Reproduction: Cetaceans.

Transcription

1 Fish 475: Marine Mammalogy 24 May 2010 Reproduction: Cetaceans. Course website: Text reading reference: Chapter 10

2 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.

3 Cetacean reproduction: Mysticetes Breeding systems differ between the two largest families (right whales and rorquals): Right whales: Extreme sperm competition, with proportionately very large testes and external genitalia John Tessler

4 Reproduction in the mysticetes (baleen whales): Breeding systems differ between the two largest families (right whales and rorquals): Rorquals: Cetacean reproduction Testes and genitalia proportionately much smaller than in right whales. Breeding system more typically characterized by malemale competition and possible polygyny (more like pinnipeds. National Geographic Society

5 Cetacean reproduction Reproduction in the mysticetes (baleen whales): High-latitude feeding grounds Calving interval is variable in some species (best known for rorquals and gray whales), Likely depending on environmental conditions especially food supply: 3 Good conditions: 1. Conception 2. Birth 3. Weaning Low-latitude breeding grounds

6 Cetacean reproduction Reproduction in the mysticetes (baleen whales): High-latitude feeding grounds Calving interval is variable in some species (best known for rorquals and gray whales), Likely depending on environmental conditions especially food supply: 3 Less favorable conditions: 1. Conception 2. Birth 3. Weaning 1 2 Low-latitude breeding grounds 1

7 Reproduction: Odontocetes

8 1 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

9 2 Reproduction in odontocetes Classical evidence for malemale 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

10 3 Reproduction in odontocetes Ecological setting for the evolution of male-male competition: 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.

11 Reproduction in odontocetes 4 Examples of odontocete species known to be sexually dimorphic in size: Sperm whales Belugas Killer whales

12 Reproduction in odontocetes 5 Examples of odontocete species known to have prominent secondary sexual characteristics in males: Sperm whales Narwhals Killer whales Beaked whales

13 Reproduction in odontocetes 6 Variation in life history: Dolphins and porpoises: Tortoises and hares?

14 7 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).

15 Reproduction in odontocetes 8 Variation in life history: Porpoises (most data are from two species, harbor porpoise and Dall s porpoise): Annual birth interval; Terry Pyle Early age of first reproduction (3-4 yrs) Short reproductive life (<10 yrs); Short lactation (< 1 yr).

16 9 Reproduction in odontocetes Examples of linkage of social and reproductive systems: Bottlenose dolphins: Male bands and dispersal for reproduction;

17 10 Reproduction in odontocetes Examples of linkage of social and reproductive systems: Killer whales: Superpods and male dispersal for reproduction.

18 Reproduction in sirenians 11 Life history similar to odontocete Cetaceans: 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 sexual dimorphism or male-male competition. Jeff Foote

19 12 Reproduction in sirenians Exception: Development of tusks in adult male dugongs

20 13 Reproduction in marine otters 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 yrs; Males territorial during breeding season, with slight sexual dimorphism in size (males larger)

21 14 Reproduction in marine otters Marine otters: Poorly known: Litter size is two (smallest litter size of any otter species, but larger litter size than any marine mammal except polar 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

22 Reproduction in polar bears 15 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 yrs.