Eco Preservation Society


Costa Rica’s Mysterious Mangroves – A Treasured and Exotic Habitat

by Richard Garrigues

In the nebulous zone between high and low tide, where freshwater meets saltwater and the ground is neither liquid nor solid, grow the mangroves.

Inhabitants of inter-tidal zones throughout the tropics and subtropics, mangroves are a most curious collection of plants. It is easy to make the erroneous assumption that the different kinds of mangrove trees are closely related species adapted to the unique conditions in which they grow. Even their English common names (red mangrove, black mangrove, white mangrove, buttonwood mangrove, etc.) lend to the idea that these are merely different species of the same plant family, as if they were maples or oaks.

In reality, the mangroves are a wonderful example of convergent evolution—a situation in which totally unrelated organisms have evolved certain similarities simply because those are the characteristics best suited for making use of a particular resource. And in this case the resource is a place where a plant might grow if it can overcome the two major difficulties faced by mangroves: the salinity of the sea water which saturates the ground they grow in and the absence of oxygen in that same saturated mud.

In Costa Rica there are seven species of mangrove trees from four very different plant families: the red mangroves (Rhizophora mangle and R. harrisonii, Rhizophoraceae), the black mangroves (Avicennia germinans and A. bicolor, Verbenaceae), the tea mangrove (Pelliciera rhizophorae, Theaceae), the white mangrove (Laguncularia racemosa, Combretaceae), and the buttonwood mangrove (Conocarpus erectus, Combretaceae). In Costa Rica, any and all of these plants are called mangle (man-gley) and the association in which they grow a manglar.

Of the mangroves found in Costa Rica, the red mangrove is the most easily recognized with its striking aerial prop roots, which often branch one or more times before reaching the ground. The primary function of these roots is not to support the tree but to aid in the aeration of the plant’s sap system.

The black mangrove, and to some extent the white mangrove, cope with the lack of air in the mucky substrate by developing vertical extensions from their roots which stick above the soil level and (at low tide) accomplish oxygen exchange. The tea mangrove has pronounced buttresses which act as aerators. The buttonwood mangrove effectively avoids this problem by growing on the back edges or higher ground within a mangrove swamp, thus reducing the likelihood of having the soil around its roots supersaturated except at extreme high tides.

Mangroves have developed various ways to deal with the problem of high salt concentrations in the water around them. Some species secrete salt from their roots and/or leaves. Pacific coast black mangroves can be observed in the dry season with salt crystals along the outer edges of their leaves (secretion of salt through the leaves happens throughout the year, but is not usually observed in the rainy season because the rain washes off the salt).

In some mangroves, such as the red mangrove, salt is stored in the older leaves which soon fall off the tree. And in other species, it appears that salt is simply tolerated in much higher levels than is common in most plants.

As a result of the rather severe conditions where mangroves grow, there is not much plant diversity. Correspondingly, the animal life associated with mangroves is not nearly as diverse as it is in other lowland habitats in Costa Rica. Nevertheless, what mangrove swamps may lack in numbers of species they make up for with numbers of individuals.

At certain times of the year the tops of mangrove trees are filled with nesting birds. In the Tempisque River, the Isla de Pájaros, or Bird Island, is an impressive example of this phenomenon. Each year hundreds of Wood Storks, Roseate Spoonbills, Anhingas, and Neotropical Cormorants reproduce on this protected patch of mid-river mangroves.

In the mangrove of Damas Island you will find White Faced Monkey which many a visitor will have a close encounter. But please, do not feed the monkeys.

Part of the reason for the concentration of nesting and roosting birds in the mangroves could be that it serves as a sanctuary from terrestrial and climbing predators. The bases of the trees are under water almost nearly of the time and even when they are exposed by receding tides, the soft mud that surrounds them is a deterrent to many creatures.

Below the water’s surface in areas where mangroves grow one can find a high diversity of life forms. Among the mangrove’s root systems many marine organisms live or spend a portion of their lives. Such creatures include algae, corals, barnacles, sponges, oysters, crabs, lobsters, shrimps, octopi, and fishes. The importance of mangroves to the health of the marine ecosystem is immeasurable.

Unfortunately, in Costa Rica and the rest of the world, mangrove forests are being destroyed and their sites converted to fish pens, rice paddies, salt-drying ponds, cattle pasture, tourist developments and human settlements. Mangrove wood makes good fuel and excellent charcoal, but over-harvesting has contributed to their demise. Additionally, the red mangrove is an important source of tannin (used in processing leather), but the stripping of the bark to get the tannin kills the individual trees.

All mangroves in Costa Rica are protected by law, but there is not always someone around to enforce the law. Nevertheless, there are still large areas of mangroves lining estuaries and mouths of rivers and streams along the Pacific coast of Costa Rica. Mangrove development is not as common on the Caribbean coast, because there is little variation in the height of the tides, but one area where some very tall red mangroves can be seen is along the extensive canal system between Limón and Tortuguero.


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Costa Rica’s Endangered Jaguars

One of the largest of Central American, and Costa Rica’s largest, carnivores, an endangered species, it was once fairly common in coastal mangroves, lowland savannas, and wet and dry shrub lands and forest up to about 1000m elevation. But because its conspicuous tracks, the high value of its pelt, its reputation as a stock killer, and its vulnerability to hound pursuit and still hunting, this cat is now rare except in parts of large unhunted reserves. It occurs in Costa Rica on the Tortuguero, Santa Rosa, Corcovado and Rio Macho National Parks, and lower levels of Cordillera Talamanca.

Jaguars are rarely seen in daylight, but occasionally one suns on a cliff or log . They scratch tree trunks, but its not sure that they urine-mark objects or make territorial scratches on the ground. They are fairly aquatic and easily swim rivers, small lakes, and straits between mangrove islets. They favor damp sites such as streambeds in gallery forests, where footprints often reveal jaguar’s presence, approximate size , and travels. At any season jaguars of any sex may roar at night.

Although jaguars seem to prefer peccaries as prey, they also take monkeys, agoutis, deer, birds, fish, lizard, turtles, and other animals. Mud tracks reveal feeding on dead fish, alligators, iguanas and any other carrion left by receding waters.

Jaguars seem not to avoid the scent of a man, and one may follow a man walking in a trail. Although unprovoked attacks on men are rare, in Panama a jaguar recently charged a man who was carrying a bag of trapped birds.

The season of births probably varies regionally. Gestation is about 3 months, and the usual litter is two. Apparently males take no part on the rising of the young, which may accompany the mother for a year. Females reach sexual maturity at about 3 years of age and do not breed in successive years if their young survive. The main threat to the remaining jaguars in Central America is the clearing of forest for crops and grazing. When roads penetrate a primitive zone, the jaguar and white-lipped peccary ( Tayassu pecari ) are the first mammals to disappear. Jaguars seem to be poor colonizers of cutover lands or new areas regardless of the abundance of prey there. Jaguars range from northern Mexico to northern Argentina. The puma has much greater ecological and geographic range and occurs along with jaguars throughout Costa Rica.

Rare film of a Costa Rican Jaguar in the wild

Also see:
Saving Mono Titi – The Documentary

Filed under: Wildlife Conservation, , , , , , , , ,

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