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.