Post-Breeding Dispersal and Summer Home Range of Female American Toads (Bufo americanus)

Forester, Don C.; Snodgrass, Joel W.; Marsalek, Katherine; Lanham, Zachary

doi:10.1656/1092-6194(2006)13[59:pdashr]2.0.co;2

Cited by 33 publications

(27 citation statements)

References 28 publications

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“…Field surveys along the extensive Hg contamination gradient at the South River demonstrated that (1) B. americanus inhabiting the contaminated floodplain bioaccumulate Hg in their tissues, with adults exhibiting mean Hg concentrations 3.5-fold higher than those observed upstream of the Hg point source (Bergeron et al 2010b); (2) females maternally transfer Hg to their offspring (Bergeron et al 2010a); and (3) larvae developing within contaminated floodplain breeding habitats accumulate additional Hg, resulting in fourfold higher Hg concentrations than larvae from reference sites (Bergeron et al 2010b). Because adult B. americanus may migrate up to 1 km between feeding and breeding sites (Forester et al 2006), contaminated females may oviposit in either contaminated (within the floodplain) or uncontaminated (outside the floodplain) breeding pools. Alternatively, uncontaminated females living outside the floodplain may enter the floodplain to breed.…”

Section: Background On Individual-level Effects Of Hg On Bufo Americanusmentioning

confidence: 99%

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Willson

Hopkins

Bergeron

et al. 2012

Ecological Applications

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Abstract. Concern that environmental contaminants contribute to global amphibian population declines has prompted extensive experimental investigation, but individual-level experimental results have seldom been translated to population-level processes. We used our research on the effects of mercury (Hg) on American toads (Bufo americanus) as a model for bridging the gap between individual-level contaminant effects and amphibian population viability. We synthesized the results of previous field and laboratory studies examining effects of Hg throughout the life cycle of B. americanus and constructed a comprehensive demographic population model to evaluate the consequences of Hg exposure on population dynamics. Our model explicitly considered density-dependent larval survival, which is known to be an important driver of amphibian population dynamics, and incorporated two important factors that have seldom been considered in previous amphibian modeling studies: environmental stochasticity and sublethal effects. We demonstrated that decreases in embryonic survival and sublethal effects (e.g., reduced body size) that delay maturation have minor effects on population dynamics, whereas contaminant effects that reduce late-larval or post-metamorphic survival have important population-level consequences. We found that excessive Hg exposure through maternal transfer or larval diet, alone, had minor effects on B. americanus populations. Simultaneous maternal and dietary exposure resulted in reduced population size and a dramatic increase in extinction probability, but explicit prediction of population-level effects was dependent on the strength of larval density dependence. Our results suggest that environmental contaminants can influence amphibian population viability, but that highly integrative approaches are needed to translate individual-level effects to populations.

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Section: Background On Individual-level Effects Of Hg On Bufo Americanusmentioning

confidence: 99%

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Willson

Hopkins

Bergeron

et al. 2012

Ecological Applications

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“…The resulting multinuclear home range structure (inset, fig. 1) is most likely a general phenomenon in pond-breeding amphibians (Semlitsch 1981;Forester et al 2006). In addition, large home ranges are considered to mitigate the impacts of fluctuating environmental conditions (Ferguson et al 1999), which are characteristic of dynamic floodplains (Arscott et al 2001;Naiman et al 2005).…”

Section: The Impact Of Direct and Indirect Effects Of Habitat And Biomentioning

confidence: 99%

Behavior‐Based Scale Definitions for Determining Individual Space Use: Requirements of Two Amphibians

Indermaur¹,

Gehring²,

Wehrle³

et al. 2009

The American Naturalist

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Understanding individual space use remains a major issue in ecology, and it is complicated by definitions of spatial scale and the interplay of multiple factors. We quantified the effect of habitat and biotic and individual factors on space use by amphibians (Bufo bufo spinosus [BB] and Bufo viridis [BV]) that were radio-tracked in their terrestrial summer habitat. We analyzed two spatial scales, 50% core areas and 95% home ranges (excluding 50% core areas), thought to represent resting and foraging areas, respectively. The 50% core area of BB was best explained by habitat structure and prey density, whereas the 50% core area of BV was determined solely by habitat structure. This suggests that the resting and foraging areas of BB are not spatially separated. The 95% home range of BB was determined by prey density, while for BV both habitat structure and prey density determined home range size. We conclude that the terrestrial area requirements of amphibians depend on the productivity and spatiotemporal complexity of landscapes and that differential space use may facilitate their co-occurrence. Behavior-based a priori hypotheses, in combination with an information-theoretic approach and path analyses, provide a promising framework to disentangle factors that govern individual space use, thereby advancing home range studies. [BV]) that were radiotracked in their terrestrial summer habitat. We analyzed two spatial scales, 50% core areas and 95% home ranges (excluding 50% core areas), thought to represent resting and foraging areas, respectively. The 50% core area of BB was best explained by habitat structure and prey density, whereas the 50% core area of BV was determined solely by habitat structure. This suggests that the resting and foraging areas of BB are not spatially separated. The 95% home range of BB was determined by prey density, while for BV both habitat structure and prey density determined home range size. We conclude that the terrestrial area requirements of amphibians depend on the productivity and spatiotemporal complexity of landscapes and that differential space use may facilitate their co-occurrence. Behavior-based a priori hypotheses, in combination with an information-theoretic approach and path analyses, provide a promising framework to dis-

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“…3b), indicating that aquatic prey and habitats were not important foraging areas for these toads; these results are supported by our habitat selection data, which showed that both toad species were found relatively far from ponds (Fig. 1b), and by previous studies showing that toads did not visit ponds except for breeding (Rothermel and Semlitsch 2002;Forester et al 2006). Lithobates sphenocephalus was intermediate between the two toads and the other two frog species both in !…”

Section: Discussionsupporting

confidence: 87%

“…In these cases, by the time the consumer population reaches high densities, many of the prey will be gone or infrequent enough that they are not worth searching for and all the individuals use the same remaining resources. In the case of the toads, they are both active foragers and their populations are fairly evenly spread across of the landscape (Forester et al 2006). As a result, they may not reach high enough densities at any given location to have strong effects on their prey populations.…”

Section: !mentioning

confidence: 99%

The evolution and ecology of individual specializations amongst a group of dietary generalists.

Cloyed¹

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This dissertation examines individual diet specializations (IS) in a group of ecologically similar and evolutionarily related frogs and toads. Individual specialization is known to have widespread ecological and evolutionary effects.In an initial literature review (Chapter 2) I build a comprehensive theoretical framework showing how different types of population diversity can help, halt, or hinder sympatric speciation. I argue that IS can be maintained indefinitely in populations yet fail to lead to speciation because it is influenced by ecological conditions that may change.Additionally, IS can potentially aid niche partitioning among similar species, increasing species coexistence and resulting in less of the ecological opportunity required to develop more discrete polymorphisms.Stable isotopes are an increasingly common ecological tool for determining diets and habitat usage. However, to use them accurately, researchers need taxon-specific trophic discrimination factors and isotopic incorporation rates on any tissue used for stable isotope analysis. I determined these important isotope properties in adult frogs for the first time (Chapter 3), which not only allows me to use them in the following sections of v! my dissertation, but also allows other researchers to use stable isotopes to study frog and toad diets.Using stable isotope analyses, I examined how IS is influenced by ecological conditions (Chapter 4). I measured IS in five species of frogs and toads and determined which of three ecological parameters (resource diversity, intraspecific competition, and interspecific competition) affected IS in each species. I found that species differed in which ecological parameter best explained IS. Resource diversity most frequently affected IS, with conspecific density second in importance. My results showed that different ecological conditions support IS in different species.Finally, again using stable isotopes, I investigated whether intrapopulation niche variation could aid niche partitioning among the same five species of frogs and toads (Chapter 5). I found that species differed in their niches, but that subsets of individuals overlapped among species. The limited number of individuals overlapping between species decreases their interaction strength, which can contribute to niche partitioning and thus to species coexistence.vi!

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Post-Breeding Dispersal and Summer Home Range of Female American Toads (Bufo americanus)

Cited by 33 publications

References 28 publications

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Making leaps in amphibian ecotoxicology: translating individual‐level effects of contaminants to population viability

Behavior‐Based Scale Definitions for Determining Individual Space Use: Requirements of Two Amphibians

The evolution and ecology of individual specializations amongst a group of dietary generalists.

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