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22 Cards in this Set
- Front
- Back
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Control of reproduction
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Hypothalamus releases GnRH, anterior pituitary, stimulates FSH and LH release
FSH: males stimulate spermatogenesis, females stimulate development of ovarian follicles LH: males stimulate secretion of testosterone, females stimulates ovulation |
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Mating timing
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Expect reproduction to be sensitive to environment cues, geared for optimum survival
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Photoperiod
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Sun out during day over year
Changes with latitude Closer to 12/12 hour at equator Day length provides signals on temp and food availability Days lengthen towards summer Small mammals: mate when days lengthen, long day breeders, larger with ~1 year gestation Larger mammals: <1 year gestation breed at a different time of the year for optimum birth conditions, short-day breeders |
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How does light produce an effect?
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Photoreceptor, clock, connection to neuroendocrine system
Light enters eye - separate neurons in optic nerve to hypothalamus - suprachiasmatic nuclei (SCN) - nerve impulse from SCN to thorax to Superior Cervical Ganglion - pineal gland - released melatonin No pineal - repro light insensitive - stops hamster reproduction on short days |
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Food availability
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Montane vole: plant metabolite in actively growing plants, ingestion causes reproduction
Different metabolite in drying grasses suppresses female reproduction Decreased food reduces reproductive capacity and GnRH secretions Males: steroidogenesis, testosterone production Females: suppresses ovulation, reverse by giving LH |
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Ovulation can be induced socially
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Rabbits: copulation induces ovulation
Cohesive group: constant monitoring, smell important, individuals increase reproductive success by suppressing rivals: hormones, infanticide, harassment Social rank: dominant produces most young, pheromones, stress affects adrenal cortex, corticosteroid levels affect LH |
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Mice
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Male urine containing pheromones induced maturation and ovulation
Female urine up-regulates male pheromone production and suppresses prepubertal females' maturation |
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Mating systems
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Males maximise fitness by fathering many
Females maximise fitness by ensuring offspring survival Females limit male success, paternity can be uncertain Females limited by food and resources, invest more in each offspring, should be selective in mate choice, male-male competition, sexual dimorphism, female choice (size, age, behaviour, symmetry) |
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Monogamy
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1 male, 1 female, exclusive, rare in mammals
Little difference between the sexes Marmoset males carry young Distribution of resources and female and offspring survival |
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Mate assisted hypothesis
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Parental care non-shareable and indispensable to offspring survival
Pairing with unmated male better than an already mated male Fewer survive without male Obligate: both parents required for offspring to survive Facultative: density of females or food low |
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Mate guarding hypothesis
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Males can be most successful by defending exclusive access to a single female
Males less successful with 2 mates than 1 |
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Female enforced hypothesis
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Aggression from mated females prevents males from acquiring additional mates
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Extra-pair mating
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Male fathers extra litters
Female to increase genetic diversity of young |
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Polygyny
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Majority, Short/long-term bonding between a male and multiple females
Harems: can be long-term, baboons, viruna |
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Promiscuity
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No bonding or long-term relationship
Multiple mates for males and females Solitary animals, some herd species Benefits to male clear, females may benefit by improvement in offspring quality and number More males = more fertilisation, more offspring, fewer deaths, good genes Females a desired "resource", agreeing to copulate avoids male harassment, infanticide, multiple mating reduces chances it would be his offspring |
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Polyandry
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1 female and several males
Some bonding Matriarchal Rare |
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Parental care
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All mammals receive minimum care
Results in conflict, parents want to provide enough for survival, offspring want as much as possible, mostly female provided Males care when monogamous and occasionally polygamous, relates to certainty of paternity |
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Alloparental care
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Care by individuals other than parents
Usually relatives High risk of dispersal Increase inclusive fitness DIrect benefit: mother learns |
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Female defence polygyny
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Single male directly defends several females
When females aggregare for a reason or when they can be herded Quite common |
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Resource defence polygyny
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Single male defends resources acquired by females
When resources are clustered but females can move at will |
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Scrabble competition polygyny
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Single male acquires several females by finding them before other males do
Occurs when females and resources are widely dispersed |
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Leks
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Several males congregate to display
Females visit and select mates Display grounds, no resources Rare in mammals |
