Dwarf Crocodile (Osteolaemus tetraspis) Fact Sheet: Physical Characteristics

Kofron and Steiner 1994; Pauwels et al. 2007; Villiers 1958; K Lovich, personal communication

General Appearance

• Body shape
  • Smallest crocodile species
    • Maximum recorded total combined body and tail length of c. 2 m (6.6 ft); typically much smaller (Vliet 2012)
    • Largest recorded length of wild crocodiles from study in Gabon (n=617 animals): 157cm (Eaton and Link 2011). 
    • Ratio of body length to head length averages 6.6:1, corresponding to a relative body to head size that is intermediate between the Nile crocodile (7.0:1) and the slender-snouted crocodile (5.8:1).
    • No apparent dimorphism in relative body length exists between sexes in Gabon. (Eaton 2009)
    • As it reaches maturity in managed care, proportionally more than doubles its weight for each 30 cm (1 ft) of growth in length between 91-182.9 cm (3-6 feet) (Dowling and Brazaitis 1966)
      • Proportionally greater increase than larger crocodilian species
    • Males are generally heavier than females (Dieter 2000; K. Lovich, personal communication)
      • In managed care may become quite bulky and wide, more pronounced in males
      • Adult males typically weigh 18.1- 45.4 kg (40-100 lb)
        • Reports of older males reaching up to 68.0-81.6 kg (150-180 lb); rarely found in the wild due to exploitation by the bush meat trade and trafficking
      • Adult females typically weigh 3.6-34.0 kg (30-75 lb) and may reach c. 40.8 kg (90 lb)
  • Tail
    • 40-50% of total length (Pauwels et al. 2007)
• Facial characteristics (from Trutnae and Sommerlad 2006)
  • Face and snout
    • Face
      • Widest at the base of the snout
      • Length c. 30% longer than width
    • Eyes
      • Brown
      • Pupil a vertical slit
        • Tapetum membrane behind the retina reflects a reddish-blue eye-shine
      • Placed above the corners of the mouth, on top of the head
        • Capable of sight above the water while the body remains submerged
      • Thick upper and lower eyelids
        • Capable of closure
          • Often closed in sleep
    • Snout short
      • Smooth upper surface
    • Nose
      • Sits on the top of the tip of the snout
      • 2 nostrils
        • Seal shut when the animal submerges
        • Separated lengthwise by a groove
  • Teeth
    • Number
      • Upper jaw with 16-17 teeth
      • Lower jaw with 14-15 teeth
    • Shape
      • Conical, with a single pointed tip
• Adult appearance (from Trutnae and Sommerlad 2006 unless otherwise noted)
  • Body scaled
    • Back
      • Dark from above, nearly black
      • Yellowish patches on the tail and jaw (Waitkuwait 1989)
    • Belly
      • Pale yellowish with many blackish patches (Waitkuwait 1989)
    • Tail
      • Lacks dorsal, keel on scales at the tail base
    • Neck
      • 4 large, bony plates arranged in a square on the nape of the neck; known as a nuchal shield
  • Limbs and feet
    • 5 toes on forelimbs (claws absent on 4th and 5th digits)
    • Reduction to 4 toes on hindlimbs, with absence of claw on the 4th digit
• Juvenile appearance (from Trutnae and Sommerlad 2006)
  • Back similar to adult
    • Yellow cross bands on upper sides of the body
• Anatomy videos (BBC Earth Unplugged)
  • Anatomy of a Dwarf Crocodile: Part 1
  • Crocodile Dissection and Lung Inflation, Part 2

• Secretory glands (from Weldon and Wheeler 2001)
• Believed to secrete pheromones
• Similar glands present in all extant (living) crocodilians
• Age class variation in the chemical composition of secretions
• Two sets of secretory glands
• Prominent gular glands
• Pair of skin glands on the underside of the snout
• Obscured by skin folds
• Located near the back of the jawline
• Paracloacal glands
• Embedded in the cloacal walls on each side of the vent
• African Dwarf Crocodiles produce a unique secretion primarily composed of dianeackerone-related steroidal esters (Weldon and Wheeler 2001; Yang et al. 1999)
• Adaptations for water regulation (from Trutnae and Sommerlad 2006)
• Skin composed of 3 layers
• Outermost layer essentially dead
• Thick and keratinized
• Keratin is a fibrous protein; it is the same molecule that composes the hair and fingernails of mammals
• Helps protect against dehydration on land
• Specializations for protection (from Trutnae and Sommerlad 2006)
• Bony, armor-like scales (scutes)
• Skin specializations
• Often reinforced with bone; bony scales known as osteoderms
• Present on the back, sides, belly, and tail of the Dwarf Crocodile
• Transparent, 3rd eyelid (nictitating membrane)
• Closes prior to attacking prey or submerging in the water
• Sweeps laterally (sideways) across the eye
• Adaptations for prey capture (from Trutnae and Sommerlad 2006)
• Teeth
• Conical shape designed to penetrate and hold, not cut and chew
• Structure compliments the strong jaw muscles; enables a strong secure grip
• Ears
• Capable of hearing above and below the water
• Crocodilians have the most developed hearing among reptiles

Comparison to other West African crocodiles (from Waitkuwait 1989)

• 3 species (as currently recognized) inhabit western Africa
  • African Dwarf (genus Osteolaemus)
  • Nile (genus Crocodylus)
  • Slender-snouted crocodiles (currently awaiting formal designation as genus Mecistops; previously within Crocodylus)
• Distinguishing features
  • Size
    • African Dwarf Crocodile much smaller than others (1.97-5.58 ft)
    • Nile Crocodile reaches 4-5 m (13.1-16.4 ft)
    • Slender-snouted Crocodile reaches 3-4 m (9.8-13.1 ft)
  • Nuchal (neck) scales
    • African Dwarf has 3 transverse series of scales
      • 2 large scales in first 2 series; 2 very small scales in third series
    • Nile and Slender-snouted crocodiles have 2 transverse series of scales
      • First series: 4 scales in the Nile Crocodile, 2 scales in the Slender-snouted Crocodile
  • Coloration
    • African Dwarf appears black from above with yellowish patches on the tail and jaw
      • Belly pale yellowish with many blackish patches
    • Nile Crocodile appears bright olive to bronze or dark green from above
      • Belly pale yellowish
    • Slender-snouted Crocodile appears dark olive from above
      • Belly yellowish with dark patches

Dwarf Crocodile Eye.  Image credit: © San Diego Zoo Wildlife Alliance. All rights reserved.

Dwarf Crocodile Face, Teeth & Snout. Image credit: Ken Bohn, © San Diego Zoo Wildlife Alliance. All rights reserved.

Dieter (2000)
Dowling and Brazaitis (1966)
Eaton and Link (2011)
Kofron and Steiner (1994)
Pauwels et al. (2007)
Trutnae and Sommerlad (2006)
Vliet et al. (2012)
Waitkuwait (1989)
Weldon and Wheeler (2001)
Yang et al. (1999)