The Reptiles of Costa Rica
Reptiles arose in the Palaeozoic Era, 300 million years ago. Today there are over 6000 reptile species, sharing the following traits: they are of mostly inconspicuous colours and behaviour; their heart is divided into several chambers to increase blood pressure (and hence muscular activity); most reptiles’ skin is covered with scales to reduce water loss from their body surface.
There are 3 groups of reptiles: Crocodiles, Turtles, Lizards/Snakes
A fascinating attribute of reptiles is that their sex is largely determined by the temperature at which the eggs develop in the ground. This is because all crocodilians and many turtles and lizards do not have the sex-determining X or Y chromosomes. Hence, temperature conditions decide for their sex. Some turtle eggs, for instance, develop as females when incubated at temperatures above 30° C, and as males when incubated at temperatures between 24-28° C!
(This is an important fact to remember when calculating the size of marine turtle refuges: as temperatures vary on beaches, there is the risk of protecting a beach where only male turtles will hatch. This will not enable the specie to reproduce further. It is therefore fundamental to implicate this knowledge and make sure that beach areas are protected where similar amounts of male and female turtles will hatch.)
Crocodiles (esp: cocodrilo)
Some 23 crocodile species (crocodiles, alligators, caimans) dwell in most sub-tropical and tropical areas of the world. They spend most of their time in water (but breathe through lungs) and are exclusive meat-eaters. Interestingly, crocodiles show astonishing parental care for being reptilians. They guard their nests and sometimes even help hatchlings to free themselves from the nest. Crocodilians can reach ages of over 60 years in the wild. Note that pretty much all crocodilian species are threatened or endangered.
The American crocodile is a large crocodilian that can reach lengths up to 7 metres (4 m being average adult size).
It is not always easy to distinguish crocodiles from caimans. The snouts are a good indicator: caiman’s snouts are broader and rounded, those of crocodiles more pointed. Their behaviour is a further sign: caimans are generally shyer. So another rule of thumb to determine a crocodilian is the following: if it runs away it’s a caiman, if it eats you it’s a crocodile…
The Caiman is generally shy and of small size (up to 2.5 m). It is the most widespread crocodilian in the world and can be found on both the Caribbean and Pacific slopes of Costa Rica.
Turtles are a 200 million year old species that can be divided in water (sea/freshwater) and land turtles. Their characteristic feature is the shell, which consists of two layers: an inner layer of bone and an outer layer of scale-like plates. They are able to retreat their feet and head into the shell for protection. Turtles can live for 25 to 65 years. There are only marine and freshwater, but no land turtles in Costa Rica.
A specific characteristic of sea turtles is that their legs developed into flippers. Four sea turtle species can be found in Costa Rica: the green, hawksbill, olive ridley and leatherback turtles. All sea turtles are endangered because of overhunting (which is a diminishing, but still existing problem) and beachside development. Marine turtles are probably most famous for their breeding habits: every 2-4 years the females come ashore the same beaches they have been born on to lay eggs. This happens within about an hour at nighttime. The eggs (ca. 100) are deposited in a hole half a meter under ground. About 2 months later the hatchlings emerge simultaneously from the eggs and walk towards the ocean. Not more than 5% of these young turtles survive their first days of life as they are yet unprotected (their shells being soft). Later, when the shell hardens, the survival of adult turtles ranges around 80%.
Green turtles are found on both coasts. They nest between July-October on the Atlantic and from October-March on the Pacific coast. Green turtles have a length of about 80 cm and weigh between 65-120 kg. Nutrition: algae and sea grasses.
Leatherback turtle is the largest and most impressive turtle specie with lengths up to 2.5 m and weights up to 1 ton! They can be observed on the Pacific coast between October and March, when they come to lay their eggs. The name stems from their leathery skin with small embedded bones, which they have instead of a shell. Bathers will be happy to know that leatherbacks feed mainly on jellyfish.
Lizards are mostly carnivorous and insectivorous but some larger ones eat plants. Snakes probably evolved from lizards (when their legs retreated due to unemployment) and are exclusively carnivores.
Many lizards have an interesting self-preserving mechanism: when grabbed forcefully by the tail, they can break it off. This is known as “tail autonomy” and can actually be observed with many lizards (e.g. geckos).
Of about 600 iguanid species, 38 can be found in Costa Rica. Let us take a look at the three most common ones:
They are easy to spot due to their– as the name tells – green colour. Tail included, they can grow longer than 2 metres and weigh up to 10 kg. Green iguanas spend most of their lazy lives on trees, but are also good swimmers. The spines along their back and tails evoke memories of a long-gone dinosaur era (male spikes are longer and thicker than the female’s). Despite their very sharp teeth, they are herbivores, but young green iguanas usually also feed on insects. Thanks to sharp claws on their hind legs, iguanas are excellent climbers.
Breeding occurs during dry season, when the female lays clutches of ca. 40 eggs. After 11-15 weeks of incubation the hatchlings emerge. As they lack dorsal spines, they are more resembling to female iguanas than males.
First described in 1758, by the Swedish botanist Carl Linnaeus, this specie is also locally known as “chicken of the tree” (“gallina de palo”). This is due to their being an easily accessible source of meat. With increasing prosperity the demand for iguana meat is currently decreasing. Let us hope that the food shortage threatening particularly the poorer areas of the world won’t change this (not just for the iguana’s sake, of course).
First time visitors to Costa Rica might confound Ctenosaurs with Green Iguanas, as they are difficult to distinguish. Ctenosaurs, however lack the peculiar head spines and crest (but they do have spines on their back) and are of darker colours. The ctenosaurs’ habitat are dry areas. Like green iguanas, they are mainly herbivores (but they do feed on occasional lizards or small mammals). They are of similar length (up to over 1 m incl. tail) but more active than green iguanas and hence better hunters.
With a speed of 35 km/h the Costa Rican “ctenosaura similis” actually attained the local sprint record.
Basilisks are also known as “Jesus Christ Lizards” due to their ability to run over water surfaces for distances up to 20 metres. They mostly feed on plants, but are omnivorous and eat insects, small mammals and lizards.
Don’t we just love geckos? Their swift movements on the wall, the bird-like sounds they utter and the amount of mosquitoes and cockroaches they devour make them our favourite house lizards. Of around 750 species worldwide, 9 species can be found in Costa Rica. Geckos are night-active small lizards with large eyes, usually of a inconspicuous dark or grey colouring. Their length is usually between 5-10 cm without tail (double that with tail; because lizards can drop their tail, they are measured from snout to vent).
It is still widely unknown what exactly enables geckos to defy gravity and adhere to vertical surfaces. It seems that tiny hair-like structures on the toes allow attachment to walls (by what is known as van der Waals force).
There are 162 snake species in Costa Rica, of which 22 are poisonous. Despite their bad reputation the chances of actually seeing a venomous snake are rather slim. They are not only sedentary and nocturnal, but also hard to spot for the untrained eye.
There are two main groups of venomous snakes in Costa Rica: Pit Vipers and Coral Snakes. Pit vipers include the notorious Fer de Lance, the Eyelash Viper, the Bushmaster and the neotropical rattlesnake. Pit vipers can be detected by their triangular head, which sticks noticeably out of the body. Their venom breaks down tissue near the bite location and can affect the nervous system. The Fer de Lance (terciopelo) is a large specie, responsible for most bites in the country.
Colubrids – of which most are unpoisonous – are the most common snakes. It is hard to distinguish them, but the main difference is the lack of venom-injecting fangs on the upper jaw. Mostly, they have long and slender bodies that enable them to live on trees (in contrast, vipers are slower and more heavy-bodied).
With maximum lengths of over 3 metres, the bushmaster is the largest venomous snake of the Neotropics. Because they live a nocturnal life (like most venomous snakes) they are hard to spot. Unlike most vipers, bushmasters don’t give birth to live young, but lay clutches of around 10 eggs.
Coral snakes are of bright colours. They have short fangs at the front of the mouth and their venom is toxic to the nervous system. Very often, however, the snake’s bite is “dry”, i.e. no poison is injected with the bite (this is due to the long time it takes to produce the venom. Experienced snakes know that humans are too big to eat; if snakes waste their poison on such a species they might have to spend the next couple of days without food – until new venom is produced).
The Bothrops asper belongs to the family of pit vipers. Pit vipers are named that way due to the cavities between their nostrils – heat sensitive organs to detect other creatures. The Fer de Lance is of brownish colour with diagonal stripes and diamonds and reaches lengths around 2 metres. The snake is called Terciopelo in Costa Rica and mostly feeds on mammals like birds or opossums. They lead a terrestrial life, but can sometimes be found on trees when they are young. Their habitat consists of moist forest, but they can sometimes also be found in drier areas. Fer de Lances give birth to live young, usually between 20-60 at a time and one foot of length.