Download Reproduction: Cetaceans.

Fish 475: Marine Mammalogy
24 May 2010
Reproduction: Cetaceans.
Course website:
http://faculty.washington.edu/glennvb/fish475
Text reading reference: Chapter 10
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 sperm
competition, with
proportionately very large
testes and external
genitalia
John Tessler
Cetacean reproduction
Reproduction in the mysticetes
(baleen whales):
Breeding systems differ
between the two largest families
(right whales and rorquals):
Rorquals:
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
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
1. Conception
2. Birth
3. Weaning
2
1
Low-latitude breeding grounds
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
1. Conception
2. Birth
3. Weaning
2
Low-latitude breeding grounds
1
Reproduction: Odontocetes
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
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
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.
4
Reproduction in odontocetes
Examples of odontocete
species known to be sexually
dimorphic in size:
Sperm whales
Belugas
Killer whales
5
Reproduction in odontocetes
Examples of odontocete
species known to have
prominent secondary sexual
characteristics in males:
Sperm whales
Narwhals
Killer whales
Beaked whales
6
Reproduction in odontocetes
Variation in life history:
Dolphins and
porpoises:
Tortoises and hares?
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).
8
Reproduction in odontocetes
Variation in life history:
Porpoises (most data are
from two species, harbor
porpoise and Dall’s
porpoise):
Terry Pyle
Annual birth interval;
Early age of first
reproduction (3-4 yrs)
Short reproductive life
(<10 yrs);
Short lactation (< 1 yr).
9
Reproduction in odontocetes
Examples of linkage of
social and reproductive
systems:
Bottlenose dolphins:
Male bands and
dispersal for
reproduction;
10
Reproduction in odontocetes
Examples of linkage of
social and reproductive
systems:
Killer whales:
Superpods and male
“dispersal” for
reproduction.
11
Reproduction in sirenians
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
12
Reproduction in sirenians
Exception:
Development of tusks in adult
male dugongs
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 10-12 yrs;
Males territorial during breeding season,
with slight sexual dimorphism in size (males larger)
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
15
Reproduction in polar bears
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.