Monogamy Mating Systems How do sexes cooperate or compete during sexual reproduction to maximize individual fitness Monogamous Polygyny Polyandry Promiscuity http www youtube com watch v UiPx N9 T26I Monogamy A mating system in which one male mates with just one female and includes the formation of a Pair bond Stable relationship between members of a breeding pair that share common territory and parental duties How long does monogamy last Seasonal monogamy Entire breeding season Serial monogamy Single nesting Consecutive series of monogamous matings within a mating season Perennial monogamy Mate for life Albatrosses swans geese Seasonal Monogamy Pair bonds formed for breeding season Male defends female from other males May aid in feeding mate during breeding season May aid in parental care of young Seasonal Monogamy Emperor Penguin They have a single mate every year Fidelity to mate in that year is high Fidelity between years drops to 15 Narrow window of opportunity to establish mate for the season Can t wait forever Migrate To Breeding Ground Travel upwards of 70 miles inland Antarctica Protection Safety from ice breaking Inhospitable environment does not support a high density of predators Penguins Fly Underwater Evolved to move efficiently underwater Walking is awkward slow and energetically costly Tobogganing Mediates cost of walking Faster Colonial Nesters Form loose colonies Predator avoidance Wind cold protection Conserves energy when caring from young Fasting Mating Courtship Vocalizations bowing Identify sex Identify individual Courtship song Mate attraction Mate selection Copulatory pose stimulates sexual behavior Parental Care Extreme parental care invested in a single egg Incubated by both parents Exposed eggs experience temperatures of 60 C Embryo freezes Parade mutuelle and chant Mother transfers egg to father http www youtube com watch v Ycn e4ftW1P8 feature related Evolution of Monogamy Extreme environmental conditions High degree of biparental care required Skewed sex ratio Unequal ratio of males and females within colony Ex 39 5 males 60 5 female Serial Monogamy House wren Male establishes territory in spring Begins building nests May built up to 12 different nests After pairing with the female he will show her all the nests he has built She will rebuild nest and lay eggs House wren Female will lay 5 6 eggs Incubation lasts 12 15 days Males will bring female food as she incubates Young will leave nest in approx 16 17 days Males will attempt to attract a second mate to sire a second brood Perennial Monogamy Evolves when reproductive success is correlated with duration of pair bond Requires bi parental care of young Perennial Monogamy Ex Swans and Geese Large size Can protect female and offspring Arctic nesting Avian predators small mammalian predators Need protection Synchronous breeding Little opportunity for serial breeding Barnacle Goose Studies show geese that maintain long lasting pair bonds produce more offspring than geese with short pair bond duration Highly competitive societies Pair works in close association Without working together pairs would have a hard time acquiring resources Negative impact to both Barnacle Goose Society Live in large colonies Store fat female will use 40 60 body mass in reproduction Reproduction is expensive Need access to feeding areas to be successful Social dominance is critical to gaining feeding area access How do Barnacle Geese Gain Dominance Dominance increases with Pair bond formation Better at competing for nest and feeding territories Pairs with offspring Family groups stay together Larger families more clout What does this mean for single birds Barnacle Goose Pair Bond Male assistance is necessary in order for female to acquire enough nutrient reserves to breed Males fight off competitors while female feeds Male protects offspring from predators Barnacle Goose Pair Bond Site fidelity to feeding and breeding sites Choose a mate that is familiar with the territory How else might a familiar mate be advantageous Extra pair Copulation Copulation with an individual outside of pair bond Hmmmm Monogamy Molecular biology changed understanding of mating systems DNA fingerprinting allowed evaluation of offspring parentage Why EPC Males Increase potential reproductive fitness Females Better sperm Genetic variation Gouldian Finch Females have increased stress level Higher levels of circulating corticosterone when paired with poor quality males 4X higher than females paired with preferred mates Extra Pair Fertilization Offspring produced by fertilization from a parent outside of pair bond Females can control use of sperm Sperm dumping or segregating 3 5 of mammals exhibit social monogamy Out of over 4000 species only a few dozen are monogamous Led to new definitions of monogamy Mixed Parentage Clutches Ex Bluebirds Offspring of more than one female Offspring of more than one male Both Types of Monogamy Social monogamy Correlated with dual parental care 92 of birds Genetic monogamy Rare Up to 70 of offspring are from extra pair fertilizations Forms of Monogamy Facultative monogamy If released from environmental constraints they would exhibit an alternate mating system such as polygyny Ex Dabbling ducks Obligate monogamy Mates remain monogamous even when mate is killed Ex Prairie Vole Facultative Monogamy Dabbling ducks Synchronous breeding More males than females Males unable to monopolize more than one female Protection from predators rival males Defends female feeding territory Protection of offspring Facultative Monogamy Facultative Monogamy Rocky Mountain Pika Distinct home ranges Neighboring home ranges occupied by opposite sex Females exhibit social repulsion i e they don t hang out Ecological constraints cause facultative monogamy Low food supply short active season Widely dispersed females Males can t support multiple females How Does Monogamy Work Let s look at proximate and ultimate causation Voles Prairie Vole Perennial monogamous Forms pair bond Montane Vole Promiscuous Does not form pair bond http www youtube com watch v Oh8x9KDkYTc http www youtube com watch v 5ddlKQwDIe8 Remember Monogamy is Rare Coolidge Effect Coolidge Effect Most Mammals Prefer to Mate with Novel Females Proximate vs Ultimate Proximate Physiological foundation Ex Presence of Neurotransmitters Genetic component Ex Voles with vasopressin receptor gene V1aR Ultimate Adaptive value to male reproductive success Increase in male fitness Phylogenetic