You are here
قراءة كتاب Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala
تنويه: تعرض هنا نبذة من اول ١٠ صفحات فقط من الكتاب الالكتروني، لقراءة الكتاب كاملا اضغط على الزر “اشتر الآن"
Amphibians and Reptiles of the Rainforests of Southern El Petén, Guatemala
c11">Phrynohyas spilomma
PLATE 7
Fig. 1. Edge of rainforest along airstrip at Chinajá, El Petén, Guatemala.
Fig. 2. Rainforest at edge of savanna at Toocog, El Petén, Guatemala.PLATE 8
Interior of rainforest at Chinajá. Notice size of buttresses on large tree (Ceiba pentandra).PLATE 9
Interior of rainforest at Toocog. Notice less dense vegetation as compared with Pl. 8.PLATE 10
Fig. 1. Rainforest along Río San Román, 16 kilometers north-northwest of Chinajá.
Fig. 2. Rain pond in forest at Toocog. This was a breeding site for six species of frogs.Ecology of the Herpetofauna
Our two visits to Chinajá and Toocog afforded the opportunity to gather data on the ecology of the rainforests of southern El Petén and to study the relationships between the environment and members of the herpetofauna. Tropical rainforests present the optimum conditions for life, and it is in this environment that life reaches its greatest diversity. Here, too, biological inter-relationships are most complex. This complexity is illustrated by the presence of many species of some genera, all of which are found together in the same geographic region. In the rainforests of southern El Petén there are six species of Anolis, five of Hyla, four of Bothrops, and three of Coniophanes. Obviously, the diversity of ecological niches in the rainforest is sufficient to support a variety of related species. Of the examples mentioned above, fairly adequate ecological data were obtained for most of the species of Anolis, which will be used to show the ecological diversity and vertical stratification of sympatric species in the rainforests.
Of the six species of Anolis, all except A. sericeus are typically found in humid forests. Anolis sericeus sericeus is poorly represented in the collections from southern El Petén, where it may be in competition with Anolis limifrons rodriguezi that resembles Anolis s. sericeus in size, coloration, and habits. Therefore, Anolis sericeus sericeus is excluded from the following discussion. The common terrestrial species is Anolis humilis uniformis; sometimes this small species perches or suns on the bases of small trees or buttresses of some large trees. When disturbed it takes to the ground and seeks cover in the leaf litter or beneath logs or palm fronds. Anolis lemurinus bourgeaei is about twice the size of Anolis humilis uniformis and is usually observed on buttresses of large trees or on the lower two meters of tree trunks. Individuals were seen foraging on the ground along with Anolis humilis uniformis. At no time were Anolis lemurinus bourgeaei observed to ascend the trunks of large trees; they always took refuge near the bases of trees. Anolis limifrons rodriguezi is found on the stems and branches of bushes. It is a small species that sometimes is observed on the ground but was never seen ascending large trees. Anolis capito is about the same size as Anolis lemurinus bourgeaei and lives on the trunks of large trees. In the tops of the trees lives a large green species, Anolis biporcatus.
Similar segregation habitatwise can be demonstrated for other members of the herpetofauna. The avoidance of interspecific competition in feeding is well illustrated by three species of snakes that probably are the primary ophidian predators on frogs. Drymobius margaritiferus margaritiferus is diurnal and terrestrial; it feeds on frogs at the edges of breeding ponds by day. Also during the day Leptophis mexicanus mexicanus feeds on frogs in bushes and trees. At night the activities of both of these species is replaced by those of Leptodeira septentrionalis polysticta, which not only feeds on the frogs in the trees and bushes, but descends to the ground and even enters the water in search of food.
From the examples discussed above, the importance of the three dimensional aspect of the rainforest is apparent. The presence of a large and diverse habitat above the ground is of great significance in the rainforest, for of the non-aquatic components of the herpetofauna in the rainforests of southern El Petén, 42 per cent of the species spend at least part of their lives in the bushes and trees. Another important part of the forest is the subterranean level—the rich mulch, underground tunnels, and rotting subterranean vegetation. Of the 78 species of amphibians and reptiles in southern El Petén, seven are primarily fossorial, and half-a-dozen others are secondarily fossorial. Probably the fossorial members of the fauna are the least well represented in the collection, for such widespread species as Dermophis mexicanus mexicanus, Rhadinaea decorata decorata and Tantilla schistosa schistosa were expected, but not found.
In the following discussion of the ecological distribution of amphibians and reptiles in the rainforest I have depended chiefly on my observations made in southern El Petén, but have taken into consideration observations made on the same species in other regions, together with reports from other workers. The reader should keep in mind that the evidence varies from species to species. Of some species I have observed only one animal in the field; of others, I have seen scores and sometimes hundreds of individuals. For species on which I have few observations or rather inconclusive evidence, the circumstance of inadequate data is mentioned.
In analyzing the ecological distribution within the forest, it is convenient to recognize five subdivisions (habitats); each is treated below as a unit.
1. Aquatic.—This