments, where one parent is … and the response of the other parent is tested.

Answer 66

removal, removed (i.e. does the remaining parent compensate incompletely)

Question 67

a) Orange tufted sunbirds (Markman et al. 1996) in Israel- - control pairs left …
- experimental treatment in which … were removed from the pair at the time of nest provisioning

Widowed … … their effort …, relative to the work of control …. The total amount of food provided was … at control nests.

This had a significant … effect on the growth of offspring (i.e. lower body mass over time when male removed)

Answer 67

unmanipulated, males

females increased, incompletely, females, higher
(they did not make up for the male shortfall)

• supports central incomplete compensation prediction

Question 68

…-… of experimental removal studies on this prediction relatively consistently support it: compensation is generally incomplete when one parent is removed from biparental care-giving species.

Answer 68

Meta-analysis

Question 69

It has been argued that removal experiments are not a good test of the predictions of biparental care theory, because…

A better approach is to conduct:

b) … experiments, where one parent is … in some way, such that their effort is reduced, and compensation by the other parent is measured

Answer 69

negotiation can’t occur with a partner who is not present

handicapping, handicapped

Question 70

b) Methods of handicapping across bird species have included:
- adding small … (reduces flying and foraging efficiency)
- … feathers together (again, reduces flying efficiency)
- administering … (sing more, court more, increase territoriality, provide less care)

Answer 70

weights (good as can remove weights after experiment so bird is not affected in long term), tying, testosterone (rarely used as more invasive)

Question 71

b) a meta-analysis of these (54) studies (Harrison et al. 2009) found that…

Answer 71

across species the prediction was empirically supported

• handicapping did decrease feeding effort
• partner responded by providing more care (increased their own feeding effort)
• overall care (feeding effort) was still lower

Question 72

Harrison et al.’s paper shows that there is a lot of variation across species in the degree to which…

This is likely to be due to variation in the extent of … between parents over the provision of biparental care.

Answer 72

individuals compensate and the outcomes of these handicap experiments

conflict

Question 73

… of bird species have biparental care.

Answer 73

81% (Cockburn 2006) - large majority predominantly monogamous

Question 74

The intensity of conflict over care varies within and between mating systems.

In some cases, monogamy is …, meaning both parents are essential for successful reproduction (i.e. if one didn’t help, the other would not be able to successfully raise offspring alone). Why may this be the case?

Answer 74

obligate

In pretty much all seabird species, parents must forage far from their nest (e.g. wandering albatrosses may travel thousands of miles for food while their partner incubates the egg)
In other species, the parents have specialised parenting roles, e.g. in amazon parrots and birds of prey such as ospreys, females provide all incubation of the eggs and males provision the female with food. Females are completely dependent on the males for food, males are dependent on the females to provide incubation for their offspring. In hornbills, females seal themselves into the nest and moult their flight feathers - extraordinary level of dependence on partner (for up to 137 days in some species!)

Question 75

Consequences of obligate monogamy:
- interests of both parents become closely …, and therefore … between them is greatly reduced.

Therefore, in species where male care is essential…

Answer 75

aligned (as both depend on each other), conflict

extra-pair paternity rates are much lower than in other socially monogamous species (EPP may jeopardise male willingness to provide food that they and their young are completely dependent on) (Birkhead & Møller 1996)

Question 76

Obligate monogamy is the minority though. In the great majority of bird species, it seems, to some extent, that monogamy is somewhat …. Male care is not essential, although it usually increases …. And males can potentially gain fitness by seeking alternative reproductive opportunities with other females.

Answer 76

facultative, productivity

Question 77

In another series of … experiments, males were removed from monogamous pairs and the effect of this on reproductive success was tested and compared with control pairs. In some species there was a substantial effect, e.g. in song sparrows (51%), seaside sparrows (66%) and dark-eyed juncos (38%), the reproductive success of the brood is greatly reduced by the removal of the male (not to zero though). Nevertheless, male care is NOT essential for reproduction. In species such as the …., male care appears to have very little effect on reproductive success (100% RS compared to controls in this species).

In these species, it may be beneficial to a male to … the female and seek extra-pair copulations, provided he finds enough partners to compensate for the reduced RS of his partner.

So in general, if desertion has no effect on RS —> DESERT

OR

If male desertion reduces RS to 1/x, DESERT if can get > x partners

Answer 77

removal, ptarmigan

desert

e.g if RS is reduced to 50%, 1/x = 0.5 therefore 1 = 0.5x, therefore x = 2, so if the male finds 2 partners this is compensated for

Question 78

Unsurprisingly, although many birds are characterised as being monogamous, desertion does occur very routinely in many species, i.e. male polygyny is very common.

Across 122 European passerines, … are sometimes polygynous, and, in 20% of these, this occured in over 5% of breeding attempts (Møller)

So … monogamy is common.

Answer 78

39%,

facultative

Question 79

This goes both ways, in that we may also expect to see females deserting their male partners to seek additional reproductive opportunities when the chance arises. This is likely to be rarer as females have to invest more in clutches and usually provide incubation for the brood. Nevertheless we do see this in some species, for example in … owl, where the female may desert her 1st brood, leaving the male to look after it while she goes and seeks another male. If successful in this, she fledges … more young (on average). This has been shown to be a good strategy when…

Answer 79

Tengmalm’s, 79%

there is plenty of food around (in abundant years, we see the most polyandry)

Question 80

Conclusions: What determines the intensity of conflict?

Life history contraints

• how much care is needed (e.g. in mammals females are more likely to raise young solely than in birds as they invest a lot during long period of gestation and lactation, during which males are likely to desert. Males can provide much earlier on in the reproductive cycle in birds so male care may be selected for more highly).
• how dependent are offspring on care? less need for biparental care in some species

Ecological differences
- distribution and abundance of resources (influences likelihood of monogamy vs polyandry/polygyny

Social conflicts
- individuals always try to maximise RS, sometimes at partner’s expense (e.g. obligate vs facultative monogamy)

Answer 80

good stuff

Question 81

Intensity and outcome of conflict between parents varies across species, largely as a result of…

Answer 81

the degree of necessity of biparental care on reproductive success. - my own words