Meetnetten.be - Chorus counts for Amphibia in Flanders, Belgium

Study Extent

1. Pelobates fuscus, or the common spadefoot toad, is found in fishless cattle drinking pools and relatively nutrient-rich ponds, but also in cut brook and river meanders in a fairly open, sandy environment. These are often water features in (buffered) heathlands, but also near dikes and even vegetable gardens and extensively managed fields. This type of habitat is rare in Flanders. The common spadefoot currently only occurs in the central part of Limburg. 2. Hyla arborea, or the common tree frog, is found in the scrubland of the Limburgse Kempen, a restricted section of the Antwerpse Kempen near the Belgian-Dutch border, and the dunes of the Zwin. In recent years, the Flemish population has increased. 3. Epidalea calamita or the Natterjack toad is a true pioneer species that thrives in dynamic environments. The species reproduces from April to August, when the animals gather in breeding pools and the males call loudly.

Sampling

For the tree frog and spadefoot toad the number of calling males is counted in the reproductive habitat at least twice a year. 1. Male Pelobates fuscus call from the bottom of the waterbody. The calls being fairly weak, counting the exact number of calling males by ear can be challenging. This is particularly the case when other anurans such as Hyla arborea are calling simultaneously. Therefore, the use of an underwater hearing device or hydrophone is advocated. Each waterbody is investigated with waders, in order to approach the calling animals upto hearing distance. 2. Hyla arborea: Monitoring in the framework of the Tree Frog Monitoring Network is done by counting the number of calling males, or in some cases, by estimating the number.
3. For the Natterjack toad monitoring network, calling choruses need to be monitored three times. The number of calling males is counted or in some cases, when the population turns out to be too large, estimated. The number of calling males is counted exactly at each visit. For up to 50 animals the sounds are still good to distinguish and localize so that this is easy (Bauwens & Speybroeck, 2014; Groenveld et al., 2011). With more animals a more rough estimate can be given. Sampling was done using the protocol described in De Bruyn et al. (2015), updated by Speybroeck et al. (2020), and explained to volunteers in Lewylle et al. (2017).

Quality Control

Data are collected using a predefined sampling protocol.

Method steps

1. Researchers from INBO and Natuurpunt Studie define and document the appropriate sampling protocol for the target species.
2. Fieldwork is planned and coordinated by Natuurpunt Studie, using https://meetnetten.be.
3. Data are collected in the field by specialized volunteers, using the predefined sampling protocol.
4. Volunteers enter the collected data in https://meetnetten.be.
5. A custom SQL view is created in the meetnetten.be database to map the original data to Darwin Core as an event core with an occurrence extension
6. The Darwin Core views are connected to the INBO IPT and documented with metadata.
7. The dataset is published and registered with GBIF.

The target Caudata species for Meetnetten.be are listed at https://meetnetten.be/#group-1. Other salamanders observed during the sampling are also included. This dataset covers the amphibian chorus counts protocol, for which there are 3 target species.

1. Animalia
   rank: kingdom
2. Chordata
   rank: phylum
3. Amphibia
   rank: class
4. Caudata
   rank: order
5. Anura
   rank: order
6. Hyla arborea
   rank: species
7. Epidalea calamita
   rank: species
8. Pelobates fuscus
   rank: species

Flanders, Belgium