Crocodilian Captive Care FAQ (Caiman, Alligator, Crocodile)

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This is a detailed care guide for serious keepers of caimans, alligators and crocodiles. If you're looking for a friendly, loving and easy to care for pet, this guide is definitely not for you!

FAQ CONTENTS

0. CREDITS

1. CONTENTS

2. INTRODUCTION

3. SPECIES

4. PURCHASING

5. HOUSING

6. FEEDING

7. HANDLING

8. HEALTH CARE

9. MISCELLANEOUS

10. APPENDICES

9. MISCELLANEOUS

	9.1	How do you sex a crocodilian?
	9.2	Can I keep the caiman with other animals?
	9.3	Should I monitor the caiman's progress?
	9.4	Where can I find a good home for my caiman?
	9.5	Where can I find more information on the Internet and in books?

9.1 How do you sex a crocodilian?

Figure 9.1. Vent of an adult female crocodile.

vent of mature male

Figure 9.2. Vent of an adult male crocodile. Compared with the female vent, it is larger and more convex. Be warned, however, that such differences are rarely so obvious - there is no substitute for internal examination.

Male and female crocodilians can be hard to tell apart visually. Usually, the best indication is size - males grow larger than females in all crocodilian species, and so a very large individual is more likely to be a male. In some species, females may have narrower snouts, and a more slender body, but such traits are highly unreliable indicators of sex. In larger crocodilians, the shape of the vent can provide a guide to the animal's sex. Females tend to have smaller, narrower and flatter vents (Fig. 9.1) whereas males have larger, wider, and more convex vents (Fig. 9.2). This difference is due to the increased elasticity of the vent in males necessary to allow eversion of the penis during copulation. However, the differences visible in these pictures are rarely so clear-cut. There's only one realistic way to be 100% certain - looking inside the vent.

Figure 9.3. The tip and shaft of a sub-adult male's penis, partially everted from the cloaca.

clitoris of adult female

Figure 9.4. The tip of an adult female's clitoris, similar in appearance to the tip of the male's penis but much smaller. It is usually not possible to evert the clitoris any more than this from the cloaca.

fully everted penis

Figure 9.5. Fully everted penis of large adult male crocodile. The groove running down the centre conveys semen to the tip, and the two masses at the base are the muscles used to evert the penis during copulation. The male's testes are inside the body cavity.

And just in case you're confused, males have a single penis, not a pair of hemipenes like most other reptiles. It can be confusing because the tip of the male's penis is split into two halves, so if you're just peeking inside the vent, you might think you were looking at a pair of hemipenes. Once the male extends himself, however, you'll be in no doubt whatsoever.

To be certain of a crocodilian's sex, you need to either feel or visually identify the penis (male) or clitoris (female). In big animals, this is very easy - look at the photos to the left and you will see there is no doubt which is male and which is female. In smaller animals, however, it requires a lot more experience and skill to do it properly and not make a mistake. It's a good idea to find someone with suitable experience (e.g. a vet, or zoo personnel) to show you how to perform it safely and accurately.

The actual procedure in large animals involves inserting a clean finger into the vent and feeling for the copulatory organ. Don't be afraid to push your finger in some way - you will not harm the animal. The male has a single, very obvious penis (Fig. 9.3) with a fleshy head and a cartilaginous shaft. It originates from the wall of the cloaca directly in front of the vent on the belly side, and curls backwards so the shaft and head lies directly beneath the vent opening. So, if you feel a slightly soft, cylindrical tube with a fleshy end, you've got a male. In fact, turning a male over will often cause it to evert its penis for you (and void the contents of its cloaca too), leaving you in no doubt. Females have a clitoris in the same location which is quite similar in shape to the male's penis, but it is much smaller (Fig. 9.4) and not cartilaginous. Unless you're experienced, it can be possible to mistake the clitoris for a small penis in younger animals, although the distinction is usually clear in larger males (Fig. 9.5). Again, females will often try and void the contents of their cloaca when you turn them over, but in this case you won't see the penis emerge, though you may just see the tip of the clitoris in the corner of the vent.

Although this procedure does not harm the animal if performed correctly, crocodilians generally object to such demeaning behaviour. Therefore, the animal should be restrained by a second person throughout the procedure.

Sexing hatchlings and small juveniles is a different matter. There are two commonly used methods: some prefer one, some prefer the other.

1. Spreading the vent: For the first method, you need a pair of blunt forceps, haemostat, or similar device. You use these - with extreme care - to spread the vent apart so you can see down into the cloaca (see right). Having a torch or a good light source behind you is often a good idea.

Get someone else to hold the animal, turn it upside down, and place it on a solid surface. You don't want the animal struggling and moving around whilst you've got those forceps in there, so holding it down must be done properly. With the fingers of one hand, pull the lips of the vent apart, and with the other hand slowly insert the closed forceps. It's a good idea to put a few drops of oil or water on the forcep tips so they slide in more easily. Once you've gone down no more than 5 to 10 mm (with a hatchling), slowly and gently open the forceps up, which should spread the vent. Assuming you've got light available, you should be able to see down inside the vent. It'll be pink and dark in there, but you're looking for what's called the "cliteropenis" - it's called that because the male's penis and the female's clitoris are relatively similar in appearance (undifferentiated) with hatchlings. This structure is attached to the ventral, anterior surface (in English, that is the underside of the upper surface in front of you, assuming the animal is upside down and the head is facing away from you). It's small, and shaped like a small V.

diagram of penis and clitoris in hatchling

This is the hard part, and it's something you'll only get good at with experience. In the male, this structure is larger, longer, more tubular and has a more rounded head, compared with the female's structure (which some describe has having a slightly more triangular base). The diagram (left) shows a rough approximation of what the cliteropenis looks like in C. johnstoni (after Webb, Manolis and Sack 1984). Because the male's penis is slightly longer, it's slightly easier to spot in the male than the female. As it grows, the male's penis extends down and sits directly inside the opening of the vent. Once a hatchling has reached 6-12 months old, simply spreading the vent should reveal the penis sitting there. Some people say the penis has a slightly darker tip than the clitoris, but nobody has proven this to be characteristic of males.

As the animal gets bigger, sexing the animal gets a lot easier. Basically, the male's penis grows much faster than the female's clitoris, so the difference in size and shape between the two becomes increasingly obvious. You have to be careful, though, because often there is a lot of overlap between the size of the penis and the size of the clitoris - some sub-adult females can occasionally have a slightly larger clitoris than the penis of rather unlucky males of the same size, but of course in bigger animals this overlap disappears.

2. Popping: This second method can only be used in young hatchlings - it doesn't work with older and larger animals. This method is referred to as "popping", because you use pressure on the tail to literally pop out the male's penis (if it's there). As before, this needs to be done very carefully, without applying an excessive amount of pressure, otherwise you'll injure the animal. Although you can do this by yourself, it's a lot easier with a second person to help you.

Figure 9.6. Holding a crocodilian upside down like this usually causes muscle relaxation. The head is restrained gently with one hand, leaving the other free to perform the procedure.

popping a dwarf caiman by bending the tail upwards

popping a dwarf caiman by bending the tail upwards

Figure 9.7. A dwarf caiman being popped by bending the tail gently upwards and applying pressure to either side of the vent. You can see the cliteropenis emerging from the vent. You can see that the tail does not need bending very far for the method to work.

popping a dwarf caiman by bending the tail upwards

Figure 9.8. A close-up of the vent being popped by gently bending the tail upwards and applying pressure on either side of the vent. In this case, the animal is clearly a male - the penis projects some distance above the vent.

popping a dwarf caiman by bending the tail downwards

popping a dwarf caiman by bending the tail downwards

Figure 9.9. Although bending the tail upwards is the better method, the animal can also be popped by bending the tail downwards. This stretches the vent and the penis emerges, although it is not as clearly visible as in Fig. 9.8.

popping a larger caiman

Figure 9.10. Larger crocodilians, like this 3.5 ft American alligator, can also be popped. However, once the vent is large enough to insert your finger into, popping becomes redundant.

The images on the left illustrate the procedure. Please remember to be gentle with the animal - use common sense and do not apply too much pressure either bending the tail or squeezing the sides of the vent. Hatchlings are fragile and should be treated with care.

It's easier if you hold the animal away from a surface. Hold the animal upside down in one hand (Fig. 9.6) which should cause it to relax. The other hand is now free to bend the tail and spread the vent. You can either bend the tail towards the animal's belly (Fig. 9.7) so that you compress the vent, or you can bend the tail away from the belly so you stretch the vent (Fig. 9.9). The former method is preferable with caimans. Again, use common sense here - don't bend the tail too far or you'll break the poor little guy's back. Next, using your thumb and index finger, pull the vent apart from either side, and then apply pressure to either side of the vent (Fig. 9.7). This takes a little practice, and you might need to shift pressure forwards and backwards until you hit the right spot (with a second person holding the animal you can use both hands which can be a lot easier). What happens is that the vent should start to spread outwards, and then the tip of male's penis should literally pop into view (Fig. 9.8) . If you don't see an obvious cliteropenis like that in Fig. 9.8 then it's much more likely that you've got a female. Don't apply too much pressure - if there is no obvious penis then stop as you almost certainly have a female. The popping method is easier and quicker than probing the vent, and works very well in some species especially caimans, but probing the vent is more reliable when done by an experienced person.

Before you get the urge to rush off and sex your crocs, just bear in mind that it gets a lot easier as the animal gets larger. Unless you have a very good reason to sex a hatchling or juvenile, it's probably better to wait so you can be sure. Conversely, the larger the croc, the greater its ability to object by sinking its teeth into your arm!

There is more information on sexing hatchlings in the following papers: the first refers to A. mississippiensis, which the authors suggest is impossible to sex until the animal is at least several weeks or months old; the second refers to C. porosus and C. johnstoni, which conversely the authors could sex as day-old hatchlings with a accuracy of 95% using the probing technique.

Joanen, T. and McNease, L. (1978). The cloacal sexing method for immature alligators. Proc. Ann. Conf. S.E. Assoc. Fish & Wildl. Agencies 32: 179-181

Webb, G.J.W., Manolis, S.C. and Sack, G.C. (1984). Cloacal sexing of hatchling crocodiles. Australian Wildlife Research 11, p.201-202

flared tip of male caiman penis

The flared tip of a spectacled caiman's penis.

9.2 Can I keep my caiman with other animals?

It's generally not a good idea to keep your caiman with other animals, given that the caiman may well regard them as food. In some cases, other animals may even regard your caiman as food! It is not uncommon to hear reports of turtles and even fish nibbling away at a caiman's tail or toes, especially when they don't have sufficient food themselves. However, some owners have reported that caimans get along well with turtles, as long as the turtle is too big to fit inside the caiman's jaws. An adult caiman is quite capable of crushing a smaller turtle's shell. One owner reports that a caiman bit the head of a turtle while they tussled over a piece of food, and also that snapping turtles make poor companions with smaller caimans, whom they regard as food. Turtles are also quite capable of passing parasites (e.g. leeches) onto crocodilians.

Caimans are often kept together with other crocodilians, but their compatibility depends upon the species and size. Some species are highly intolerant of others. More importantly, if there is a large size difference between the animals, there is a very good chance that the larger animal will kill and eat the smaller one - even if they are the same species (cannibalism is common amongst crocodilians). On the other hand, I've seen very large caiman exhibits populated with species of varanid lizards. It depends on the amount of space available, and whether there is suitable habitat partitioning between the different occupants. However, for most home set-ups, it is recommended to keep the caiman in a separate enclosure. Fights between larger, aggressive males can often maim and kill one or both individuals, so consider this advice carefully.

9.3 Should I monitor the caiman's progress?

It is definitely a good idea to monitor your caiman's growth - measure its total length and snout-vent length on a regular basis, and try to weigh it. This information satisfies more than just an interest in your animal's growth rate, but can provide vital clues on your caiman's health - a loss of weight, for example, is one of the earliest indicators of a more serious problem. Your vet will also find this information very useful if the day comes that your caiman requires treatment. Regular vet visits are always a good idea, and data from the occasional blood panel can provide valuable information to assist future diagnosis and treatment.

9.4 Where can I find a good home for my caiman?

You need a very good reason for asking this question. It is mentioned here for one simple reason - to prevent people from dumping unwanted caimans in the nearest stream or pool. Releasing caimans into the wild might seem to be an eco-friendly thing to do, but it will result in one of two outcomes. Either your spurned pet will die, or it will become a serious nuisance. Released pet caimans in Florida are disrupting native wildlife, and crocodilians released into areas where there are normally none can still bite unsuspecting people and eat family pets. If you absolutely have to get rid of your animal, don't release it into the wild.

You'll find that local zoos, aquaria or crocodile farms will almost certainly not be interested in your animal - nor the dozens of similar animals they are asked to take each month. Perhaps the best bet is to contact other private crocodilian enthusiasts or herpetological societies who would much rather give it a good home than see it released to die. Few other people would be experienced or qualified enough to take an aggressive crocodilian off you.

If you still can't find anyone to take the animal, perhaps you should reconsider. The only alternative is euthanasia - is your caiman really so disposable?

9.5 Where can I find more information on the Internet and in books?

There isn't much information on caiman care on the Internet, but recently some excellent work is now available to read. There is also a good selection of quality information on crocodilians, whether you're researching biology or just searching for decent photographs.

For information specific to caiman care, visit:

http://www.algonet.se/~prl/croc/ - an excellent caiman husbandry article by Ragnar Lonn

http://crocodilian.com/paleosuchus - Colin Stevenson's highly commendable website dedicated to the Paleosuchus genus

http://www.tiho-hannover.de/croc - Tim Wiegmann's Crocodile Library is highly recommended, containing many articles by amateur keepers in Germany on keeping and breeding crocodilians

http://crocodilian.com/crocfaq - this document's home on the Internet

For general crocodilian info, visit:

http://crocodilian.com - species information, biology database, sound library and links by Dr Adam Britton [maintainer of this FAQ]

http://www.flmnh.ufl.edu/crocs.htm - conservation of crocodilians by the Crocodile Specialist Group

http://www.erols.com/reptiles - John White's reptile page, containing a gallery of crocodilian pictures

http://members.xoom.com/Gator_dude/Crocsite.htm - Billy Heinbuch's crocodilian page, with conservation information and a picture gallery

Both crocodilian.com and the Crocodile Specialist Group site contain dedicated link pages to a wide range of different crocodile sites.

Discussion forums on crocodilians:

http://www.kingsnake.com/forum/gator/ - WWW-board for discussion about alligators and other crocodilians

CROCLIST, a mailing list hosted by Ragnar Lonn and Adam Britton, is dedicated to the discussion of all crocodilian issues, from husbandry to biology and conservation. Anyone who is interested can join by sending an email to:

	LISTSERV@LISTSERV.ALGONET.SE

With the message body consisting of the text:

	SUBSCRIBE CROCLIST

Contributions to the list can be sent to CROCLIST@LISTSERV.ALGONET.SE where they are distributed to all the list members. There is also an archive of old postings to the CROCLIST. It can be viewed with a web browser at http://listserv.algonet.se/archives/croclist.html

Although there are plenty of books available on crocodilians, nearly all of them are aimed at providing basic natural history facts and coffee table pictures to the general reader. At present, there are few useful books available to those interested in captive husbandry of crocodilians. There are several recommended books which contain some relevant information, however.

For general information on crocodilians:

Ross, C.A. (1989). Crocodiles and Alligators. Weldon Owen Pty Ltd, New South Wales. 240 pages

Webb, G.J.W. & Manolis, C. (1989). Crocodiles of Australia. Reed Books Pty Ltd, New South Wales. 160 pages

For veterinary care:

Fowler, M. (1986). Zoo & Wild Animal Medicine. 2nd edition. W.B. Saunders Co., PA. [contains a modest amount of information on crocodilians]

Frye, F.L. (1981). Biomedical and Surgical Aspects of Captive Reptile Husbandry. Veterinary Medicine Publishing Company, Edwardsville, Kansas. pp. 458 [contains much of the groundwork for modern reptile medicine]

Mader, D.R. (1996). Reptile Medicine and Surgery. W.B. Saunders Co., PA. 512 pages [general information, with little specific to crocs]

For wildlife management:

Webb, G.J.W., Manolis, S.C. & Whitehead, P.J. (1987). Wildlife Management: Crocodiles and Alligators. [includes information on captive farming techniques]

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