There are 25 species. Little changed in 100 million years. Armour plating consists of plates of bone and horn. Lay eggs on land and generally show considerable parental care of their young. Raised nostrils can be closed when diving. Prey is ripped apart or held under water until drowned. Feet show partial webbing to aid swimming. Snout shape and dentition are major differences between groups:
Environment: Aquatic (fresh water), Terrestrial (land)

• Gavials - Very long and slender snouts. Eat mainly fish and crabs.
• Crocodiles - Both upper and lower teeth are visible when mouth is shut. Snout fairly slender.
• Alligators, Caimans - Broad snouts. Only upper teeth are visible when mouth is shut. Many hibernate in winter.

My opinion of hit television show The X Files went downhill after a recent episode. The programme featured a mysterious dog-eating creature in a Canadian lake, which turned out to be a large alligator.

Alligators are reptiles, so are cold blooded. In northern climates, while they might be able to survive a summer, it is far from the blistering sultry heat of South Carolina or Florida.
Large alligators are also extremely heavy. If they leave the water to snap up a dog, they would leave typical heavy three-toed footprints impossible to hide or mistake for anything in that boggy terrain.

That is how dinosaurs left their footprints to slowly fossilise, plodding millions of years ago across similar marshy ground.

On Hilton Head Island, South Carolina, an eight-foot alligator ambushed a resident out filling his bird feeder one evening.
Apparently, the alligator had been used to being fed titbits as well, so when none were forthcoming on this occasion, it took matters into its own hands.
I have seen the way residents live on Hilton Head. These former plantation lands are low lying and have been divided up into high-quality golf courses.
In broad swathes between the fairways, just back from the rough, are extensive winding lines of houses.
Everywhere, there are ponds connected to one another by ditches and streams and pipes. Every pond which contains some cover – just one overhanging bush will do – or a small island, contains a smallish alligator.

Usually each pond contains just one alligator – they are so aggressive and territorial they make sure no others can share the limited amount of feeding.

Once they grow on to 1.5 metres or so, the park service usually locates them to somewhere more appropriate before they can become a danger.
However, it is fairly common for them to nab the occasional dog now and then.

Around 20-30 years ago, alligators in America had been hunted to a dangerously low level. With protection, they have increased, so today there are thousands of them.
This can sometimes create real problems, occasionally placing conservationists in direct conflict with the needs of ordinary people.

In northern Australia, Darwin is polluted with salt-water crocodiles, a highly aggressive member of the genus.
Darwin's Harbour has crocodile traps set to catch them as they enter.
Elsewhere, they are encouraged as a major tourist draw. Trouble is they have increased to such an extent that, in many places, they are a menace. Swimming and most water sport are out of the question.

So it is hard not to feel sympathy for riverbank residents along the Orinoco River in South America.
For many years, they have been enjoying a modern lifestyle of swimming and water ski-ing. One day, they woke up to discover conservationists had well-developed plans to re-introduce the Orinoco Crocodile, a creature virtually extinct on that river.

Which brings us back to Britain. A local authority in north-east England announced a "caiman amnesty". A number of people bought hatchling Spectacled Caimans (a form of South American crocodile) from a pet shop to keep as unusual and distinctive little pets. These have now grown to about two-thirds of a metre in length and are apparently being abandoned here and there. The local authority has decided to deal with what they see as a continuing nuisance all in one go - hence the amnesty. It will be interesting to watch developments.

Scottish Osprey Prey to Crocodile

Our poor bird must have dived at a fish and in the commotion, both bird and fish together were gulped down by a croc. How do we know this? Doudou Ndong, a fisherman on the Gambia river, last year captured a croc. In its stomach was the ring from the leg of the osprey. He sent it off to the address printed on the side. Sadly, that will be one less bird to return next Easter to join the ranks of the 150 or so pairs which now breed in Scotland.