Mustelids

Named as they smell - well-defined anal scent glands

Otters one type of mustelid - 3 groups:

• Pteronura (S. American giant otter)
• America Lontra otters
• Sea otter, Eurasian otters, small-clawed and clawless otters

Some data suggests that Pteronura not part of otter clade - sister taxon to otter + weasel clade w/in Mustelidae

Most species freshwater predators of fish, molluscs, crustaceans

Breed and den in burrows - often long distance from water edge

Poor fossil record of otters

Multiple lineages developed bunodont (rounded) dentitions w/ enlargement of molars = cracking hard molluscs/food

Some lineages evolved badger-like teeth

New species of fossil otter - Siamogale melilutra 

• Miocene lignite beds in SW China

CT restoration of skull = combo of otter-like and badger-like cranial and dental characteristics

Belongs to Lurtrine because of posession of larger infraorbital canal and ventral expansion of temporal bone

Intermediate between species

Large - SA:V ratio is small, reduces heat loss

Slow metabolic rate for size - don't waste unnecessary energy which is used for heat generation

No insulating blubber - normal subdermal fat

Especially dense and fine fur - ~125,000pcm3

• Prevents water coming into direct contact with skin = no heat loss

Body streamlined

• Nose, eyes and ears high on sides of head = remain above water when swimming
• Large eyes and spherical for acute vision underwater and in low light

Webbed paws = propulsion

• Digits highly detrous and touch sensitive = pick up prey

Long sensitive whiskers (functionally same as lateral line) aid in prey detection in water and on land

Coastal populations adapted their diet to include marine fish and invertebrates - echinoderms and crabs

Sometimes referred to as 'sea otters' but not actually 

• True sea otter is Enhydra lutris

4 species - 1 marine Lontra felina

• Pacific coast of S. America

Endemic to Americas

Lontra felina

• Feeds both on water and rocks on fish/invetebrates/sea bird chicks
• Float on back when eating prey
• Does not use anvils like N. American sea otter
• Small - <1.2m length, 3-6kg
  • Unusual - only taken to marine life very recently

Endemic to N. Pacific coastal redions of Asia and N. America

Most aquatic of all otters - rarely on land

• Dive to 100m
• Massive ribcage with large lungs - compress down underwater 2.5x size land mammals
• Enormous, long webbed feet = propulsion in swimming
• Short, flattened tail

Hunt by sight (large eyes) and touch (dextrous, prehensile hands)

Diet dominated by crabs, molluscs, urchins

• Uses anvils - cracks hard prey on rocks to break them open
• Massive premolars and molars = crush hard prey
• Powerful jaws in short, deep snout

Biggest species - <45kg and 1.6m long

External ears = excellent hearing ability

Must eat 20-25% body weight to maintain heat production

Grooming forces air bubbles down fur next to skin = insulation for warmth and buoyancy

Forepaws with retracting claws - foraging and grooming

Involved in sequential megafaunal collapse/trophic cascade in North Pacific Ocean

Reduction in Great Whale biomass - post-world war II whaling

Main prey of Orca = forced to feed on other species

Including otters, fur seals, harbour seals and stellar sea lions

Reduction in sea otter numbers = removed control of Strongylocentrotus urchins

= Overgrazed giant kelp beds

Knock-on consequences to communities that relied on this habitat

Orca numbers only the same due to switched feeding strategies