Lecture 12 - parental care

Question 1

whos reproductive potential is higher males or females?

Answer 1

• male reproductive potential is higher than females

Question 2

what are males reproductive potential limited by?

Answer 2

access to females

Question 3

what are females reproductive potential limited by?

Answer 3

access to resources

Question 4

what is the general model for the evolution of mating systems?

Answer 4

the distribution of resources determines female dispersion, which in turn determines male dispersion

Question 5

what happens to mating systems when you introduce male parental care?

Answer 5

the system switches- Now, the male becomes an important resource for females

Question 6

what is an operational sex ratio?

Answer 6

OSR – the ratio of sexually receptive males to sexually receptive females

Question 7

what determines the OSR?

Answer 7

the link between female and male dispersion and hence the mating system

Question 8

what do sex roles depend on?

Answer 8

potential reproductive rate

Question 9

what does potential reproductive rate depend on?

Answer 9

relative provision of parental care

Question 10

what study did Clutton-Brock & Vincent (1991) do and what were the results?

Answer 10

A comparative study - went through the literature and grouped them into categories - e.g. in some cases males provide a lot of parental care but they still have a high potential reproductive rate

• found that sex roles were very tightly linked with reproductive rate
• illustrated the impact that male care has on male and female reproductive potential, the intensity of competition and sex roles

Question 11

what are 2 types of monogamy?

Answer 11

a) Obligate monogamy

b) Facultative monogamy

Question 12

what is the typical mating system among birds?

Answer 12

monogamy

Question 13

what is obligate monogamy?

Answer 13

both sexes are essential for successful reproduction

Question 14

what are 2 situations in which obligate monogamy seems to occur?

Answer 14

(i) Parents must forage a long way from nest e.g. sea birds
(ii) Parents have specialised caring roles e.g. many birds of prey and parrots
- males provision incubating females

Question 15

describe why obligate monogamy is essential in hornbills

Answer 15

female seals herself into nest

• complete moult of flight feathers
• female and chicks depend on male for all food for up to 137 days
• Sometimes the females actually eat the smallest chicks in the brood - if the male doesn’t bring enough food the females will eat all the chicks
• So at first it seems the males are in full control but actually the female has a way of gaining some control

Question 16

Interests of parents are aligned in monogamous mating systems - because of this what can you expect from the parents?

Answer 16

• conflict between parents is reduced

- A lot less EPP in monogamous systems

Question 17

what is facultative monogamy?

Answer 17

male care not essential, although it usually increases productivity, so monogamy is facultative

Question 18

how can you test facultative monogamy?

Answer 18

test by removal experiments

Question 19

what did removal experiments show about facultative monogamy?

Answer 19

if desertion has no effect on reproductive succes = desert

if male desertion reduces reproductive success to 1/x = desert if you can get >x partners

Question 20

when does facultative monogamy usually occur?

Answer 20

usually results from limited opportunity for polygamy, due to competition among males and/or among females

Question 21

which sex usually deserts in facultative monogamy?

Answer 21

usually male because they have greater opportunity for desertion (internal fertilization), and more to gain (higher reproductive rate). However, this is not always the case – in some species (e.g. Tengmalm’s owl), females desert to find a new mate and increase their reproductive success, leaving males to care for the first brood = CONFLICT BETWEEN THE SEXES

Question 22

what should monogamy actually be looked at?

Answer 22

‘failed polygamy’

Question 23

what did moller find when looking at mating systems in passerines?

Answer 23

39% sometimes polygynous- Males on the look our to be polygynous when the opportunity arises

Question 24

when does polygyny occur?

Answer 24

If resources or females are patchily distributed, males may be able to defend multiple partners and become polygynous

Question 25

what are 2 reasons that females accept polygyny even if it means they have to share a male’s care with other females?

Answer 25

(a) No cost of polygyny to females

(b) there is a cost but they have i) no choice or ii) the benefits outweigh the costs

Question 26

which sex prefers polygyny?

Answer 26

males

Question 27

what is are 2 examples of when females have no choice but to partake in polygyny?

Answer 27

1) female-biased pop sex ratio: 1M:1.5F

2) females are deceived by males

Question 28

what is an example of males deceiving females into polygyny?

Answer 28

pied flycatcher - migratory birds - males attract females to their nest box - then fly’s away to another nest box and attracts another late arriving female after migration - once she lays eggs, he fly’s back to first female

Question 29

describe when benefits outweigh the costs for polygynous breeding?

Answer 29

When faced by a choice between breeding with an unpaired male (i.e. becoming monogamous) or an already paired male (i.e. becoming polygynous), the cost of polygyny may be outweighed by the benefit of access to good resources, and/or the benefit of conferring the male’s ‘good genes’ on offspring. In other words, paired males may be better than unpaired males, or may defend better resources.

Question 30

what is the ‘Polygyny Threshold Model’

Answer 30

• choose polygyny if difference in quality exceeds polygyny threshold

Question 31

what evidence is there for the polygyny threshold model?

Answer 31

Good genes? – little evidence

Better resources? – limited evidence

Question 32

which sex prefers polyandry?

Answer 32

females

Question 33

what are the 2 types of polyandry?

Answer 33

(a) Cooperative polyandry

(b) Sequential polyandry

Question 34

what is cooperative polyandry?

Answer 34

Increased productivity from more paternal care outweighs costs of shared paternity

Question 35

an example of cooperative polyandry

Answer 35

e.g. Galapagos hawks - groups have one female and 1-8 males, who share copulations, paternity and parental care.
•Raising single chick needs > 1 male

Question 36

what is sequential polyandry?

Answer 36

More often, females lay a series of clutches for multiple males, each of whom cares for that brood. These species are characterised by sex role reversal
- males have little choice

Question 37

why does sequential polyandry occur?

Answer 37

male-biased sex ratio
- abundant food and precocious chicks allows uniparental care
Males (for once) are stuck in ‘cruel bind’

Question 38

What determines the intensity of conflict? (3 things)

Answer 38

Life history constraints
Ecological differences
Social conflicts

Question 39

describe the effect of life history constraints?

Answer 39

whether both parents are able to provide care or not (e.g. lactation), and how much care offspring need (e.g. altricial [dependent] v precocial [relatively independent]).

Question 40

describe the effect of ecological factors

Answer 40

the distribution and abundance of resources will influence the dispersion of mates and the potential for polygamy (e.g. abundant food may facilitate polygyny or sequential polyandry, sparse food may facilitate obligate monogamy or cooperative polyandry)

Question 41

describe the effect of social conflict

Answer 41

individuals will try to maximize their own reproductive success at their partner’s expense, often through coercion or deception (e.g. facultative monogamy).