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: It is shown that the Mediterranean habitats of Chile, Spain and California are characterized by similar size distributions of small mammal species available to raptors, and that these prey resources are exploited by taxonomically related assemblages of owl species that exhibit similar distributions of body size.
Abstract: We show that the Mediterranean habitats of Chile, Spain and California are characterized by similar size distributions of small mammal species available to raptors, and that these prey resources are exploited by taxonomically related assemblages of owl species that exhibit similar distributions of body size. Barn owls (Tyto alba) in the three mediterranean areas are similar in that they take almost every small mammal species present. However, Spanish barn owls differ from those in Chile and California in that they take significant amounts of insects, amphibians and reptiles, and also in that the mean size of mammalian prey in their diet is considerably smaller than that for Chilean and California barn owls. These features are attributed to the reduced abundance of larger-sized small mammals in Spain, which presumably forces the barn owls to prey more heavily on the smallest mammals available and also on low-reward nonmammalian prey. The trophic parameters of barn owls in a Colorado grassland fall well within the range of variation exhibited by mediterranean barn owls and this is, associated with size distributions of mammalian prey and of syntopic owls which are similar between the two habitat types. The essential features determining the predation pattern of the barn owl in different parts of its range seem to be the statistical distribution of mammalian prey sizes available, the relative abundance of these prey and the configuration of the assemblage of syntopic owls.
58 citations
TL;DR: The activity, thermal ecology, habitat use, and diet of this species were studied in the region of Valinhos, Sao Paulo State, Southeastern Brazil, an area with a highly seasonal climate and suggests that this lizard thermoregulates.
Abstract: -Mabuya frenata is a relatively common skink in the region of Valinhos, Sao Paulo State, Southeastern Brazil, an area with a highly seasonal climate. The activity, thermal ecology, habitat use, and diet of this species were studied in the vincinity of Valinhos. Lizards were active throughout daylight periods, but the activity pattern differed among seasons, being more uniform in the rainy season than in the dry season. The mean body temperature of active M. frenata was 31.6 + 3.2 C and was correlated with air and substrate temperatures, although direct insolation may also be an important heat source for this lizard. Unlike environmental temperatures, the mean activity temperature of M. frenata did not differ among seasons, which, combined with field observations, suggests that this lizard thermoregulates. The microhabitat preferred for M. frenata was granitic boulders. The diet included a great variety of arthropods, although termites were the dominant items. The diet of M. frenata did not differ between sexes nor among seasons and was related to prey availability in the environment urnal of Herpetology, Vol. 32, No. 2, pp. 229-237, 1998 pyright 1998 Society for he Study of Amphibians and Reptiles e Ec logy of the Skink Mabuy frenata in an Area of Rock tcrops in South aste n Brazil Despite the fact that the scincid genus Mabuya contains about 13 South American species, most of which are abundant and widely distributed, few ecological studies have been carried out on these skinks in South America. Among the most recent of these are the autecological studies of Vitt and Blackburn (1991), and Vrcibradic and Rocha (1995, 1996) and those of Vitt and Blackburn (1983) and Blackburn and Vitt (1992) on reproductive patterns. Several other studies conCorresponding Author: E-mail: cfdrocha@uerj.br t in miscellaneous comments on the ecology of different South American Mabuya species (e.g. Fitch, 1968; Gallardo, 1968; Vanzolini and Rebouqas-Spieker, 1973, 1976; Vitt, 1991, 1995; Sazima and Haddad, 1992; Avila-Pires, 1995; Rocha and Vrcibradic, 1996; Vitt and Zani, 1996). The great majority of these studies have been carried out in Brazil, where most of the South American Mabuya species occur. Some aspects of the ecology of Brazilian Mabuya are fairly conservative among species: they usually have similar activity patterns (Vitt and Blackburn, 1991; Vrcibradic and Rocha, 1995, 1996), thermal ecol229 This content downloaded from 207.46.13.160 on Mon, 17 Oct 2016 05:19:36 UTC All use subject to http://about.jstor.org/terms D. VRCIBRADIC AND C. F. D. ROCHA ogies, and body temperatures (Vitt and Blackbur, 1991; Vrcibradic and Rocha, 1995; Rocha and Vrcibradic, 1996) and consume a wide spectrum of prey (Vitt and Blackburn, 1991; Vitt, 1995; Vrcibradic and Rocha, 1995, 1996), although there is considerable interspecific variation in microhabitat preferences (Vrcibradic and Rocha, 1996). Mabuya frenata, the subject of this study, reaches an adult snout-vent length of 75-90 mm and occurs in open areas of South America, from central-western and southeastern Brazil to Bolivia, Paraguay, and Argentina (Peters and Donoso-Barros, 1986; Norman and Naylor, 1994). In spite of its wide distribution, published information on its ecology is scarce and mostly anecqdotal (Gallardo, 1968; Vitt, 1991; Sazima and Haddad, 1992). Apart from this fact, we chose to study this species because it is characteristic of "cerrado" habitats and, while there is some information available on the ecologies of Mabuya species from the Amazonian rainforest (Vitt and Blackburn, 1991), caatinga (Vitt and Blackbur, 1983; Vitt, 1995) and from coastal open sand-dune habitats (restingas) (Vanzolini and Reboucas-Spieker, 1976; Vrcibradic and Rocha, 1995; Rocha and Vrcibradic, 1996), there is a lack of ecological data on Mabuya species in cerrado areas [except for some few data on M. frenata in a cerrado area of central Brazil, in the context of the local lizard community (Vitt, 1991)]. Although our study area is an altered environment, it is located within the "cerrado" morphoclimatic domain and it houses a fairly large population of M. frenata. In this study, we investigate the thermal ecology, activity patterns, microhabitat use, and diet of M. frenata in an area where it is relatively abundant, and make comparisons with other Mabuya species. MATERIAL AND METHODS Study Area.-This study was conducted in a grassland area in Valinhos municipality (22?56'S, 47?55'W), Sao Paulo state, southeastern Brazil. The climate of the region is markedly seasonal, with a warm and rainy season from October to March and a cold and dry season from April to September (Van Sluys et al., 1994). The mean annual temperature is 20.7 ? 2.2 C and the total annual rainfall is 1300-1400 mm (Van Sluys, 1991; Van Sluys et al., 1994). This area has been used for some time as pasture and little is known about its original vegetation, which has been greatly altered during successive years of anthropic disturbance (Van Sluys, 1991). Vegetation of the area is presently dominated by species in the Malvaceae, Compositae, and Verbenaceae. There are numerous gr nitic boulders in the area, scattered along the surface of the hills. Collecting Methods and Analysis.-Lizards were collected monthly from December 1993 to December 1994 with an air rifle. Within 30 sec of capture, each lizard's body temperature (Tb) and the temperatures of the air (Ta; at 1 cm above the point where the lizard was originally sighte ) and of the substrate (T) on which it was sighted, were recorded. Body and air temperatures were measured with a Schultheis quickreading thermometer (read to the nearest 0.2 C); substrate temperatures were taken with a Schultheis bi-metal surface thermometer (read to the nearest 1.0 C). The time of collection of each lizard was recorded. Monthly observations of lizard activity were mad during 15-min periods within each hourly interval from 0700 to 1800 h. The number of active lizards counted during each interval was used to estimate daily activity patterns. Those observations were conducted in a sub-area adjacent to that where collections were made, but separated from it by about 100 m. No collections were made in that sub-area, because the continuous removal of lizards could affect the results of ou observations on their daily patterns of ac-
57 citations
01 Jan 1997
TL;DR: Although inter- and intraspecific correlations exist among the number of lamellae on different toes of the fore- and hindfeet, examining the number on a single toe may be insufficient for ecomorphological analyses.
Abstract: We investigated whether a relationship exists between the number of lamellae and the height and diameter of perches utilized by a diverse set of anoline lizards. Although the number of lamellae on both the fore- and hindfoot is related to both ecological variables, these results are confounded by body size. When the effect of size is removed, the number of lamellae is related to perch height, but not perch diameter. When the data are analyzed in a phylogenetic framework, results are similar, but only the number of lamellae on the forefoot is related to perch height. Consequently, although inter- and intraspecific correlations exist among the number of lamellae on different toes of the fore- and hindfeet, examining the number of lamellae on a single toe may be insufficient for ecomorphological analyses.
56 citations
TL;DR: For the population, the volume of food taken across seasons appeared sufficient to increase energy reserves during the dry season and maintain body weight during the wet season and no body weight loss between seasons for any age-sex class of lizards.
Abstract: A stomach analysis of 340 lizards collected in 33 samples over a 12 month period showed that Anolis opalinus eats arthropods, primarily ants by number (70%). By volume, however, ants comprised only 12% of the food bulk, with lepidopteran larvae and orthopterans being the main food items (46%). The lizards fed predominantly on soft bodied prey, except for ants. We found almost no evidence for food niche partitioning in the size dimorphic A. opalinus. All age and sex classes of lizards had eaten similar sized prey and prey taxa. When a significant difference was detected among classes, it was frequently the smaller lizards which had eaten the larger prey. In fact, season had more effect on diversifying the diet than did size of the lizards' trophic structures (i.e., mouths) or any possible feeding preferences. Niche overlap indices for prey length (0.86-0.94) and prey taxa (0.82-0.93) among all age-sex classes ran higher than those reported for a mainland anole with almost no sexual size dimorphism. Comparison of variables between the seasons (dry-Nov.-Mar., wet-AprilOct.) showed that lizards tended to ingest about the same volume of food (approx. 17 mm3 of food/g of lizard body wt). However, lizards ate more, but smaller prey in the dry season and fewer, but larger prey in the wet season. Relative fat body and liver weights were highest in the dry season and lowest in the wet season. Adult males and especially adult females experienced the greatest weight loss in these energy reserve organs; this was attributed in part to breeding activities. Coefficient of condition calculations (body wt/SVL) showed no body weight loss between seasons for any age-sex class of lizards. For the population, the volume of food taken across seasons appeared sufficient to increase energy reserves during the dry season and maintain body weight during the wet season.
56 citations
TL;DR: Results indicate that when in allopatry, M. evotis and M. auriculus have similar food habits, and competition for food is avoided by changes in food preferences of M.evotis .
Abstract: Two extremely similar insectivorous bats, Myotis evotis and M. auriculas , differ in food preferences when sympatric (Black, 1974). Myotis auriculus preys generally upon moths and some beetles, whereas M. evotis specializes on beetles. Does this specialization of M. evotis persist in allopatry, indicating that it has evolved as a food specialist, or in the absence of its close competitor, does it eat both moths and beetles without a strong preference? What sort of effect, if any, does M. evotis exert on the diet of M. auriculus in areas of sympatry? Both species were captured in areas of allopatry during the summer of 1972. Fecal samples were collected and analyzed using Black's (1974) technique. My results indicate that when in allopatry, M. evotis and M. auriculus have similar food habits. Thus, in sympatry, competition for food is avoided by changes in food preferences of M. evotis . Furthermore, each species exhibits sexual differences in foods taken in areas of allopatry, indicating that intraspecific niche subdivision occurs in each of these bats only in the absence of the potential competitor.
55 citations
References
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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.
218 citations
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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
119 citations
"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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