Spot-necked Otter (Hydrictis maculicollis) Fact Sheet: Physical Characteristics

General

• A slim bodied, short-legged mustelid
• White markings on underside of neck and chest
• Webbed hands and feet, claws on all four limbs
• Long tapering tail slightly flattened top to bottom (Larivière 2002)

Pelage

• Varies from chocolate to reddish brown; albinos and partial albinos sometimes occur. (Larivière 2002) 
• Chin and upper lip white. (Larivière 2002)
• Usually throat and chest mottled with cream-colored or white patches; markings sometimes absent. (Benza et al 2009)
  • Mottling pattern highly variable; used by researchers to identify individuals.
• Fur offers superior insulation; no blubber
  
  • Outer layer of guard hairs 2-4 cm (.8-1.6 in) long.
  • Under fur very dense; traps air for thermo-insulation.
• River otters have about 60,000 hairs/cm sq. (Tarasoff 1974)
• Dogs, by comparison have fewer than 9000 hairs/cm sq. (Kruuk 2006)
• Sea otters' fur even more dense, with up to 164,000 hairs/cm sq. (Kruuk 2006)
• Older individuals' fur more reddish brown.

• Males slightly larger and heavier than females (Kruuk 2006)

(Larivière 2002)  (Benza et al 2009) (Procter 1963) (Melquist et al 2003)

General

• Similar to European otter, Lutra lutra, in body mass and food habits.
• Whole body very flexible; can easily touch nose to tail. (Harris 1968)

Head

• Large; road in rear, narrowing to a short wide muzzle
• Long whiskers (vibrissae) may aid in finding fish in murky water. 
• Nose pad hairless
• Ears short and round

Teeth

• 36
• Lower canines re-curved
• Upper canines straight and sharp

Legs and feet

• Legs short and stocky.
• Feet plantigrade (walk "flat-footed" as do humans and other primates, hedgehogs, racoons, bears, skunks and many other mammals). (Melquist et al 2003)
• Fully webbed hands and feet, each digit with a sharp 10 mm (.4 in) claw.
• Manipulate small objects with great skill.
  • A river otter could retrieve by hand a small pellet less than 3 mm (0.12 in) from underwater. (Melquist et al 2003)

Hearing

• Excellent hearing (Benza et al 2009)

Vision

• Nearsighted (adaptation for underwater vision). (Melquist et al 2003)
• In air: good vision at short distances up to 3 m (10 ft), not good over 10 m (33 ft) (Procter 1963)
• Sharpness of vision studied in highly aquatic sea otters (Mass & Supin 2002);
  • Iris muscles allow adjustments of curvature for the lens surface; good focus possible both in air and underwater
  • Not yet known if slightly less aquatic Spotted-necked Otter has this adaptation.
• Eurasian otters see blue, yellow, and green light but not red; may be an adaptation for seeing underwater where blue-green wavelengths dominate. (Melquist et al 2003)
• Eyes are orange-red in adults.  

Olfaction

• Sense of smell not well studied but their scent marking is well known, implying chemical communication. (Melquist et al 2003).

Benza et al (2009)
Harris (1968)
Kruuk (2006)
Larivière (2002)
Mason & Macdonald (1990)
Mass & Supin (2002)
Melquist et al (2003)
Perrin et al (2000)
Tarasoff (1974)