The Ecological Significance of Sexual Dimorphism in Size in the Lizard Anolis conspersus.
27 Jan 1967-Science (American Association for the Advancement of Science)-Vol. 155, Iss: 3761, pp 474-477
TL;DR: Anolis conspersus selects prey from a wide range of taxa and shows no obvious intraspecific specialization not connected to differences in microhabitat and prey size.
Abstract: Adult males of Anolis conspersus capture prey of significantly larger size and occupy perches of significantly greater diameter and height than do adult females; similarly, these three dimensions of the niche are significantly larger for adult females than for juveniles. Adult males on the average eat a smaller number of prey, and the range in size of prey is larger. The relationship between the average length of the prey and that of the predator is linear when the predator size is above 36 millimeters, but becomes asymptotic when it is below that value. Subadult males as long as adult females eat significantly larger food than do the latter, but only in the larger lizards is this correlated with a relatively larger head. Anolis conspersus selects prey from a wide range of taxa and shows no obvious intraspecific specialization not connected to differences in microhabitat and prey size. The efficiency of this system for solitary species is pointed out.
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TL;DR: Comparisons of diet and food availability indicate that thesespecies feed indiscriminately on a range of terrestrial and aquatic invertebrates and demonstrate the capacity to compensate for fluctuations in food availability by feeding on less lucrative prey.
Abstract: Faecal analyses were used to investigate the diets of the endangered frogs Litoria nannotis, L. rheocola and Nyctimystes dayi in Tully Gorge, North Queensland. Comparisons of diet and food availability indicate that thesespecies feed indiscriminately on a range of terrestrial and aquatic invertebrates. Changes in morphology and foraging behaviour significantly influenced diet composition and created subtle shifts in the degree of selectivity displayed in prey choice. Interspecific differences in numeric and volumetric diet composition were attributed to variations in gape size and microhabitat selection. Within the diets of L. nannotis and L. rheocola, a decline in prey selectivity observed during the dry season reflected a reduction in foraging activity. Differences in the gape size and foraging behaviour of males and females of L. nannotis were responsible for sex-specific differences in diet composition. L. nannotis also diplayed an ontogenetic shift in prey size and type. As snout-vent length increased, L. nannotis consumed fewer, but larger prey and increasingly discriminated against dipterans, dipteran larvae and hemipterans. Importantly, L. nannotis, L. rheocola and N. dayi demonstrated the capacity to compensate for fluctuations in food availability by feeding on less lucrative prey.
21 citations
TL;DR: How the foraging ecology of Anolis oculatus, a solitary species confined to the island of Dominica, Lesser Antilles, varies with habitat and season in relation to the quantity and quality of available food is described.
Abstract: In general, populations of Anolis lizards on West Indian islands face few predators, are at high density and are thought to be limited by food. This paper describes how the foraging ecology of Anolis oculatus, a solitary species confined to the island of Dominica, Lesser Antilles, varies with habitat and season in relation to the quantity and quality of available food.
Availability of invertebrate food (determined using pitfall traps and sticky traps) was greater in a dry scrub woodland site, Cabrits National Park (CNP), compared with a montane rainforest site, Palmiste Ridge. In the former, there were general increases in abundance, volumes of softbodied prey and sizes of invertebrates from dry season to wet season. Concomitant dietary changes, as determined principally by stomach flushing, included an increase (by volume) in the proportion of soft-bodied prey. Dietary analyses confirmed the importance of ants (Formicidae) in the diet of A. oculatus, although for large individuals (mainly adult males) at the rainforest site, soft-bodied prey such as Oligochaeta and Orthoptera were, in volumetric terms, more important. Prey capture observations showed that large A. oculatus fed mainly above ground. Anolis oculatus at the montane rainforest site used higher perch heights than those in dry scrub woodland, although in both habitats, small individuals (mainly juveniles) fed mainly at ground level on ants. In the dry season in CNP, the diet (in volumetric terms) of smaller Anolis was dominated by hardbodied prey such as ants, springtails (Collembola), barklice (Psocoptera) and beetles (Coleoptera). large Anolis used springtails and barklice to a lesser extent, resulting in relatively low food niche overlap values between size classes and a reduced potential for intraspecific competition compared with the wet season.
21 citations
TL;DR: The purpose of this study was to determine how the gastrointestinal helminthofauna varies according to the age and sex of the lizard, Enyalius perditus, captured in Ibitipoca State Park in the state of Minas Gerais, Brazil, and to discuss the ecological and behavioral significance of these relationships.
Abstract: The purpose of this study was to determine how the gastrointestinal helminthofauna varies according to the age and sex of the lizard, Enyalius perditus, captured in Ibitipoca State Park in the state of Minas Gerais, Brazil, and to discuss the ecological and behavioral significance of these relationships. Fifty-five specimens of E. perditus were captured in drop traps, then killed, necropsied, and examined for the presence of helminths in the gastrointestinal tract. Nematodes, including Strongyluris oscari, Oswaldocruzia subauricularis, and Aplectana vellardi, were found. This was the first record of the last-named species in reptiles, and the first record of the first 2 species in E. perditus. The number of helminths increased with snout-vent length and, therefore, age of the lizards. Male E. perditus lizards were more heavily infected by nematodes than females; the largest numbers of nematodes occurred in the caecum and large intestine.
21 citations
TL;DR: On differential microhabitat distribution in a population of C. dilepis in Kenya during the dry season and relate this to environmentally imposed stresses faced by the population is reported.
Abstract: In a wooded grassland in central Kenya during the dry season, male and female Chamaeleo dilepis exhibited differences in perch plants, perch heights, general body coloration, and rates of movement. By the end of the rainy season, the first three of these differences were no longer evident. Defoliation of a large proportion of the shrubs and lack of water probably created a dry season resource shortage for this population of chameleons. Thus, this expansion of the total niche may be viewed as ameliorating intraspecific competition, and it may be permitted by the absence of congeners in the habitat. NICHE EXPANSION BY INTERSEXUAL RESOURCE PARTITIONING has been documented primarily in birds following the initial suggestion of Rand (1952). It has been interpreted as a mechanism which alleviates intersexual competition under conditions of resources limitation (e.g., Hogstad 1977) or as a means of maximizing resource utilization in the absence of heterospecific competitors (Selander 1968). Differential habitat occupancy by the sexes has been reported for lizards (Jenssen 1970; Rand 1962, 1967). Schoener (1967) speculated that for arboreal species it might facilitate the build-up of dense populations in structurally rich habitats. Among chameleons, seasonal intersexual prey partitioning was found for Chamaeleo pumilis by Burrage (1973), and sexual dichromatism has been reported for C. hohnelii (Bustard 1965), C. namaquensis (Robinson 1978), and C. dilepis (Brain 1961). In the latter three cases, we might expect intersexual color differences to serve the function of matching the background colors of different microhabitats, although other explanations are possible. In this paper we report on differential microhabitat distribution in a population of C. dilepis in Kenya during the dry season and relate this to environmentally imposed stresses faced by the population. STUDY AREA AND METHODS The study area was situated on the eastern slope of Lukeya Hill (1?33'S, 37?5'E, elev. 1837 m), in the Athi Plains 38 km southeast of Nairobi. The vegetation in the area can be characterized as wooded grassland (Greenway 1973), with low bushes (Grewia tembensis) and scattered trees, mainly thorned torchwood (Balanites glabra) with individual yellow barked gall-acacias (Acacia seyal) and glossy-leaved commiphora (Commiphora schemperi). Ground cover consisted mostly of red oat-grass (Themeda triandra) with scattered stands of drop-seed grass (Sporobolus fimbriatus). The area is grazed by both domestic and wild herbivores. The climate is characterized by two distinct wet seasons, November to January and late March to mid-May, with an average annual rainfall of 900 mm. The study was conducted during the dry season, between 4 February and 25 March 1981. The grasses were dry and brittle, and many shrubs were leafless; only Balanites retained a green color. No rain fell until the night of 17 March, when the "long rains" began. Two independent studies in the Athi Plains have shown that insect density increases markedly during the rainy season. Dingle and Khamala (1972) found that insect biomass increased almost fourfold between March and May, and Denlinger (1980) found that densities of flying insects in Nairobi National Park were positively correlated with rainfall. Thus, the study period was likely one of depressed food as well as water availability for Chamaeleo dilepis. Five gravid female and four adult, male chameleons were fitted with 27 mHz transmitters constructed to fit across the mid-dorsal ridge like a saddle. They were glued to the animals with epoxy at the level of the pectoral girdle. Lifespan of the transmitters was about two months, and they had a transmitting range of 40 m. The devices fell off when the animals molted, but they could be re'Received 14 September 1982, revised 31 March 1983, accepted 19 April 1983. BIOTROPICA 16(1): 69-72 1984 69 This content downloaded from 157.55.39.183 on Fri, 22 Apr 2016 06:52:42 UTC All use subject to http://about.jstor.org/terms TABLE 1. Perch plants and body color of Chamaeleo dilepis before and after the 1981 rainy season, FebruaryMarch data are frequencies offirst sightings of radiotagged animals, June data represent individual sleeping animals, Female Male Chi-square
20 citations
TL;DR: A weak pattern of latitudinal differences in restingas regarding the general consumption of items by T. torquatus is found, probably because this is a generalist and opportunistic lizard, which consumes most of the available types of potential food items in the habitat.
Abstract: The diet composition of lizards of a given species may vary among different populations. The feeding ecology of the tropidurid lizard Tropidurus torquatus was studied in 10 coastal areas in Brazil in order to detect to what extent the diet varies along its geographic range. A non-metric multidimensional scaling technique revealed three groups of localities according to the diet composition: one characterized by a relatively high consumption of Isoptera, one characterized by a relatively high proportion of plant matter, and one in which there was a great importance of Formicidae. We found a weak pattern of latitudinal differences in restingas regarding the general consumption of items by T. torquatus, probably because this is a generalist and opportunistic lizard, which consumes most of the available types of potential food items in the habitat. However, lizards from northern populations consumed a larger quantity of smaller items (e.g., Isoptera) than those from southern populations. In the southern populations, on the other hand, larger items such as Coleoptera, Lepidoptera larvae and fruits were more frequently consumed. It is likely that the observed interpopulational variation in some aspects of the feeding ecology of coastal T. torquatus is mainly given by food availability.
20 citations
Cites methods from "The Ecological Significance of Sexu..."
...We measured leaf volume by multiplying their three dimensions (length, width and depth) (Schoener 1967)....
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TL;DR: The eight species of the genus Anolis in Puerto Rico can be divided into four morphological similarities as discussed by the authors : perch height, perch diameter, high-shade preference and low-shading preference.
Abstract: The eight species of lizards of the genus Anolis in Puerto Rico can be divided into four morphological similarities. One, Anolis curvieri, is very different from the rest and has not been discussed here. The other seven species fall into three groups. Each of these groups occupies a different structural habitat which can be defined in terms of perch height and perch diameter. Within each of these three groups the species have very similar but not indential structural habitats but differ very widely in climatic habitat defined in terms of shade. Shade preferences seem to result from the temperature preferences of the species involved. In each group there is one species with high shade preference which is essentially restricted to the mountains. Each group also has a species with a lower shade preference which occurs in the lowlands and extends up into the mountains in exposed or sunny situations. One of the three groups has an additional species which is restricted to the hot and southwest corner of Puerto Rico. When one compares the temperature preferences or eccritic temperatures of the various species, one finds in each group that the highland species has a lower eccritic temperature than does the lowland species. There is little temperature difference between the lowland species and arid southwest species in the group where this additional third species is present. The species within each structural habitat show many morphological similarities which may be the result of their being closely related or may be the result of adaptation to similar environments. The differences in microhabitat between the Puerto Rican anoles separate them spatially though not completely. In species occupying different structural habitats in the same area the overlap may involve part of the home range of most of the individuals in the area. In species occupying the same structural but different climatic habitats the overlap may involve all of the home range of some individuals but of only a small fraction of the individuals in the total population. The spatial separation among Puerto Rican Anolis can be suggested to be of ecological significance because it reduces interspecific competition and because it allows the various species to adapt more precisely to different parts of the available habitat. Thus members of a genus may exploit the habitat more efficiently.
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01 Jan 1964
TL;DR: The life of the rainbow lizard , The life of a rainbow lizard, مرکز فناوری اطلاعات £1,000,000 ($2,000; £1,500,000)
Abstract: The life of the rainbow lizard , The life of the rainbow lizard , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی
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"The Ecological Significance of Sexu..." refers background in this paper
...On the basis of essentially the same pattern of staining, other investigators have reached the same conclusion (3, 4), or have attributed staining additionally or alternatively to the processes of the bipolar cells (5, 6), the ganglion cells (4, 5), or centrifugal fibers from the optic nerve (7)....
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...A greater proportion of large insects were found in larger adult males than in adult females of Anolis lineatopus and Agama agama (4, 5); similarly, juveniles take smaller food than adults (5-7)....
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