DoL B Week 20 - Asynchronous Aquatic Mammals

What are the Pinnipedes?

• Contain 3 families

  • Odobenidae (walrus)

  • Otariidae (eared seals)

  • Phocidae (true seals)

• Feed offshore and give birth on land

What are the characteristics of Odobenidae (walrus)?

• Both sexes have tusks

• Skulls are specialised for feeding on clams and other benthic invertebrates

What are the characteristics of Otariidae (eared seals)?

• Distinguished from true seals by a flap of skin called the pinna near the ear opening

• Large foreflippers for propulsion

• Hind flippers used on land to walk - more agile than true seals on land

What are the characteristics of Phocidae (true seals)?

• Use hind flippers for swimming

• Main muscle mass is at rear

• Not agile on land

• Produce click vocalisations → potential echolocation

What is the social organisation of elephant seals like?

• Highly polygynous (harem - male has many females) - example of resource defence

• No paternal care after mating

• Bloody fights on mating beaches to assume dominant position

• Alpha male may inseminate up to 100 females per season

• Subdominant males hang round harems and intercept females as they return to the sea

What are the characteristics of the order Sirenia?

• Manatees and dugongs

• Warm, tropical waters

• Only marine mammals to feed primarily on plants

  • Stomachs not compartmentalised - long intestines and large mid-gut caecum for cellulose digestion instead

• Expend little energy due to poor quality diet → move slowly

• Constant replacement of teeth allows feeding on plants containing abrasive silica

What are the suborders of the order Cetartiodactyla?

• Whales and dolphins

• Mysticeti - baleen whales

• Odonticeti - toothed whales

(Alongside artiodactyls - i.e. pigs, ruminants etc. - but these are not marine)

What are the characteristics of Mysticeti (baleen whales)?

• Largest whales (blue whale largest mammal)

• Paired nostrils separate all the way through to a double blowhole

• Baleen plates (series of horny plates) instead of teeth to filter feed

  • Thickness and number of plates related to prey type

What are the characteristics of Odontoceti (toothed whales)?

• Jaws extend as beak-like snout

• Forehead rises in rounded curve called the melon

• Possess single nostril with single blowhole

• Little light underwater and sound travels well (better than in air) so they echolocate

How do toothed whales physically produce echolocation clicks?

• Sound produced by ‘monkey lips’ (dorsal bursa complex) in nasal passages

• Melon focuses sound at forehead

• Returning sounds channelled through oil-filled sinuses in lower jaw to the inner ear

• Inner ear isolated from skull by bubbly foam to reduce interference from other resonances