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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

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.

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

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

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

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

Reproduction: Odontocetes

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

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

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

Reproduction in odontocetes

Examples of odontocetespecies known to be sexuallydimorphic in size:

Sperm whalesBelugasKiller whales

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Reproduction in odontocetes

Examples of odontocetespecies known to haveprominent secondary sexualcharacteristics in males:

Sperm whalesNarwhalsKiller whalesBeaked whales

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Reproduction in odontocetes

Variation in life history:

Dolphins and porpoises:

Tortoises and hares?

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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

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).

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Terry Pyle

Reproduction in odontocetes

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Examples of linkage ofsocial and reproductive systems:

Bottlenose dolphins:

Male bands anddispersal forreproduction;

Reproduction in odontocetes

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Examples of linkage ofsocial and reproductive systems:

Killer whales:

Superpods and male “dispersal” for reproduction.

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

Reproduction in sirenians

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Exception:

Development of tusks in adult male dugongs

Reproduction in marine otters

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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)

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

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.