marine mammal reproductive structures, strategies, & patterns mare 390 dr. turner
TRANSCRIPT
Marine Mammal Reproductive Structures, Strategies, & Patterns
MARE 390 Dr. Turner
Testes, One, Two
Phocid – testes inguinalOtariids – testes scrotalWalrus – inguinal; scrotal during matingPinnipeds – 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 DolphinDistance 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 22-24 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 11 9-12 1N. Elephant 40 11 1N. fur seal 6 12 1Walrus 50 14-16 2-4Porpoises 8 8-11n/aBottlenose 20 12 n/aSperm Whale 1050 14-16 3Blue Whale 2500 11-12 2-3
Gestation
Mass (kg) Gest.(mo) Int.(Y)Manatee 30 12-13 2-5Dugong n/a 14 3-7Sea Otter 2 6-7 1Polar Bear 0.7 8 2-4
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 8-9.5 1.5-3N. Elephant 7 4N. fur seal 8 4Walrus 10-11 4-5Sea Otter 4 2-3Polar Bear 4 4
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 longer3. 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 PolygynyCharacteristics:1. Males arrive before females2. Females receptive close to place of birth3. Rookery substrate stable but discontinous4. 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 PolygynyCharacteristics:
Most dominant male (Alpha) defends females from other subordinate males
Phocid Mating Systems
Most males defendFemales – 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 individualssubgroups – 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 3.4 50 9N. Elephant 4 54 5-12N. fur seal 18 42 14Walrus 100 14-32 5-11Porpoise 32 46 11Bottlenose 76 14 12-18Sperm Whale 100 15-35 8-10Blue Whale 24-28 35-50 11-14
Length(w) Fat% Prot.%Manatee 52 n/a n/aDugong 78 n/a n/aSea Otter 20-30 21-26 9-12Polar Bear 130 17-36 9-13
Lactation
Got Milk!