MATING SYSTEMS AND PARENTAL CARE
Immense diversity of breeding systems, in terms of:
courtship & mate acquisition (e.g. bowerbirds – males try to attract females with elaborate bowers and blue objects)
mating systems & pair bonds (e.g. angelfish – male attaches onto female)
parental care (e.g. killer whales – orcas take care of offspring for many years)
Sex roles (or gender roles) = behavioural roles of males and females in the context of reproduction.
TYPES OF MATING SYSTEM: 4 TYPES, WITH B,C & D COLLECTIVELY KNOWN AS POLYGAMY
a) MONOGAMY
Male and female form a ‘pair bond’. Each male and female has one mate during a breeding season (or breeding event) – so could be single
year monogamy/ lifetime monogamy. Sometimes bi-parental care. Occurs in rodents, birds, primates, fish. Definition: pair partners have
exclusive breeding access to each other.
Why do these species escape Bateman’s Principle?
Bateman’s Principle states that males and females have different ways of maximising reproductive success – monogamy seems to violate this
principle. Why do males stick do a single breeding partner? Why do females forgo mate choice for good genes or other benefits of multiple
mates?
Mate-guarding hypothesis: male is enforcing monogamy by guarding his mate. Either because female remains receptive after 1st mating, or
because likelihood of finding a 2nd female is low. E.g. in peacock spiders, male mates with female and
reproductive organs break off and prevent female from mating with other males, ensuring paternity
despite the female remaining receptive after first mating. 2nd situation seen in angelfish when the male
attaches onto the female – difficult to find females.
Mate-assistance hypothesis:
Protection: male provides benefit to mate which in turn benefits reproductive success.
E.g. field crickets: if male stays with female he can protect her from predation. Successful
predation events are higher for an isolated female than an isolated male, and if the female is paired then there is a much
lower probability of predation. The male is protecting the female and in turn protecting his offspring.
, Biparental care: 2 parents provide better care than 1, e.g in primates, social carnivores (wolves), many altricial birds, frogs, fishes, burying
beetles, etc. If male leaves female, he would have a cost in his reproductive success as his offspring won’t do as well. Data: male care of
offspring effects fitness in the California mouse – the mean number of offspring reared by female mice falls sharply in the
absence of a helpful male partner. The number of young born with male present/absent is the same, but when the male
provides care there is a greater likelihood the young will survive to be weaned. In this case, if the male left he would have
0.5 offspring on average, and if he stays he has the benefit of 1.5 offspring on average.
Compensation: monogamous parents ‘compensate’ if one partner is handicapped in some way when raising young.
They do this by feeding and caring for offspring more. Usually NOT completely compensated – one parent cannot
completely make up for the loss of monogamy/ biparental care.
Study: artificially put weights onto birds and measure male and female’s feeding of the offspring. If the male is
weighted (so ‘handicapped’), the female feeds the offspring more than she would do otherwise, and vice versa.
Data:
Social ≠ genetic mating system:
Many socially monogamous animals are NOT truly ‘monogamous’ (not genetically monogamous). Extra-pair
copulations (EPCs) & Extra-pair Fertilisations (EPFs) are common – accounts for 21% of male reproductive
success in red-winged blackbirds. EPFs detected by DNA fingerprinting: shows different territories of pairs,
how successful they were in their own pair and how many EPFs between males in connected territories
(displays this as common).
b) POLYANDRY – MALES MATE WITH MULTIPLE FEMALES
Why be polyandrous?
Bateman’s principle states that the goal of males is to mate with multiple females, but what is the benefit for females of having
multiple mates?
Social mate is not ‘best’ choice – good genes (may not be able to get the ‘best’ male to take care of offspring, but can still pass
on these advantageous genes to offspring)
Genetic variety of offspring – in the context of pathogens, a greater variety of immune responses in offspring increases the
probability that at least one will survive.
Immense diversity of breeding systems, in terms of:
courtship & mate acquisition (e.g. bowerbirds – males try to attract females with elaborate bowers and blue objects)
mating systems & pair bonds (e.g. angelfish – male attaches onto female)
parental care (e.g. killer whales – orcas take care of offspring for many years)
Sex roles (or gender roles) = behavioural roles of males and females in the context of reproduction.
TYPES OF MATING SYSTEM: 4 TYPES, WITH B,C & D COLLECTIVELY KNOWN AS POLYGAMY
a) MONOGAMY
Male and female form a ‘pair bond’. Each male and female has one mate during a breeding season (or breeding event) – so could be single
year monogamy/ lifetime monogamy. Sometimes bi-parental care. Occurs in rodents, birds, primates, fish. Definition: pair partners have
exclusive breeding access to each other.
Why do these species escape Bateman’s Principle?
Bateman’s Principle states that males and females have different ways of maximising reproductive success – monogamy seems to violate this
principle. Why do males stick do a single breeding partner? Why do females forgo mate choice for good genes or other benefits of multiple
mates?
Mate-guarding hypothesis: male is enforcing monogamy by guarding his mate. Either because female remains receptive after 1st mating, or
because likelihood of finding a 2nd female is low. E.g. in peacock spiders, male mates with female and
reproductive organs break off and prevent female from mating with other males, ensuring paternity
despite the female remaining receptive after first mating. 2nd situation seen in angelfish when the male
attaches onto the female – difficult to find females.
Mate-assistance hypothesis:
Protection: male provides benefit to mate which in turn benefits reproductive success.
E.g. field crickets: if male stays with female he can protect her from predation. Successful
predation events are higher for an isolated female than an isolated male, and if the female is paired then there is a much
lower probability of predation. The male is protecting the female and in turn protecting his offspring.
, Biparental care: 2 parents provide better care than 1, e.g in primates, social carnivores (wolves), many altricial birds, frogs, fishes, burying
beetles, etc. If male leaves female, he would have a cost in his reproductive success as his offspring won’t do as well. Data: male care of
offspring effects fitness in the California mouse – the mean number of offspring reared by female mice falls sharply in the
absence of a helpful male partner. The number of young born with male present/absent is the same, but when the male
provides care there is a greater likelihood the young will survive to be weaned. In this case, if the male left he would have
0.5 offspring on average, and if he stays he has the benefit of 1.5 offspring on average.
Compensation: monogamous parents ‘compensate’ if one partner is handicapped in some way when raising young.
They do this by feeding and caring for offspring more. Usually NOT completely compensated – one parent cannot
completely make up for the loss of monogamy/ biparental care.
Study: artificially put weights onto birds and measure male and female’s feeding of the offspring. If the male is
weighted (so ‘handicapped’), the female feeds the offspring more than she would do otherwise, and vice versa.
Data:
Social ≠ genetic mating system:
Many socially monogamous animals are NOT truly ‘monogamous’ (not genetically monogamous). Extra-pair
copulations (EPCs) & Extra-pair Fertilisations (EPFs) are common – accounts for 21% of male reproductive
success in red-winged blackbirds. EPFs detected by DNA fingerprinting: shows different territories of pairs,
how successful they were in their own pair and how many EPFs between males in connected territories
(displays this as common).
b) POLYANDRY – MALES MATE WITH MULTIPLE FEMALES
Why be polyandrous?
Bateman’s principle states that the goal of males is to mate with multiple females, but what is the benefit for females of having
multiple mates?
Social mate is not ‘best’ choice – good genes (may not be able to get the ‘best’ male to take care of offspring, but can still pass
on these advantageous genes to offspring)
Genetic variety of offspring – in the context of pathogens, a greater variety of immune responses in offspring increases the
probability that at least one will survive.
