Reproduction week 6 Flashcards
Intended learning outcomes
- Describe the diversity of reproductive strategies found in pinnipeds
- Describe the diversity of reproductive strategies and social systems found in cetaceans
- Discuss the effects of breeding habitat, resource availability and predators on reproductive strategy
Why is it important?
- Reproduction is (obviously) essential to any species
- The key to successful reproduction:
– Good body condition and fitness of females (and males)
– Availability of food or energy stores (blubber)
– Habitat to protect the females and their offspring - A species reproductive strategy affects its ability to cope with human activities and climate change!!
Standard reproductive cycle
- Parturition (birth)
- Lactation (days-years)
- Weaning
- Resting (days-years)
- Mating (ovulation and mating)
- Gestation (9-11 months)
Male reproductive costs
Sperm production and mating
– Mating is costly
* Male-male competition (body size, sexual characters)
* Attracting females (body size, sexual characters)
– Sperm is cheap!
* Sperm competition (testis size)
* Few males successful – many are unsuccessful
Male-male competition
- Sexual size dimorphism
– Large males: sperm whales, beaked whales, larger dolphins, otarids, elephant seals, grey seals, hooded seals
– Large females: porpoises, small dolphins - Fighting and body scars
– Beaked whales, Risso’s dolphin, humpbacks - Ornaments
– Narwhal tusks, male beaked whale teeth, killer whale fin, hooded seal nasal sack (red balloon), ribbon seal males - Vocalisation/song
– Fin whales, perhaps bowhead whales, many phocids (ringed, harbour, bearded and leopard seals)
Male sperm competition
- Large testis size indicates sperm competition
- Mysticetes
– Not larger than expected relative to body size, except for right and bowhead whales - Odontocetes
– Larger testis than expected relative to body size
– Harbour porpoise (4% of body weight)
– Dusky dolphin (8-9% of body weight)
– Human testis (0.08% of body weight)
Female reproductive costs
- Producing offspring and lactating is costly!
– Egg production, mating, pregnancy, lactation and nursing
– Birth mass, pup growth, lactation interval, milk composition - Trade-offs
– Pup/calf wants as much energy as possible
– Mother wants to increase fitness of pup/calf, but also conserve energy for herself and future pups/calves - Different lactation and nursing strategies
– Fasting: mothers fasten during lactation
– Foraging cycles: mothers forage during lactation
– Nursing: mother and offspring stay together - Many females are successful–few are unsuccessful
Female lactation strategies
Fasting, foraging and nursing
Fasting lactation strategy
Lactation duration: short (weeks)
Fasting duration: all of lactation
Milk fat content: high (60%)
Pup/calf growth: rapid
pup/calf foraging: no
Rules of thumb> Phocids and mysticetes
Foraging lactation style
Lactation duration: intermediate (months
Fasting duration: variable (days)
Milk fat content: intermediate
Pup/calf growth: intermediate
pup/calf foraging: no
Rules of thumb> Phocids and Otariids
Nursing lactation strategy
Lactation duration: long (years)
Fasting duration: short (hours-days)
Milk fat content: low (20%)
Pup/calf growth: slow
pup/calf foraging: yes
Rules of thumb: Odontocetes, walrus, Sirenia and polar bears
Pinniped reproductive cycle
- Synchronous breeding (with exceptions)
- 1 year cycle (with exceptions)
- Stable habitat: Otariids
– Long lactation
– Slow pup growth
– Forages while lactating
– Large relative investment - Unstable habitat: Phocids
– Short lactation
– Rapid pup growth
– Fasts while lactating (with exceptions)
– Low relative investment - Oestrus and mating shortly after weaning
– Phocids: mating at end of lactation or at weaning
– Otarids: mating 1-2 weeks after birth
– Walruses: mating 10 months after birth - Delayed implantation of fertilized egg
– Timing to fit the annual cycle
– Time for resting, recovery and/or molting
Pinniped breeding habitats
- Female behaviour affected by
– Environment for protecting offspring from weather, climate and predators
– Availability of food resources - Male behaviour affected by
– Distribution of females
– Aggregated females => polygyny
– Dispersed females => monogamy/mild polygyny - Habitat and breeding system is closely linked!!
Pinniped land breeders
- Otariids and some phocids (elephant seals+grey seals)
- Stable habitat; often limited space
- Females aggregated; males control access
- Long nursing period
- Polygyny, sexual size dimorphism
Pack ice breeders (Pinnipeds)
- Many Arctic phocids (Hooded and bearded seal)
- Predators; unstable habitat; unlimited space
- Females dispersed; males cannot control access
- Short nursing period
- Mating in water (except hooded seal)
- Serial monogamy, or mild polygyny
Fast ice breeders
- Mainly Antarctic phocids, and the Arctic harp seal
- Stable habitat
- Some female aggregation and male control
- Relatively short nursing period
- Mating often in water
- Mild polygyny
Phocid lactation strategies
Mothers often forage a bit during lactation period
Lactation duration and milk production is related to habitat
Example 1 of phocid lactation: hooded seal
- Unstable environment (pack-ice)
- Very short (3-4 days) lactation period
- Stored lipids converted to milk; fat content is 60%
- Pups drink 10 liters per day; increase from 25 to 50 kg
- No lanugo fur in pup; it rapidly builds an insulating blubber layer After weaning and mating, females go to sea to forage
Example 2 of phoned lactation: Harp seal
- Breeds in somewhat stable environment (fast ice) in large groups
- Intermediate lactation (12 days)
- 10L milk/day; pup gains 2-3 kg/day
- Female fasten during lactation period
- Lanugo fur; insulation and camouflage
- Feeding migrations after breeding
Example 3 of phoned lactation: Northern elephant seal
- Breeds in stable environment (land/beaches)
- Long (4 week) lactation period
- 60% of the mothers energy expenditure is for lactation
- Pups gain approx 4 kg per day; from 40 to 160 kg
- No lanugo fur; pup is born on land during summer
- After weaning, females (mothers) go to sea to forage for months
- Pups remain on site for 8-10 weeks after weaning
Otarid lactation strategies
mother alternates between fasting while nursing during attendance periods and foraging at sea.
They wean the pups after a long lactation period.
Example 4 of otarid strategies: Anarctic fur seal
- Stable environment; long lactation (4 months); low milk fat (40%)
- Mother only fast a week, then start foraging
- Females spend 4-9 days foraging + 2 days lactating
- Pup mass increase from 5 kg to 10-15 kg; weaning mass depends on how successful mother is at foraging
- After weaning, pups go to sea to forage
Example 5 of Otarid strategy: Australian sea lion
- Exception to the rule; asynchronous breeding!
- Breeds every 17-18 months; 5-9 month breeding season
- The different populations’ breeding periods are out of sync with each other…
- Limits recovery from sealing!
Walrus lactation strategies
- Mother and pup go to sea a few days after birth
- Pup learns to forage by mother
- 2 year lactation: 5 months milk, then milk and food
- Can lactate/suckle while at sea!
- Fat content is 15-30%
Pinniped mating strategies
Territory/resource defence polygyny
Female defence polygyny
Maritory/resource defence polygyny
Mate guarding (triads)
Lek
Scramble competition (stalking)
Territory/resource defence polygyny
- Males defend a geographical resource/territory
- Few male aggressions after establishment of hierarchy
- Male reproductive fitness determined by
– Size and quality of territory/resource
– Body size
– Fasting ability
– Fighting/defence ability
Female defence polygyny
- Elephant seals
- Males defend group of females (harem); not a territory
- Males establish hierarchies among each other
- Less than 10% of males mate during their lifetime
- Male reproductive fitness determined by
– Size of harem
– Body size
– Fasting ability
– Fighting/defence ability - Sneakymales/females?
Maritory/resource defence polygyny
- Males defend access to water/air (maritory)
- Male reproductive fitness determined by
– Size and quality of territory
– Body size, visual displays, vocal displays
– Fighting in ringed seals!
Mate guarding (triads)
- Males defend one female (at a time)
- Mating once the pup is weaned
- Serial monogamy, or limited female defence polygyny
- Hooded seals, grey seals and crab eater seals
Lek
- Males aggregate and display (without contact) to attract females
- Females visit site and selects male
- Walrus, leopard seal and harbour seals
Scramble competition (stalking)
- Widely distributed females => limited resource!
- Multiple males stalk a single female, and compete with each other for mating opportunities
- Preventing recovery in Hawaiian monk seal??
Pinniped sociobiology
- Pinnipeds often aggregate in groups on land/ice
– Limited space
– Protection of pups/young
– Predator avoidance
– Thermoregulation
– Social interactions? - Site fidelity (philopatry)
– Females (and some males) return to same breeding site
– Sheltered, stable environment, food, no predators, protection of young, etc => same sites used for millennia!
– …and they were likely born there themselves - Social structure/groups?
– Not well-studied in pinnipeds, so many unknowns!!
– Dominance hierarchies, pup “kindergardens” and indications of social networks in otarids, and perhaps harbour seals?
– Mother-pup bonds and “learning” in walrus, and perhaps some phocis (harbour seals) and otarids?
– Some species migrate in groups, but often solitary feeding, and no evidence of actual cooperation - Otarid kindergarden; females take turn in watching pups when other females forage
Female life-history and reproduction of cetaceans
- Large interspecific variation in female life-history events
- Correlation between female body size and age at sexual maturity
Mysticete mating strategies: reproductive cycle
1.Parturition (calving)
2.Lactation
3.Weaning
4.Resting
5.Mating (and ovulation)
6.Gestation
Mysticetes breeding
- Breeding generally occur individually, or in small groups
- Female produce a single calf; typically 1-3 years between births; big investment for females!
- Relatively short lactation period (months)
- Rapid growth of calf
- Mating system differences
– Large testis; sperm competition (right whales) – Small testis; male-male competition (rorquals) - Seasonal migrations between low latitude breeding grounds and high-latitude foraging grounds in several species…
Seasonal migrations: mysticetes
- Most mysticetes (except Bryde’s whale)
- High latitude feeding; low latitude breeding
- Long migrations; long fasting period
- Advantage of breeding in warm waters
– Thermoregulation easier; calf needs time to build blubber
– Reduce risk of orca predation on calves
Seasonal migration between high-latitude (polar) foraging and low-latitude (tropic) breeding grounds
Frequency of seasonal migration depends on female body condition (and hence food availability)
Frequency of seasonal migration depends on female body condition (and hence food availability) (Mysticetes)
- Good condition; 1-2 year cycle
– Winter; low-latitude; give birth (and mate)
– Summer; high-latitude; feeding
– Fall; weaning of calf during migration
– Winter; low-latitude; (give birth and) mate - Poor condition; 3-? year cycle – Winter; low-latitude; give birth
– Summer; high-latitude; feeding
– Fall; weaning of calf
– Winter; migrate or skip migration to stay at high-latitude feeding
– Summer; high-latitude; feeding
– Winter; low-latitude; mate
Example: Humpback whales
- Breeding
– Females give birth at low latitude breeding sites - Mating
– Females (with/without calf) become receptive
– Male principal escort (PE)- Close to female, while chasing others away
- Timing and level of aggression is key!
– Male secondary escorts and challengers - Fight with PE and each other to establish hierarchy
Odontocete mating strategies
- Large variation in life histories, social systems and mating
- Porpoises, river dolphins (“R species”)
– Early sexual maturity; short nursing, birth interval and lifespan
– Small pod size; large testis
– Sperm competition - Dolphins, sperm whales and beaked whales (“K species”)
– Late sexual maturity; long nursing, birth interval and lifespan
– Often social; small testis; some secondary sexual characters
– Male-male competition
– Strong social structure centred around females
Example: orca social structure and mating
- North Pacific ecotypes
– Transients: mobile; feed on marine mammals
– Residents: stationary; feed on fish – Offshores: sharks, fish? - Orca social structure and mating
– Highly structured matrilineal social groups consisting of grandmothers, mothers and their offspring
– Males stays with own group (mom), but mate in other groups
(sociobiology) Group size and social structure of cetaceans determined by:
– Food availability vs. intraspecific competition
– Mating strategy
– Predator avoidance
– Inshore vs offshore habitat
(sociobiology) What is the social structure and relationships of cetaceans, and how do we determine it?
- Large variation in social structure and networks
– Non-modular (no structure); mysticetes and porpoises (??)
– Fission-fusion; most dolphins, and perhaps beaked whales
– Matrilineal; pilot whales, killer whales, monodontids
– Clans; sperm whales - Large variation in social structure!
(sociobiology) Foraging cooperation in some cetaceans
– Humpback whales
– Killer whales, and many other dolphin species – Group size depends on amount/size of prey
(sociobiology) Mysticetes social structure
– Unstructured (non-modular) social system
– Whales often solitary, except mother-calf pairs and when aggregating on feeding and breeding sites
(sociobiology) Odontocete social structure
Large variation; correlate loosely with body size)
– Solitary, except mother-calf pairs (porpoises)
– Fission-fusion with loose bonds, and some long-term relationships (most dolphins, and perhaps beaked whales)
– Matrilineal societies with long-term bonds on multiple levels among relatives (pilot whales, killer whales, monodontids)
– Clans are smaller matrilineal societies (sperm whales)
Female post-reproductive life-span
- Rarely seen in mammals (except humans)
*Fitness benefit by grandmothers helping offspring and relatives finding food, predator protection and “teaching” calfs how to be whale… - In humans, post-reproductive life-spans are a strong driver of evolution of culture…
- Beluga, narwhal, short- finned pilot whale (and orca) groups consist of high proportion of post- reproductive females
- Evolved multiple times!
- What about other social
cetacean species…?
