frogs {blmeco}

Counts of the number of frogs in a water body

Description

Counts of the number of frogs in ponds of the Canton Aargau, Switzerland.

Usage

data(frogs)

Format

A data frame with 481 observations on the following 10 variables.

count1

number of counted frogs during the first visit

count2

number of counted frogs uring the second visit

elevation

elevation, meters above sea level

year

year

fish

presence of fish (1 = present, 0 = absent)

waterarea

area of the water body in square meters

vegetation

indicator of vegetation (1 = vegetation present, 0 = no vegetation present)

pondid

name of the pond, corresponds to observation id

x

x coordinate

y

y coordinate

Details

The amphibian monitoring program started in 1999 and is mainly aimed to survey population trends of endangered amphibian species. Every year, about 30 water bodies in two or three randomly selected priority areas (out of ten priority areas of high amphibian diversity) are surveyed. Additionally, a random selection of water bodies that potentially are suitable for one of the endangered amphibian species but that do not belong to the priority areas were surveyed. Each water body is surveyed by single trained volunteer during two nocturnal visits per year. Volunteers recorded anurans by walking along the waters edge with precise rules for the duration of a survey taking account of the size of the surveyed water body and noting visual encounters and calls. As fare as possible, encountered individuals of the Pelophylax-complex were identified as Marsh Frog (Pelophylax ridibundus), Pool Frog (P. lessonaea) or hybrids (P. esculentus) based on morphological characteristics or based on their calls. In the given data set, however, these three taxa are lumped together.

Source

The data is provided by Isabelle Floess, Landschaft und Gewaesser, Kanton Aargau.

References

Schmidt, B. R., 2005: Monitoring the distribution of pond-breeding amphibians, when species are detected imperfectly. - Aquatic conservation: marine and freshwater ecosystems 15: 681-692.

Tanadini, L. G.; Schmidt, B. R., 2011: Population size influences amphibian detection probability: implications for biodiversity monitoring programs. - Plos One 6: e28244.

Examples

data(frogs)