Originally named as Felis pardalis, the ocelot kept this name up until the late 20th century. At that point, the genus Leopardus was resurrected, having first been used for the ocelot by John Edward Gray in 1842. Gray's original description of the genus doesn't fit at all with what we now know (and was almost completely ignored by everyone else at the time, anyway) but, even by the 1960s, it had become clear that there was a striking difference between the Leopardus cats and every other cat species in the world: they have only 36 chromosomes, instead of 38. This presumably reflects an ancient change in their ancestors, although whether it occurred before or after the proto-ocelots entered South America from the North is impossible to know.
Today, ocelots live everywhere from northern Mexico to southern Brazil, with a couple of populations straying across the border into small patches of territory in the extreme south of Arizona and Texas. Many sources list ten different subspecies across this wide range, but recent analyses have failed to prove the existence of more than four of these, and there may only be two, with a dividing line somewhere around Panama.
Ocelots are relatively large for "small cats", being around three times the weight of the domestic animal, and with the largest males reaching around 100 cm (39 inches) in length, not counting the tail. Their colour is highly variable, which probably explains the large number of subspecies mistakenly identified, being anything from yellowish to reddish or grey, marked with spots that can be either solid or (more usually) open, and in various different shapes.
(The word "ocelot", incidentally, comes from the Aztec word ocelotl, which apparently meant "jaguar". It was coined by the Comte de Buffon in the 18th century, who presumably figured that, since jaguars already had a name, he might as well use this one for the smaller animal).
Ocelots primarily dwell within tropical and subtropical forests, avoiding mountainous regions or those far from water. Indeed, given how widespread they are, it's surprising how picky they can be about the specific habitat they live in, so that they are most common in very specific locations that just happen to be found across a broad swathe of the continent.
Perhaps the most important requirement for them is dense vegetation cover from which to strike at their prey. In Arizona and Texas, for example, neither of which are known for their dense jungles, ocelots live in thick thornscrub. As one might expect, they also avoid areas with heavy human activity, such as logging, and they tend to thrive where humans are rare. Fortunately, while this has negative implications for their survival in a number of specific localities (such as the US), continent-wide there are plenty of places that fit what they're looking for and the species as a whole is not endangered.
Obviously, ocelots also want prey to hunt and, for them, this mostly consists of larger, rat-sized, rodents. Since they're good at swimming, and tend to live near water, marsh rats and rice rats often form a significant part of their diet, along with the common black rat, cotton rats, agoutis, and so on. Obviously, they don't restrict themselves to rodents and they will eat, say, rabbits, armadillos, and opossums. In some areas, reptiles seem an unusually large part of their diet.
Monkeys also seem to be a common prey item. Some of these are marmosets, which are quite small, but capuchins and howler monkeys also fall prey to ocelots. They might not eat very many individual monkeys, but the ones they do eat are large enough that they can form a majority of their diet by weight. Ocelots are also strong enough to take down deer fauns, or even the adults of some smaller species.
Like many cats, they are nocturnal animals, and their hunting strategy often consists of hiding somewhere in wait until something suitable comes past rather than actively going out to look. This is reflected in their forelimb musculature, which is not suited for chasing prey, but still has toes that are more flexible and mobile than those of domestic cats, presumably to manipulate larger food items. They can sit motionless for up to an hour at a time while doing this, and spend the rest of the night moving slowly around their home territory. In some places, especially rich jungles, their population density can be high; each ocelot may occupy several square kilometres of territory, but, even though they are solitary, those of the wider-ranging males will overlap with those of around four local females where possible.
It may also be notable that as many as 17 different ocelots have been recorded as sharing a single defecation site, presumably in order to leave behind scent messages for each other. They may live alone, but they at least want to know who else is around. This is likely to be particularly important when they want to breed, which probably happens about once every other year for females. Unlike many smaller cats, they tend to only give birth to one kitten at a time, after an unusually long pregnancy (for a small cat) of about 80 days. They stay with their mother for two years or more, although there's every indication that their eventual departure is peaceful rather than being some forceful eviction.
As with ocelots, there's some dispute about the number of subspecies. There are, however, at least three, two in South America, roughly divided by the Amazon River, and one in Central America and Mexico.
Recently, two all-black margays were spotted in camera traps, one in Colombia, and one in Costa Rica. While the all-black coat pattern is common in jaguars and leopards ("black panthers") and, for that matter, some other species more closely related to the margay, it has never been seen in ocelots. Even in margays, it's presumably a rare mutation, given how long it took for anyone to find one.
Margays are even more bound to forest habitats than are ocelots, living almost exclusively in dense tropical and subtropical woodlands. While there is a recent report of margays living in scrub habitat in eastern Brazil, in general, they don't even like to approach the forest edge, which is part of the reason they're rarely seen in the wild. In fact, they are widely regarded as the most arboreal of South American cats, and may spend a considerable portion of their time climbing about in trees rather than walking on the ground.
This is reflected in some of the more subtle details of their anatomy. Their tail is proportionately longer than that of ocelots, helping to serve as a balance when climbing, and their toes are more flexible. Notably, they can climb head-downwards, which is the most efficient way to do it if you want to see where you're going, but which most non-arboreal mammals find difficult. They can also hang from a branch by their feet, due to their ability to rotate their ankles through 180 degrees.
This, of course, is all related to their diet, which contains rather a lot of squirrels and tree-climbing opossums. Having said that, they have broad tastes, and also hunt some ground-dwelling animals such as cane rats and rabbits, as well as ground-nesting birds. Like ocelots, they will eat monkeys, and have even been observed mimicking the calls of a baby tamarin apparently in an attempt to attract and eat one of the adults (it failed, in this instance, but it seems unlikely it would have learned to do this if it never worked).
In general, margays seem to be less common than ocelots and they seem to actively avoid areas where the latter are found in large numbers. Where the two are present in the same area, they are active at roughly the same time, which probably reflects the activity of their prey. Like ocelots, margays are nocturnal, and they sleep during the day in bundles of vines or other safe locations off the ground.
The breeding habits of the two species also seem very similar, peaking in the summer, and resulting in the birth of, usually, only a single kitten. Despite the smaller size of the margay, pregnancy lasts about the same length of time (which is to say, two weeks longer than in the domestic cat, which is much closer in size to a margay than to an ocelot). Unlike many cats, however, including ocelots, margays are apparently capable of ovulating without having to mate first; whether this would provide any sort of advantage to them is far from clear.
Ocelots and margays are the only small spotted cats found as far north as Mexico, but the genus Leopardus also includes a number of other, often rather similar, cats found further south. It is to some of those that I will turn next.
[Photos by Tony Hisgett and "Gab 2212", from Wikimedia Commons.]