Ecology, Distribution, Harvest, and Conservation of the Amazonian Manatee Trichechus inunguis in Ecuador

Abstract

Recent summaries of the distribution of the Amazonian manatee Trichechus inunguis record specimens from much of the Central Amazon Basin in Brazil, eastern Peru, and extreme southeastern Colombia, but not Ecuador. During October and November of 1983 we searched for manatees in the Rio Aguarico and Rio Cuyabeno systems of Napo Province, eastern Ecuador. Herein we document the existence of Amazonian manatees in Ecuador, provide rough estimates of their current distribution, describe several aspects of their ecology in Ecuador, document use of manatees by indigenous peoples, and document the current commercial harvest of manatees for meat. Manatees were observed by us at several separate localities in the Amazonian lowlands of eastern Ecuador. Additionally, we report several observations by others as well as a published historical record previously overlooked. Our observations of manatees are from blackwater habitats in undisturbed, primary, lowland rainforest in water with a pH of 5.5 to 6.0 and temperature of 25.0 to 30.7?C. In the upper Cuyabeno region, the Siona Indians, who have harvested manatees for generations, have a self-imposed ban on manatee hunting to protect the few remaining animals in their waters. Settlers, the military, and a commercial meat hunter continue to actively harvest Amazonian manatees in Ecuador and adjacent Peru. Much of the meat obtained is used by either the Ecuadorian or Peruvian military. We found manatees abundant at only one locality, Laguna Lagarto Cocha. However, this population is being actively hunted, and the meat sold to the local military outposts. We estimate that if the current level of harvest continues unabated, Amazonian manatees will be gone from Ecuador within 10-15 years. RESUMENRecientes sumarios de la distribuci6n de los manaties amaz6nicos Trichechus inunguis registran especimenes de la mayor parte de la cuenca amaz6nica en Brasil, el oriente de Peru, y el suroriente de Colombia, pero no de Ecuador. Durante octubre y noviembre de 1983 nosotros fuimos en busca de manaties en los sistemas de los rios Aguarico y Cuyabeno de la Provincia del Napo, Ecuador oriental. Aqui documentamos la existencia de manaties amaz6nicos en Ecuador, proveemos estimaciones aproximadas de su actual distribuci6n, describimos varios aspectos de su ecologia en Ecuador, documentamos el uso de manaties por gentes indigenas, y documentamos la cosecha comercial actual de manaties para carne. Manaties feuron observados por nosotros en varias localidades separadas en las tierras bajas del Ecuador oriental. Adicionalmente, reportamos varias observaciones por otros, asi como tambien registros hist6ricos publicados que fueron previamente pasados por alto. Nuestras observaciones de manaties son de habitaciones en aguas negras en selva iluviosa primaria no alterada de tierras bajas, en aguas con un pH de 5.5 a 6.0 y temperatura de 25.0 a 30.7?C. En la regi6n del alto Cuyabeno, los indios de la tribu Siona, quienes han cosechado manaties por generaciones, se han impuesto asi mismos prohibicion...

Food Plants Eaten by Amazonian Manatees (Trichechus inunguis, Mammalia : Sirenia)

“…The hyacinth Eichornia crassipes was the third most frequent plant in t he digestive tracts and faeces analyzed, constituting 11.2% of the Amazonian manatees diet. Marmol (1976) in Peru and Timm et al (1986) in Ecuador, also found Amazonian manatee feeding on this species. Some have noted that the West Indian manatees only ate the emergent part of hyacinth, ignoring the roots (Lomolino, 1977).…”

“…It ranges from Marajó Island (Brazil) to the sources of the Amazon basin rivers in Columbia, Peru and Ecuador (Timm et al, 1986). It is present in all the major draining system tributaries of the Amazon river, where its distribution is apparently restricted to two locations: calm waters and lakes with aquatic vegetation (Best, 1984;Rosas et al,1991;Rosas, 1994).…”

“…It is present in all the major draining system tributaries of the Amazon river, where its distribution is apparently restricted to two locations: calm waters and lakes with aquatic vegetation (Best, 1984;Rosas et al,1991;Rosas, 1994). Amazonian manatees are herbivorous, non-ruminant, and feed on a large variety of aquatic and semi-aquatic plants (Timm et al, 1986). H owever, aquatic grasses are probably their preferred food (Montgomery et al 1981;Best, 1984;Gonçalves-Colares & Colares, 1992).…”

Prediction Equation of Body Weight of Amazonian Manatee (Trichechus inunguis) Calves in Captivity Using Biometry

“…The Sirenia order is the only order of aquatic mammal's survivors that are exclusively herbivorous [4]. This animal is an endemic species of the Amazon basin, occupying water bodies in Brazil, Colombia, Ecuador and Peru [1,3,[5][6][7], being reported in the latter mainly in rivers within Loreto region [2,8,9].…”

Interactions Between Calves of Amazonian Manatees in Peru: A Study Case

“…The Amazonian manatee is a non-ruminant herbivore that feeds on a wide variety of aquatic and semiaquatic plants (Guterres et al, 2008). The species plays an important role in the ecosystem, returning more than half of the ingested material to the environment as feces and urine, and is therefore essential to primary production (Best, 1984;Timm et al, 1986). The commercial exploitation (Domning, 1982), along with the slow rate of reproduction (Rodrigues et al, 2008), have seriously reduced the Amazonian manatee population (IUCN, 2008).…”