Anuran Communities Research Articles

Does Foraging Activity Change with Ontogeny? An Assessment for Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

Does Foraging Activity Change with Ontogeny? An Assessment for Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

Direct and indirect effects of the introduced toad Bufo marinus (Anura: Bufonidae) on populations of native anuran larvae in Australia

Introduced species are frequently believed to have adverse effects on native biota and ecosystems. However, much of our knowledge of the ecological impacts of introduced species is anecdotal, and the mechanisms controlling these effects are often poorly understood. I used replicated artificial pond experiments to investigate the impact of eggs and hatchlings of the introduced toad Bufo marinus on populations of native anuran larvae (Limnodynastes ornatus and Litoria rubella) in Australia. Bufo marinus eggs and hatchlings are highly toxic to predatory native tadpoles. Under naturalistic conditions, populations of predatory L. ornatus tadpoles experienced significantly reduced survival when exposed to Bufo eggs and hatchlings. The impact of Bufo on L. ornatus survival was positively correlated with Bufo density. However, the toxic effects of Bufo on L. ornatus indirectly facilitated the survival of later‐breeding L. rubella by altering predator‐prey interactions between L. ornatus and L. rubella. Limnodynastes ornatus tadpoles are voracious predators of L. rubella eggs and hatchlings. Consequently, the negative impact of Bufo on populations of L. ornatus tadpoles reduced the intensity of predation by L. ornatus tadpoles on L. rubella eggs and hatchlings, thereby increasing L. rubella survival. The results demonstrate that B. marinus plays an important role in structuring native larval anuran communities via direct and indirect mechanisms, and that Bufo may have both negative and positive effects on populations of native anuran larvae. As far as I am aware, these are the first quantitative data to demonstrate that introduced fauna may affect populations of native biota via toxic effects.

Structure of an anuran community in a montane meadow in southeastern Brazil: effects of seasonality, habitat, and predation

AbstractIn order to assess the main factors influencing its structure, an anuran community was studied from August 1996 to July 1997, in a 1200 m high rocky meadow site at the Serra do Cipó, Minas Gerais, Brasil, a region with markedly seasonal climate. The study site included three temporary habitats: a stream, a puddle, and a swamp. Thirteen anuran species were recorded at the study site. Species of tadpoles differed in microhabitat as to their position in water column, annual occurrence period, and water flow in the occupied sites. Aquatic vegetation, depth and occupied habitat (stream, swamp, or puddle) were of secondary importance in telling species apart. Calling sites of males were distinguished based on occupied habitat and annual activity period. Most species started their reproductive activities at the onset of the rains, in an opportunistic way. Water availability in the habitat seems to be the most important factor affecting temporal distribution of reproductive activities in the anuran community. Competitive interactions could not be detected in the community. The most important tadpole predators recorded at the study site were belostomatid water bugs and dragonfly nymphs. Their abundance peaks occurred after those of tadpoles, as predicted for predator-prey populations with interconnected cycles. Mortality rates were high for tadpoles, and predation is the most likely cause. Differences recorded among species, considering time of occurrence, tadpole microhabitats, and male calling sites, may reflect distinct specific adaptations and preferences.

Direct and indirect effects of predation on tadpole community structure in the Amazon rainforest

Abstract The relationship between the distribution of predators (fish, odonates and water beetles) and prey assemblages (amphibian larvae) was investigated in the tropical rainforest of central Amazonas, Brasil. The anuran community uses a variety of waterbodies for reproduction, ranging from streams and streamside ponds to isolated forest ponds. Predators in this system include fish in streams and streamside ponds, and invertebrates (primarily odonate naiads and beetles) in forest ponds. Tadpole species richness and assemblage structure were related to fish density and species richness. No relationships between tadpole assemblages and abiotic pond characteristics were detected. The presence offish explained much of the variation in both species composition and species richness within and among ponds. Some species of tadpole were consistently found to coexist with high densities of fish. Path analyses suggest that while fish have a strong direct effect on tadpole associations and species richness, they also have an indirect effect through invertebrate predators (odonate larvae and coleopteran beetles). Prey survival‐strategies such as palatability and behaviour may explain how tadpole species composition is affected by predators at the community level. These findings suggest that the observed patterns of habitat use by larval anurans may be structured in response to the distribution of key predators (fish) in this system.

Interspecific competition between larvae is not an important strncturing force in mixed communities of Rana and Bufo on an English sand‐dune system

We investigated the roles of competition and predation in the structuring of mixed anuran communities (Rana temporaria and Bufo bufo) in an English sand‐dune system. Rana temporaria breeds earlier in spring than B. bufo. but the latter species was numerically superior in all ponds at the study site. We measured survival and growth rates of larvae in three duplicate sets of natural ponds. In one set we removed B. bufo spawn, leaving only R. temporaria: in a second sel we removed R. temporaria spawn, leaving only B. bufo: and in a third set we left boih together. The third set also contained substantial numbers of predatory fish (Perea fluviatilis and Gasterosteus aeuleatus). Rana temporaria survival was lower than that of B, bufo in all ponds, on average by sixfold. Rana temporaria fared better on its own than in the mixed‐species ponds, but lower survival in the latter ponds was probably due to fish predation rather than to Inierspecific competition. By eonlrast, B. bufo survival was sevenfold higher in mixed‐species compared with single‐species ponds, probably because they are distasteful to fish and thus benefited indirectly from fish‐predation of invertebrates, Protothieca rieharsi. a mediator of interference competition between anuran larvae under laboratory conditions, was present in some of the dune ponds but was not correlated with larval growth inhibition. Taken together the evidence implicated predation of larvae and intraspecific competition, rather than interspecific competition, as the dominant structuring forces in this community.

The Effects of Size on the Diets of Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

The Effects of Size on the Diets of Six Sympatric Species of Postmetamorphic Litter Anurans in Central Amazonia

Tadpole bullies: examining mechanisms of competition in a community of larval anurans

Tadpole bullies: examining mechanisms of competition in a community of larval anurans

Tadpole bullies: examining mechanisms of competition in a community of larval anurans

We examined interference competition during interspecific interactions of larval anurans to determine its importance. We conducted laboratory experiments to examine behavioral and chemical interference competition between tadpoles of the southern leopard frog (Rana utricularia) and those of the green treefrog (Hyla cinerea). Water preconditioned byR. utricularia tadpoles significantly decreased the growth and increased the mortality of H. cinerea tadpoles compared with control treatments. In addition, R. utricularia tadpoles inhibited the feeding rate ofH. cinerea tadpolesby harassing them, and these interactions significantly decreased the growth and increased the mortality of theH. cinerea tadpoles. Rana utricularia tadpoles apparently use both chemical interference and aggressive behavior in securing a competitive advantage over H. cinerea tadpoles, and the H. cinerea tadpoles suffer from these interactions. Intraspecific chemical and behavioral interference competition also significantly decreased the growth of larval H. cinerea. In natural ponds, R. utricularia tadpoles that inhibit the growth and increase the mortality of H. cinerea tadpoles may increase their own chances of survival and metamorphosis, while H. cinerea tadpoles that avoid interactions with conspecifics and with R. utricularia tadpoles may increase their own chances of survival and metamorphosis.

Seasonal variation in nocturnal calling activity of a savanna anuran community in central Brazil

AbstractWe studied the calling activity of a savanna anuran assemblage and correlated two climatic parameters, rainfall and air temperature, with anuran calling. We made observations from September 1991 until March 1993 and quantified nocturnal calling activity by counting the number of calling males for each species present in a permanent pond. Bufo paracnemis had the shortest calling activity period and Physalaemus cuvieri had a seasonal calling period, lasting a maximum of four months. Diversity of calling males and species richness reached a peak in the first three months of the rainy season. Comparisons with other populations indicate that the reproductive period of P cuvieri varies along its geographical distribution in a manner related to regional climatic conditions.

Changes in the Composition of a Ranid Frog Community Following Bullfrog Extinction

-Natural experiments have often shown that lowered competition or predation results in patterns of ecological release, density compensation, or predatory release of target species. At Point Pelee National Park, Ontario, Canada, from 1992 to 1994, we conducted extensive surveys of habitats to document patterns of relative abundance and distribution of amphibians and to compare these patterns with those documented in studies conducted in 1972 and 1991. Bullfrogs (Rana catesbeiana) have not been observed since spring 1990 and are now considered to be locally extinct in the park. Relative abundance of the green frog (R clamitans) has increased 4X since bullfrog extinction. Similarities in the natural history of bullfrogs and green frogs suggest that interactions should be greatest between this pair. The predaceous habits of bullfrogs are well-documented, and the experimental literature suggests that bullfrogs and green frogs are competitors. Changes in the pattern of ranid relative abundance that we observed suggest that the bullfrog is important in structuring amphibian communities.

Anuran egg predation and heterocannibalism in a breeding community of East African frogs

This is the first published account of a terrestrial anuran exhibiting interspecific egg predation. Adults of both sexes of Afrixalus fornasinii (Bianconi 1849) prey on the eggs and developing larvae of Chiromantis xerampelina Peters 1854, Hyperolius (probably H. tuberilinguis Smith 1849), and also the eggs of conspecifics. A. fornasinii is the first African anuran known to exhibit predation upon conspecifics' eggs (heterocannibalism). Data on the appearance of species over time are given for a breeding site in a coastal East African forest. The delayed appearance of A. fornasinii at breeding sites during the rainy season may be synchronized to take advantage of terrestrial egg masses deposited earlier by other species. We suggest that the unique leaf-gluing mode of egg deposition in the genus Afrixalus Laurent 1944 may serve as defense against intraspecific egg predation.

Fedundity and breeding sites of an anuran community in a seasonal tropical environment

At Panguana, a study site in Amazonian Peru, the anuran community consists of 73 species. As evidence of the diversity of this community, the snout‐vent length of 48 species ranged from 14.2 mm (Eleutherodactylus carvalhoi) to 180.0 mm (Leptodaclylus pentadactylus) and the ovarian complement of 40 species from 5 (Dendrobates quinquevittatus) to 2431 eggs (Bufo typhonius) (type 1). Seasonality of rainfall at Panguana affected the breeding patterns of the anurans by limiting the availability of aquatic sites. Because of their different modes of reproduction the frogs were unevenly dispersed at these breeding sites. Explosive breeding at the beginning of the rainy season is characteristic for the seasonal environment of Panguana.

Structure et organisation du peuplement d ’Anoures de Cocha Cashu, Parc National Manu, Amazonie péruvienne

The structure, relative abundance and density of the anuran community of Cocha Cashu, in the amazonian rainforest of Peru (350 m, 11° 55' S, 71° 18' W, Manu National Park) was studied during 395 days of field work, from September 1985 to November 1989. The study compared the two major types of upper amazonian habitats, floodplain forest and upland forest. The entire assemblage is composed of 81 species (Table I). There are more diurnal species in the upland forest than in the floodplain forest. Although each type of habitat has twenty terrestrial species and twelve food specialists, mainly ant eaters, these guilds account for significantly different proportions on each of the assemblages (Tables II and III). Sixty six species (out of 71) were observed in 250 days of transect sampling in the floodplain, whereas 49 species were counted in only 55 days on the uplands (Fig. 9) ; ten of these species do not occur in the floodplain and 39 are common to both habitats. Although relative abundance curves of both habitats are similar (Fig. 1 0), relative abundances of the 39 shared species differ significantly for each type of habitat (Fig. 1 1). Most of the Anuran species are small. Mean males’ Snout-Vent-Length ranges from 13.5 mm in Eleutherodactylus cf. carvalhoi to 136 mm in Leptodac-tylus pentadactylus, and at least 80 % weigh less than 10 g (Table V). None of the species accounts for more than 1 5 % of the relative abundances in floodplain or in the upland, suggesting a rather equitable distribution of abundance. No significant differences between the two types of habitats were found in terms of numbers of species, grouped by mode of reproduction (Table V). However, when relative abundance of individuals grouped by mode of reproduction were compared, all but the species laying their eggs in vegetation overhanging water and those building terrestrial foam nests without free tadpoles, showed significant differences (Table VI). The Cocha Cashu floodplain data are compared to those from Santa Cecilia (Ecuador, 350 m, 0° 03' N 77°11'W), the richest site in Anuran species (87 species) until now. There are no differences in the number of species by mode of reproduction, but, except for the Dendrobatidae, all relative abundances of individuals by mode of reproduction differ significantly between the two sites (Tab. VII). Densities were estimated by two methods : 219 censuses of male calling activity of ten forest breeding species (Table VIII), and 80 forest litter plots. Densities estimated by these two methods did not coincide. Plots revealed an uneven distribution of frogs in the forest and densities similar to other amazonian sites, but lower than those estimated for Central America (Table XI). Although most species were observed on transects, pit-fall traps were effective on catching active nocturnal terrestrial species not easily observed by other methods (Table XII). None of the methods used here to estimate diversity or density are efficient enough to sample adequately the entire community. The possible causes of the anuran species richness at Cocha Cashu are briefly discussed. The number of species at Cocha Cashu and Santa Cecilia being very similar (respectively 81 and 87 species) despite the striking differences in rainfall regime between the two sites, high atmospheric humidity cannot be considered as the only determinant of the high species diversity of anurans in tropical rainforests. The importance of historical factors, and more particularly of the effect of river dynamics on the heterogeneity of the Upper Amazonian environment, is emphasized.

Reproductive Phenology, Population Structure, and Habitat Use of the Frog Eleutherodactylus johnstonei in Barbados, West Indies

-I report on population structure, growth, reproduction, and use of retreats by an abundant but poorly-known terrestrial frog, Eleutherodactylus johnstonei, in two contrasting habitats in Barbados, West Indies. A population inhabiting a forest site exhibited early maturity, small adult body size, short residency time, high juvenile to adult ratio, and low density, when compared to a population inhabiting an untended flower bed. At both sites, reproduction peaked in the early part of the wet season (JuneAugust), but males called about a month later in the flower bed site. Most growth took place during the wet season, and growth rates did not differ between sites. I suggest that both quality and quantity of retreat sites and the length of time available for activity are key factors in shaping life history characteristics of E. johnstonei at these sites. urnal of Herpetology, Vol. 25, No. 4, pp. 424-430, 1991 yright 1991 Society for the Study of Amphibians and Reptiles roductive Phenology, Population St ucture, and Habitat Use of e Frog Eleutherodactylus joh stonei in Barbados, W t Indies Eleutherodactylus johnstonei is a widespread and abundant neotropical species, native to several islands in the Lesser Antilles (Schwartz, 1967, 1978; Hardy and Harris, 1979). It commonly inhabits disturbed areas but also occurs in mesic, mature forests (Schwartz, 1967). Stewart (1979) and Stewart and Martin (1980) examined the role of introduced Eleutherodactylus (including E. johnstonei) in anuran communities in Jamaica, but life history of E. johnstonei in the Lesser Antilles is poorly known. Bayley (1950) studied its natural history, and Lemon (1971) investigated spacing of calling males in Barbados. Here I report on population structure, reproductive phenology, growth, and habitat use by 'Present Address: Department of Zoology, The University of British Columbia, Vancouver, B.C., Canada V6T 1W5. leutherodactylus johnstonei is a widespread and ndant neotropical species, na iv to several lands in the L sser Antilles (Schwartz 1967, 78; Hardy and Harris, 1979). It c mmonly inE. johnstonei in two habitats in Barbados, where the species is probably indigenous (Marsh, 1982; but see Schwartz, 1967). My objective was to examine intraspecific variation between populations occupying contrasting habitats. One study site was in a flower bed, and the other site was in a mature forest along a seasonallyactive stream. Based on the abundance of potential retreat sites due to the dense ground vegetation in the flower bed, I predicted that it would support a greater density of frogs with higher individual growth rates and a longer breeding season than the forested site.

A survey of the reptiles and amphibians of Bondi State Forest and surrounding areas, near Bombala, New South Wales

Reptiles and amphibians in and around Bondi State Forest were surveyed between 1980 and 1984. Nineteen species of reptiles and 15 species of frogs were recorded from Bondi State Forest. Five additional reptiles and two additional frogs were recorded from surrounding areas. Bondi State Forest has elements of both warm and cool temperate fauna. The conservation of reptile and frog communities in this area does not depend upon reservation of large areas of forest habitat. Rather, small reserves may be adequate to conserve populations of most species. Existing riparian strips and retained coupes are probably adequate to conserve viable populations of most species of reptiles and frogs in the area.

The ecomorphology of Bornean tree frogs (family Rhacophoridae)

Ecomorphological studies generally assume a causal relationship between morphology and ecology mediated by performance. That assumption was tested in a community of Bornean tree frogs of the family Rhacophoridae. Biomechanical models allow a priori predictions about expected intra- and interspecific correlations among toepad area, hind-limb length, body mass, sticking ability, jumping distance, microhabitat, vertical height and substrate. Both intra- and interspecifically, size and shape variables showed patterns of association with ecology predicted on the basis of maintaining relative as well as absolute levels of performance. Unexpectedly, the form-function relationship between toepad area and sticking ability differed intra- and interspecifically. These findings indicate the need for more empirical work examining morphology-performance relationships and their use in ecology.

Vocal Diversity in Frogs of the South American Temperate Forest

Mating calls and other vocalizations emitted in breeding areas by 11 leptodactylid and rhinodermatid species of the temperate austral forest in Chile were analyzed. Assemblages of sympatric calling species were always composed of a small number of species (4 maximum), which results in a simple acoustical environment relative to anuran communities in tropical rainforests. Acoustical separation among species is assured by differences in spectral and temporal components of the calls and diverse preferences for calling sites. Dominant frequencies were related to species size. The limited number of congeneric species coexisting in sympatry and the lack of mating calls in species of three leptodactylid genera con- tributes to the simplicity of the acoustical environment in southern Chile. Modes of call variation within and among genera suggest that the extant vocal diversity in this batrachofauna may have arisen during the course of independent evolutionary histories and that interactions among sympatric taxa have had a

Changes in the composition of mountain stream frog communities in the Atlantic mountains of Brazil: Frogs as indicators of environmental deteriorations?

Observations during the past 15 years on mountain stream breeding frogs in the Atlantic Mountains around Santa Teresa in the State of Espirito Santo, Brazil, indicate that some species, in particular the Hylodinae and Cycloramphus fuliginosus, have disappeared after 1981. The most likely causes for these extinctions were some extremely dry winters. However, similar extinctions reported by Heyer et al. (1988) from the states of Rio de Janeiro and Sao Paulo suggest that there might be an unknown common underlying cause, and the acidity of the stream water makes acid rain one of the possible causes.

Ecology and Calls of Four Species of Amazonian Forest Frogs

First data on breeding biology and vocalization by the primary forest dwelling frog species Osteocephalus buckleyi, Chiasmocleis shudikarensis, Bufo dapsilis, and Leptodactylus rhodomystax, was obtained in the Central Amazon of Brazil in 1980, 1983, 1984, and 1985. Breeding habitat requirements of these species are quite specialized and emphasize the need for more ecological information on Amazonian forest frog species if efforts to preserve them in forest reserves are to be effective. Calling by Osteocephalus buckleyi and Chiasmocleis shudikarensis and Bufo dapsilis demonstrates certain vocal behaviors exhibited extensively by Amazonian forest frog species which may reflect predator avoidance strategies. A field survey of the frogs in the Insti- tuto Nacional de Pesquisas de Amazonica- World Wildlife Fund (U.S.) (I.N.P.A.- W.W.F.) primary forest reserves near Ma- naus in the Central Amazon of Brazil is part of I.N.P.A.-W.W.F.'s Minimum Crit- ical Size of Ecosystems (M.C.S.E.) project. The objectives and methods of the M.C.S.E. project are outlined in Lovejoy et al. (1984) and Lewin (1984) but basically, the project is an attempt to understand the ecology of primary Amazonian rainforest. Informa- tion on how plants and animals respond to restriction within forest fragments of different size will be used as the basis for conservation planning and design of na- ture reserves and national parks. The main goals of M.C.S.E.'s frog sub- project are to identify all species of primary forest frogs present in the I.N.P.A.-W.W.F. area, their habitat requirements for breed- ing, and their normal distributions and abundances within undisturbed primary forest. These data are needed to discern the effects of isolation within forest islands on breeding populations of frogs. An impor- tant tool used in the survey is knowledge of species vocalizations because most species of Amazonian forest frogs are dif- ficult to locate visually. An acoustic species list greatly extends the range of a survey and aids immeasurably in identification of habitat preferences and learning about the general ecology of the animal. Therefore all types of vocalization by a species are recorded and vocal patterns observed. First results of the anuran survey are presented in Zimmerman and Hodl (1983), Zimmer- man (1983), Zimmerman and Bogart (1984), and Zimmerman and Bierregaard (1986). The present study considers the identi- fication, ecology, and acoustics of four species of Amazonian forest frogs about which little or nothing was previously known: Osteocephalus buckleyi, Chiasmocleis shudikarensis, Bufo dapsilis, and Leptodactylus rhodomystax. Breeding biology and vocal behavior of these species illustrate certain characteristic features of the forest anuran community such as specificity of breeding habitat, infrequency of breeding, and in- frequent calling. The requirement of spe- cialized breeding habitat by many species and opportunistic breeding observed in some species has important implications for conservation. The widespread use of vocal patterns such as synchronized cho- rusing and low calling rates among forest frogs is interpreted as a predator avoidance strategy.

Within-Habitat Relationships Between Invading Bufo-Marinus and Australian Species of Frog During the Tropical Dry Season

Four tropical Australian frog species do not alter their dry season patterns of habitat and/or food utilisation following invasion by introduced Bufo marinus. Breadths of utilisation of habitat and food resources by B. rnarinus are less than those of one or more native species. Levels of overlap of resource use between B. marinus and native frog species are not different from those occurring among the native species. Differences in body sizes of native species and B. marinus are not related to levels of resource overlap. The population sizes of individual species, species richness and equitabilities of native frog communities in the dry season are not influenced by the presence of B. marinus. B. rnarinus has no observable impact on recovery of native frog communities or populations following experimental perturbation. At the time of year when resources are likely to be most limiting (the dry season), B. marinus is a relatively 'narrow-niched' invader with no measurable competitive impact on a native frog community that may be in a state of disequilibrium.