Crawfish Frogs Research Articles

Crawfish Frog Behavioral Differences in Postburned and Vegetated Grasslands

AbstractAmphibians are threatened globally and, with the increased emphasis on using prescribed fire as an important tool to manage ecosystems, it is essential to understand how amphibians respond when exposed to habitats managed by fire. Most studies have focused on survivorship and population-level effects; how survivors react to postburn landscapes has received less attention. Crawfish frogs (Lithobates areolatus Baird and Girard) are an obligate crayfish burrow-dwelling North American grassland species in steep decline. Individuals spend their nonbreeding season associated with a single crayfish-built burrow, which protects them from dangers, including fire. We compared activity patterns and behaviors of crawfish frogs occupying vegetated and postburned prairie grassland habitats. In total, 24 581 images representing six weeks of observations on eight crawfish frogs (four each in vegetated and postburn habitats) were analyzed. While the number of individuals followed was small, our dataset demonstrated interesting differences in activity patterns and behaviors. In particular, while frogs occupying postburn and vegetated habitats exhibited similar nocturnal behaviors, diurnal behaviors were different. In daylight, crawfish frogs in vegetated habitats spent more time on their feeding platform away from their burrow entrance, while frogs in postburn areas spent most of their time at or in their burrow entrance. Further, frogs in postburn areas first emerged later in the day than frogs in vegetated areas. We conclude that while crawfish frog adults occupying a postburn landscape exhibit different behaviors compared to animals in vegetation, prescribed burns have little effect on adult crawfish frog survivorship and few indirect effects on fitness.

Population and Conservation Genetics of Crawfish Frogs,Lithobates areolatus, at Their Northeastern Range Limit

Abstract Crawfish Frogs (Lithobates areolatus) are a North American ranid, considered near threatened globally with populations in decline throughout their range. We studied populations of Crawfish Frogs on local and regional scales at their northeastern range limit to (1) assess the level of genetic diversity within populations, (2) estimate fine-scale genetic structure, and (3) estimate genetic differentiation between populations at the regional level. We used 10 microsatellite loci to genotype frogs collected from three regional sites in Indiana separated by 50–172 km and at one of these sites within a network of three breeding ponds <1 km apart. Heterozygosity estimates revealed high levels of diversity within these populations (mean HO: 0.54–0.67 per site), which is encouraging for future management. The degree of population subdivision was low at the regional level (FST = 0.071 for sites within 172 km). Genetic differentiation was related to geographic distance between sampling sites, as predicted b...

Obligate crayfish burrow use and core habitat requirements of crawfish frogs

AbstractCrawfish frogs (Lithobates areolatus) have experienced declines across large portions of their former range. These declines are out of proportion to syntopic wetland‐breeding amphibian species, suggesting losses are resulting from unfavorable aspects of non‐breeding upland habitat. Crawfish frogs get their common name from their affinity for crayfish burrows, although the strength of this relationship has never been formally assessed. We used radiotelemetry to address 4 questions related to upland burrow dwelling in crawfish frogs: 1) what burrow types are used and how do they function to affect crawfish frog survivorship; 2) what are the physical characteristics and habitat associations of crawfish frog burrows; 3) what are the home range sizes of crawfish frogs when burrow dwelling; and 4) where are crawfish frog burrows situated with respect to breeding wetlands? We tracked crawfish frogs to 34 burrows, discovered another 7 occupied burrows, and therefore report on 41 burrows. Crawfish frogs exclusively occupied crayfish burrows as primary burrows, which they inhabited for an average of 10.5 months of the year. With one exception, crawfish frogs also used crayfish burrows as secondary burrows—temporary retreats occupied while exhibiting breeding migrations or ranging forays. Burrows were exclusively located in grassland habitats, although crawfish frogs migrated through narrow woodlands and across gravel roads to reach distant grassland primary burrow sites. Home range estimates while inhabiting burrows were 0.05 m2 (the area of the burrow entrance plus the associated feeding platform) or 0.01 m3 (the estimated volume of their burrow). Crawfish frog burrows were located at distances up to 1,020 m from their breeding wetlands. To protect crawfish frog populations, we recommend a buffer (core habitat plus terrestrial buffer) of at least 1.2 km around each breeding wetland. Within this buffer, at least 3 critical habitat elements must be present: 1) extensive grasslands maintained by prescribed burning and/or logging, 2) an adequate number of upland crayfish burrows, and 3) no soil disturbance of the sort that would destroy crayfish burrow integrity. © 2012 The Wildlife Society.

Comparative Morphometrics in Ranid Frogs (Subgenus Nenirana): Are Apomorphic Elongation and a Blunt Snout Responses to Small-bore Burrow Dwelling in Crawfish Frogs (Lithobates areolatus)?

The subgenus Nenirana of North American ranid frogs encompasses Pickerel Frogs (Lithobates palustris), Crawfish Frogs (L. areolatus), Gopher Frogs (L. capito), and Dusky Gopher Frogs (L. sevosus). All four species inhabit caves, crevices, stump holes, and/or burrows when not in breeding wetlands. Crawfish Frogs obligately inhabit crayfish burrows as their primary retreat sites, and in this study we examine whether the deep, small-bore crayfish burrows used by Crawfish Frogs have influenced Crawfish Frog morphology. Specimens of all four species of Nenirana were radiographed and snout–urostyle length, maximum headwidth, head length, femur length, and tibiofibula length were measured from films. Our results suggest that if Crawfish Frog morphology is a response to life in burrows, it is due in part to having the size characteristic of being the largest member of the clade and in part through the shape characteristic of generally exhibiting an intermediate morphology between Pickerel Frogs and the two Gopher Frog species. Not all shape metrics, however, are intermediate; among Nenirana, Crawfish Frogs have the longest hindlimbs and the relatively bluntest snouts. Further, Crawfish Frogs exhibit positive allometry in headwidth, a reversal of the ancestral pattern exhibited by Pickerel Frogs. None of the morphological features of Crawfish Frogs fit neatly into known or predicted functional/morphological cause-and-effect relationships associated with burrow occupancy. It may be that the ranid body plan is generalized enough to permit Crawfish Frogs to inhabit, despite being unable to dig, deep small-bore burrows without undergoing major morphological changes.

Seasonal pattern of Batrachochytrium dendrobatidis infection and mortality in Lithobates areolatus: affirmation of Vredenburg's "10,000 zoospore rule".

To fully comprehend chytridiomycosis, the amphibian disease caused by the chytrid fungus Batrachochytrium dendrobatidis (Bd), it is essential to understand how Bd affects amphibians throughout their remarkable range of life histories. Crawfish Frogs (Lithobates areolatus) are a typical North American pond-breeding species that forms explosive spring breeding aggregations in seasonal and semipermanent wetlands. But unlike most species, when not breeding Crawfish Frogs usually live singly—in nearly total isolation from conspecifics—and obligately in burrows dug by crayfish. Crayfish burrows penetrate the water table, and therefore offer Crawfish Frogs a second, permanent aquatic habitat when not breeding. Over the course of two years we sampled for the presence of Bd in Crawfish Frog adults. Sampling was conducted seasonally, as animals moved from post-winter emergence through breeding migrations, then back into upland burrow habitats. During our study, 53% of Crawfish Frog breeding adults tested positive for Bd in at least one sample; 27% entered breeding wetlands Bd positive; 46% exited wetlands Bd positive. Five emigrating Crawfish Frogs (12%) developed chytridiomycosis and died. In contrast, all 25 adult frogs sampled while occupying upland crayfish burrows during the summer tested Bd negative. One percent of postmetamorphic juveniles sampled were Bd positive. Zoospore equivalents/swab ranged from 0.8 to 24,436; five out of eight frogs with zoospore equivalents near or >10,000 are known to have died. In summary, Bd infection rates in Crawfish Frog populations ratchet up from near zero during the summer to over 25% following overwintering; rates then nearly double again during and just after breeding—when mortality occurs—before the infection wanes during the summer. Bd-negative postmetamorphic juveniles may not be exposed again to this pathogen until they take up residence in crayfish burrows, or until their first breeding, some years later.

Strong Site Fidelity and a Variety of Imaging Techniques Reveal Around-the-Clock and Extended Activity Patterns in Crawfish Frogs (Lithobates areolatus)

Crawfish frogs (Lithobates areolatus) base their nonbreeding activities in and around the entrances of crayfish burrows. This site preference allows individual crawfish frogs to be monitored using still and video imaging techniques. We used three camera types offering different continuities, scales, and resolutions of data to observe the frogs' activity patterns and nonbreeding behaviors. Together, these techniques allowed us to observe two behaviors in crawfish frogs previously unreported for amphibians: (1) circumdiel activity patterns, and (2) long periods (days) of surface activity. Although these behavioral findings are at this time specific to crawfish frogs, we suspect that they may not be unusual activity patterns for other frogs, as well. The use of imaging techniques that take advantage of these frogs' dependence on burrows and use of burrow entrances has allowed us to observe these patterns for the first time.

Diet Composition and Overlap between Recently Metamorphosed Rana areolata and Rana sphenocephala: Implications for a Frog of Conservation Concern

Interspecific competition for resources is predicted to be high in dense populations of closely related species and should lead either to species partitioning resources along one or more niche axes, or exclusion of the competitively inferior species. Between 19 June and 19 July 2003, we collected 71 recently metamorphosed Rana areolata (Crawfish Frogs) and 69 recently metamorphosed R. sphenocephala (Southern Leopard Frogs) from a single pond in northeastern Oklahoma and compared their morphology and diet. We found that recently metamorphosed R. areolata and R. sphenocephala are morphologically similar. Further, diets of both species were similar: hemipterans predominated, prey items were similarly sized, and dietary niche breadths overlapped, but R. areolata had significantly lower volumes of prey in their stomachs. Because of the high risk of desiccation, especially in Great Plains populations, newly metamorphosed Rana are not expected to disperse far from their natal ponds. During this first season, Rana also experience rapid growth. Dietary restrictions directly influence growth rate, which in turn are known to have major consequences during later life stages, ultimately affecting fitness. Rana areolata is a species of conservation concern across its range. Competitive interactions with other species of Rana have been proposed to be contributing to declines in R. areolata. Our results indicate that competitive interactions with R. sphenocephala have the potential to negatively affect prey consumption, and ultimately fitness, in R. areolata.

Genetic Consequences of Population Reduction and Geographic Isolation in the Critically Endangered Frog, Rana sevosa

Abstract Anthropogenic habitat fragmentation and reduction are major causes of population declines and extinction. As these processes intensify, our ability to rescue imperiled taxa is critically dependent on an understanding of historical, demographic, and genetic parameters of diminishing populations. We assessed the effects of recent geographic isolation and population reduction on genetic variability for endangered Dusky Gopher Frogs, Rana sevosa. Only two populations of R. sevosa exist, each is geographically isolated and restricted to a single breeding pond, and one of them may have gone locally extinct. Therefore, we studied the largest and perhaps only population of R. sevosa. The only option for comparison to non-isolated populations was of its ecologically similar sister species (other Gopher Frogs, R. capito) and of the sister species to R. sevosa and R. capito (Crawfish Frogs, R. areolata). Variation in seven microsatellite DNA loci was assessed for each population to determine the effects of ...

Antimicrobial peptides from the skin secretions of the New World frogs Lithobates capito and Lithobates warszewitschii (Ranidae)

Taxonomic revisions within the anuran family Ranidae have established the genus Lithobates that currently comprises 49 species of frogs from the New World. Peptidomic analysis, using reversed-phase HPLC with on-line detection by electrospray mass spectrometry, has led to the identification of multiple antimicrobial peptides in norepinephrine-stimulated skin secretions of the North American frog Lithobates capito and the Central American frog Lithobates warszewitschii. Structural characterization of the peptides demonstrated that the L. capito secretions contained brevinin-1 (1), esculentin-1 (1), esculentin-2 (1), ranatuerin-2 (3), and temporin (2) peptides. L. warszewitschii secretions contained brevinin-1 (1), esculentin-2 (1), ranatuerin-2 (2), and temporin (1) peptides. Values in parentheses indicate number of peptides in each family. Temporin-CPa from L. capito, with the atypical structure IPPFIKKVLTTVF·NH 2, also showed atypical growth-inhibitory activity having greater potency against Escherichia coli (MIC = 25 μM) and Candida albicans (MIC = 25 μM) than against Staphylococcus aureus (MIC = 50 μM). Phylogenetic analysis based upon the amino acid sequences of 37 ranatuerin-2 peptides from 17 species belonging to the genus Lithobates provides support for currently accepted taxonomic relationships. L. capito is sister-group to Lithobates sevosus in a clade that also contains Lithobates areolatus, and Lithobates palustris. L. warszewitschii is most closely related to the Central American species Lithobates tarahumarae and Lithobates vaillanti.

Development and characterization of polymorphic microsatellite DNA loci for the endangered dusky gopher frog, Rana sevosa, and two closely related species, Rana capito and Rana areolata

AbstractA microsatellite library was developed using genomic DNA of the endangered dusky gopher frog, Rana sevosa. Polymerase chain reaction (PCR) primers and conditions are presented for R. sevosa (eight loci) and two sister taxa — other gopher frogs, Rana capito (seven loci) and crawfish frogs, Rana areolata (three loci). Polymorphism of each microsatellite locus was evaluated for each species. All loci have moderate to high genetic variation in terms of allelic richness (four to 10 alleles per locus), observed heterozygosity (0.595–0.946), and expected heterozygosity (0.531–0.856).

Antimicrobial peptides and protease inhibitors in the skin secretions of the crawfish frog, Rana areolata

The dorsal skin of the crawfish frog, Rana areolata, is associated with numerous prominent granular glands. Proteomic analysis of electrically stimulated skin secretions from these glands enabled the identification and characterization of eight peptides with antimicrobial and hemolytic activity belonging to the previously identified brevinin-1, temporin-1, palustrin-2, palustrin-3, esculentin-1 (two peptides), and ranatuerin-2 (two peptides) families. The primary structures of the peptides were consistent with a close phylogenetic relationship between R. areolata and the pickerel frog, Rana palustris. Three structurally related cationic, cysteine-containing peptides were identified that show sequence similarity to peptide Leucine–Arginine, a peptide with immunomodulatory and histamine-releasing properties from the skin of the northern leopard frog, Rana pipiens. The skin secretions contained a 61-amino-acid-residue peptide that inhibited porcine trypsin and possessed a 10-cysteine-residue motif that is characteristic of a protease inhibitor previously isolated from the parasitic nematode, Ascaris suum. A 48-amino-acid-residue protein containing eight cysteine residues in the whey acidic protein (WAP) motif, characteristic of elafin (skin-derived antileukoproteinase) and secretory leukocyte protease inhibitor, was also isolated. The data suggest that protease inhibitors in skin secretions may play a role complementary to cationic, amphipathic α-helical peptides in protecting anurans from invasions by microorganisms.

Frogs flee from the sound of fire.

Fire has an important role in the sensory ecology of many animals. Using acoustic cues to detect approaching fires may give slow-moving animals a head start when fleeing from fires. We report that aestivating juvenile reed frogs (Hyperolius nitidulus) respond to playbacks of the sound of fire by fleeing in the direction of protective cover, where they are safe. This is a novel response to fire not known to occur in other animals. Moreover, we identify the rapid rise-time of the crackling sound of fire as the probable cue used. These results suggest that amphibian hearing not only has evolved through sexual selection, but also must be viewed in a broader context.

Allozyme Evidence for the Separation ofRana areolataandRana capitoand for the Resurrection ofRana sevosa

The taxonomic status of Rana capito is unclear. Allozymes were surveyed for Rana areolata and populations throughout the range of R. capito, including representatives of the three putative subspecies. Fixed differences were exhibited at two loci, supporting the separation of R. capito and R. areolata. The westernmost population of R. capito, in the range of Rana capito sevosa, could be diagnosed from the remaining populations of R. capito. These remaining populations exhibited no substantial genetic divisions. We recommend the resurrection of R. sevosa as a distinct taxon.

Terrestrial burrowing ecology of newly metamorphosed frogs (Rana pipiens complex)

I examined the burrowing performance of newly metamorphosed Rana areolata, Rana blairi, and Rana sphenocephala in laboratory aquaria. Three treatments were used to determine whether metamorphs, when deprived of a water source, actively dig their own burrows, and if they utilize natural irregularities in substrate profiles or preexisting burrows as shelter from evaporative desiccation. Analysis of covariance (initial body mass covariate) revealed that individuals of all three species actively burrowed and passively utilized preexisting experimental burrows, but active burrowing, which consisted of substrate excavation using only the hind limbs, took much longer. Metamorphs that used preexisting burrows conserved water more efficiently than those that actively dug their own burrows. Rana blairi experienced the highest percent water loss across all treatments and was the only species to suffer mortality during the experiment. These data suggest that burrowing, by minimizing evaporative water loss, may be a critical adaptive behavior for metamorphic frogs in semi-arid environments.

Asymmetric competition in larval amphibian communities: conservation implications for the northern crawfish frog, Rana areolata circulosa.

Asymmetric competition in larval amphibians can influence population dynamics and community structure. This density-dependent regulatory mechanism may be of particular importance for rare or endangered species such as the northern crawfish frog, Rana areolata circulosa. Interspecific competition of R. areolata with two congenerics, R. blairi and R. sphenocephala, was examined in artificial ponds. Analysis of covariance (differential mortality covariate) indicated that interspecific competition increased larval period length and decreased metamorphic body mass of R. areolata. The number of metamorphs produced was lower for R. blairi ponds when reared with R. areolata at high density. Body mass at metamorphosis was larger for R. sphenocephala when reared with R. areolata, suggesting that R. areolata facilitates larval growth in R. sphenocephala. These results indicate that the larval performance of R. areolata was reduced in the presence of interspecific competitors. Although many conservation efforts emphasize the preservation of critical habitat or particular rare species, interactive effects of biotic components in the focal community may also be important demographic regulators.

Asymmetric competition in larval amphibian communities: conservation implications for the northern crawfish frog,

Asymmetric competition in larval amphibians can influence population dynamics and community structure. This density-dependent regulatory mechanism may be of particular importance for rare or endangered species such as the northern crawfish frog, Rana areolata circulosa. Interspecific competition of R. areolata with two congenerics, R. blairi and R. sphenocephala, was examined in artificial ponds. Analysis of covariance (differential mortality covariate) indicated that interspecific competition increased larval period length and decreased metamorphic body mass of R. areolata. The number of metamorphs produced was lower for R. blairi ponds when reared with R. areolata at high density. Body mass at metamorphosis was larger for R. sphenocephala when reared with R. areolata, suggesting that R. areolata facilitates larval growth in R. sphenocephala. These results indicate that the larval performance of R. areolata was reduced in the presence of interspecific competitors. Although many conservation efforts emphasize the preservation of critical habitat or particular rare species, interactive effects of biotic components in the focal community may also be important demographic regulators.

The Role of Relative Body Size in a Predator-Prey Relationship between Dragonfly Naiads and Larval Anurans

Size-limited predator-prey systems can be the ecological background for natural selection on prey growth rate and body size. In a laboratory experiment on one such system, individual predatory Tramea lacerata (Odonata: Anisoptera: Libellulidae) naiads of varying sizes were exposed to three densities of Rana areolata (Anura: Ranidae) tadpoles in each of five size classes. Predation rate decreased with increases in tadpole body size. Larger naiads consumed slightly more tadpoles than did smaller naiads when tadpoles were very small, but at larger tadpole sizes, naiad size did not affect the predation rate. Although the number of tadpoles consumed increased with increasing tadpole density, the proportion of the total number that were eaten decreased with increasing density. When tadpoles were very small, naiads that ate more prey grew larger. When tadpoles were larger, there was little variation in the number eaten and no detectable relationship between the number eaten and subsequent naiad growth. These data resolve several paradoxical reports in the literature.

Rana areolata in Southern Oklahoma-Northern Texas

Rana areolata in Southern Oklahoma-Northern Texas

A Partial Description of the Tadpole of Rana areolata circulosa and Notes on the Natural History of the Race

In 1939 one of us (Philip Smith) while enrolled at Southern Illinois Normal University at Carbondale, intensively pursued a field study of Rana areolata circulosa under the direction of Dr. Fred R. Cagle. Actual work on it, concentrated in the vicinity of Herrin, Illinois, began in 1938, and was continued through 1940. Unforeseen developments prevented completion of the project, although in 1942 Cagle published excerpts from the data then accuinulated. The notes recorded during the study are available at the present time, in addition to a small portion of thle preserved materials. Among the latter are five mature and transforming tadpoles, especially valuable since the larval stage of this species has never been described. With our description of the tadpoles, we include certain apparently novel materials from Smith's notes. Unfortunately all the small jars containing stomach contents and tadpoles at various stages of development were completely dry when reexamined in the summer of 1947 after a few years of storage. The material would have been a total loss had it not been possible to restore it partially by the technique described recently by Van Cleave and Ross (1947). In fact Dr. Van Cleave kindly treated the dried specimens for us. The tadpoles were rendered flexible enough to permit manipulation, although they remained shrunken in appearance. The mouth disks appear normal, but body proportions are unquestionably distorted; accordingly, while the description of the mouthparts may be considered more or iess accurate, the measurements are undoubtedly subject to correction on the basis of fresh material.

A new gopher frog from the Gulf Coast, with comments upon the Rana areolata group

A new gopher frog from the Gulf Coast, with comments upon the Rana areolata group