Mating Systems Flashcards
What is Bateman’s principle
“the theory that females almost always invest more energy into producing offspring than males, and therefore in most species females are a limited resource over which the other sex will compete”
How do males and females differ in time/ energy investments in offspring
- Males – invest time and energy in male competitions – gives them maximum number of mating
- Females – invest time/ energy to gain mate and parental care – maximises number of offspring
What does Bateman’s principle suggest about sexual selection in males and females
Males optimise offspring QUANTITY
Females optimise offspring QUALITY (of sperm = quality of genetics)
What 3 things are considered by a female choosing a mate?
Pheromones
Courtship rituals
Phenotypes (=good genes)
What are the 3 types of Polygamy
Polygyny
Polyandry
Polygynandry
Define Polygyny
1 males mates with lots of females
Define Polyandry
1 females mates with lots of males
Define Polygynandry
Everyone mates with everyone
Name a species that is Polyandry
Anglerfish
Name a species that is Polygyny
Elephant seal Spotted hyena Gorillas Hamadyras baboon Pheasants Red Deer Lions Bengal Tiger
What is Monogamy
One mate for a mating season or lifetime
What animal group is monogamy most common in
birds/ aves
What does DNA analysis show about monogamous bird species
Promiscuity occurs.
The offspring aren’t always genetically fathered by the resident male
What percentage of mammal species are monogamous?
3%
What percentage of Avian species are monogamous?
90%
What percentage of monogamous birds’ offspring are actually fathered by another male
30%
What does Bateman’s Principle suggest about monogamy?
Monogamy isn’t very/ at all beneficial to males (doesn’t select for quantity)
What are 3 hypotheses for male monogamy
Mate-Guarding Hypothesis
Mate-Assistance Hypothesis
Female-Enforcement Hypothesis
How does the Mate-Guarding Hypothesis explain male monogamy?
Males that stay with female, prevent other males mating with her.
When is the mate-guarding hypothesis most beneficial?
When mates are hard to find
Or when the male becomes sterile after copulation
Give an example of male suicide
Redback Spiders
Become sterile after copulation so place self in female’s jaws
Why do Redback Spider males commit male suicide?
- Large male: female ratio = females are hard to find
- Males become sterile after copulation
When is male sacrifice favoured?
- When less than 20% of males find a female
- When the male becomes sterile after copulation
What is the male-assistance hypothesis?
Suggests males stay with partner because male assistance increase offspring survival and therefore lifetime reproductive output (Increased survival of young outweighs young gained from seeking extra mates)
Give an example of animals that support the male-assistance hypothesis
Swans Emperor Penguins Seahorses Primates Rodents
How does parental care work in seashorses?
Males carry eggs in brood pouch
They synchronise reproductive cycle with females
Both avoid extra pair copulations
Explain the female-enforcement hypothesis for monogamy
- Female ensures the male does not have offspring that might compete with her own
- She actively interferes with the male’s signally to attract other mates – usually some form of aggression
Give an animal that supports the female-enforcement hypothesis
Razorbills Burying Beetles (Necrophorus)
How do burying beetles support the female-enforcement hypothesis?
- After setting up one nest with a female, a male will want to attract another female (beneficial for HIM)
- Male may add additionally females to the nest (releasing pheromones)
- First female will attack the male if she detects these pheromones
How do Djungarian Hamsters support the male-assistance hypothesis?
- Males help infants being born
- No significant association between monogamy and male care
- Males don’t leave because if they are out looking for a female, they leave themselves open to cuckoldry
How do songbirds support the male-assistance hypothesis?
- Both males and females can produce milk
- Provide more food
- Increases breeding success when food is scarce
What happened to Male Spotless Starling behaviour when testosterone levels were reduced?
Testosterone levels reduced, they provided more food for broods and had higher fledgling rates per brood
What happened to Male Spotless Starling behaviour when testosterone levels were increased?
Less food was provided to the brood
Ended up with lowest fledgling rate
How does male presence in snow buntings (birds) affect young?
When male snow buntings were removed, females reared fewer than 3 young
When males helped, 4x more young were reared
How does hatching rates differ in biparental and uniparental starlings?
Biparental = 97% eggs hatched Uniparental = 75% eggs hatched
How do Tree Swallows support the male-assistance hypothesis?
Polygynous Tree Swallow males fathered 0.8 fledglings
Monogamous Tree Swallow males fathered 3.0 fledglings (over 3x more)
How do Horned Beetles demonstrate alternative mating strategies?
- Nutrition affects body size
- More nutrients = bigger horns in males
- Long horns = mate-guarding behaviour
- Small/ no horns = adopt sneaking strategy (dig tunnel to intercept female tunnel without begin noticed)
Both strategies = effective
How to Red Paper Wasps demonstrate alternative mating strategies?
- Smaller wasps = Patrollers
- Larger wasps = Territorial (will chase away intruders)
- Owning territory leads to greater number of mating opportunities
- Territorial males rub abdomens across territory to apply pheromones, attracting females
- Patrollers are too small to compete, so resort to sneaking behaviours – will sneakily mate with females in other territories when territorial male is temporarily away or distracted
What are secondary sexual characteristics?
any physical characteristic developing at puberty which distinguishes between the sexes but is not directly involved in reproduction
