reproduction: cetaceans. - university of washington › glennvb › fish475 › lecture... ·...
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Fish 475: Marine Mammalogy24 May 2010
Reproduction: Cetaceans.
Text reading reference: Chapter 10
Course website:http://faculty.washington.edu/glennvb/fish475
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Cetacean reproduction
Some general patterns:
Long gestation (typically about 1 year);
Long birth interval (at least one year, but may be much longer for some odontocetes);
Often closely linked to seasonal migratory patterns;
Parental care entirely maternal;
Delayed implantation does not occur.
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Cetacean reproduction: Mysticetes
Breeding systems differ between the two largest families (right whales and rorquals):
Right whales:
Extreme spermcompetition, withproportionately very large testes and externalgenitalia
John Tessler
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Cetacean reproduction
Reproduction in the mysticetes(baleen whales):
Breeding systems differbetween the two largest families(right whales and rorquals):
Rorquals:
Testes and genitaliaproportionately muchsmaller than in rightwhales. Breeding systemmore typicallycharacterized by male-male competition andpossible polygyny (morelike pinnipeds.
National Geographic Society
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Cetacean reproduction
Reproduction in the mysticetes(baleen whales):
Calving interval is variable insome species (best known forrorquals and gray whales),Likely depending onenvironmental conditions –especially food supply:
Good conditions:
1. Conception2. Birth3. Weaning
1
Low-latitude breeding grounds
High-latitude feeding grounds
2 1
3
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Cetacean reproduction
Reproduction in the mysticetes(baleen whales):
Calving interval is variable insome species (best known forrorquals and gray whales),Likely depending onenvironmental conditions –especially food supply:
Less favorable conditions:
1. Conception2. Birth3. Weaning
1
Low-latitude breeding grounds
High-latitude feeding grounds
2
3
1
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Reproduction: Odontocetes
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Reproduction in odontocetes
“Patterns”:
1. Evidence for male-male competition in some species;
2. Diversity of life history strategies;
3. Complex relationship of social and breeding systems in many species.
Stephan Wong
1
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Reproduction in odontocetes
Classical evidence for male-male
competition:
1. Sexual dimorphism in body size;
2. Prominent secondary sexual characteristics in males;
3. Absence of sperm competition – reduced proportionate size of testes and male genitalia.
Stephan Wong
2
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Reproduction in odontocetes
Ecological setting for theevolution of male-malecompetition:
1. Concentration, in both time and space, of resources necessary to support lactating females and newly-weaned juveniles;
2. Limited availability of habitat appropriate for breeding activity.
3
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Reproduction in odontocetes
Examples of odontocetespecies known to be sexuallydimorphic in size:
Sperm whalesBelugasKiller whales
4
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Reproduction in odontocetes
Examples of odontocetespecies known to haveprominent secondary sexualcharacteristics in males:
Sperm whalesNarwhalsKiller whalesBeaked whales
5
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Reproduction in odontocetes
Variation in life history:
Dolphins and porpoises:
Tortoises and hares?
6
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Reproduction in odontocetes
Variation in life history:
Dolphins:
Long birth interval (2-7 yrs);
High age of first reproduction (4-17 yrs);
Long reproductive life (20 yrs or more);
Lengthy lactation (2-3 yrs).
7
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Reproduction in odontocetes
Variation in life history:
Porpoises (most data are from two species, harbor porpoise and Dall’s porpoise):
Annual birth interval;
Early age of first reproduction (3-4 yrs)
Short reproductive life (<10 yrs);
Short lactation (< 1 yr).
8
Terry Pyle
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Reproduction in odontocetes
9
Examples of linkage ofsocial and reproductive systems:
Bottlenose dolphins:
Male bands anddispersal forreproduction;
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Reproduction in odontocetes
10
Examples of linkage ofsocial and reproductive systems:
Killer whales:
Superpods and male “dispersal” for reproduction.
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Reproduction in sirenians11
Life history similar to odontoceteCetaceans:
High age of first reproduction (3-15 yrs);
Long birth interval (3-6 yrs);
Long period of lactation (2-4 yrs);
Long reproductive life (20 yrs or more).
Little evidence of sexualdimorphism or male-malecompetition.
Jeff Foote
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Reproduction in sirenians
12
Exception:
Development of tusks in adult male dugongs
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Reproduction in marine otters
13
Sea otters:
Similar to porpoises and otariids:
Annual pupping, delayed implantation capability;
Lactation 4-6 months;
First reproduction at 3-4 yrs;
Breeding life of 10-12 yrs;
Males territorial during breeding season, with slight sexual dimorphism in size (males larger)
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Reproduction in marine otters
14
Marine otters:
Poorly known:
Litter size is two (smallest litter size of any otter species, but larger litter size than any marine mammal exceptpolar bears);
Breeding system likely similar to other otters, with complex linkages to social system. Breeding activity probably occurs largely on land or in fresh water
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Reproduction in polar bears15
Reproductive patterns strongly influenced by annual cycles in sea ice distribution and quality.
Delayed implantation capability;gestation 8 months;
Litter size 1-3, newborn cubs altricial;
Birth interval 3-4 years;
Period of lactation about 2 yrs;
Age of first reproduction 4-8 yrs;
Breeding life span 10-12 yrs.