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69 Mating Systems and Parental Care
Key Idea: The life histories, mating systems, and parental care behaviours of animals have evolved to maximise reproductive success in a particular environment. A mating system describes which males mate with which females, under which circumstances. Different mating systems offer different reproductive advantages to the individuals involved and are determined in part by the social structure of the species. Each particular mating system is usually associated with a certain pattern of parental care and is closely tied to the resources available for breeding.
Dotted arrows represent failed attempts at mating between males (M) and females (F). Dashed outlines surround unmated individuals
Mating system and behaviour
Polygyny
Males control access to more than one female. Males are often territorial and may control access to females directly or by defending valuable resources. In lek polygyny, females select mates from groups of males based on the quality of the male’s display or territory. After mating, males frequently show no parental care. Parental care is left to the female.
Examples: Most mammals The best or strongest male is selected for breeding. This provides the offspring with the best genes (at least from the male).
Monogamy
A breeding pair forms a partnership for the breeding season or for life. Neither sex can monopolise more than one member of the other sex. Both parents look after the young.
Examples: 90% of bird species Likely when the habitat contains scattered, renewable resources or scarce nesting sites. Shared care spreads risk and improves survival of young.
Parental care Advantages
Polygynandry
An organised association of several males and females, and multiple mating takes place between group members. Mating activity is not equal (some males mate more often than others). All group members contribute to the care of the young. Increases genetic diversity and decreases male competition for mates and aggression towards the young.
Polygynous: Elephant seal
Monogamous: Emperor penguin
Polyandry
Female mates with more than one male. Polyandry occurs in some mammals (cats) and birds, and in eusocial insects and mammals (mole rats). In birds, the female forms very brief associations with males, and mates with several males in succession. The males may care for their own offspring. The female abandons the male, leaving them to incubate the eggs and care for the young. In species where the males provide prenuptial gifts, females gain nutritional benefit. Genetic benefits and higher offspring survival rates may also result from this system.
1. Describe the adaptive value of each of the following mating systems:
(a) Polygyny:
(b) Polyandry:
(c) Polygynandry:
(d) Monogamy:
2. What factor might be important in determining which sex cares for the young and why?
