SIO 133 -‐ Marine Mammal Behavior, and Social Systems: Ma;ng
John Hildebrand, Scripps Inst. Oceanography, UCSD
Ma;ng Strategies • Individuals behave to maximize reproduc;ve success
• Male and female reproduc;ve strategies together make up the "ma;ng system” • Female (mammals) invest more heavily in rearing offspring • Males in maximizing the number of mates
• These strategies generate structures and physiological adapta;ons ~ e.g. sexual dimorphism • The sexes do not necessarily agree and may some;mes be in conflict.
Cetacean Reproduc;ve PaVerns
Odontocetes Calf every 2-‐8 years Weaning 0.5 –10+yrs Feeds during lacta;on Ma;ng over extended season
Mys;cetes Calf every 1-‐2 years Weaning 5-‐12 months Fasts during lacta;on Fixed season for ma;ng/calving
Both: Rela;vely high level of investment in young
Prolonged Development
Odontocete Social Groups Low adult mortality
High juvenile mortality must protect offspring to increase reproduc;ve success
Stolen and Barlow 2003
Odontocete Parental Care
Females responsible for care
Alloparental care taking care of offspring other than your own
Tizzi et al. ALLOPARENTAL CARE IN TURSIOPS TRUNCATUS: A CASE REPORT
Senescent Females in KW and PW
Female life history paVerns • reproduc;ve period is conserved in pilot whales and Killer whales • extended post-‐reproduc;ve life span Infancy is defined as the period of nursing. Juvenile period includes post-‐ weaning to age at first birth Whitehead and Mann 2000
Matriarch as repository of ecological knowledge? Hum
an Pilot Killer
Primates
Female Reproduc;ve Strategies • Females maximize their reproduc;ve success … by being
good mothers and may benefit from choosing males with “good genes” (males that are dominant, older, immunologically Incompa;ble, etc.) … given the energe;cs and other constraints of searching for mates. • LiVle is known about female choice. Do females have Preferred companions? Exert cryp;c female choice?
Male Reproduc;ve Strategies • Males maximize their reproduc;ve success … by
ma;ng with as many females as possible and most devote the bulk of their energies to this pursuit • No known male parental care in marine mammals
• The poten;al for males to mate with many females depends on temporal & spa;al distribu;on and mobility of females • Males compete with other males for access to females both pre-‐ and post-‐ ma;ng
Pre-‐ma;ng Compe;;on • Contest Compe22on –aggressive interac;ons
to limit access of other males to females (size and weaponry) • Scramble Compe22on –compe;;on to disperse and find sexually recep;ve females (agility and speed)
• Mate Choice Compe22on –compe;;on in courtship to be chosen by the female (display)
Weaponry Beaked Whales: based on scarring paVerns, Males appear to use their teeth as weapons In aggressive encounters with other males (females lack teeth)
Display Display may take several forms • Modified appendages • Pigment paVerns • Acous;c display (song, sperm whale clang)
Male Spinner dolphin
Sperm Whale Clang Minke Whale Boing
Odontocete Ma;ng Systems Resident Killer Whale – ma;ng during mul;pod
“gree;ng ceremonies” between subpopula;ons -‐Bigg, BarreV-‐Lennard and others
Sperm Whale – Extreme polygyny with roving males Whitehead et al.
BoVlenose Dolphins – sequen;al female defense polygyny – with male alliances sexual coersion and polyestrous females – Conner, Mann and others
Sperm whale groups -‐ Female
Matrilineal groups (~10) Interact with other groups for short period Female bond based on cooperative care of young - Leave calves at surface during feeding dives Emerging understanding of complexity
Sperm whale groups -‐ Male
Males disperse (> 6 yrs)
Increasingly solitary
Form loose breeding associations
Roam between female groups
Sexual Dimorphism: Males > Females
Fusion -‐ Fission System
Fusion - Groups join for reproduction or feeding
Fission - Groups split to stable sub-units
Male Bottlenose Dolphin Grouping
- Strong, stable alliances (2-3 members) - Pairs join larger groups for mating - Super alliances = short term grouping - Aggressively separate females from
groups
Connor et al. 2006 Synchrony, social behaviour and alliance affilia;on in Indian Ocean boVlenose dolphins, Tursiops aduncus
Female Bottlenose Dolphin Grouping
Not as strong as male alliances Vary by location Reproductive Status Typically 4-7 Individuals Mothers with most recent offspring
Mys;cete Ma;ng Solitary Promiscuous Body size: Females > Males
presumed for fetal and calf development Breeding discrete phase of each year Migrate between produc;ve feeding grounds
and lower la;tude breeding grounds Best data on humpback, gray, and right whales More data on males than females
Pinnipeds Amphibious: • Solitary forager at sea • Return to land or ice for parturi;on Aggrega;on of Females on Land • Avoid harassment by males • Protect pups Ice breeding seal dispersed
Mating system Male parental care Sexual dimorphism Breeding substrate Mating substrate Lactation
Polygyny No High Land Land Long
Slight polygyny No Low Ice or land Water Short
Polygyny No High Land Land Short
Pinniped Ma;ng Systems
Characteristic No. of species Female density
Otariids 15 Gregarious
Most phocids 15 Solitary to Moderately Gregarious
H. grypus and Mirounga spp. 3 Gregarious
Cassini 1999 Behavioral Ecology
Sea OVers Live close to coastal forage areas • Females claim year-‐round territories • Females aggregate in small groups “raps” • Males aggregate outside reproduc;ve ;mes • Adult males establish territories that overlap with one or more female