Marine Mammal Reproductive Structures, Strategies, & Patterns MARE 390 Dr. Turner

Testes, One, Two Phocid – testes inguinal Otariids – testes scrotal Walrus – inguinal; scrotal during mating Pinnipeds – bacculum (penis bone) Cetaceans & Sirenians – fibroelastic penis “We're talking about S-E-X in front of the C-H-I-L-D-R-E-N." – Maude Flanders "What?!?! Sex cauldron? I thought they closed that place down“ – Krusty the Clown

Sex Your Seal Ma’am? Teats & position of genital opening

I’m Too Sexy for my Dolphin Distance between Anal & Genital slit ♀ both within common groove ♂ separation between; testes internal cavity

Is that a manatee in your pocket..? Distance between Anal & Genital slit ♀ short distance ♂ separation between; testes internal cavity

Reproduction ↑ Fitness of female = ↑ Fitness offspring Females: cost of egg, pregnancy, lactation, postnatal care Males: invest energy in competition with other males (physical & sperm)

Reproduction Pinniped, Ursid, mustellid mating typically on land; some phocids shallow water

Reproduction Cetaceans – belly-to-belly

Reproduction Sirenians – belly-to-belly

Gestation Placental mammals – 18 days to months Marine mammals: sea otter (6-7mo) to Sperm whale (16.5mo) ↑ Gestation time = ↑ Fetus size

Gestation Mass (kg) Gest.(mo) Int.(Y) Harbor seal N. Elephant N. fur seal6 121 Walrus Porpoises8 8-11n/a Bottlenose20 12n/a Sperm Whale Blue Whale

Gestation Mass (kg) Gest.(mo) Int.(Y) Manatee Dugongn/a Sea Otter Polar Bear

Delayed Implantation Delayed implantation – development of the blastocyst is slow or negligible Is obligate in pinnipeds, ursids, and mustelids Period of delayed implantation allows flexibility of timing of parturition, and is controlled by photoperiod

Delayed Implantation Dev.Gest(mo)Delay Impl.(mo) Harbor seal N. Elephant 74 N. fur seal84 Walrus Sea Otter4 2-3 Polar Bear44

Pinniped Reproduction

Pinniped Reproductive Cycle

Cetacean Reproductive Cycle

Change in latitude in grey whales Migration

Mating Systems High degree of variability in reproductive systems 2 major groups: polygyny & promiscuity Polygyny – successful male mating with several females Promiscuity – males associate with several females during a variable amount of time

Evolution of Polygyny

Mating Systems Driven by sexual selection – competition 1. Contest comp. – Direct comp. over ♀ 2. Endurance comp. – ♂ Endure longer 3. Scramble comp. – Search/locate ♀ 4. Mate choice comp. – Entice/attract ♀ 5. Sperm comp. - ↑ Quality/Quantity of sperm

Pinniped Mating Systems Male otariids typically utilize Resource Defense Polygyny Characteristics: 1. Males arrive before females 2. Females receptive close to place of birth 3. Rookery substrate stable but discontinous 4. Few aggressive interactions once dominance is established

Otariid Mating Systems Most males defend Territories – not females

Pinniped Mating Systems Male phocids typically utilize Female (Harem) Defense Polygyny Characteristics: Most dominant male (Alpha) defends females from other subordinate males

Phocid Mating Systems Most males defend Females – not Territories

Phocid Mating Systems Elephant Seals – High level polygyny – alpha controls large harems

Phocid Mating Systems Monk Seals – Low level polygyny – alpha controls individual females

Odobenid Mating Systems Walrus – either display a Female-Defense Polygyny (like Phocids) or a Lek-like behavior (similar to Otarriids)

Odobenid Mating Systems Lek - gathering of males, of certain animal species, for the purposes of competitive mating display

Cetacean Mating Systems Mysticetes – little social behavior beyond mother-calf pair Many utilize sperm competition – attempt to dilute out other males sperm Odontocetes – exist in groups of variable size for persist longer than any member’s life span

Odontocete Social Groups Arranged as schools, pods, or units Size varies by species & geographic location Mating structure a mixture of promiscuous & polygynous Male-male competition – sexual dimorphism

Spinner Social Groups Aggregate in schools of up to 100 individuals subgroups – up to 12 Subgroups travel in echelon formation

Orca Social Groups

Sperm Whale Social Groups Similar to orca groups Males leave pods and form juvenile groups Solitary adult males rove among female groups

Sirenian Mating Systems Similar to mysticetes- little social structure past mother-calf pairs Animals congregate into herds during summer months to breed Dugongs found in larger associations than manatees

Lactation Strategies Most energetically expensive aspect of reproduction Best interest to pass as much energy as possibly even at expense of future offspring 3 strategies: Fasting, Foraging Cycle, Aquatic Nursing

Fasting Lactation Strategy Example: Northern elephant seal Duration of fasting: All of lactation Duration of lactation: Short (4-weeks) Fat content of milk: High (55%) Pups forage during lactation: No

Foraging Cycle Lactation Strategy Example: Antarctic fur seal Duration of fasting: Variable (few days) Duration of lactation: Intermediate (4-months) Fat content of milk: Intermediate (40%) Pups forage during lactation: No

Aquatic Nursing Lactation Strategy Example: Walrus Duration of fasting: Short (hours-days) Duration of lactation: Long (2-3 years) Fat content of milk: Low (2-3%) Pups forage during lactation: Yes

Lactation Length(w) Fat% Prot.% Harbor seal N. Elephant N. fur seal Walrus Porpoise Bottlenose Sperm Whale Blue Whale

Length(w) Fat% Prot.% Manatee52 n/an/a Dugong78 n/an/a Sea Otter Polar Bear Lactation

Got Milk!