Crocodile Nutrition Guide

Written by Zutrition . Posted in Diet, Reptiles

nile crocodile kruger national park

BACKGROUND

Crocodiles (subfamily Crocodylinae) or true crocodiles are large aquatic tetrapods that live throughout the tropics in Africa, Asia, the Americas and Australia. Crocodylinae, in which all its members are considered true crocodiles, is classified as a biological subfamily.

A total of 14 extant species have been recognized (see list below).

Species name Distribution
American crocodile (Crocodylus acutus) Throughout the Caribbean Basin, including many of the Caribbean islands and South Florida.
Slender-snouted crocodile (Crocodylus cataphractus) Central and Western Africa
Orinoco crocodile (Crocodylus intermedius) Colombia and Venezuela
Freshwater crocodile (Crocodylus johnsoni) Northern Australia
Philippine crocodile (Crocodylus mindorensis) Endemic to the Philippines
Morelet’s crocodile (Crocodylus moreletii) Atlantic regions of Mexico, Belize and Guatemala
Nile crocodile (Crocodylus niloticus) Sub-saharan Africa
New Guinea crocodile (Crocodylus novaeguineae) The island of New Guinea
Mugger crocodile (Crocodylus palustris) The Indian subcontinent and surrounding countries
Saltwater crocodile (Crocodylus porosus) Throughout Southeast Asia, Northern Australia and surrounding waters
Cuban crocodile (Crocodylus rhombifer) Found only in the Zapata Swamp of Cuba
Siamese crocodile (Crocodylus siamensis) Indonesia, Brunei, East Malaysia and southern Indochina
Desert crocodile (Crocodylus suchus) Western and Central Africa
Dwarf crocodile (Osteolaemus tetraspis) Western Africa

Size greatly varies between species, from the dwarf crocodile to the saltwater crocodile. Species of Osteolaemus grow to an adult size of just 1.5 m (4.9 ft) to 1.9 m (6.2 ft), (source: Crocodilian Species List. Retrieved on 2012-04-14) whereas the saltwater crocodile can grow to sizes over 7 m (23 ft) and weigh 2,000 kg (4,400 lb) (source: Guinness Book of World Records. Retrieved on 2013-04-08.)

 

HUNTING AND DIET

Crocodiles are ambush predators, waiting for fish or land animals to come close, then rushing out to attack. Crocodiles mostly eat fish, amphibians, crustaceans, molluscs, birds, reptiles, mammals and occasionally cannibalize on smaller crocodiles. What a crocodile eats varies greatly with species, size and age. From the mostly fish-eating species like the slender-snouted and freshwater crocodiles to the larger species like the Nile crocodile and the saltwater crocodile that prey on large mammals, such as buffalo, deer and wild boar.  Diet shows great diversity. Diet is also greatly affected by size and age of the individual within the same species. All young crocodiles hunt mostly invertebrates and small fish. Gradually moving onto larger prey.

As cold-blooded predators, they have a very slow metabolism, so they can survive long periods without food. Despite their appearance of being slow, crocodiles have a very fast strike and are top predators in their environment, and various species have been observed attacking and killing other predators such as sharks and big cats. [1] [2]

Unfortunately the nutrition of crocodiles is still poorly understood but, as far as is known, they can not make use of vegetable-based proteins. A further constraint is the fact that reptiles can so easily do without food. They can not be starved into eating what they do not like. Attempts to use dried and reconstituted or salted preparations have failed because the crocodiles simply won’t eat. This means that where animal protein is only seasonally plentiful (often the case with fish) freezer storage is essential.

Crocodiles have the most acidic stomach of any vertebrate. They can easily digest bones, hooves and horns. It was (BBC channel 1 program Inside The Perfect Predator, Thursday 25 March 2010) reported that a Nile crocodile that has lurked a long time underwater to catch prey builds up a large oxygen debt. When it has caught and eaten that prey, it closes its right aortic arch and uses its left aortic arch to flush blood loaded with carbon dioxide from its muscles directly to its stomach; the resulting excess acidity in its blood supply makes it much easier for the stomach lining to secrete more stomach acid to quickly dissolve bulks of swallowed prey flesh and bone. Many large crocodilians swallow stones (called gastroliths or stomach stones), which may act as ballast to balance their bodies or assist in crushing food. [3]

Crocodile teeth are set deep in the jawbone and are conical or peg-like and slightly curved. Throughout life new teeth repeatedly form, like small white cones, beneath the old ones which they replace. The teeth can not therefore be used for estimating the age of a crocodile. The powerful jaws are well equipped for holding and crushing but they can not chew or grind food into smaller pieces. Food which is too big to be swallowed whole has to be shaken, torn or twisted apart by one or more crocodiles.

Digestion is efficient and passage through the digestive system is quite rapid for a reptile. In the Nile crocodile it has been estimated at somewhat more than 72 hours (Pooley & Gans, 1976). It is quite usual to find stones in the stomachs of wild crocodiles. Whatever other functions they may have they must certainly aid digestion by their grinding action while the stomach is churning . Stones in the crop of some birds have a similar function.

Irrespective of body temperature, crocodiles will not accept food if they are frightened or in a state of stress because of previous handling or other disturbance. They can survive for months without food but gradually lose weight, weaken and become even less interested in feeding. Obviously, it is important to maintain a routine of regular, frequent feeding.
Needless to say, crocodiles do not grow while they are fasting but neither do they grow very much if they are only given enough food for survival. In short, growth and size are related much more to food intake than to age. [5]

DIET AND FEEDING

Providing individuals with enough food to ensure optimal growth is important, but overfeeding should be avoided as it can lead to obesity and associated disease (Pooley 1990). Growth rates of crocodilians are rapid during the first few months of life and require feeding at least 6-7 times a week (Whitaker and Andrews 1998). Once individuals reach sub-adult size they only need to consume 8-10% of their body weight a week (Whitaker and Andrews 1998). However, size, body condition, species, age, sexual maturity, breeding condition, and season can all influence individual requirements. Determining the optimum rate of feeding for individuals in a facility basically requires some trial and error (Pooley 1990; Whitaker and Andrews 1998). Generally, crocodilians will increase their level of consumption during warmer months of the year, while decreasing it in the cooler months (Pooley 1990).

Despite accounts of different species in the wild feeding on carrion and ‘storing’ food until it is rancid, crocodilians prefer fresh food (Webb and Manolis 1989). Crocodilians also fare better when fed a diet that is high in protein, as research suggests that crocodilians utilize protein over fat as an energy source (Hutton and Webb 1994; Smith and Marais 1994). If the food source does not already include high levels of calcium, in the form of bones, it is important that a calcium supplement be included (Hutton and Webb 1994). Crocodilian skin contains bones known as osteoderms.  So, by providing calcium rich food, it not only eliminates bone disorders and abnormalities but can improve the quality of skin (Webb and Manolis 1989; Pooley 1990).

Vitamin supplements should also be provided to further boost immune systems and minimize mortality (Hutton and Webb 1994; Smith and Marais 1994). It is believed that providing individuals with the appropriate amounts of amino acids, vitamins, and minerals, can significantly reduce the detrimental effects of stress in captive crocodilians (Smith and Marais 1994). This is important as, despite the best husbandry and management practices, crocodilians will still inevitably suffer certain levels of stress under captive conditions (Elsey et al. 1994). It is recommended that food be presented in bite-sized portions to reduce the mess caused by individuals when feeding (Webb and Manolis 1989; Pooley 1990). If meat is to be frozen, it should be fresh and sealed in plastic. Meat should never be refrozen once thawed, as this will result in high levels of bacteria (Pooley 1990). Red meat is commonly the preferred food source for crocodilians (Elsey et al. 1994; Hutton and Webb 1994). However, minced meat and meat high in fat should be avoided as it will only foul the water which will create an environment for disease (Lang 1987a; Elsey et al. 1994; Hutton and Webb 1994). Fresh or fresh-frozen chicken heads, carcasses, and fish are also other options. In the wild, fish constitute the main prey item of American crocodiles (Britton 2001). Regardless, it is important to provide crocodilians with a varied diet for optimum results (Pooley 1990). Feeding captive crocodilians a mono-diet of fish has been correlated with an inability to produce fertile eggs in Morelet’s crocodiles (Hunt 1980).

Any savings achieved as a result of providing lower quality food will ultimately be offset by negative implications on the crocodiles (Pooley 1990; Elsey et al. 1994). A poor diet will lead to decreased fertility, stunted growth, bone and teeth disorders, and reduced immunity to disease (Pooley 1990). It is especially important to strictly adhere to a high protein and calcium rich diet for hatchlings and juveniles less than one year, as they are highly susceptible to disease and mortality (Hutton and Jaarsveldt 1987; Webb and Manolis 1989). [6]

Mazuri manufactures and sells a Crocodilian Diet that is nutritionally complete for captive crocodiles.  Read more here

Mazuri® Crocodilian Diet Guaranteed Analysis

  • Crude protein not less than ………………….. 45.0%
  • Crude fat not less than ………………………… 9.5%
  • Crude fiber not more than ……………………. 3.0%
  • Calcium (Ca) not less than …………………… 2.50%
  • Calcium (Ca) not more than …………………. 3.50%
  • Phosphorus (P) not less than ……………….. 1.50%
  • Salt (NaCl) not less than …………………….. 0.30%
  • Salt (NaCl) not more than …………………… 0.80%

Mazuri® Crocodilian Diet Approximate Nutrient Composition

NUTRIENTS

  • Protein, %…………………………………………… 45.5
  • Arginine, % ………………………………………….. 2.50
  • Cystine, % …………………………………………… 0.65
  • Glycine, % …………………………………………… 2.90
  • Histidine, % …………………………………………. 1.10
  • Isoleucine, % ……………………………………….. 1.35
  • Leucine, % ……………………………………………. 3.3
  • Lysine, % …………………………………………….. 2.85
  • Methionine, % ……………………………………… 0.80
  • Phenylalanine, % …………………………………. 1.70
  • Tyrosine, % …………………………………………. 1.14
  • Threonine, % ……………………………………….. 1.50
  • Tryptophan, % ……………………………………… 0.44
  • Valine, % …………………………………………….. 2.20
  • Fat, % …………………………………………………. 10.0
  • Omega-3 Fatty Acids, % ………………………….. 0.32
  • Omega-6 Fatty Acids, % ………………………….. 1.26
  • Fiber (Crude), % ……………………………………. 2.5
  • Neutral Detergent Fiber, % ……………………… 6.6
  • Acid Detergent Fiber, % ………………………….. 2.5
  • Starch, % …………………………………………….. 20.0
  • Metabolizable Energy*, kcal/kg ………………… 3580

MINERALS

  • Ash, % ……………………………………………….. 11.8
  • Calcium, % ………………………………………….. 3.10
  • Phosphorus, % …………………………………….. 1.83
  • Phosphorus (non-phytate), % ………………….. 1.70
  • Potassium, % ………………………………………. 0.73
  • Magnesium, % …………………………………….. 0.19
  • Sodium, % …………………………………………… 0.24
  • Chlorine, % …………………………………………. 0.43
  • Sulfur, % …………………………………………….. 0.40
  • Iron, ppm ……………………………………………. 700
  • Zinc, ppm ……………………………………………. 238
  • Manganese, ppm …………………………………… 105
  • Copper, ppm ………………………………………….. 20
  • Iodine, ppm …………………………………………… 2.4
  • Cobalt, ppm …………………………………………… 1.0
  • Chromium, ppm …………………………………….. 0.89
  • Selenium, ppm ………………………………………. 0.87

VITAMINS

  • Thiamin, ppm …………………………………………. 35
  • Riboflavin, ppm ………………………………………. 37
  • Niacin, ppm ………………………………………….. 231
  • Pantothenic Acid, ppm …………………………… 100
  • Choline, ppm ………………………………………. 2200
  • Folic Acid, ppm ……………………………………… 7.0
  • Pyridoxine, ppm ……………………………………… 31
  • Biotin, ppm ………………………………………….. 0.25
  • Vitamin B12, mcg/kg ………………………………. 255
  • Ascorbic Acid, ppm …………………………………. 75
  • Vitamin A, IU/kg ………………………………… 17970
  • Vitamin D3, IU/kg ………………………………… 2350
  • Vitamin E, IU/kg …………………………………. 105.0
  • Vitamin K (as menadione), ppm ………………. 4.8

Food Requirements of Young Crocodiles. Based on feeding records of C. porosus and C. novaeguineae in Papua New Guinea. [4]

Size
Total length (cm)
Food consumed per
week. Approx. fresh
weight (grams)
Approx. % of body
weight eaten per
week
45 – 60 80 – 210 26
61 – 90 210 – 415 20
91 – 120 415 – 940 15
121 – 140 940 – 1,310 13
141 – 160 1,310 – 1,910 12
161 – 180 1,910 – 2,430 11

 

UPDATE:

CROCODILE CONFESSION: Meat-Eating Predators Consume Fruit, Study Says [8]

Press Release – WCS-led study examines overlooked role fruit-eating crocodilians may play in forest regeneration

Berries, legumes, nuts, and grains consumed by crocs and alligators

NEW YORK (August 21, 2013) — It turns out that alligators do not live on meat alone.  Neither do Nile crocodiles.  A new study led by the Wildlife Conservation Society says that the American alligator and a dozen other crocodile species enjoy an occasional taste of fruit along with their normal meat-heavy diets of mammals, birds, and fish.

The study gives new insight into the possible role that crocodilians, some of which have large territories, may play in forest regeneration through digesting and passing seeds from fruits.

The study appears in the July issue of the Journal of Zoology.  Authors include: Steven Platt of the Wildlife Conservation Society; Ruth M. Elsey of the Louisiana Department of Wildlife and Fisheries; Hong Liu of Florida International University and the Fairchild Tropical Botanic Garden; Thomas R. Rainwater of the U.S. Fish and Wildlife Service; James C. Nifong of the University of Florida; Adam E. Rosenblatt and Michael R. Heithaus of Florida International University; and Frank J. Mazzotti of University of Florida.

The authors looked at 18 species of crocodilian ranging from the American alligator to the fearsome Nile crocodile and found 13 of the species consumed some form of fruit including a variety of berries, legumes, nuts, and grains.

While the authors say some of the fruit ingestion may have been incidental to prey capture, evidence shows that other fruit is consumed deliberately and in large quantities. Much remains to be learned about how crocodilians process carbohydrates and other plant-based nutrients, though studies suggests that fruit eating is likely to yield nutritional rewards for crocodilians.

“Although underreported, fruit eating appears widespread among crocodilians,” said the study’s lead author, Steven Platt of the Wildlife Conservation Society.  “Given the biomass of crocodiles in many subtropical and tropical wetlands and their capacity for ingesting large numbers of fruits, we consider it likely that crocodilians function as significant seed dispersal agents in many freshwater ecosystems.”

References:

1.  “Saltwater Crocodile, Saltwater Crocodile Profile, Facts, Information, Photos, Pictures, Sounds, Habitats, Reports, News – National Geographic”. Animals.nationalgeographic.com. Retrieved 2010-03-16.

2.  “Crocodilian Species – Nile Crocodile (Crocodylus niloticus)”. Crocodilian.com. Retrieved 2013-04-26.

3.  Grigg, Gordon and Gans, Carl (1993) Morphology And Physiology Of The Crocodylia, in Fauna of Australia Vol 2A Amphibia and Reptilia, chapter 40, pp. 326–336. Australian Government Publishing Service, Canberra.

4.  FAO The Management of Crocodiles in Captivity

5.  FAO The Management of Crocodiles in Captivity

6.  University of Florida Housing Crocodilians in Captivity

7.  Mazuri Crocodilian Diet

8.  Wildlife Conservation Society 

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