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Robert Powell and Robert Henderson

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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 Henderson and Peter Tolson

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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 Powell and Robert W. Henderson

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

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Henry S. Fitch and Robert W. Henderson

Abstract

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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Peter J. Tolson and Robert W. Henderson