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CROCODOPOLIS world of crocodilians TM SCIENCE · CULTURE · INDUSTRY · NEWS · COMMUNICATION · CONSERVATION
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FEATURES Photo: Bill Moss book previews
Image: Edition Chimaira
Crocodilians: Their Natural History & Captive Husbandry
By Ludwig Trutnau & Ralf Sommerlad 2006, Edition Chimaira 570 pages
Read excerpts from the newly-published book.
EXCERPTS
· From FORWARD, by Grahame Webb · TABLE OF CONTENTS · From CROCODYLUS CATAPHRACTUS
Copyright © 2006 Ludwig Trutnau, Ralf Sommerlad and Edition Chimaira. Reproduced with permission.
(Editor's note: Some of the text has been formatted graphically to fit this page. The content remains intact.)
Please scroll down to view excerpts.
From FORWARD By Grahame Webb In writing "Crocodilians - Their Biology and Captive Husbandry", Ludwig Trutnau and Ralf Sommerlad have made a great contribution to overcoming this problem. Their book provides a wealth of new and old information about all aspects of crocodilians (evolution, taxonomy, physiology, anatomy, behaviour, ecology, feeding, attacks on humans, conservation, management, sustainable use), and will interest anyone with a professional or amateur interest in crocodilians. The first hand experience and new knowledge about captive husbandry will be invaluable to those with an interest in this area. The book also draws on a great deal of the European literature on crocodilians, which for a variety of reasons - language amongst them - has tended to lesser known outside Europe. It is heartening to see references to classic German studies from the early 20th Century, that did no much to pioneer our understanding of crocodilian structure and function. What makes this book particularly special is that in addition to the authors being skilled in crocodilian science, which they compile and present with great clarity, they are all experienced keepers of crocodilians. This growing interest group, united by the enjoyment of caring for and being close to crocodilians, is rapidly becoming a key player in general research and more important, in the conservation of wild crocodilian populations threatened with extinction. The energy and commitment within this growing cadre of people is remarkable. They value crocodilians for new reasons, but because they value them, they put resources into their conservation. _________________________________
Table
of Contents
Part
1: General
Introduction
Origins
of Crocodilians
Evolution
of Crocodilians
Positioning
Crocodilians within Vertebrates
Systematics
of Modern Crocodilians
Status
of Modern Crocodilian Populations: IUCN Definitions and WA Appendices
Key
for Alligatorinae, Crocodylinae, and Gavialinae
Key
for Belly Hides of Alligatorinae, Crocodylinae, and Tomistominae
Part
2: Physiological Characteristics
General
Skin
and Skin Elements
Musculoskeletal
System
Teeth
Digestive
System
Urogenital
System and Inner Secretory Glands
Vascular
System und Respiratory System
Nervous
System
Sensory
Organs
Part
3: Distribution and Habitats
Modern
Distribution
Habitats
Populations
and Population Development
Part
4: Behavior of Crocodilians
Prey,
Hunting, and Digestion
Growth,
Weight, and Lifespan
Predators
und Parasites
Diseases
and Causes of Death
Handling
Crocodilians
Tickbirds
and Crocodilians
Respiration
Sleep
Vocalization
Hibernation
and Rest Periods
Thermoregulation
and Basking
Sex
Differences, Sex Ratios, Temperature-dependent Sex Determination, and
Sexual Maturity
Courtship
and Mating
Nesting
and Egg Laying
Parental
Care and Hatching
Crocodilian
Hybrids and Genetics
Part
5: Crocodilians and Humans
Beliefs,
Myths, Religion, and Persecution
Attacks
on Humans by Crocodilians
Trade
in Crocodilian Products
Farms
for Breeding Crocodilians
A
Plea for Crocodilians
Part
6: Crocodilians in Captivity
Crocodilians
as Pets
Crocodilians
in Zoos
Feeding
Breeding
Diseases
Part
7: Characteristics, Distribution, Habitats, Biology, Husbandry, and
Breeding
of Each Species
Subfamily
Alligatorinae
Genus
Alligator – True Alligators
Alligator
mississippiensis
– American Alligator
Alligator sinensis
– Chinese Alligator
Genus
Caiman – Caimans
Caiman crocodilus
– Spectacled Caiman
Caiman
yacare –
Yacare Caiman
Caiman
latirostris
– Broad-snouted Caiman
Genus
Melanosuchus – Black Caiman
Melanosuchus
niger –
Black Caiman
Genus
Paleosuchus – Dwarf Caimans
Paleosuchus
palpebrosus
– Cuvier's Dwarf Caiman
Paleosuchus
trigonatus–Schneider's
Dwarf Caiman
Subfamily
Crocodylinae
Genus
Crocodylus – True Crocodiles
Crocodylus acutus
– American Crocodile
Crocodylus cataphractus – Slender-snouted Crocodile
Crocodylus intermedius – Orinoco Crocodile
Crocodylus johnsoni
–Johnston's Crocodile
Crocodylus mindorensis – Philippine Crocodile
Crocodylus moreletii
– Morelet's Crocodile
Crocodylus niloticus
– Nile Crocodile
Crocodylus novaeguineae – New Guinea Crocodile
Crocodylus palustris
– Swamp Crocodile
Crocodylus porosus
– Saltwater Crocodile
Crocodylus rhombifer
– Cuban Crocodile
Crocodylus siamensis
– Siamese Crocodile
Genus
Osteolaemus – African Dwarf Crocodile
Osteolaemus
tetraspis
– African Dwarf Crocodile
Subfamily
Tomistominae
Genus
Tomistoma – False Gharials
Tomistoma
schlegelii – False Gharial
Subfamily
Gavialinae
Genus
Gavialis – Indian Gharials
Gavialis
gangeticus
– Indian Gharial
part
8: References Index
_________________________________
From Crocodylus cataphractus Cuvier, 1824 – African Slender-snouted
Crocodile
Other Names:
African Slender-snouted Crocodile, Cocodrilo Hociquifino Africano,
Crocodile à Museau Allongé d Afrique, Crocodile à Museau Etroit,
Faux-gavial d'Afrique, Long-snouted West-African Crocodile, African
Gharial, Long-nosed Crocodile, African Sharp-nosed Crocodile, Faux
Gavial Africain, Loricate Crocodile, Subwater Crocodile, Khinh, Cabinda,
Panzerkrokodil, Westafrikanisches Krokodil
Subspecies:
Crocodylus
cataphractus cataphractus
Cuvier,
1825 – West African slender-snouted crocodile.
Crocodylus
cataphractus
congicus
Fuchs,
Mertens
& Wermuth,
1974
– Central African slender-snouted crocodile.
According
to Brazaitis (2001),
there exist no subspecies to Crocodylus
cataphractus.
Status:
CITES, Appendix I.
DEFICIANT
DATA. Threat stems from illegal hunting for skin
harvesting, for food, and habitat destruction. Synonyms and Taxonomic Notes:
1789
Lacerta gangetica
Gmelin,
partim, Linn. Syst. Nat. Ed.
13,
1:1057.
– Terra typica: “Senegal and Ganges.“
1801
? Crocodilus niger
Latreille
in Buffon, Hist. nat. Rept. Ed. Déterville,1:120.
– Terra typica: Senegal River.
1825
Crocodilus
cataphractus
Cuvier, Rech. Oss. foss., Ed.
3,
52:
58;
Plate 5, Fig.1,
2.
– Terra typica: unknown.
1835
Crocodilus
leptorhynchus
Bennet,
Proc. zool.
Soc.
London, 1835:
129.
- Terra typica: near Fernando Poo.
1844
Mecistops bernettii
Gray
(nomen substitutum pro Crocodilus
leptorhynchus
Bennett
1835),
Cat. Tort.
Crocod.
brit. Mus.:
57.
1889 Crocodilus cataphractus Boulenger, Cat. Chelon. Rhynchoceph. Crocod.Brit. Mus.: 279.
The
holotype is a dried specimen in the osteological collection at the Royal
College of Surgeon’s Museum in London. The terra typica is given as
"Senegal and Ganges" “BY”
STREICHEN (
Fuchs,
Mertens &
Wermuth,1974).
Overall Length: Up to
4 m (Villiers
1958),
2.5-2. m (Wermuth
& Fuchs
1978),
3-4
m (Ross &
Magnusson
1989), no more than
3
m (Steel
1989),
3-4 m (Waitkuwait
1989),
4
m,
large adults rarely over
3
m. Hatchlings measure 25 cm in average.
Characteristics: Snout is noticeably elongated and 2.5-3.5 times as long as wide at its
base. The surface of the head is smooth. Humps and wrinkles in front of
the eyes are missing. Young animals have 5, adults 4 teeth in the
premaxilla. The mandibles are fused rostrally up to the 7th
or 8th teeth.
Dental Formula:
5 (4) +
13–14
. 15–16
There
is a pair of large postoccipitals on the neck in a transversal row,
lateral to them smaller scales. The 4 large nuchals are arranged in a
square. To the right and left of them is a smaller scale, which may be
missing. The dorsals, which are usually not clearly separated from the
nuchals, form 6 longitudinal and 18-19 transversal rows. The ventrals
are arranged in 21-24 rows in Crocodylus
cataphractus cataphractus
and 24-27 rows in Crocodylus
cataphractus
congicus. Crocodylus
cataphractus
cataphractus has 3 scales in a transversal row in the middle of the
body, Crocodylus
cataphractus congicus 4-5.
Coloration:
Adult African slender-snouted crocodiles are dark olive on their upper
side, juveniles brownish or with dark blotches. The belly is porcelain
white with dark blotches on the sides. Clear dark blotches can also be
found on the front and hind legs, as well as on the lower jaw, in
individually varying arrangements.
Distribution:
Senegal, Gambia, Guinea-Bissau (?), Guinea, Sierra Leone, Liberia, Mali,
Ivory Coast, Burkina-Faso, Ghana, Togo, Benin, Niger (?), Nigeria,
Cameroon, Chad, Central African Republic, Gabun, Tansania, Angola,
Zambia (Crocodylus cataphractus
cataphractus)
(Fig. 219).
Congo,
Zaire(Crocodylus cataphractus
congicus)
The
exact distribution limits for the two subspecies have not been
established.
Other:
According to the newest phylogenetic studies (Schmitz
et. al., 2003), Crocodylus
cataphractus is not to be classified in the genus Crocodylus.
A precise study to determine the taxonomic status of Crocodylus cataphractus has unfortunately not been presented.
Habitat: Crocodylus
cataphractus inhabits large and small rivers, lakes, ponds, and
swamps of the western and central African rain forests. From there it
ventures into the drier savannahs. It can also be found in brackish
water lagoons and swampy forests of the coastal regions of Guinea and in
the Cameroon delta. There, Crocodylus
cataphractus is the most common crocodilian species. It prefers
bodies of water that are covered with or overhung by dense, shade-giving
vegetation. M.
Schumann,
who manages a wild animal farm in Guinea-Bissau, wrote to us that C.
Cataphractus is a shy inhabitant of forest rivers in that area.
Ecology and Behavior: According to
Waitkuwait (1989),
Crocodylus cataphractus
avoids bright sunlight and prefers shady areas where it leads a secluded
life (Fig. 218b). It lives primarily in areas that are far away from
civilization. Occasionally, Crocodylus
cataphractus has been observed
in immediate proximity of humans. In Ghana, African slender-snouted
crocodiles live in the village pond of Danfa, where the locals get their
water (Owusu-Nsiah,
1997). It can be assumed that there are other small villages
in the tropical humid-hot areas of Africa where slender-snouted
crocodiles live in close proximity to humans.
In
the wild, the diet of Crocodylus
cataphractus is made up of the larvae of aquatic insects and
amphibians, aquatic snails, and small fish
(Cott
1961).
According to
Villiers
(1958) and
Steel (1989), it
lives on a diet of fish, frogs, water turtles, aquatic snakes, lizards,
and aquatic birds. Its size allows it to attack small to medium-sized
mammals, such as duikers (Cephalophinae),
various rodents (Rodentia),
civets, genets, linsangs (Viverrinae),
and monkeys (Colobus,
Cercopithecidae) that approach the river to drink.
Detailed
information on the reproduced behavior, nest building, egg laying and
care of the young of Crocodylus
cataphractus in the wild are given by
Villiers (1956,
1958)
and Waitkuwait (1982,
1986). In West Africa,
courtship and mating take place in February and March. At the beginning
of the rainy season, from March to May, the female uses its front and
hind legs to sweep together a nest mound from plant materials. The
crocodiles will build their nests from plant materials at the beginning
of the rainy season at river shores. The nest building season roughly
overlaps with that of the sympatrically living dwarf crocodile (Osteolaemus
tetraspis), but Crocodylus cataphractus
builds its nest faster. The two species build their nests in different
habitats. In average, a female deposits 16 unusually large eggs.
Waitkuwait
examined 31 nests, which had the following dimensions: height 58.68 +-
11.6 cm, length 134.7 +-136.7 cm, and width 154.4 cm +_ 26.9 cm. All
these nests were in close proximity to the water, usually on elevated
riverbanks. The distances from the water were 2.2-3.8 m, where the nests
were 1.1-2.5 m above the water level. In 1981-1983, the distances
between 12 nests were measured. The average distance was 1.13 km in
1981, 0.7 km in 1982, and 1.66 km in 1983. The observer concluded from
this that the females seek out a different nesting spot within their
territory every year, or that they define a new territory every year, or
that not all females reproduce every year.
Crocodylus
cataphractus
is most actively building nests in the rain forests of the Ivory Coast
during the rainy season from March 21-August 4; that is, for 136 days. A
few days to at most one week after a nest has been finished, the female
lays 9-23 eggs, which are 8.23-8.87 cm long and 5.14-5.44 cm wide.
During the whole incubation period, the female protects her nest from
water since it is right next to the water. During this time, high water
levels in the small rain forest rivers are significant for hatching
success.
At
nest temperatures of 26-34ºC, the 30-35 cm long young hatch after
90-100 days. Shortly before and during hatching, the young make croaking
sounds, to which the female responds by opening the nest. She moves the
eggs around with her mouth until the last shells have come off. Then she
transports the young to the water in her mouth. Losses of Crocodylus cataphractus affect mainly eggs and new hatchlings. The potential predators on African slender-snouted crocodiles in the rainforests of the Ivory Coast are according to Waitkuwait (1982, 1986) Nile monitors (Varanus niloticus), softshell turtles (Trionyx triunguis), herons (Egretta alba, Ardea purpurea), raptors (Accipitridae), otters (Lutra maculicollis, Aonyx capensis), marsh mongoose (Atilax paludinosus), African palm civets (Nandinia binotata), civets, genets, linsangs (Viverrinae), African golden cats (Felis aurata), and leopards (Panthera pardus).
Husbandry and Breeding:
Steel
(1989)
calls Crocodylus cataphractus
shy and fearful. My ( LT) personal experiences with an African slender-snouted
crocodile agree to a large part with this characterization. The animal,
which I have been keeping for years, leaves the water only in the
afternoon and basks only occasionally under the heat lamp for short
periods of time. During the first two years, it disappeared into the
water whenever I entered the room. Over time, my presence seems to have
become less of a disturbance, since it remains on the land area if I
don't move around too much. The African slender-snouted crocodile under
my care willingly accepts fish, mice, rats, poultry chicks, birds,
mammalian meat, internal organs, and bones from slaughtered animals.
Almost weekly, I get to observe how it attacks mice and rats at lighting
speed: The crocodile swims noiselessly towards its prey. The eyes and
nostrils touch the surface of the water or reach just barely above it.
The attack is sudden and violent, where the crocodile grasps the prey
and pulls it underwater. Prey is only eaten after it is dead. To eat,
the crocodile lifts its head out of the water, shakes its head until the
animal is positioned properly, and swallows. During swallowing, the
throat expands. Mice that are running around on the land area are
located from the water and dragged into it. Dead animals or meat is
located with the help of an excellent sense of smell. Fish swimming next
to the crocodile were grasped with quick sideways movements of the head. Crocodylus cataphractus is kept in several European and American zoos and has been bred successfully several times, for example at the zoos of Aalborg (Denmark) and Emmen (Netherlands) (Fig. 218a). Successful captive hatchings were achieved, for example, by the Metro Zoo in Miami (5 in 1985 and 8 in 1990). Hatchling care in a large enclosure at varying air and water temperatures of 22-32ºC is not difficult at all. They are fed fresh freshwater fish, poultry chicks, chicken parts, and small mammals, and vitamin supplements are given from time to time. As mentioned earlier, successful reproduction has been reported from Europe and United States. Pierre De Witt, assistant curator at the zoo in Emmen (Netherlands), where Crocodylus cataphractus has been bred successfully several times, told me (L.T.) the following in a written communication from October 7, 1997, "The Emmen Zoon owns 1.1 adults and 3 juveniles born in 1995 of this species. The two adult animals live in the same enclosure. The young are cared for in a separate container. The two adult Crocodylus cataphractus have been living together since 1980. They arrived at that time in Emmen as juveniles. Whether the two crocodiles, which today are a little over 20 years old, were born in the wild or in captivity, is unknown. The female is about 2.5 m long and weights 175 kg, the male is 2.8 m long and weighs 200 kg. The enclosure in which the pair is kept is 17 m long and 3.5 m wide. A water area is enclosed on two sides by a land area. The substrate of the land area is sand. The surfaces of the two land areas are the same size as the water area. The water depth is 80 cm. The water is filtered 24 hours a day. The air humidity in the enclosures is 85%, the air temperature in winter around 20ºC, in summer around 26ºC. The water temperature is around 20ºC. The animals have no access to the outdoors. Since a transparent roof covers the enclosure, the length of the day inside is the same as outside. The crocodiles are fed once a week with prekilled rats (50%), prekilled fish (40%), and chicks (10%). At each feeding, each animal receives 1-1.5 kg of food. The amounts of food and feeding frequency are the same all year round. The two African slender-snouted crocodiles mated multiple times in spring. A few weeks later, the female was diagnosed with pregnancy. With exception of the sand, there were no additional nesting materials in this enclosure. The female built a nest mound from sand, which had a diameter of 100 cm, a height of 50 cm, and which was heated from below by the floor heater. The female laid 25-33 eggs in April and Mai. The eggs were incubated in a Baby-Couveuse incubator. They hatched after 90-100 days. The hatch rate was 20 and 25%. Almost all the young survived the first 3 months. 15% of the eggs were infertile and in the remaining 50-60%, dead embryos were found. The young African slender snouted crocodiles were raised at a water temperature of 29ºC and an air temperature of 32-35ºC. The relative air humidity was 80%. The young were fed live and dead fish, offered on tweezers or thrown into the water. The young are still alive today and in good condition."
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