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Dwarf Crocodile (Osteolaemus tetraspis) Fact Sheet: Reproduction & Development

Courtship

Courtship & Mating

  • Male reproductive behaviors (summarized in Waitkuwait 1989 unless otherwise noted)
    • Male-female interactions
      • Males produce low-pitched and resonant drumming vocalization (from Beck 1978)
        • Individuals in managed care drum c. 2 months prior to the female laying eggs
        • Drumming often continues throughout the night (Helfenberger 1981)
      • Mates participate in neck rubbing
        • Partners rub one another’s head and jaw
    • Male-male interactions
      • Males engage in bouts of fighting

Reproduction

Reproduction

  • Seasonal reproduction, Cote d’Ivoire (from Waitkuwait 1989)
    • Nest construction begins at the end of the dry season
      • Period associated with an abundance of fallen leaves needed to build nests
    • High rainfall amounts experienced during the subsequent nesting period
      • Period extends > 274 days
    • Not uncommon for nest construction to occur outside the nesting period
      • c. 1 in 3 nests built at other times of the year
  • Mound nesters (from Waitkuwait 1989 unless otherwise noted)
    • Nest structure
      • Mounds of leaves and rotting vegetation
        • Decomposition believed to release heat and aid embryo development
      • Four sided structure
        • Flat on two sides and steeply sloped on the remaining sides
        • Furrow across the top created by the female lying on the nest or creeping over it
      • Dimensions highly variable
        • Likely vary according to environmental temperature
        • Nest size and structure are strongly influenced by the materials available to mothers
    • Nest construction
      • Female builds the nest
      • Forelimbs collect materials from a few meters surrounding the nest area
        • Debris is typically pushed against the base of a tree (Eaton 2010a)
    • Nest site placement
      • Not located immediately next to water
        • Average distance from water 16.9 m (55.4 ft)
      • Height above water table
        • Placed 1-2 m above the water line (Riley and Huchzermeyer 1999)
  • Maternal nest guarding (from Waitkuwait 1989)
    • Visit and guard nest during incubation period
  • Interbirth interval (time between consecutive births)
    • Annual reproduction (Waitkuwait 1989; Hara and Kikuchi 1978)
      • 1 clutch per season is typical; rarely 2 (Trutnae and Sommerlad 2006)

Egg Laying & Incubation

Clutch characteristics (from Hara and Kikuchi 1978 unless otherwise noted)

  • Clutch size
    • Mean clutch size 10-14 eggs (Waitkuwait 1989, Eaton 2004)
    • Range 6-17 eggs (Beck 1978; Groombridge 1982; Waitkuwait 1989)
  • Egg features
    • Elliptical in shape
    • White, smooth appearance
      • Yolk slightly visible through the shell for a few days
        • Fertile eggs are distinguishable from unfertilized ones
      • Become opaque and more rigid within several days
  • Egg dimensions
    • c. 69 x 37 mm (2.7 x 1.5 in) (Waitkuwait 1989)
    • Broad ranges reported in a population raised in managed care
      • 60.9-70.5 mm x 39.0-42.7 mm (2.4-2.8 in x 1.5-1.7 in)
  • Egg weight
    • 56.7-70.5 g (2.0-2.5 oz)

Incubation & Hatch

  • Incubation (from Waitkuwait 1989)
    • Length of incubation
      • Variable
        • c. 100 days
        • Breeding in managed care: 68-126 days (Hara and Kikuchi 1978; Sims and Sing 1978; Waitkuwait 1989)
    • Incubation temperature and humidity
      • Nest mound temperature range of 26-34oC
        • c. 5oC higher than ambient
      • Minimal fluctuation in humidity and temperature within a single nest
        • <0.5oC
        • Air space of the egg chamber almost always at saturation point
    • Sex determination and incubation (from Trutnae and Sommerlad 2006)
      • Temperature and timing determine gender among crocodilians
        • No published reports on the influence of temperature on sex determination in Dwarf Crocodiles
        • Many other crocodilian species produce females at lower incubation temperatures; in some, females are produced at high and low incubation temperatures and males at mid-range temperatures
  • Hatching
    • Process of hatching (from Waitkuwait 1989 unless otherwise noted)
      • Cracks develop on eggs a few days prior to hatch
        • When inside the egg, young vocalize by croaking heavily when movement occurs in the nesting area
      • Mother reacts to calls of young by excavating the nest to assist hatching
      • Typically emerge 1-2 days after the appearance of the first crack, observation in managed care (Hara and Kikuchi 1978)
        • Longer intervals possible (Hara and Kikuchi 1978)
    • Hatchling characteristics
      • Size
        • Body mass
          • 43.5-51.1 g (1.5-1.8 oz) (Hara and Kikuchi 1978)
        • Length
          • Mean total length:
            • 279.3 mm (11 in), one study of wild crocodiles (Waitkuwait 1986); 180-223 mm (7.1-8.8 in) (Eaton 2004)
          • Managed care bred hatchlings variable in size
            • Total length: 199-238 mm (7.8-9.4 in) (Hara and Kikuchi 1978)
            • Snout-vent length: 105-124 mm (4.1-4.9 in) (Hara and Kikuchi 1978)
      • Appearance (from Beck 1978)
        • Boldly colored
          • Back dark, nearly black
            • Predominant color interspersed with irregular, creamy yellow cross bands
          • Belly light
            • Graduates to an intense yellow on the jaw
  • Interbirth interval
    • Annual reproduction (Waitkuwait 1989; Hara and Kikuchi 1978)
      • 1 clutch per season is typical; rarely 2 (Trutnae and Sommerlad 2006)

Life Stages

Hatchling (from Waitkuwait 1989 unless otherwise noted)

  • Care
    • Mother (and possibly father) remains near young to provide protection for some time (Eaton 2004)
      • Young call (vocalize) to mother
    • In managed care, male known to be involved in care, similar to female (Trutnae and Sommerlad 2006)

Adults

  • Mature c. 5 years of age (from Waitkuwait); estimated maturity 6.8 – 15.7 years(Eaton 2011)
    • Reach maturity at approx. 1 m (39.4 in) in length (Kofron and Steiner 1994; Eaton 2011)
    • Growth continues after reaching sexual maturity
  • No evidence of reproductive senescence
    • Offspring fathered by male >67 years of age in managed care (ZIMS 2015)

Longevity & Mortality

Longevity in managed care

  • Up to 70 years, one male raised in managed care (ZIMS 2015)
  • Commonly survive >40 years (ZIMS 2015)

Longevity in the wild

  • No reports

Mortality

  • Predation (from Waitkuwait 1989 unless otherwise noted)
    • Humans are the primary predator of Dwarf crocodile (Thorbjarnarson and Eaton 2003)
    • Natural predators
      • Hatchlings are most susceptible
      • Present at low density in tropical forests
        • Do not likely represent a threat to crocodile populations

 

Juvenile Dwarf Crocodile

baby dwarf crocodile

Juvenile dwarf crocodile (Osteolaemus tetraspis) in the Ankasa Resource Reserve, Ghana.  Image credit: © Francesco Veronesi at Flickr. Some rights reserved.

Page Citations

Beck (1978)
Eaton (2004)
Eaton (2010a)
Eaton (2011)
Groombridge (1982)
Hara and Kikuchi (1978)
Helfenberger (1981)
Kofron and Steiner (1994)
Riley and Huchzermeyer (1999)
Sims and Sing (1978)
Thorbjarnarson and Eaton (2003)
Trutnae and Sommerlad (2006)
Waitkuwait (1986)
Waitkuwait (1989)
ZIMS (2015)

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