Digital Recorders Increase Detection of Eleutherodactylus Frogs (original) (raw)
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Temporal Variation in Anuran Calling Behavior: Implications for Surveys and Monitoring Programs
Copeia, 2000
Recent awareness of amphibian declines has raised the need for effective monitoring programs. Call surveys are a standard approach to monitoring populations of most anuran species. Temporal variation in calling activity, however, may result in failure to detect some species. Automated recording systems (ARS) allow consistent sampling for extended periods with little or no disturbance to calling anurans. We used an ARS to measure temporal variation in anuran calling activity during the summer of 1997 at a Carolina bay on the U.S. Department of Energy's Savannah River Site, South Carolina. We documented considerable interspecific variation in calling activity, a phenomenon that, using traditional call survey techniques, would result in failure to detect some species. In particular, we found that Southern Leopard Frogs (Rana sphenocephala), thought to breed only in early spring and fall in the region, called consistently from midnight until dawn during July. Because protocols for most call surveys dictate that the listener survey only during early evening hours, most call surveys would not detect the presence of this species. Our results indicate that temporal variation in anuran calling activity warrants further investigation and should be considered when developing anuran monitoring programs.
Comparison of anuran acoustic communities of two habitat types in the Danum Valley Conservation Area
2007
Abstract. We compared advertisement calls of frog assemblages in two different habitats, (i) an open area along a dirt road with ponds and secondary vegetation; (ii) a fast flowing stream in primary forest. Eleven frog species were recorded and significant differences in the dominant call frequencies between the two observed frog communities were discovered. Stream-breeding species produce higher frequencies than species occurring in the roadside habitat. Noisy habitats have an influence on dominant frequency and demand acoustic adaptations to increase the signal-to-noise ratio. Selective logging represents a major threat to stream-breeding anurans in Sabah. Pollution of clear water threatens the stream-dependent herpetofauna.
Counting chirps: acoustic monitoring of cryptic frogs
1. Global amphibian declines have resulted in a vital need for monitoring programmes that follow population trends. Monitoring using advertisement calls is ideal as choruses are undisturbed during data collection. However, methods currently employed by managers frequently rely on trained observers and/or do not provide density data on which to base trends. 2. This study explores the utility of monitoring using acoustic spatially explicit capture– recapture (aSCR) with time of arrival (ToA) and signal strength (SS) as a quantitative monitoring technique to measure call density of a threatened but visually cryptic anuran, the Cape peninsula moss frog Arthroleptella lightfooti. 3. The relationships between temporal and climatic variables (date, rainfall, temperature) and A. lightfooti call density at three study sites on the Cape peninsula, South Africa, were examined. Acoustic data, collected from an array of six microphones over 4 months during the winter breeding season, provided a time series of call density estimates. 4. Model selection indicated that call density was primarily associated with seasonality fitted as a quadratic function. Call density peaked mid-breeding season. At the main study site, the lowest recorded mean call density (0Á160 calls m À2 min À1) occurred in May and reached its peak mid-July (1Á259 calls m À2 min À1). The sites differed in call density, but also the effective sampling area. 5. Synthesis and applications. The monitoring technique, acoustic spatially explicit capture– recapture (aSCR), quantitatively estimates call density of calling animals without disturbing them or their environment. In addition, time of arrival (ToA) and signal strength (SS) data significantly add to the accuracy of call localization, which in turn increases precision of call density estimates without the need for specialist field staff. This technique appears ideally suited to aid the monitoring of visually cryptic, acoustically active species.
SALAMANDRA-BONN-, 2007
We compared advertisement calls of frog assemblages in two different habitats, (i) an open area along a dirt road with ponds and secondary vegetation; (ii) a fast flowing stream in primary forest. Eleven frog species were recorded and significant differences in the dominant call frequencies between the two observed frog communities were discovered. Stream-breeding species produce higher frequencies than species occurring in the roadside habitat. Noisy habitats have an influence on dominant frequency and demand acoustic adaptations to increase the signal-to-noise ratio. Selective logging represents a major threat to stream-breeding anurans in Sabah. Pollution of clear water threatens the stream-dependent herpetofauna.
The Importance of Ambient Sound Level to Characterise Anuran Habitat
PLoS ONE, 2013
Habitat characterisation is a pivotal step of any animal ecology study. The choice of variables used to describe habitats is crucial and need to be relevant to the ecology and behaviour of the species, in order to reflect biologically meaningful distribution patterns. In many species, acoustic communication is critical to individuals' interactions, and it is expected that ambient acoustic conditions impact their local distribution. Yet, classic animal ecology rarely integrates an acoustic dimension in habitat descriptions. Here we show that ambient sound pressure level (SPL) is a strong predictor of calling site selection in acoustically active frog species. In comparison to six other habitat-related variables (i.e. air and water temperature, depth, width and slope of the stream, substrate), SPL had the most important explanatory power in microhabitat selection for the 34 sampled species. Ambient noise was particularly useful in differentiating two stream-associated guilds: torrents and calmer streams dwelling species. Guild definitions were strongly supported by SPL, whereas slope, which is commonly used in stream-associated habitat, had a weak explanatory power. Moreover, slope measures are non-standardized across studies and are difficult to assess at small scale. We argue that including an acoustic descriptor will improve habitat-species analyses for many acoustically active taxa. SPL integrates habitat topology and temporal information (such as weather and hour of the day, for example) and is a simple and precise measure. We suggest that habitat description in animal ecology should include an acoustic measure such as noise level because it may explain previously misunderstood distribution patterns.
Freshwater Science, 2020
For conservation of endangered species, basic ecological information is indispensable. Environmental DNA (eDNA) is increasingly used to estimate the presence/absence of aquatic organisms such as frog species. However, the efficiency of detecting eDNA may depend on the ecological characteristics of the target frog species. Here, we adopted an eDNA approach for detecting 3 endangered Japanese species (Babina subaspera, Odorrana splendida, and O. amamiensis). We compared eDNA detection with a traditional acoustic survey method in 3 different seasons. Detection of species was not always consistent between the 2 methods, probably because acoustic surveys target only calling adult males but eDNA detects individuals of both sexes and at any life-history stage in water. Moreover, the differences in detection patterns between the 2 methods among species may be correlated with different characteristics of mating behavior (e.g., calling volume) and life history of tadpoles (e.g., migration ability). The optimal season for detection by eDNA method also differed between the 3 species, probably because of differences in breeding season and larval characteristics. We show that results obtained from eDNA detection methods and traditional field observation techniques, including acoustic surveys, are not always consistent with each other but rather depend on the ecological characteristics of the respective target species. It is therefore necessary to consider the ecological traits of frog species, such as breeding season and seasonal shifts in tadpole abundance, when applying eDNA methods for distribution surveys.
Surveying a Threatened Amphibian Species through a Narrow Detection Window
Copeia, 2013
Crawfish Frogs (Lithobates areolatus) are a relatively widespread but understudied North American species suspected to be in steep decline. Discussions to petition this species for federal listing have begun and therefore effective techniques to survey and monitor populations must be developed. Crawfish Frogs produce unusually loud breeding calls, making call surveys the most efficient way to assess populations; however, their peak breeding period lasts for only a few nights, sometimes for only one night. We used automated calling survey techniques at two wetlands where the numbers of Crawfish Frog males present were known (±1%) for the entire length of the breeding season to examine detection probabilities in relation to season, time of day, weather variables, survey duration, and the numbers of males present. We then used these data to ask three simple but important questions: 1) When should researchers listen-that is, what times and under what environmental conditions should surveys for Crawfish Frogs take place? 2) How long should surveys last? and 3) What can call surveys tell us about the size of a population? The most supported model for detection included the quadratic relationship of time and date, a positive linear relationship with temperature, and a negative linear relationship with recent rain, while the most supported model for estimating abundance included the quadratic relationship of time and date, and call rate. Five-minute surveys should suffice during peak breeding for known large populations; 15-minute surveys with repeat visits should be used for small populations or when sampling new areas. These findings should improve manually collected (auditory) call survey efficiencies for Crawfish Frogs, surveys that are being organized to provide the first objective data on the status of this species across its range.
Zootaxa, 2017
Vocalizations of anuran amphibians have received much attention in studies of behavioral ecology and physiology, but also provide informative characters for identifying and delimiting species. We here review the terminology and variation of frog calls from a perspective of integrative taxonomy, and provide hands-on protocols for recording, analyzing, comparing, interpreting and describing these sounds. Our focus is on advertisement calls, which serve as premating isolation mechanisms and, therefore, convey important taxonomic information. We provide recommendations for terminology of frog vocalizations, with call, note and pulse being the fundamental subunits to be used in descriptions and comparisons. However, due to the complexity and diversity of these signals, an unequivocal application of the terms call and note can be challenging. We therefore provide two coherent concepts that either follow a note-centered approach (defining uninterrupted units of sound as notes, and their en...