Marine Mammals: Part 1 Marine Vertebrates: Lecture 7

Notochord; Dorsal, hollow nerve tube; pharynx with slits, post-anal tail (with segmented muscle bands) Cranium formed from neural crest cells Plus paired appendages (2 pair)

Class Mammalia: Key characteristics  Mammary glands (milk production)  Hair  Endothermic  Efficient circulatory system (4-chambered heart)  Efficient respiratory system (diaphragm)  Internal fertilization  Relatively large brains  Differentiation of teeth  Development of malleus and incus in middle ear (reptiles already have stapes)

Order Carnivora Ursidae: polar bears Mustilidae: sea otters

(Sub)order Pinnipedia Phocidae Otariidae Odobenidae

Order Sirenia Manatees and dugongs

Order Cetacea Suborder Odontoceti Suborder Mysticeti

Osmotic balance Acquiring water  Diet  Drink  Metabolically-produced water Water loss  Skin, sweat glands, exhalation Excretion of water and ions  Kidneys Concentrating ability mirrors reptile/bird salt glands

Thermoregulation Heat retention: Fur vs. blubber  Dry fur is a more efficient insulator than blubber  Specializations of marine mammal fur Fur seals and sea otters Polar bears Regulation of heat via blood flow changes  Regulating flow to capillary beds Esp. hairless regions of body  Countercurrent exchange Large size and shape  Surface to volume low…  Comparison to land mammals

Order Carnivora Family Ursidae

Adaptations to marine existence Streamlining  No prominent shoulder humps  Small head; small ears Adaptations for swimming  Paws are larger, partly webbed  Also allows for more even distribution of weight on ice  Long neck (how of value?)  Dog paddle! Thermoregulation  Thicker fur  Clear, hollow guard hairs  These may actually absorb ultraviolet light)  >2x the size of grizzlies (up to 1800 pounds)

Habitat/Feeding ecology Circumpolar distribution  Stable, but not continuous, (mostly) annual pack ice  Can’t find prey without Seal specialists; will also hunt other marine mammals  Follow leads or finding holes made by their prey. Male vs. female foraging  Males venture further out onto less-stable pack ice Avoid the most unstable ice near the ice edge  ideal pupping grounds for seals  Females remain on more-stable pack ice closer to den sites. Locate ringed seal pups in dens beneath snow or in small ice caves in the pack ice  Use their sense of smell

Life History Mating  April/May  ~3:1 Male:Female “operational sex ratio” (Why?)  Induced ovulation:  Delayed implantation Maternity dens (~ mid- October) Young born in December/January Young are pounds at birth!  Usually two. Break out of dens (~ March/April)  Young ~25-30 pounds  Female is hungry… Cubs with mother for 2.5 years

Conservation status: Threatened Key threats  Habitat loss Global climate change  Harvesting  Water pollution

Order Carnivora Family Mustilidae: sea otters!

Overview/ adaptations to marine existence Size: quite small for a marine mammal  pounds Dive stats: 120 feet; 4 minutes breath-hold Thermoregulation (water is  F)  Fur  High metabolic rate (25% of body weight per day) Swim on their backs Use webbed hindflippers in an alternate motion for propulsion; also use their flattened tail.  Relatively slow for marine mammals, ~2-3 kt cruising speed. Forelimbs are very mobile, resemble arms and hands for collecting/manipulating food

Habitat/feeding ecology Live in kelp forests  Wrap themselves and their young in the kelp... Feed on a wide variety of benthic invertebrates  sea urchins, abalone, crabs, sea stars, clams, scallops, etc…  May play important role in maintenance of kelp beds Tool users (bang creatures with exoskeletons, shells, and even endoskeletons on rocks) Kelp itself provides some protection from predation.

Sea otter: Historic distribution

Sea otter: Current distribution

Conservation status: Endangered  CA sea otter population: steady, some slow growth  AK (Aleutian Islands) huge decline Orca predation  Major threats Coastal pollution Oil spills Cat litter and Toxoplasma gondii Decline of other marine mammals…