13 - unlucky for some, but not for all otternuts! There are a total of thirteen different otter species across the globe, so here's a wee bit more about these aquatic beauties.

1. Eurasian Otter (Lutra lutra) - see A1319456
2. Cape Clawless Otter (Aonyx capensis) - An endangered otter species found from South Africa, north through Ethiopia and Senegal. Unlike its name suggests, it isn't totally clawless. It has three claws on the middle toes on each of its hind feet. A rather curious feature which no-one seems to know the cause of. Probably, as in most species, it is an adaptation to its habitat. They are a mildly social animal. Mildly, as in the sense that they form small family groups.
3. Asian Short-clawed or Oriental Small-clawed Otter (Aonyx cinerea) - The smallest of all the otters. It forms larger groups than the Cape Clawless and its distribution is in southern and eastern Asia, hence the name. More needs to be discovered as regards its status in the wild, as with many of the otter species.
4. Sea Otter (Enhydra lutris) - The only truly marine otter, it spends virtually all of its time in the sea. It even mates and gives birth to the cubs in the sea, spending only brief periods on shore for thorough grooming. The mother supports her cub on her belly while floating on her back. While resting, the sea otter attaches itself to giant kelp by rolling itself up in it, thus acting as an anchor. This is essential, especially in rough seas. Another neat trick of the sea otter is that it carries a favoured stone during each feeding bout in the folds of its skin which it then uses to crack open its favourite food, Abalone, and other shellfish. The sea otter is the heaviest of the otters, weighing in at around 45kg, but is still not the largest otter. That title must go to the Giant Otter. Sea otters are endangered and this is partly due to the excessive hunting of them in the past. They have the most dense fur¹ of any otter and their pelts were highly prized. They form large groups or rafts as they're called, within easy reach of the coastlines around North America, Northern Japan, Kamchatka and the Commander Islands, thus making them easy targets. Thankfully they are now protected²
5. Giant Otter (Pteronura brasiliensis) - The name, although not very original, is none the less apt for this species of otter. Measuring approximately 2m in length and weighing 32kg, it's definitely a giant. In fact, it's one of the largest carnivores in South America. They live in very large groups in the oxbow lakes of the Amazon and its tributaries. A favoured prey species is, believe it or not, Piranhas! Don't suppose there would be many animals, other than, say, the Cayman, who would brave the infamous teeth of the Piranha! Giant otters are extremely vocal and can most often be heard long before they are seen. They keep in constant touch with family members by whistling loudly to each other. Very clever adaptation to life in the Amazon jungle and its murky waters.
6. Sea Cat (Lutra felina) - Unfortunately, not a lot is known about this particular endangered species of otter. A coastal otter found on Pacific coasts from Peru to the most southerly tip of South America. Much more study needs to be carried out to discover their true numbers and lifestyle. This information is vital if the species is to be successfully protected.
7. Neotropical Otter (Lutra longicaudis) - A solitary species, but still the most widespread otter in Central and South America. Guessing as to the reason for their widespread distribution, it could be suggested that each solitary otter requires a very large territory, as in the case of the Eurasian Otter. Thus, although widespread, it's still lacking in population density. Therefore, this otter is classified as endangered.
8. Spotted Necked Otter (Lutra maculicollis) - Resident in all African countries south of the Sahara, though absent from rainforest habitat. The social dynamics of the Spotted Necked Otter are somewhat reminicent of human dances. They form large, separate male and female groups, and ne'er the twain shall meet! Well, except for mating that is.
9. Southern River Otter (Lontra provocax) - A very little-known freshwater species, probably due to the fact that it is critically endangered. Its current known distribution is in parts of southern Chile and western Argentina. It should be a priority to discover more about this otter in order to help increase their numbers and protect their habitat. At least to attempt to halt the decline in numbers.
10. American River Otter (Lontra canadensis) - The American version of the Eurasian Otter with many similarities. As the name suggests, it is resident in the U.S, although it is absent from the mid states. This is due to the American River Otter being legally hunted in 38 of America's states. Not something to be proud of! It would help the American River Otter's cause a great deal if all you U.S otternuts would write to your politicians demanding an outright ban on the hunting of this beautiful animal. Democracy being the life-blood of America, "government of the people, by the people, for the people"³, and all that, means you can really make a difference!
11. Smooth Coated Otter (Lutra perspicillata) - Another social otter from South East Asia, including Indonesia and China, whose populations are classified as vulnerable. They are known to live alongside the Asian Short-clawed Otter as they share similar requirements for habitat and food.
12. Hairy Nosed Otter (Lutra sumatrana) - Just know you're wondering, so.... The answer is "Yes, they do have a hairy nose". "Why has it got a hairy nose?" you ask. Well, it's probably to aid in detecting their prey in particularly murky waters, just like they do with their whiskers (vibrassae). This species was once widespread throughout southern Thailand, Indochina, Malaysia and Indonesia. By 1998 it was thought to be extinct, but, luckily, projects funded by the International Otter Survival Fund (IOSF) found it in Thailand and Vietnam. These projects are ongoing and more information can be got from their site, where kind donations are also gratefully received. The Hairy Nosed Otter has also been discovered in Cambodia recently. Hunting, yet again, is a serious threat to their numbers.
13. Congo Otter (Aonyx congica) - Last, but certainly not least, the strange Congo Otter. Strange, in that, it is the least aquatically adapted otter of them all. Although closely related to the Cape Clawless Otter, it lacks both thick insulating fur and webbing on the feet. Well, that's not strictly true, they have partial webbing on their hind feet, but their front feet are totally free of webbing. They are to be found in Central Equatorial Africa and have yet to be evaluated as to their conservation status.

Summary

Well, all you budding otternuts out there, hope you've been able to get just a small taster of the world that is the Otter. A good deal more information was given on some of the species than on others. Unfortunately, this can't be helped as so much is yet to be discovered about certain otters and their habitats. Although this probably isn't meant to be a soapbox, PLEASE DO WRITE TO YOUR U.S POLITICIANS TO ASK/DEMAND AN OUTRIGHT BAN ON HUNTING THE POOR AMERICAN RIVER OTTER!!!! Thank you!

References

International Otter Survival Fund