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Heliotherms in tropical rain forest: the ecology of Kentropyx calcarata (Teiidae) and Mabuya nigropunctata (Scincidae) in the Curuá-Una of Brazil
- Laurie J. Vitt, Peter A. Zani, A. Claudia Marinho Lima
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- Journal:
- Journal of Tropical Ecology / Volume 13 / Issue 2 / March 1997
- Published online by Cambridge University Press:
- 10 July 2009, pp. 199-220
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Kentropyx calcarata (Teiidae) and Mabuya nigropunctata (Scincidae) occur together in lowland tropical forest of the Amazon near the Rio Curuá-Una of Brazil. During the wet season of 1995 these lizards were common at forest edge along narrow roads that transect forest, in treefalls and along streams where sun reaches the ground. Both species are heliothermic, basking to gain heat. Their association with open patches results from high activity temperature requirements in an environment where sun availability is low. Null temperature distributions from forest and treefalls showed that forest does not offer opportunities for heat gain similar to treefalls. Moreover, the large proportion of time spent basking by both species indicates the importance of these patches for thermoregulation. K. calcarata is slightly larger in body length and heavier at a given body length than M. nigropunctata. Both species are active foragers that seek out prey while moving through the habitat, feeding on orthopterans, roaches and spiders. M. nigropunctata also eat significant numbers of insects that occur on vegetation, such as hemipterans. Prey size is larger in K. calcarata and associated with lizard body size. Prey size does not vary with body size in M. nigropunctata and prey are typically relatively small.
Many of the ecological differences between these two lowland forest species appear to be historical: the ecology of K. calcarata is very similar to that of other species of Kentropyx and teiids in general and the ecology of M. nigropunctata is most similar to that of other studied species of south American Mabuya.
Behavioural ecology of Tropidurus hispidus on isolated rock outcrops in Amazonia
- Laurie J. Vitt, Peter A. Zani, Janalee P. Caldwell
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- Journal:
- Journal of Tropical Ecology / Volume 12 / Issue 1 / January 1996
- Published online by Cambridge University Press:
- 10 July 2009, pp. 81-101
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A population of the tropical lizard Tropidurus hispidus, isolated on a granitic rock outcrop in tropical forest of northern Brazil, was studied during the 1993 wet season. Four types of observational studies revealed that lizards are active throughout most of the day. During 10-minute intervals, individual lizards moved five times for an average of 240 cm and tongue-flicked once. Habitat temperatures vary considerably during the day, with rock and air temperatures in sun exceeding body temperatures of lizards during much of the activity period. During most of the day, lizards thermoregulate by moving among shady, filtered sun, and sunny microhabitats maintaining body temperatures near 35°C. Temperatures of lizards active during cloudy periods were significantly lower than temperatures of lizards during sunny periods, indicating that clouds decrease the ability of lizards to effectively thermoregulate. Most feeding occurs in the afternoon at edges of rock outcrops with ants, insect larvae, termites and beetles dominating the diet. Comparisons with a near-by savanna population revealed differences in body size (males only), activity period (longer on rocks), body temperatures (higher on rocks), number of prey categories consumed (lower on rocks), mean size of prey (larger on rocks), number of prey eaten (fewer on rocks) and microhabitat use (more restricted on rocks).
5 - Feeding ecology in the natural world
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- By Laurie J. Vitt, Sam Noble Oklahoma Museum of Natural History and Zoology Department University of Oklahoma, Eric R. Pianka, Section of Integrative Biology School of Biological Sciences University of Texas at Austin
- Edited by Stephen M. Reilly, Ohio University, Lance B. McBrayer, Georgia Southern University, Donald B. Miles, Ohio University
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- Book:
- Lizard Ecology
- Published online:
- 04 August 2010
- Print publication:
- 12 July 2007, pp 141-172
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Summary
Introduction
Foraging mode, originally defined on the basis of clear differences in behaviors used to find and capture prey (MacArthur and Pianka, 1966; Pianka, 1966; Schoener, 1971) has become a central paradigm in lizard ecology (see, for example, Huey and Pianka, 1981; Vitt and Congdon, 1978; Cooper, 1994a, b, 1995a, b; Perry, 1999; Perry and Pianka, 1997; Perry et al., 1990). Sit-and-wait (often referred to as “ambush”) foragers pursue prey detected visually from short distances, often returning to the same perch after capturing a prey item. Wide (often referred to as “active”) foragers move through the environment in search of prey that are often hidden, using a combination of visual and chemical cues to locate and discriminate prey. Trade-offs between energy invested in capture versus search for these two foraging modes are key elements of optimal foraging theory (MacArthur and Pianka, 1966; Charnov, 1976; Kamil, 1983). Identification of this foraging dichotomy has stimulated lizard research in many areas, including ecology, behavior, life histories, and physiology, to mention a few.
The foraging mode paradigm is much more complex than previously envisioned, as evidenced by research presented in other chapters in this book. For example, what appeared to be a sharp historical separation of foraging modes (see, for example, Pianka and Vitt, 2003; Vitt et al., 2003) is replete with exceptions embedded in major clades, suggesting either loss of or multiple origins of traits often linked to foraging mode (see, for example, Cooper, 1997; Cooper et al., 1997).
Ease and effectiveness of costly autotomy vary with predation intensity among lizard populations
- William E. Cooper, Valentín Pérez-Mellado, Laurie J. Vitt
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- Journal:
- Journal of Zoology / Volume 262 / Issue 3 / March 2004
- Published online by Cambridge University Press:
- 23 February 2004, pp. 243-255
- Print publication:
- March 2004
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Costly anti-predatory defences are used in ecological time and maintained in evolutionary time by natural selection favouring individuals that survive through their use. Autotomy of expendable body parts is a striking example of a defence having multiple substantial costs, including loss of ability to use the same defence, loss of energy, and decreased growth, reproductive success and survival following autotomy, plus the energetic cost of replacing the lost body part in species capable of regenerating them. Our study shows that autotomy in the lacertid lizard Podarcis lilfordi reduces sprint speed, indicating decreased capacity to escape as well as the loss of energy. Autotomy carries substantial cost, and thus should be avoided except as a last resort. Ease of autotomy and post-autotomic movements were studied in three populations of lacertid lizards. Two were islet populations of P. lilfordi from Aire (lowest predation pressure) and Colom (intermediate predation pressure) off Minorca. The third was a mainland population of Podarcis hispanica, a closely related species from the mainland of the Iberian Peninsula where predation pressure is higher than on the islets. As predicted, a suite of autotomic traits increases the effectiveness of autotomy as a defence as predation pressure increases. With increasing predation pressure, the frequency of voluntary autotomy increases, latency to autotomy decreases, pressure on the tail needed to induce autotomy decreases, vigour of post-autotomic tail movements increases, and distance moved by the shed tail increases. Additional changes that might be related to predation pressure, but could have other causes, are the presence of tail coloration contrasting with body coloration except under the lowest predation pressure (Aire) and longer tails in the mainland species P. hispanica. Correspondence between predation pressure and the suite of autotomic traits suggests that autotomy is an important defence that responds to natural selection. Comparative data are needed to establish the generality of relationships suggested in our study of only three populations.
Distribution, extent, and evolution of plant consumption by lizards
- William E. Cooper Jr, Laurie J. Vitt
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- Journal:
- Journal of Zoology / Volume 257 / Issue 4 / August 2002
- Published online by Cambridge University Press:
- 01 August 2002, pp. 487-517
- Print publication:
- August 2002
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Animal diets crucially affect fitness, yet many aspects of their ultimate determinants are unknown. The distribution and extent of herbivory in lizards, its evolutionary history, and ecological factors that may favour it are discussed. Most lizards are exclusively or primarily carnivorous, yet many species eat some plants and a few are almost exclusively herbivorous. Based on a literature survey of diets of over 450 lizard species, the distribution and degree of omnivory and herbivory are described. Some plants occur in the diets of slightly over half of lizard species, and plants formed 10% or more of the dietary volume of 12.1% of species, and 90% or more of the diet of 0.8% of species. The greatest percentage of omnivorous species (> 10% plant diet), over 30% in each, and highest mean percentage plant matter in the diet are in Iguanidae, Corytophanidae, Gerrhosauridae, Agamidae, Xantusiidae, and Tropiduridae. Numerous other omnivores occur in Lacertidae and Scincidae and fewer in several additional families. Herbivorous lizards (> 90% plant volume) tend to be folivorous and to possess adaptations for processing leaves, including specialized dentition for cutting or reducing leaves, elongated intestines, colic valves that slow passage of food, and intestinal flora that digest cellulose. Omnivorous lizards lacking such specializations may eat some leaves, but consume much more fruit, flowers, and seeds, plant parts that are easy to digest, likely to be very abundant seasonally, and may be highly nutritious. Some lizards eat nectar and pollen; even sap is eaten by at least one gecko. Ontogenetic increase in plant consumption and decrease in prey consumption is known, but its generality has been controversial. Such ontogeny has been demonstrated in three iguanid species, a skink, a lacertid, two tropidurids, a phrynosomatid, and two corytophanids, but it does not occur in some other species. The importance of specific foods may vary with age. Omnivory and/or herbivory have originated in many lizard families, with at least nine origins in Iguania and 23 in Scleroglossa. Origins have been rare in Gekkonoidea and Anguimorpha and common in Scincomorpha, especially in Lacertidae and Scincidae. Losses of omnivory have been much less frequent than gains. Only a few origins can account for all the herbivory in lizards. Concentrated changes tests show that there is a significant association in Lacertidae, Lacertiformes, Lacertoidea, Scincidae, and Scleroglossa between insularity and omnivory. Insular lizards may broaden their diets to compensate for limited availability of prey. Addition of other factors that reduce availability of prey, i.e. extreme aridity and cave-dwelling, to insularity, strengthened the relationship to omnivory in Lacertidae and Lacertoidea. We were unable to demonstrate a role of aridity independent of insularity, but present anecdotal evidence suggests that it may promote evolution of plant consumption. Large body size in lizards has long been associated with herbivory, and more recently, with omnivory in lacertid lizards. Using a conventional regression approach in which each species is considered to supply an independent data point, this relationship was confirmed for all lizards. Although larger species have diets with more plants, plant consumption accounts for only 9% of the variation in body length, which is not surprising given that other factors such as predation, competition, and sexual selection affect body size. The frequency of transitions body size associated with transitions to omnivory or carnivory was also examined. In Iguania, Scleroglossa, and all lizards, transitions supporting the hypothesis that omnivory favours increase in body size were significantly more frequent than non-supporting transitions. This suggests that substantial plant consumption favours evolution of larger size, probably because of the energetic considerations first presented by Pough (1973). Because actively foraging lizards move widely through the habitat to locate prey and tongue-flick to locate prey by chemical cues, we hypothesized that they may be more likely to evolve omnivory than ambush foragers, which wait motionless for prey and do not tongue-flick to locate or identify prey. The basis of this prediction is that the wider seaching of active foragers predisposes them to contact with a greater variety and quantity of plants and that chemosensory tongue-flicking used by omnivores to identify plant food might be easier to evolve in active foragers that already use pre-chemical discrimination. The prediction is supported by a significantly greater per species frequency of origins of omnivory by active foragers than by ambushers. A scenario for the progressive evolution of omnivory and herbivory from ancestrally carnivorous lizards is discussed.
Prey use among sympatric lizard species in lowland rain forest of Nicaragua
- Laurie J. Vitt, Peter A. Zani
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- Journal:
- Journal of Tropical Ecology / Volume 14 / Issue 4 / July 1998
- Published online by Cambridge University Press:
- 01 July 1998, pp. 537-559
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The diets of 17 lizard species (seven families) studied simultaneously in a Caribbean lowland forest of Nicaragua were compared. Lizards varied in body size over nearly one order of magnitude. Twelve species for which there were adequate samples separated by prey types and most diet overlaps were low. A pseudocommunity analysis on volumetric diet data revealed significant guild structure in the assemblage. At each nearest neighbour rank in niche space, observed overlaps were higher than expected based on chance alone when all values in the consumer-resource matrix were randomized. There was no difference between observed and pseudocommunity overlaps with zero positions in the consumer-resource matrix retained (conserved-zero overlaps) indicating that the zero structure of the community matrix was important in maintaining structure and that lizards were converging on key resources. Individual prey size varied among species and mean prey size was significantly correlated with body size of lizard species. A phylogenetic analysis revealed no relationship between similarity in prey use (dietary overlap) and evolutionary relationships — more closely related species did not eat more similar prey types. Based on this analysis of Nicaraguan lizard diets and comparisons with other New World tropical lizard assemblages, it is suggested that factors contributing to the organization of tropical lizard assemblages are complex including historical differences in morphology (size), prey types and sizes, habitat structure and species interactions.
Ecological relationships among sympatric lizards in a transitional forest in the northern Amazon of Brazil
- LAURIE J. VITT, PETER A. ZANI
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- Journal:
- Journal of Tropical Ecology / Volume 14 / Issue 1 / January 1998
- Published online by Cambridge University Press:
- 01 January 1998, pp. 63-86
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Sympatric lizards in a transitional forest of Roraima, Brazil, dividing Amazon rain forest from savanna, contained a lizard assemblage of 16 species representing six families. Lizards varied in size, activity (diurnal versus nocturnal), microhabitats used, exposure to various conditions of light availability, prey types, and prey sizes. Overlaps in microhabitat occurrence varied from 0 (no overlap) to 1.0 (total overlap) whereas overlaps in prey types varied from 0.005 to 0.607. Microhabitat overlaps were higher overall than dietary overlaps. Pseudocommunity analyses on microhabitat data indicate that the community is not randomly assembled and that two distinct guilds exist, a leaf-litter guild and an arboreal guild, each with four species. Similar analyses on diet data revealed no apparent guild structure ast the first rank (nearest neighbour). Lizard diets did not differ from a random assortment based on prey type. At lower levels, the assemblage was structured with respect to food. Variation in prey use among lizard species was tied more closely to the effect of lizard body size on prey size (lizards ate different-sized prey items). Although exploitative competition among species may maintain structure within this assemblage it does not necessarily cause the observed differences. Several species are nearly identical ecologically to sister taxa in other environments and within different lizard assemblages suggesting that composition of the local assemblage limits the species that can enter the assemblage. Finally, lack of structure at the lowest (most similar) neighbour ranks may reflect the impact of a transitional habitat on stability of species interactions at the local level.