Frog Survival Research Articles

Carryover Aquatic Effects On Survival Of Metamorphic Frogs During Pond Emigration

In organisms with complex life cycles, physiological stressors during early life stages may have fitness-level impacts that are delayed into later stages or habitats. We tested the hypothesis that body size and date of metamorphosis, which are highly responsive to aquatic stressors, influence post-metamorphic survival and movement patterns in the terrestrial phase of an ephemeral pond-breeding frog by examining these traits in two populations of northern red-legged frogs (Rana aurora aurora). To increase variation of body size at metamorphosis, we manipulated food availability for 314 of 1045 uniquely marked tadpoles and estimated the probability that frogs survived and emigrated using concentric rings of drift fencing surrounding ponds and Bayesian capture-recapture modeling. The odds of surviving and emigrating from the ponds to the innermost drift fences, approximately 12 m, increased by factors of 2.20 (95% credibility intervals 1.39-4.23) and 2.54 (0.94-4.91) with each millimeter increase in snout-vent length and decreased by factors of 0.91 (0.85-0.96) and 0.89 (0.80-1.00) with each day's delay in metamorphosis for the two ponds. The odds of surviving and moving to the next ring of fencing, 12 m to approximately 40 m from the ponds, increased by a factor of 1.20 (0.45-4.06) with each millimeter increase in size. Our results demonstrated that body size and timing of metamorphosis relate strongly to the performance of newly metamorphosed frogs during their initial transition into terrestrial habitat. Carryover effects of aquatic stressors that reduce size and delay metamorphosis may have population-level impacts that are not expressed until terrestrial stages. Since changes in both aquatic and terrestrial systems are implicated in many amphibian declines, quantifying both immediate and delayed effects of stressors on demographic rates is critical to sound management.

Drainage Ditches Facilitate Frog Movements in a Hostile Landscape

Ditches are common in landscapes influenced by agricultural, forestry, and peat mining activities, and their value as corridors remains unassessed. Pond-breeding amphibians can encounter hostile environments when moving between breeding, summering, or hibernation sites, and are likely to benefit from the presence of ditches in the landscape. Within a system consisting of ditch networks in bogs mined for peat in eastern New Brunswick, Canada, I quantified the breeding, survival, and movements of green frogs (Rana clamitans melanota) in drainage ditches and also surveyed peat fields. Frogs rarely ventured on peat fields and most individuals frequented drainage ditches containing water, particularly in late summer. Though frogs did not breed in ditches, their survival rate in ditches was high (88%). Ditches did not hinder frog movements, as frogs moved independently of the current. Results indicate that drainage ditches containing water enable some movements between habitats isolated by peat mining, in contrast to peat surfaces, and suggest they function as amphibian movement corridors. Thus, such drainage ditches may mitigate the effects of peat extraction on amphibian populations. At the very least, these structures provide an alternative to hostile peat surfaces. This study highlights that small-scale corridors are potentially valuable in population dynamics.

The impact of larval predators and competitors on the morphology and fitness of juvenile treefrogs.

Studies of phenotypic plasticity typically focus on traits in single ontogenetic stages. However, plastic responses can be induced in multiple ontogenetic stages and traits induced early in ontogeny may have lasting effects. We examined how gray treefrog larvae altered their morphology in four different larval environments and whether different larval environments affected the survival, growth, development, and morphology of juvenile frogs at metamorphosis. We then reared these juveniles in terrestrial environments under high and low intraspecific competition to determine whether the initial differences in traits at metamorphosis affected subsequent survival and growth, whether the initial phenotypic differences converged over time, and whether competition in the terrestrial environment induced further phenotypic changes. Larval and juvenile environments both affected treefrog traits. Larval predators induced relatively deep tail fins and short bodies, but there was no impact on larval development. In contrast, larval competitors induced relatively short tails and long bodies, reduced larval growth, and slowed larval development. At metamorphosis, larval predators had no effect on juvenile growth or relative morphology while larval competitors produced juveniles that were smaller and possessed relatively shorter limbs and shorter bodies. After 1 month of terrestrial competition among the juvenile frogs, the initial differences in juvenile morphology did not converge. There were no differences in growth due to larval treatment but there were differences in survival. Individuals that experienced low competition as tadpoles experienced near perfect survival as juvenile frogs but individuals that experienced high competition as tadpoles suffered an 18% decrease in survival as juvenile frogs. There were also morphological responses to juvenile competition, but these changes appear to be due, at least in part, to allometric effects. Collectively, these results demonstrate that larval environments can have profound impacts on the traits and fitness of organisms later in ontogeny.

Influence of Ribeiroia ondatrae (Trematoda: Digenea) infection on limb development and survival of northern leopard frogs (Rana pipiens): effects of host stage and parasite-exposure level

Recent evidence suggests that infection by larvae of the trematode Ribeiroia ondatrae accounts for a significant proportion of limb malformations currently observed in amphibian populations of North America. However, the effects of R. ondatrae infection on northern leopard frogs (Rana pipiens), one of the species most frequently reported with malformations, have not been adequately explored. Moreover, the risk factors associated with R. ondatrae-induced malformations have not been clearly identified. We examined the effects of timing of infection on tadpole survival and limb development. Rana pipiens tadpoles were individually exposed to R. ondatrae cercariae at the pre-limb-bud (Gosner stages 24 and 25), limb-bud (Gosner stages 27 and 28), or paddle (Gosner stages 31–33) stages of development and monitored through metamorphosis. The effects of infection were stage-specific. Infections acquired at the pre-limb-bud stage resulted in a high mortality rate (47.5–97.5%), whereas tadpoles infected at the limb-bud stage displayed a high malformation rate (16% overall), and the magnitude of effects increased with the level of exposure to cercariae. In contrast, infections acquired at the paddle stage had no effect on limb development or tadpole survival, which suggests that the timing of R. ondatrae infection in relation to the stage structure of tadpole populations in the wild is an important determinant of the degree to which populations are affected by R. ondatrae.

Developmental Plasticity and Growth Rates of Green Frog (Rana clamitans) Embryos and Tadpoles in Relation to a Leech (Macrobdella decora) Predator

We tested for predator-induced plasticity in development and growth of embryos and young tadpoles of green frogs (Rana clamitans). We expected to observe developmental plasticity in response to the leech, Macrobdella decora, because the leech represents a high, but unpredictable, risk of mortality. Embryos raised with a leech tended to delay hatching and hatched at larger size. Young tadpoles raised with a leech grew more slowly than tadpoles raised without a leech. Such changes should enhance survival of green frogs faced with the threat of leech predation.

Trait-mediated indirect effects and complex life-cycles in two European frogs

Most animals actively avoid predators. If such a reaction reduces competitive ability, for example by reducing food intake, predator presence can lead to trait-mediated indirect effects. Because predator avoidance typically leads to reduced growth rather than reduced survival, its effect on population processes is difficult to assess. This is especially true for organisms with complex life-cycles, where predator avoidance during one stage is expected to lead to traitmediated indirect effects if it has effects reaching into the following life stages. I experimentally investigated the effect of caged (thus non-lethal) dragonfly larvae on the competition between tadpoles of two frog species (Rana lessonae and R. esculenta) and on juvenile frog survival during the subsequent terrestrial stage. In response to caged predators, R. lessonae delayed metamorphosis more than R. esculenta, but they both metamorphosed heavier. These differences suggest the possibility of a competitive disadvantage for R. lessonae in the presence of predators, which could lead to trait-mediated indirect effects. However, the presence of predators did not modify competitive effects and had no measurable consequences on terrestrial survival. Regardless of the presence of predators, competition during the larval stage had large effects on metamorphosis and led to strongly decreased survival in the subsequent terrestrial stage. These results suggest that trait-mediated indirect effects are not important in this system, because the predator reaction of the tadpoles in both species had no measurable effect on the following life stage and, therefore, probably no strong effect on community dynamics.

Mechanisms of metabolic defense against hypoxia in hibernating frogs

The cold submerged frog ( Rana temporaria) serves as a useful model for many hibernating ectotherms that take refuge in hypoxic ponds and lakes until more favourable conditions of climate and food availability return. In all such animals, entry into a hypometabolic state effectively extends their survival time by lessening the impact of ATP demands on endogenous substrates. At the cellular level, metabolic depression may be brought about by decreasing energy-consuming processes and/or by increasing the efficiency of energy-producing pathways. Since the mitochondrion is the major contributor to the total energy production during aerobic metabolism and frog survival during winter depends on entry into a hypometabolic state, this review focuses on the respiratory properties of mitochondria that serve to increase the efficiency of energy production in hibernation. Energy conservation during overwintering also occurs through decreases in the ATP demand of the energy-consuming processes. For example, hibernating frogs decrease their ATP demands for Na +/K +-ATPase activity as part of a coordinated process of energy conservation wherein O 2-limitation initiates a generalised suppression of ion channel densities and/or channel leak activities. The net result is that cell membrane permeabilities are reduced, thereby lowering the energetic costs of maintaining transmembrane ion gradients.

Effects of Disease and Pond Drying on Gray Tree Frog Growth, Development, and Survival

Pathogens have important effects on host growth, behavior, and population dynamics. Nevertheless, the impact of parasitic infection on host populations may be strongly context dependent. For example, the outcome of host–pathogen interactions may be subject to change based on the level of abiotic stress experienced by the host. In northeastern Connecticut, USA, larvae of the gray treefrog (Hyla versicolor) co-occur in temporary and permanent ponds with a snail (Pseudosuccinea columella) that is frequently infected with a digenetic trematode (Telorchis sp.) whose free-swimming cercariae subsequently infect H. versicolor tadpoles. Field collections of H. versicolor tadpoles suggest that the prevalence of infection by trematodes can be as high as 71%. We measured survival, mass, and time to metamorphosis of larval gray treefrogs in an artificial pond experiment designed to determine how infection with trematode cercariae and the stress of pond drying interact to influence gray treefrog performance. We exposed gray treefrog tadpoles to infected snails, uninfected snails, or no snails, within artificial ponds that were either permanent or subjected to a 49-d drying regime. The presence of infected P. columella had strong negative effects on the performance of gray treefrog larvae. However, this effect depended on whether ponds were temporary or permanent. When tadpoles were exposed to infected snails in temporary ponds, survivorship to metamorphosis decreased by ∼30%, and mass at metamorphosis was reduced by 40%. The presence of infected P. columella had no detectable effect on larval performance of gray treefrogs in permanent ponds. Assays of infection level (mean number of cysts per individual) indicate that temporary pond animals were exposed to higher rates of infection. In contrast, uninfected snails had very little effect on H. versicolor in either temporary or permanent pools. There was, however, a small increase in time to metamorphosis for H. versicolor in permanent pools that were exposed to increased densities of uninfected snails. Our results indicate that an endemic parasite can have large effects on the performance of its native host, but that these effects may be strongly context dependent. Given this strong context dependence, an important challenge is to assay these effects within the natural environment.

Combined effects of UV-B, nitrate, and low pH reduce the survival and activity level of larval cascades frogs (Rana cascadae).

We investigated interactions between low pH, high nitrate level, and ultraviolet-B (UV-B) light on the survival and activity level of larval Cascades frogs (Rana cascadae). We used a fully factorial experimental design, with pH levels of 5 and 7; initial "pulse" nitrate exposure levels of 0, 5, and 20 mg/L; and UV-B present or absent. After a 3-week laboratory exposure, we measured survival and activity level of the larvae. The experiment was repeated two times, in two separate years. Similar effects on survival and activity level were observed in both experiments. R. cascadae survival was not significantly reduced in treatments with individual factors alone (i.e., UV-B control, pH 5 control, or high nitrate level without pH or UV-B). However, in experiments from both years, survival and activity levels of larval R. cascadae were significantly reduced in the treatment with low pH, high nitrate, and UV-B together. In both years, analysis of variance (ANOVA) indicated that pH and nitrate had the greatest effect on survival and that UV-B and nitrate had the greatest effect on activity level. Additional effects were observed in the 1998 experiment on both survival and activity level. In 1998, UV radiation and the interaction term between pH and nitrate (pH x nitrate) had a significant effect on survival. Also in the 1998 experiment, activity level was significantly reduced in treatments at neutral pH with UV, at initial nitrate doses of 5 and 20 mg/L and at neutral pH without UV at an initial nitrate dose of 20 mg/L. We suggest that the adverse effects were due to the multiple stressors acting together.

Effects of Introduced Mosquitofish and Bullfrogs on the Threatened California Red‐Legged Frog

Abstract: Exotic species have frequently caused declines of native fauna and may contribute to some cases of amphibian decline. Introductions of mosquitofish ( Gambusia affinis) and bullfrogs ( Rana catesbeiana) are suspected to have caused the decline of California red‐legged frogs ( Rana aurora draytonii). We tested the effects of mosquitofish and bullfrog tadpoles on red‐legged frog tadpoles in spatially complex, speciose communities. We added 720 hatchling red‐legged frog tadpoles to each of 12 earthen ponds. Three ponds were controls, 3 were stocked with 50 bullfrog tadpoles, 3 with 8 adult mosquitofish, and 3 with 50 bullfrogs plus 8 mosquitofish. We performed tests in aquaria to determine whether red‐legged frog tadpoles are preferred prey of mosquitofish. Mosquitofish fed on a mixture of equal numbers of tadpoles and either mosquitoes, Daphnia, or corixids until < 50% of prey were eaten; then we calculated whether there was disproportionate predation on tadpoles. We also recorded the activity of tadpoles in the presence and absence of mosquitofish to test whether mosquitofish interfere with tadpole foraging. Survival of red‐legged frogs in the presence of bullfrog tadpoles was less than 5%; survival was 34% in control ponds. Mosquitofish did not affect red‐legged frog survival, even though fish became abundant (approximately 1011 per pond). Two mechanisms may have blocked the effects of mosquitofish on tadpole survival: (1) fish ponds contained fewer predatory invertebrates, and (2) mosquitofish preferred other prey to red‐legged frogs in laboratory trials. Red‐legged frog tadpoles suffered more injuries in ponds with fish, however, and weighed 34% less at metamorphosis. The growth decrease could have been caused by injuries or by lower foraging levels in the presence of fish. Laboratory results showed that young tadpoles were less active in the presence of mosquitofish. Although both mosquitofish and bullfrogs affected red‐legged frogs, the impact of bullfrogs on the survival of red‐legged frogs may contribute more strongly to their decline.

Effects of Introduced Bullfrogs and Smallmouth Bass on Microhabitat Use, Growth, and Survival of Native Red-Legged Frogs (Rana aurora)

Effects of Introduced Bullfrogs and Smallmouth Bass on Microhabitat Use, Growth, and Survival of Native Red-Legged Frogs (Rana aurora)

Effects of low pH, metals, and water hardness on larval amphibians

The interactions between pH, metals, and water hardness in determining the suitability of vernal ponds for amphibian reproduction were investigated through a fully factorial laboratory microcosm experiment. Naturally-occurring metals (Al, Cu, Fe, Pb, Zn) at concentrations analogous to those observed in prior field studies had variable effects on acute (7 day) and chronic (28 day) exposure survival for both the Jefferson salamander, Ambystoma jeffersonianum, and the wood frog, Rana sylvatica. Acute exposure to Al and Cu significantly reduced wood frog survival; increased water hardness significantly increased acute exposure wood frog survival. Acute exposure mortality of the Jefferson salamander was significantly higher in the Al and Cu treatments; in toxic metal treatments (Al and Cu), survival was higher at the low pH level. Chronic exposure of wood frogs to Al and Cu, higher pH level, and lower hardness levels greatly reduced survival. Chronic exposure of Jefferson salamander larvae to Al and Cu significantly reduced survival. Chronic Jefferson salamander survival was significantly greater in the higher pH treatments in the presence of non-toxic metals, however, survival was significantly decreased in the higher pH treatments in the presence of Al and Cu. There were no statistically significant effects of metals, pH, or hardness on wet mass of the pre-metamorphic larvae.

Predation on Larval and Embryonic Amphibians by Acid-Tolerant Caddisfly Larvae (Ptilostomis postica)

We examined effects of predation by larvae of the caddisfly Ptilostomis postica on survival of embryonic and larval wood frogs (Rana sylvatica) and spotted and Jefferson salamanders (Ambystoma maculatum and A. jeffersonianum). Studies of predation were conducted both in the laboratory and natural ponds. We also estimated the tolerance to low pH of P. postica in laboratory trials. There were significant effects of predation by P. postica on overall hatching success of A. maculatum in one laboratory experiment; there was no difference between embryos from opaque versus clear egg mass morphs. Ptilostomis postica preyed on larvae of R. sylvatica and A. jeffersonianum in the laboratory and showed no preference in choice of prey

Hindlimb sensory neuron number increases with body size.

As an animal grows, its sensory systems face the task of maintaining sensitivity and discrimination in peripheral fields that are continually enlarging. Without the addition of neurons, existing cells would have to innervate a wider skin area, leading to a decrease in the precision with which stimuli are localized. Neurons were counted in the three dorsal root ganglia (DRGs) that innervate the hindlimb of the bullfrog (Rana catesbeiana). Profiles of neuronal nuclei containing the single nucleolus found in these cells were counted in every third section of serially cut ganglia. This means of assessing neuron number was validated by comparing these profile counts with three-dimensional reconstructions of sensory neurons. Large frogs (10-17 cm) had more than twice as many DRG neurons as small frogs (3.3-5 cm). The rate of increase was greatest between 3 and 8 cm, when over 1,300 hindlimb sensory neurons were added for each 1 cm increase in body length. The possibility that selective survival of frogs with many neurons biases estimates of mean neuron number was ruled out by the finding that frogs drawn from the same closed population, half of which were sacrificed immediately and half of which were sacrificed after 1 year's survival, showed expected differences in neuron number. Horseradish peroxidase applied to particular hindlimb nerves retrogradely labeled more neurons in large frogs than small frogs, supporting the hypothesis that added neurons extend their axons to the periphery.(ABSTRACT TRUNCATED AT 250 WORDS)

Resumption of physiological functions in the wood frog (Rana sylvatica) after freezing

We monitored the resumption of physiological functions in frogs that were frozen at -2 to -3 degrees C for 24 h and thawed rapidly (at 23-25 degrees C) or slowly (at 6-8 degrees C). Bodily functions were restored sooner during fast thawing, but this did not enhance the survival of frogs. The first physiological parameter to return was cardiac function, but during the early stages of thawing heart rates were lower than heart rates of unfrozen frogs at comparable body temperatures. Heart rates increased thereafter in conjunction with the rise in frog body temperatures. Spontaneous breathing and hindleg reflexes resumed after cardiac function, but neither response was exhibited by all frogs after the conclusion of the observation periods (3-4 h). Finally, isolated gastrocnemius muscles that had undergone in vitro freezing showed no significant (P greater than 0.05) impairment of twitch and tetanic tensions even as soon as 1 h after the onset of thawing. Body systems thus vary in their rates of recovery after nonlethal freezing episodes. Furthermore, recovery of specific body systems corresponds to essential needs that must be met immediately after thawing, such as reperfusion of body tissues.

Size-Dependent Population Dynamics of Microtus ochrogaster

Previous articleNext article No AccessNotes and CommentsSize-Dependent Population Dynamics of Microtus ochrogasterJohn R. Sauer, and Norman A. SladeJohn R. Sauer Search for more articles by this author , and Norman A. Slade Search for more articles by this author PDFPDF PLUS Add to favoritesDownload CitationTrack CitationsPermissionsReprints Share onFacebookTwitterLinkedInRedditEmail SectionsMoreDetailsFiguresReferencesCited by The American Naturalist Volume 127, Number 6Jun., 1986 Published for The American Society of Naturalists Article DOIhttps://doi.org/10.1086/284534 Views: 5Total views on this site Citations: 10Citations are reported from Crossref Copyright 1986 The University of ChicagoPDF download Crossref reports the following articles citing this article:Guoliang LI, Xianglei HOU, Xinrong WAN, Zhibin ZHANG Sheep grazing causes shift in sex ratio and cohort structure of Brandt's vole: Implication of their adaptation to food shortage, Integrative Zoology 11, no.11 (Jan 2016): 76–84.https://doi.org/10.1111/1749-4877.12163Nathan D. Chelgren, Daniel K. Rosenberg, Selina S. Heppell, Alix I. Gitelman Carryover Aquatic Effects On Survival Of Metamorphic Frogs During Pond Emigration, Ecological Applications 16, no.11 (Feb 2006): 250–261.https://doi.org/10.1890/04-0329Jason E. Tanner THE INFLUENCE OF CLONALITY ON DEMOGRAPHY: PATTERNS IN EXPECTED LONGEVITY AND SURVIVORSHIP, Ecology 82, no.77 (Jul 2001): 1971–1981.https://doi.org/10.1890/0012-9658(2001)082[1971:TIOCOD]2.0.CO;2Nigel G. Yoccoz, Keisuke Nakata, Nils Chr Stenseth, Takashi Saitoh The demography of Clethrionomys rufocanus : From mathematical and statistical models to further field studies, Population Ecology 40, no.11 (Nov 2018): 107–121.https://doi.org/10.1007/BF02765226James F. Rieger Body size, litter size, timing of reproduction, and juvenile survival in the Unita ground squirrel, Spermophilus armatus, Oecologia 107, no.44 (Sep 1996): 463–468.https://doi.org/10.1007/BF00333936JAMES E. DIFFENDORFER, R.D. HOLT, N.A. SLADE, M.S. GAINES Small-Mammal Community Patterns in Old Fields, (Jan 1996): 421–466.https://doi.org/10.1016/B978-012178075-3/50015-5R. Boonstra Population cycles in microtines: The senescence hypothesis, Evolutionary Ecology 8, no.22 (Mar 1994): 196–219.https://doi.org/10.1007/BF01238250James E. Childs, Clarence J. Peters Ecology and Epidemiology of Arenaviruses and Their Hosts, (Jan 1993): 331–384.https://doi.org/10.1007/978-1-4615-3028-2_19Glenn R. Iason The effects of size, age and a cost of early breeding on reproduction in female mountain hares, Ecography 13, no.22 (Apr 1990): 81–89.https://doi.org/10.1111/j.1600-0587.1990.tb00592.xBrian A. Maurer Dipodomys populations as energy-processing systems: Regulation, competition, and hierarchical organization, Ecological Modelling 50, no.1-31-3 (Mar 1990): 157–176.https://doi.org/10.1016/0304-3800(90)90048-L

Low temperature survival of terrestrial frogs

Low temperature survival of terrestrial frogs

Survival of frogs in low temperature.

Anurans that hibernate at or near the ground surface can survive prolonged exposure to low winter temperatures of northern latitudes by tolerance to freezing. An accumulation of glycerol during winter was correlated with frost tolerance, indicating that this compound is associated with natural tolerance to freezing in a vertebrate.

Toxicity of 2, 3, 7, 8-tetrachlorodibenzo-p-dioxin in larval and adult forms of Rana catesbeiana.

Varying doses of TCDD ranging from 25 to 1000 mug/kg were administered to the larval and adult forms of the American bullfrog, Rana catesbeiana. Doses of TCDD as high as 1 mg/kg failed to have any significant effect upon survival or completion of metamorphosis in tadpole and doses of up to 500 mug/kg had no effect on survival of adult frogs. Histopathological examination of various tissues from the metamorphosed tadpoles and adult frogs failed to show any abnormalities.

The effect of endotoxins on frog blood and survival time at several ambient temperatures.

SummaryTreatment of frogs with any of three endotoxins resulted in more rapid deaths at 30 and at 37° and a decrease in blood thrombocytes. The frogs were unaffected by bacterial endotoxin at 5 and at 20° at doses of 1 through 30 mg, and repeated injections at a 2-week interval were equally without effect. Other than thrombocytes, the formed elements of the blood were unchanged after endotoxin treatment.