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Robert W. Henderson

Abstract

Trophic relationships and foraging strategies are examined in two New World arboreal, diurnal, snake communities: Leptophis mexicanus, Oxybelis aeneus, and O.fulgidus from Mexico's Yucatán Peninsula, and Uromacer catesbyi and U. oxyrhynchus from Isla Saona, República Dominicana. Active foragers (L. mexicanus and U. catesbyi) have similar body proportions and feed primarily on diurnally quiescent prey (hylid frogs, bird eggs). Sit-and-wait strategists (O. aeneus, O.fulgidus and U. oxyrhynchus) have similar body proportions and feed on diurnally active prey (primarily lizards). Active foragers take prey that is, on the average, larger than the prey of sit-and-wait foragers, but presumably, active foragers expend more energy in locating prey. Trophic niche breadth is widest among the active foragers and narrowest for the slender vine snakes (O. aeneus and U. oxyrhynchus). Trophic niche overlap values are low for species pairs that occur sympatrically (or syntopically) with the exception of O. aeneus-O. fulgidus, but O. fufgidus preys on a wider variety of lizard taxa, preys on birds (which are absent from the diet of O. aeneus), and takes prey items that are significantly larger in size. It seems likely that, among arboreal colubrids, the sit-and-wait foraging strategy is derived from one of active foraging.

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Robert W. Henderson

Hypsirhynchus is a diurnal, terrestrial colubrid endemic to Hispaniola. It has a stocky, viperid-like body and head, with a relatively attenuated snout. It is strictly saurophagous, and undergoes an ontogenetic expansion in diet from small, largely scansorial iguanids (Anolis) to a large teiid (Ameiva chrysolaema). Comparisons are made with Uromacer frenatus dorsalis, an Hispaniolan tree snake that exhibits a similar dietary change.

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Robert Powell and Robert W. Henderson

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Rose M. Henderson, Richard A. Sajdak and Robert W. Henderson

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Peter J. Tolson and Robert W. Henderson

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Robert W. Henderson and Craig S. Berg

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Henry S. Fitch and Robert W. Henderson

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Anolis b. bahorucoensis is a slender lizard, endemic to Hispaniola, that inhabits the deep shade of the forest understory. Unlike most anoles, the male has only a weakly developed dewlap, an organ important in courtship and territorial displays (and species' recognition). At least some populations of A. b. bahorucoensis are brilliantly colored with a gaudy, contrasting pattern. Experiments conducted in the field indicate that A. b. bahorucoensis is subject to intense predation pressure from at least two large common predatory congeners, A. coelestinus and A. cybotes. These two species occurring in syntopy with A. b. bahorucoensis probably assure that every individual of the latter species is constantly in danger, from several directions simultaneously, and can only survive by instantaneous escape responses, and other anti-predator strategies, that demand priority over every other kind of activity.

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Henry S. Fitch, Hank Guarisco and Robert W. Henderson

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Anolis cristatellus, a medium-large brown anole native to Puerto Rico, its satellite islands and the Virgin Islands group, has been introduced at La Romana on the south coast of the Dominican Republic. The time and circumstances of introduction are unknown, but it is thought to have occurred before 1920 in the port area southeast of the town. The species has become well established and phenomenally abundant, occupying an area of about 12 km2 and 13 km long. However, it is closely confined to the town of La Romana and adjacent altered areas with parks, gardens and evergreen trees, more mesic in aspect than adjacent relatively natural areas that are characterized by exposed limestone surfaces and chaparral-like formation of thorny shrubs and low, gnarled trees. The introduced A. cristatellus is closely associated with at least three species of native anoles. Anolis distichus is abundant both in the area invaded by A. cristatellus and in the relatively undisturbed habitat where cristatellus is absent. The two species often occur together on the same tree, and their height preferences coincide. Their food habits are similar, but with difference in average size of prey. Ants are a major food source for both. The smaller A. distichus may avoid predation by A. cristatellus through its greater agility. Anolis chlorocyanus is similar in size to A. cristatellus, but where the two co-occur, it is almost confined to trees with smooth and slippery trunks that are avoided by cristatellus; A. cybotes, a large, aggressive, predatory species, similar in habitat preference to A. cristatellus was found only outside the cristatellus area or on its edges. It seems that A. cristatellus is limiting to cybotes perhaps by preying on its hatchlings and outproducing it with shorter generation time and more frequent egg production.

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R. Allan Winstel, Richard A. Sajdak and Robert W. Henderson

Abstract

Habitat utilization by the arboreal boid Corallus grenadensis was studied at two ecologically disparate sites on the West Indian island of Grenada: one devoted largely to agriculture, the other largely devoid of agricultural activity. Small snakes (< 600 mm SVL) were most often encountered in uncultivated scrub woodland at both sites; large snakes (>1100 mm SVL) were encountered most often in fruit trees at one site and in mangroves at the other. Snakes of medium size (600-1100 mm SVL) occurred in both kinds of habitat. These size classes correspond to an ontogenetic shift in diet (lizards to mammals), and this is associated with a corresponding shift in habitat utilization.

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Sixto J. Inchaústegui, Albert Schwartz and Robert W. Henderson