Both islands are home to the green vervet monkey, introduced by the French some 300 years ago, now dwelling on the forested areas in the mountains. They can be seen in many areas including Brimstone Hill. Scientists have been studying these attractive little creatures and many have been exported; being relatively free of disease they are used for medical research.
The monkey is the same animal as on Barbados but the Kittitians used to eat them. Another animal, the mongoose, imported by colonists to kill rats in the sugar estates and snakes never achieved its original purpose (rats being nocturnal whereas the mongoose is active by day) and survives in considerable numbers. It has contributed to the extinction of many species of lizard, ground nesting birds, green iguanas, brown snakes and red-legged tortoises. There are also some wild deer on the southeast peninsula, imported originally from Puerto Rico by Philip Todd in the 1930s. In common with other West Indian islands, there are highly vocal frogs, lots of lizards (the anole is the most common), fruit bats, insect bats and butterflies, although nothing particularly rare. St Kitts & Nevis have the earliest documented evidence of honey bees in the Caribbean. Birds are typical of the region, with lots of sea fowl like brown pelicans and frigate birds to be seen, as well as three species of hummingbirds. Fish abound in local waters (rays, barracuda, king fish and brilliantly coloured smaller species) and the increasingly rare black coral tree can be sighted in the reef of the same name.
St Kitts and Nevis are small islands, yet have a wide variety of habitats, with rainforest, dry woodland, wetland, grassland and salt ponds.The forests (of which a small percentage are rain forests) on the sister islands are restricted in scale but St Kitts is one of the few areas of the world where the forest is expanding. It provides a habitat for wild orchids, candlewoods and exotic vines. Fruits and flowers, both wild and cultivated, are in abundance, particularly in the gorgeous gardens of Nevis. Trees include several varieties of the stately royal palm, the spiny-trunked sandbox tree, silk cotton, and the turpentine or gum tree.
Visitors can explore the rainforests on foot with guides and gentle hikes through trails and estates also reap many rewards in terms of plant-gazing. Several trails are clear and do not need a guide, although it should be noted that there are no marked trails; care should be taken and advice sought. Comparatively clear trails include Old Road to Philips, the old British military road, which connected the British settlements on the northeast and southwest coasts of St Kitts without going through French territory when the island was partitioned. It should be noted, however, that with the passage of Hurricane Luis in 1995 this trail was badly damaged. Efforts have been made to clear the trail but excessive rainfall subsequently made the road difficult to traverse. There are also trails from Belmont to the crater of Mount Liamuiga, from Saddlers to the Peak, from Lamberts or the top of Wingfield Heights to Dos d’Ane lake (known locally as Dos d’Ane pond).