Marine Mammal Reproduction and Mating Systems

1
Marine Mammal Reproduction and Mating Systems
Life History Theory Reproductive
Anatomy Reproductive Physiology Reproductive
Cycles Maternal and Lactation Strategies
2
Life History Theory

• Individual animals behave to maximize their
  reproductive success (RS) over their lifetime.
• Influenced by
• decisions individuals make to maximize fitness
• phenotypic variation
• adaptations
• Constraints
• phylogenetic
• ecological

3
Marine Mammals

• All forage at sea (or in water)
• Amphibious species vs. completely aquatic
• Pinnipeds most-all reproduction on land
• Challenges
• Breathe air live in water
• Thermoregulation ? selection for larger size
• Seasonal food availability/ advantages of fasting
  ? lipid storage
• Preparing offspring for weaning in dynamic (e.g.,
  ice-breeding seals) or fully aquatic habitat

4
Reproductive Anatomy
5
(No Transcript)
6
External Anatomy Males vs. Females
Umbilicus Genital Slit Anal Slit
Mammary Gland Genital Slit Anal Slit
MALE FEMALE
7
13.4. External sexual differences of cetaceans.
8
13.6. Cetacean male reproductive system.
9
Cetacean Reproductive Anatomy MALE
testes anus penis - fibroelastic
urogenital opening
10
Reproductive Anatomy MALE
Synapomorphes with Artiodactyls 1)
fibroelastic penis 2) retractor muscle
11
Females Mammalian Uteri
bipartite bicornuate
simplex (whales, most carnivores)
(pinnipeds, ungulates) (bats, higher
primates)
12
Cetacean Reproductive Anatomy FEMALE

• Synapomorphes
• with Artiodactyls
• 3) pseudocervical folds

13
13.9. Cetacean female reproductive system.
14
corpora albacantia 13.10. Left ovary of a
Pacific whitesided dolphin showing corpora
albacantia.
15
(No Transcript)
16

• Captive studies (odontocetes)

17
(No Transcript)
18
Artiodactyl --gt Cetacean
19
Reproductive Anatomy shared with Artiodactyls

• MALES
• fibroelastic penis (i.e. no baculum)
• muscle (vs. vasodilation)
• FEMALESbicornuate uterus
• pseudocervix (folds in vaginal wall)
• diffuse placental attachment to uterus

20
Reproductive Physiology
21
Ovarian Cycle
primary follicleprimary oocyte mature
follicle secondary oocyte corpus luteum corpus
albicans
22
Left Ovary of a Pacific White-sided Dolphin
Corpus albicans
23
Calcluating age using corpora albicantia in
cetaceans

• What variables need to be known?

24
Hormones of Pregnancy and Lactation

• Similar to other mammals
• Progesterone and Estradiol
• Prolactin

25
Ovulation and Estrus

• estrus vs. estrous
• What defines estrus?
• Types of ovulation
• spontaneous
• Induced
• Monoestrous vs. Polyestrous

26
Potential Mysticete Reproductive
Cycle
27
Gestation Period (months)

• Bairds beaked whale 17
• Killer Whale 15
• Sperm Whale 15-16
• Beluga gt11
• LF SF Pilot Wl (Globicephala spp) 14.5 - 15
• Bottlenose dolphin 12
• Harbor Porpoise 10-11
• Dalls Porpoise 11-11.4
• Balaenoptera musculus 11-12
• Balaenoptera acutorostrata 10
• M. novaeangliae 11-12
• Eschrichtius robustus 13-14
• Balaena mysticetus 13-14

28
Reproductive Cycles Mystictes

• 2 3 year birth interval (in most)
• breeding migration feeding calving
  lactation weaning resting

29
Mysticete Reproductive Cycle (fin whale)
------First Year --------------Second Year------
--Pregnancy--------
-Lactation-
-Resting-
(anestrus)

• Breeding
• Migration
• Feeding

25 35 45 55 65
30
13.13 Two-year reproductive cycle of fin and
gray whales.
31
13.14 Latitudinal shifts of gray whales during
their annual migratory cycle as a function of
reproductive status.
32
Growth Curve for a Blue Whale Fetus 0 - 11 months
33
(No Transcript)
34
Birth of an Irawaddy Dolphin (Orcaella
brevirostris)
35
Cetacean Neonates

• Size relative to female
• Thermoregulatory considerations
• higher metabolic rate
• higher caloric intake
• rapid deposition of fat

36
Maternal Care and Lactation

• Fasting Phocids and Mysticetes
• Foraging Cycle
• Otariids
• Aquatic Nursing (no fasting)
• Walrus and Odontocetes

37
Lactation and Milk Fat

• Duration (d) Fat Protein
• H. Porpoise 240-360 46 11
• Spinner Dolphin 390-810 22 7
• Sperm Whale 600-1200 26 8-10
• Fin 180-210 33 4-13
• Minke 150-180 30 14
• Humpback 300-330 44 13

38
Factors that affect Duration of Dependence

• Nutritional/Physiological needs (temperature)
• Physical maturation
• Social development

39
What determines a mammals mating system?

• need for biparental care
• ratio of reproductive females to reproductive
  males OPERATIONAL SEX RATIO
• degree of estrous synchrony among females
• male access to estrous females

40
What predictions would you make about cetacean
mating systems?
Polygyny? Serial Monogamy? Polyandry? Promiscuity
41
Much less known about cetacean mating systems and
strategies compared to pinnipeds.WHY?
42
Eubalaena glacialis

• Females mate with multiple males
• No aggression between competing males
• Courting bouts 1 2 hrs
• Largest testes of any living mammal
• weigh up to about 525 kg.)
• suggests sperm competition

43
13.5. Relationship between body size and testis
size of ten species of mysticetes. The three
species with relatively larger testes are assumed
to produce proportionally larger quantities of
sperm with which to compete with the sperm of
other males. (Brownell and Ralls, 1986.)
44
Brownell and Rawls 1986. Potential for sperm
competition in baleen whales.
45
Sperm Competition

• Balaenidae
• Balaena mysticetus bowhead
• Eubalaena glacialis n. right whale
• Eubalaena australis s. right whale
• Eschrichtiidae

46
Post-reproductive females
47
Post-reproductive females

• females that spend up to 30 of their life as
  non-reproducers and exist in matrilineal or
  matrifocal groups
• What are the physiological signs?
• What is the evolutionary significance of
  post-reproductive females?

48
What cetaceans species have post-reproductive
females?

• short-finned pilot whales (Globicephala
• macrorhynchus)
• killer whales
• (Orcinus orca)
• Long-finned pilot whales (G. melaena) and sperm
  whales (Physeter macrocephalus) do not appear to
  have PRFs

49
Globicephala melaenashort-finned pilot whale

• Globi round, cephala head
• Long-finned
• Pectoral flippers 1/5 of body
• Short-finned
• Pectoral flippers 1/6 of body

50
Globicephala malaenashort-finned pilot whale
51
Habitat and Diving

• Deep water (1000 m )
• Steep slopes
• upwelling areas (e.g., underwater canyons)
• usually short dives can dive ? 1 hr
• Maximum depths
• Long-finned pilot whale 650 m
• Short-finned pilot whale 500 m

52
Food

• Cephalopods (squid)
• Fish (e.g., mackerel)

53
Mass strandings
Common in Globicephala spp.

• Form cohesive social groups
• Studies of social structure
• Photo identification
• Mass strandings (Kasuya Marsh)
• Drive fisheries

54
Genetic Data from Drive Fisheries

• Matrileal groups, but often gt 1 matriline
• 2-4 generations together
• Males in groups related and not fathers of
  offspring
• Neither males nor females (G. spp.) appear to
  disperse from natal group
• Polygynous mating system

55
Long-finned pilot whales, Cape Breton, Nova
Scotia(Ottensmeyer, C.A )

• Photo-ID

56
Long-finned pilot whales(Ottensmeyer, C.A )

• Form stable matrilineal units or pods not
  segregated by age or sex
• Exhibit natal philopatry (rare among mammals)
• mate when different family groups interact

57
Sotalia fluviatilis, F. Delphinidaetucuxi
dolphin eastern South and Central America
F gt 25 yrs senescent ovaries
Rosas et al. 2002. Reproduction of the estuarine
dolphin on the coast of Parana, southern Brazil