Presence Of Tadpoles Research Articles

Inducible offences affect predator–prey interactions and life‐history plasticity in both predators and prey

Phenotypic plasticity can have strong impacts on predator-prey interactions. Although much work has examined the effects of inducible defences, less understood is how inducible offences in predators affect predator-prey interactions and predator and prey phenotypes. Here, we examine the impacts of an inducible offence on the interactions and life histories of a cohort of predatory Hynobius retardatus salamander larvae and their prey, Rana pirica tadpoles. We examined larval (duration, survival) and post-metamorphic (size) traits of both species after manipulating the presence/absence of tadpoles and salamanders with offensive (broadened gape width) or non-offensive phenotypes in pond enclosures. Offensive phenotype salamanders reduced tadpole survival and metamorph emergence by 58% compared to tadpole-only treatments, and by over 30% compared to non-offensive phenotypes. Average time to metamorphosis of frogs was delayed by 30% in the presence of salamanders, although this was independent of salamander phenotype. Thus, offensive phenotype salamanders reduced the number of tadpoles remaining in the pond over time by reducing tadpole survival, not by altering patterns of metamorph emergence. Offensive phenotypes also caused tadpoles to metamorphose 19% larger than no salamander treatments and 6% larger than non-offensive phenotype treatments. Pooled across salamander treatments, tadpoles caused salamanders to reach metamorphosis faster and larger. Moreover, in the presence of tadpoles, offensive phenotype salamanders metamorphosed 25% faster and 5% larger than non-offensive phenotype salamanders, but in their absence, neither their size nor larval period differed from non-offensive phenotype individuals. To our knowledge, this study is the first to demonstrate that inducible offences in predators can have strong impacts on predator and prey phenotypes across multiple life stages. Since early metamorphosis at a larger size has potential fitness advantages, the impacts of offensive phenotypes on frog and salamander life histories likely have significant consequences for individuals and populations. Furthermore, increased predation on tadpoles likely causes offensive phenotype individuals to have strong impacts on pond communities. Future studies should examine the fitness consequences of morphological and life-history plasticity across multiple life stages and should address the population and community level consequences of offensive phenotypes.

Mechanisms of competition between tadpoles of Australian frogs (Litoria spp.) and invasive cane toads (Rhinella marina)

Summary Cane toads (Rhinella marina) have wrought considerable ecological damage during their invasion of tropical Australia, spurring the search for novel ways to reduce toad numbers. Previous laboratory and field studies have shown that the tadpoles of native frogs, which often co‐occur with toad tadpoles in temporary waterbodies, compete with the invaders and can suppress their survival, growth and development. Understanding the mechanisms responsible for that competitive suppression might suggest new ways to control toads: for example, a chemical produced by native tadpoles that disrupts toad development. Our laboratory experiments confirm that toad tadpoles are negatively affected by the presence of tadpoles of three native hylid frogs (Litoria caerulea, Litoria longipes and Litoria splendida) and identify direct exploitative competition for food as the primary mechanism. Manipulations of chemical cues and visual cues in the water had no significant effects on the viability of toads, whereas manipulations of direct physical contact and food supply relative to tadpole density had strong effects. The lack of chemically mediated interference competition may reflect the very short timescale of sympatry between the invader and native taxa, restricting opportunities for the evolution of such mechanisms. Re‐introducing native anurans to anthropogenically degraded sites (especially those where local frogs previously occurred, but have been lost) may provide a simple and effective way to reduce the recruitment rate of invasive cane toads.

Fish Influences on Amphibian Presence and Abundance in Prairie and Parkland Landscapes of Minnesota, USA

Many amphibian populations are declining, and increased understanding of the drivers of amphibian presence and abundance will help in their conservation. In 2005 and 2006 we estimated relative abundance of larvae of two common amphibian taxa, Tiger Salamanders (Ambystoma tigrinum) and ranid tadpoles (Northern Leopard Frog Lithobates pipiens and Wood Frog Lithobates sylvaticus), in 75 shallow lakes in prairie and parkland areas in Minnesota. We used a two-step procedure in which we first modeled presence-absence with data from all lakes and then modeled abundance only in lakes where the amphibian taxa were present. For the two amphibian taxa, a generalized linear mixed effects model was used to examine the effects of dynamic factors like fish abundance and static (timeframe of study) variables like fish community type, depth, and adjacent land cover. Fish variables had the greatest influence but differed for the presence and abundance models. Salamander and tadpole presence was inversely correlated to the abundance of benthivorous fish, while salamander abundance was best explained by total fish abundance and tadpole abundance by fish community type. We did not detect influences of land cover types on the amphibian taxa we surveyed. Our findings are important because they complement previous studies documenting that negative correlations with fish extend beyond piscivores to include both planktivores and benthivores. Hydrological changes in our study landscape (e.g., installation of drainage networks, wetland consolidation) associated with agriculture and other land uses have likely increased the distribution and abundance of fish populations, thus dampening amphibian breeding success.

Larval interactions with an invasive species (the Cane ToadRhinella marina) affect life-history traits in an Australian anuran (the Marbled FrogLimnodynastes convexiusculus)

The viability of a metamorph anuran can be influenced by its body size and the time it has taken to complete larval development. In a laboratory experiment, we show that the presence of tadpoles of the invasive Cane Toad Rhinella marina causes tadpoles of a native frog (Marbled Frog Limnodynastes convexiusculus) to metamorphose later and at smaller sizes. These effects may render frog metamorphs more vulnerable to desiccation and predation, but render them less vulnerable to Cane Toads. Marbled Frogs prey upon other anurans, including the highly toxic Cane Toad metamorphs. Small, late-emerging metamorph frogs are unlikely to encounter metamorph toads small enough to ingest; and hence, are less likely to be fatally poisoned by consuming the toxic invader. Developing in the presence of larval Cane Toads thus increases the native taxon's ability to survive the presence of toads postmetamorphosis. Predicting the ecological impacts of an invasive species on native taxa with biphasic life histories (such as mos...

Reproductive dynamics of three amphibian species in Mediterranean wetlands: the role of local precipitation and hydrological regimes

Summary1. Although the influence of water availability and precipitation regimes on amphibians has been studied at large scales, whether and how interannual rainfall and hydrological variations affect amphibians dynamics at a local scale have rarely been addressed. In this respect, accounting for variations in species detectability in space and time has also been overlooked.2. We assessed the effects of rainfall and hydrological variations on the breeding dynamics of three amphibian taxa: Pelodytes punctatus, Hyla meridionalis and Pelophylax spp. in 20 ponds of the Camargue region (southern France) over a 7‐year study period.3. We used multiple season occupancy models to test the effect of winter–spring rainfall and interannual variations in hydroperiod, mean water depth and drought events on tadpole presence in spring (March–June), a proxy for breeding dynamics.4. We used an independent survey with spatial replicates (dipnet sweeps) to disentangle the relative contributions of phenology and detectability to the absence of records in a given month. For the three taxa considered, the probability of missing a species when that species was actually present in a pond was most often negligible. Hence, we could consider that multiseason models properly tracked changes in species phenology.5. Pelodytes punctatus was first detected in March, while the two other taxa appeared later in April. Hyla meridionalis appeared as a mid‐season species with much more synchronous pond occupancy than Pelodytes punctatus. The detection peak of Pelophylax spp. was short and unexpectedly early for this taxon.6. Seasonal winter–spring rainfall was associated with a decrease in extinction rates and even more strongly with an increase in colonisation rates at individual ponds.7. Colonisation rate increased following an annual drought and was best modelled as a negative quadratic effect of the variance of pond hydroperiod. Extinction probability was best modelled by a negative quadratic effect of mean water level. Hence, breeding was more stochastic (i) in unpredictable and shallow ponds because of yearly drying up and (ii) in highly predictable and deep ponds, possibly due to the presence of predators such as fish and crayfish.8. Overall, we show that ponds with intermediate rather than extreme variations in environmental conditions currently correspond to optimal breeding sites. Our study demonstrates that amphibian monitoring coupled with fine‐scale analysis of environmental conditions is necessary to understand species dynamics in the long run and to inform conservation efforts for these species.

Effects of road deicer (NaCl) and amphibian grazers on detritus processing in pond mesocosms

Road deicers have been identified as potential stressors in aquatic habitats throughout the United States, but we know little regarding associated impacts to ecosystem function. A critical component of ecosystem function that has not previously been evaluated with respect to freshwater salinization is the impact on organic matter breakdown. The purpose of this study was to evaluate cumulative effects of road deicers and tadpole grazers on leaf litter breakdown rate (g d(-1) ) and microbial respiration (mg O(2) g leaf(-1) h(-1) ). To test this interaction, in May 2008 the authors added dry leaf litter (Quercus spp.) to forty 600-L pond mesocosms and inoculated each with algae and zooplankton. In a full-factorial design, they manipulated a realistic level of road salt (ambient or elevated at 645 mg L(-1) Cl(-) ) and tadpole (Hyla versicolor) presence or absence. The elevated chloride treatment reduced microbial respiration by 24% in the presence of tadpoles. The breakdown of leaf litter by tadpoles occurred 9.7% faster under ambient chloride conditions relative to the elevated chloride treatment. Results of the present study suggest that the microbial community is directly impacted by road deicers and heavy tadpole grazing under ambient conditions limits microbial capacity to process detritus. Road salts and tadpoles interact to limit microbial respiration, but to a lesser extent leaf mass loss rate, thereby potentially restricting energy flow from detrital sources in pond ecosystems.

The smell of success: choice of larval rearing sites by means of chemical cues in a Peruvian poison frog

Parental care is a common strategy among vertebrates to ensure successful reproduction. Anuran amphibians have evolved a remarkable diversity of reproductive methods including advanced levels of parental care. Among the most derived strategies are those of the Neotropical poison frogs (Dendrobatidae). These amphibians exhibit a wide array of behavioural traits such as egg guarding, larval transport by parental frogs and larval feeding with trophic (unfertilized) eggs. Ranitomeya variabilis from the upper Amazon basin in Peru deposits both eggs and tadpoles in phytotelmata. The exploitation of these small pools is advantageous as it lowers the risk of predation, but it is more costly because of limited resource availability. Additionally, poison frog larvae are often cannibalistic, so the identification and avoidance of conspecifics represents an adaptive behaviour for these amphibians. While studies have shown that poison frogs actively avoid depositing with conspecifics, the mechanism for assessing pool quality remains unknown. In field experiments, we found that parental R. variabilis frogs used chemical cues to recognize the presence of tadpoles in phytotelmata. Furthermore, they distinguished between cannibalistic and noncannibalistic tadpoles, a behaviour that supports the survival of their own offspring.

The disappearance of the Stuttering FrogMixophyes balbusat Macquarie Pass National Park, New South Wales

We monitored a population of Stuttering Frog Mixophyes balbus tadpoles in Macquarie Pass National Park near Albion Park on the south coast of New South Wales. The species was initially detected by the presence of tadpoles at one site in 2000. Surveys thereafter were conducted at this site and the broader catchment of Macquarie Rivulet in an attempt to detect adults and or other tadpoles. Fifteen 250 m transects located along perennial creeks were surveyed at night for 30 min each and diurnal searches for tadpoles were conducted along approximately five km of creekline. About 200-300 tadpoles were recorded at this same site in January 2005; this cohort declined to about 15 tadpoles by September 2005. A total of 20 small tadpoles were taken into captivity in January 2005 in an attempt to maintain a captive population. Swab samples taken from free-living tadpoles indicated the presence of the frog chytrid fungus, Bactrachochytrium dendrobatidis. Mixophyes balbus may no longer persist at this site and manager...

Comportamento alimentar aquático de Liophis jaegeri (Günther 1858) (Serpentes, Dipsadidae) em cativeiro

Os itens que compõem a dieta das espécies são peças fundamentais na definição de sua dimensão de nicho e interferem, em última análise, em processos de estruturação das comunidades. As necessidades relacionadas à alimentação direcionam o modo pelo qual as espécies usam o ambiente. Apesar de se tratar de uma espécie com ampla distribuição geográfica, existem poucos estudos a respeito da biologia geral e do comportamento alimentar de Liophis jaegeri. Os estudos disponíveis indicam se tratar de uma espécie associada à ambientes alagados, porém, a importância de presas aquáticas na dieta desta serpente tem recebido pouca atenção. Em geral os estudos disponíveis sugerem que a presença de presas aquáticas (peixes e girinos) no trato digestivo de indivíduos dissecados seja resultado de ingestões acidentais. No presente estudo, a partir de gravações em vídeo realizadas em cativeiro, apresentamos dados inéditos que revelam a habilidade de L. jaegeri forragear em ambiente aquático, sendo capaz de detectar, subjugar e ingerir de modo eficiente peixes da espécie simpátrica Cheirodon interruptus. Tais informações indicam que a relevância de presas aquáticas na dieta desta serpente possa ser maior do que o até então apresentado pela literatura. Consequentemente, a disponibilidade de corpos d'água e de peixes podem influenciar os padrões de distribuição e abundância de indivíduos desta serpente na natureza.

Breeding biology of Phyllomedusa azurea Cope, 1862 and P. sauvagii Boulenger, 1882 (Anura) from the Cerrado, Central Brazil

Phyllomedusa azurea and P. sauvagii are treefrogs from seasonal dry environments of Central Brazil. We report on reproductive and other natural history features of these species. The study was carried out in Serra da Bodoquena, Mato Grosso do Sul, Brazil. The reproductive period was determined by the presence of vocalizing males, amplectant pair or presence of tadpoles. The reproductive effort was measured as the ratio of gonad mass in relation to body mass (BM). The reproduction of both species was correlated with the rainy season. Female P. sauvagii produced more eggs and their eggs were larger than those of P. azurea. Both species showed sexual dimorphism in relation to the snout–vent length (SVL) and BM. The mating behaviour of both species was similar. Males in both species showed similar reproductive efforts, but females of P. azurea invested more in gonads compared to the males of P. sauvagii. Phyllomedusa azurea showed a significant relation between SVL versus number of the mature eggs (NME), and P. sauvagii between SVL versus NME and BM versus ovarian mass.

Associations between anuran tadpoles and salinity in a landscape mosaic of wetlands impacted by secondary salinisation

Summary1. The secondary salinisation of wetlands is a global problem that poses a great threat to most freshwater biodiversity, including amphibians. We examined tadpole diversity in relation to wetland conductivity (our proxy for salinity) in wetlands in south‐eastern Australia to better understand (i) how salinity and amphibian diversity interact and (ii) the threat posed by secondary salinisation.2. Six tadpole species were trapped in 56 wetlands that reflected a typical salinity gradient for the study region. We developed Bayesian models to examine the relationships between conductivity and both the probability of species occupancy and expected number of species with the imperfect detection probability of species accounted for in the models.3. The probability of occupancy for all species and expected species number was negatively associated with wetland conductivity. Our results predict that conductivity should not limit tadpole presence below about 3000 μS cm−1 at 25 °C (approximately 6% seawater) in the region, but will largely exclude amphibian larvae beyond about 6000 μS cm−1 at 25 °C (approximately 12% seawater).4. We also detected subtle among‐species differences in salinity tolerance. The results reported here show that tadpoles in the study region are likely to be negatively affected by projected future increases in salinisation.

Social foraging in Bufo americanus tadpoles

Animals can find food using information from the food itself or from conspecifics that are also looking for food. Social information can be actively communicated or based on unavoidable by-products of feeding activities. We present three experiments that explore the relative importance of odour gradients and social information as Bufo americanus tadpoles locate food sources. In the first experiment, tadpoles rapidly aggregated at food patches and discriminated between the qualities of two food patches spaced 15 cm apart in the field. In a second experiment, the initial presence of tadpoles at one food patch enhanced aggregation for 1 h, compared to an identical food patch without tadpoles spaced 114 cm apart. In a third experiment, the time required to initial contact with a single food patch did not change over a 16-fold range of food concentration, suggesting that B. americanus tadpoles have a limited ability to locate food from a distance using information from the food itself. Finding food and discriminating food patch quality from a distance is probably a major adaptive advantage of sociality in B. americanus tadpoles, although the presence or absence of active signalling remains to be determined.

Growth and Behavioral Responses of Tadpoles of Two Native Frogs to an Exotic Competitor, Rana catesbeiana

Rana catesbeiana (American Bullfrog) is exotic in western North America and is sympatric with two native species, Rana luteiventris (Columbia Spotted Frog) and Pseudacris regilla (Pacific Treefrog). In a laboratory experiment, we assessed the growth of tadpoles of R. luteiventris and P. regilla in the presence and absence of tadpoles of R. catesbeiana. We found that in the presence of tadpoles of R. catesbeiana, P. regilla exhibited rapid growth in early larval stages compared to R. luteiventris. A second experiment indicated that, when reared with R. catesbeiana, P. regilla increased activity levels; this behavioral disparity may partly explain the observed difference in growth responses of the two frog species to R. catesbeiana competition. Our results suggest that tadpoles of P. regilla display greater growth and behavioral plasticity than do R. luteiventris, when subject to competition with R. catesbeiana. Rana luteiventris may be more susceptible than P. regilla to R. catesbeiana-mediated numerical decline, if exploitative or interference competition between tadpoles is a population-limiting factor in western breeding ponds.

CHOICE OF OVIPOSITION SITE IN PLEURODEMA BORELLII (LEPTODACTYLIDAE): IMPORTANCE OF CONSPECIFIC TADPOLE SIZE

Selection should favor individuals that can assess the quality of their future offspring′s habitat in terms of its physical features and the presence of competitors or predators. Studies have shown that the presence of tadpoles at a site may deter adults from ovipositing there as the tadpoles may become competitors for resources or predators on the smaller conspecifics. Here I investigate whether tadpole size influences oviposition site selection in the leptodactylid Pleurodema borellii. The study took place at a location in northwestern Argentina, where this species naturally occurs, during five consecutive years. Six identically-sized pools were placed near an artificial pond allowing the frogs to breed without interference. Number of adults present at each pool and number of foam nests were recorded. Tadpoles were divided into three size categories (small, medium, and large) and were sampled twice a week. Adult P. borellii significantly chose two out of six of the pools to lay their eggs when small tadpoles were present, whereas they significantly avoided all the pools when medium and large tadpoles were present. The results suggest that an important factor in oviposition site selection in P. borellii is tadpole size. Females accepted a location with small tadpoles, possibly an indicator of a suitable breeding site, but they avoided locations with medium and large tadpoles that could become potential competitors as well as predators on the new progeny.

Oviposition site selection by mosquitoes is affected by cues from conspecific larvae and anuran tadpoles

Abstract The oviposition site that a female mosquito selects will influence the fitness of her larvae. We conducted a series of artificial pond experiments to compare the oviposition responses of two species of mosquitoes with the presence of tadpoles, conspecifics and chemical cues from these organisms. The two mosquito species differ markedly in larval ecology. The larvae of one species, Culex quinquefasciatus, co‐occur with numerous freshwater organisms, including tadpoles of Linmodynastes peronii (the striped marsh frog). Larvae of the other mosquito, Ochlerotatus australis, inhabit small brackish rock ponds where the main potential competitors are tadpoles of Crinia signifera (the common eastern froglet). In field trials, females of both mosquito species oviposited significantly more often in water that contained (or had previously contained) conspecific larvae. However, these superficially similar responses were mediated via different pathways: fungicide abolished the response by C. quinquefasciatus but not by O. australis. The two mosquito species also responded differently to cues associated with syntopic tadpoles. The presence of tadpoles did not influence oviposition by C. quinquefasciatus, but O. australis oviposited less often if tadpoles were present. These interspecific differences in oviposition behaviour may be adaptive to differences in larval ecology: competition with tadpoles is likely to be more significant for O. australis than for C. quinquefasciatus. Our findings thus support the hypothesis that mosquitoes oviposit selectively to avoid potential anuran larval competitors.

The effect of community composition on persistence of prey with their predators in an assemblage of pond-breeding amphibians.

We examined whether the species composition of a community influences the persistence of larval Ambystoma maculatum in assemblages composed of two larger intraguild predators (A. opacum and A. jeffersonianum) and an alternative prey species (tadpoles of Rana sylvatica). We predicted a priori that A. maculatum would have higher survival in more diverse communities containing alternative species of prey and top predators (A. opacum), the latter of which may lower the abundance of intermediate predators (A. jeffersonianum) via intraguild predation. In a factorial experiment, we manipulated the presence of larval A. opacum, A. jeffersonianum, and R. sylvatica in replicated artificial ponds containing larval A. maculatum. The presence of all three species significantly depressed biomass production in A. maculatum: biomass was highest in ponds lacking the other species and was zero in ponds initially containing all four species. Tadpoles severely reduced the growth of filamentous algae in the ponds. This, in turn, may have affected the abundance of some herbivorous prey of larval salamanders, although this possibility was not tested. The presence of congeneric predators severely restricted the presence in the water column of larval A. maculatum, which otherwise exhibited significant diel patterns of activity in the absence of predators. Together, the presence of tadpoles and a predator-mediated reduction in activity patterns may have limited foraging opportunities for A. maculatum, thus exacerbating the direct impact of predation on survival in this species. These results suggest that diverse assemblages consisting of these particular species may actually inhibit, rather than promote, inclusion of A. maculatum in some communities of pond-breeding amphibians.

Interactions among Nutrients, Periphyton, and Invertebrate and Vertebrate (Ascaphus truei) Grazers in Experimental Channels

Objectives of this study were to determine whether (1) stream algal biomass was nutrient limited, (2) stream herbivores could reduce algal biomass at different levels of productivity, and (3) a large vertebrate herbivore (Ascaphus truei) affected the abundance of insect grazers under different nutrient supply regimes. To address these objectives, we conducted a 2 3 2 factorial experiment to examine the effects of varying phosphate supply on periphyton biomass, insect grazers, and a tadpole grazer in 12 streamside experimental channels in southwestern Canada. We manipulated presence of tailed frog tadpoles (A. truei Stejneger) and varied nutrient levels using nutrient-diffusing pellets. We monitored periphyton biomass as ash-free dry mass (AFDM), insect grazer abundance, dissolved nutrients (NO 3 2 N and PO4 2 P) in water, and tadpole growth rates over 38 days. Dissolved nitrate and phosphate concentrations were temporally variable, and there were no statistical differences among treatments, but dissolved phosphate levels were 1.7 times greater in nutrientenriched channels (3.2 m gL 21) than in unenriched channels (1.7 m gL 21). Periphyton AFDM was significantly higher in channels with added nutrients, as was abundance of insect grazers, primarily Chironomidae and Ephemeroptera. Tadpoles in channels with nutrients had growth rates approximately four times higher than tadpoles in controls. Insect grazer abundance in channels with and without added nutrients was lower in the presence of tadpoles, and this reduction was greater in channels with nutrients. In contrast to other studies that have examined the impact of vertebrate herbivores on periphyton, tadpoles had no measurable effect on periphyton biomass. These data indicate periphyton and grazers were resource limited, as added nutrients increased periphyton biomass, as well as abundance (insect grazers) and biomass (tailed frog tadpoles) of herbivores.

Social and reproductive behaviour in the Madagascan poison frog, Mantella laevigata, with comparisons to the dendrobatids

I present the first behavioural study of natural populations of a Madagascan poison frog. Focal watches of marked individuals were conducted for 925h, in five populations, across two seasons. Like the New World dendrobatids, these diurnal anurans eat ants and are aposematically coloured. Data are presented that provide additional instances of convergence with the dendrobatids, including (1) extended male–male fights over defended resources necessary for reproductive success of both sexes, (2) stereotyped, highly tactile courtships in which the female may reject initial oviposition sites and (3) complex maternal care. Females return to water-filled phytotelmata, or wells, and lay trophic eggs for their tadpoles. Mantella laevigata has the minimum possible clutch size in anurans (usually one) suggesting a high degree of parental investment. Males defend wells, which attract females that oviposit in the wells. Fertilized eggs may hatch and metamorphose, or may be eaten by a tadpole already in that well, of which the territorial male is probably the father. Unfertilized eggs serve as food for tadpoles. Oviposition-site scouting behaviour of both sexes, and the dependency of tadpole presence on the position of eggs laid, provide evidence of context-dependent, and assessment, behaviour. Females leave courtships most often only after visiting potential oviposition sites, while males usually leave to engage other males in aggression, suggesting that territory maintenance may be the most important component of male reproductive success. Two other species of frogs often prevent M.laevigata from using defended oviposition sites, and larval crane flies predate the eggs of all frog species using water-filled wells.

Oviposition Site Selection inPleurodema borellii(Anura: Leptodactylidae) May Be Influenced by Tadpole Presence

Abstract Oviposition site selection was investigated in Pleurodema borellii, a leptodactylid frog from Northern Argentina. We monitored the breeding activity of P. borellii during six months at two different sized pools, which were 15 m apart. Calling males, mating pairs, number of foam nests, and metamorphosing tadpoles were recorded. When a pool filled with growing tadpoles, females avoided it and went to the other pool. Two experiments, foam nest transfers to the pool filled with tadpoles and the creation of artificially tadpole-dense populations, were conducted. Results suggest that females may be assessing whether to oviposit at a specific location, based on tadpole presence and tadpole density.

The effects of cannibalism on Amazonian poison frog egg and tadpole deposition and survivorship in Heliconia axil pools.

This study investigated the influence of cannibalism on egg and larval mortality, and on the deposition strategies of adults, in a tropical anuran breeding in very small leaf axil pools. Patterns of egg and tadpole deposition and mortality in the Amazonian poison frog, Dendrobates ventrimaculatus, were monitored in rainforest near Pompeya in Sucumbios Province, Ecuador. Oviposition and tadpole deposition typically ocurred in leaf axils of Heliconia plants. Pools typically received more than one oviposition. Egg survivorship was low, and significantly lower when eggs were deposited in pools with large tadpoles, indicating that cannibalism is an important source of mortality. Tadpole survivorship was also associated with the presence of other tadpoles: most pools ended with only one surviving tadpole, regardless of the number of tadpoles deposited in the pool. Egg deposition was signifcantly less likely for pools that had a tadpole in them, suggesting that adults can detect the presence of tadpoles and avoid ovipositing in pools that contain them. This hypothesis was tested with a series of pool choice experiments, which revealed that D. ventrimaculatus avoid placing either eggs or tadpoles into a pool which contains a large tadpole. Several hypotheses which could explain multiple deposition in this species are discussed.