Exam 2 - Lecture 6: Marine Mammal Reproduction

What are some generalized life history traits of MM?

• size

• reproductive rate

• gestation length

• blubber storage

• migrations

• sexual maturity

• sexual behavior

• reproductive cycles

• large size

• low reproductive rates => so slow to recover from population reduction

• long gestation length 7-17 months in which the babies are born in harsh environments and must be well developed to survive

• ability to store large amounts of blubber

• extensive migrations

• delayed sexual maturity (pinnipeds are 3-7 years, cetaceans 10-15 yrs)

• polygyny is common

• long reproductive cycles (1-7 years b/w births)

Carnivore reproduction of Pinnipeds

• what type of breeding pattern do they undergo?

• define post partum estrus, how long is it in Otariids and Phocids

• define embryonic diapause

• standard breeding pattern

• post partum estrus = sexual receptivity and fertility (otariids = 5-8 days, phocids = 4-60 days, determined by lactation period)

• embryonic diapause = embryo does not implant immediately but growth continues at a very slow rate to allow flexibility in the reproductive schedule; adjusts reproductive cycles depending on environmental conditions

describe in general the reproductive cycle of

• fall - spring

• spring - summer

• summer

• summer - fall

• fall - spring = active gestation

• spring - summer = parturition/pupping lactation

• summer = weaning, ovulation/mating

• summer - fall = blastocyst dormant, molting, implantation

describe Pinniped reproduction

• describe seasonality, is it synchronized

• how many offspring produced

• where do they give birth, what risks are increased by this

• highly seasonal, synchronized reproductive cycles

• usually only one offspring produced

• all return to land or ice to give birth which increases the risk of predation and disease

Pinniped reproductive anatomy of males

• what is the relationship b/w the baculum and penis

• define testes and their adaptations for aquatic life

• the baculum seeks protection in the penis while strengthening the penis

• testes = small and non-functional when non-mating creating a streamlined, scrotum in Otariids, para-abdominal in Phocids and Odobenids

Pinniped reproductive anatomy of females

• what are the unusual adaptations for aquatic life

• describe the structure of the uterus

• describe ovulation

• NO unusual adaptations for aquatic life

• uterus is bicornuate = upper parts of uterus are separate, lower parts are fused

• ovulate from alternate ovaries at each postpartum estrus

mammal uteri

• what mammals have bipartite

• what mammals have bicornuate

• what mammals have simplex

• bipartite => whales, most carnivores

• bicornuate => pinnipeds, ungulates

• simplex => bats, higher primates

define monogamous

one mate for each individual

• define polygamous

• list and define 2 types of polygamous

• polygamous = multiple mates of one gender but not the other

  • polygyny = 1 male w/ many females

  • polyandry = 1 female w/ many males

what is the breeding system of pinnipeds

• ALL pinnipeds are polygamous

• males are not needed to raise young, and instead put efforts into finding mates

list and define the 5 general mating systems

1. resource defense = males defend resources used by females

2. female defense = follow and defend females directly in the form of harems, multiple, and single male groups

3. scramble competition = finds one female, mate, and moves on to the next

4. sequential defense = sequentially defend single females through mating

5. lekking = aggregations of males engaging in competitive display to try to attract females

describe mating system for

• otariids

• phocids

• walrus

• otariids = none use scramble competition, lekking is controversial

• phocids = use all 5 types of mating systems

• walrus = resource defense and lekking

describe pinniped mating system in greater detail of the males and females

• many male seals establish dominancy hierarchies through fighting

• female choice incites male-male competition and sperm competion

define the reproduction of sea otters

• where do they give birth

• is reproduction seasonal

• type of implantation

• how long is gestation and growth period

• reproduction rate and nursing of pups

• do not return to land to give birth

• seasonal reproduction

• delayed implantation

• 6-8 month gestation w/ rapid growth period of 5-6 months

• can reproduce annually, but don’t always, pups nurse 4-8 months

sea otter breeding behavior

• what do males do?

• when do females come into estrus

• describe female choice

• define precopulatory behavior

• how is ovulation stimulated

• males defend territories when females are in estrus/heat

• females come into estrus once a year, usually days after weaning a pup

• females will choose a single male

• precopulatory behavior = touching, nuzzling, grooming

• rough treatment during mating to stimulate ovulation

describe polar bear reproduction cycle

• what environmental factors is the reproduction cycle dominated by

• when do females go into estrus

• describe implantation

• what is the gestation period and what type of young follows

• how frequent is young production

• dominated by the sea ice cycle and food distribution, they fast during ice-free period (July-Nov) bc need ice floes to travel and hunt

• females come into estrus March-May w/ yearling or 2 yr old cubs

• delayed implantation for 4-5 months, end when females den up in Sept

• gestation is 3-4 months, altricial (born helpless) young are produced

• produce young 3-4 yrs

Sirenian reproduction

• describe sexual dimorphism

• when are females sexually mature

• when are dugongs sexually mature

• is mating seasonal and synchronized

• how long is gestation

• what is produced

• how long do calves depend on mama

• how often are calves produced

• what factors postpone breeding by females

• little sexual dimorphism (tusks grown in male dugongs)

• females are sexually mature b/w 3-6 yrs

• dugongs sexually mature at 10 yrs

• mating is seasonal but NOT synchronized

• 12-14 month gestation followed by a single young; twins happen about 4% of time but often fatal

• calves depend on mom for ~1 yr, sometimes 2 yrs if mom is young

• females calf once every 2.5-5 yrs

• females can postpone breeding if: seagrass is rare, increase in FL due to exotic weeds and power plants, decrease in Amazon due to deforestation

Sirenian reproductive anatomy of males

• describe baculum

• location of testes

• NO baculum

• testes are located in abdominal cavity below kidneys (same as elephants)

Sirenian reproductive anatomy of females

• describe uterus and ovaries

• type of uterus

• what is left over after pregnancies

• uterus and ovaries are almost identical to African elephants

• bicornuate uterus

• conspicuos scaring from past pregnancies

sirenian reproduction behavior

• when does mating normally occur

• what behavior is formed

• describe mating behavior of Dugongs

• mating concentrated in spring

• manatees form mating herds => 1 female followed by >25 males

• dugongs => some form mating herds, some form leks

cetacean reproductive anatomy

• describe sexual dimorphism

• males

  • describe baculum

  • describe penis

• females

  • type of uterus, where does fetus develop

  • how much do baleen whale ovaries weigh

  • how much do dolphin ovaries weigh

• some sexual dimorphism (i.e., sperm whales, killer whales, belugas)

• males

  • NO baculum

  • penis is normally retracted into body

• females

  • bipartite uterus, fetus develops in one of the horns

  • baleen whale ovaries weigh several kg while dolphin ovaries weigh a few g

reproduction of Baleen whales

• purpose of migrations

• when do they produce young

• how often is young produced

• how long is gestation

• how long is nursing

• breeding frequency of minke whales, of right whale

• regular migrations geared towards mating

• baleens are long-lived and produce young well into old age

• produce young every 2 years

• 1 year gestation

• 6-8 months of nursing

• minke whale breed annually, right whales breed 3-4 yrs

what is the reproductive cycle of Mysticeti

reproductive 2 year cycle in which the first year is pregnancy during breeding migration, and feeding while the second year is lactation during the breeding and resting during the migration and feeding

cetacean reproduction of toothed whales (Odontoceti)

• how long is gestation

• describe lactation period

• what is reproduction intervals dependent on

• gestation ~<1 year

• variable lactation period => few months in dolphins and years is pilot and sperm whales

• reproductive intervals depend on resources varying b/w 2-5 yrs

describe mating patterns of cetaceans

• is it easy to observe

• is monogamy present

• describe female behavior and what does this cause

• what are the 4 results of female choice

• difficult to observe

• NO monogamy

• females are promiscuous which reduces male-male competition and promoted care for all young

• female choice causes sperm competition, dead-end pouches, male-male aggression, verbal aggression