Última versión Publicado por Dutch National Database of Flora and Fauna (NDFF) en Mar 28, 2018 Dutch National Database of Flora and Fauna (NDFF)

The monitoring program primarily focuses on areas where key species occur. However, the development of common species in these areas can also provide important additional information. We therefore follow all amphibians in areas where key species live, including common varieties. Data about all species is collected during field visits. The monitoring program supplies information about the current state of and changes to amphibian populations in the Netherlands in collaboration with Statistics Netherlands (CBS). Sub protocols have been developed for the different species because of the various research methods that are used.

1.203a standard protocol all amphibian species All present amphibian species are registered. Monitoring takes place from February to September (any other observations are marked as invalid). The aim is 4 field visits. The following identification methods can be used for the standard inventory procedure: when encountering a body of water, listen first, walk down the bank (carefully) and make a visual observation. Then, a hand net can be used to catch specimens. Observations of the Pelobates fuscus, Salamandra salamandra, Bombina variegata and Alytes obstetricans (and in some cases, the Hyla arborea) are marked as invalid in the monitoring program, as these are categorised under species-oriented routes.

1.203b traps All present amphibian species are registered. Monitoring takes place from February to September (any other observations are marked as invalid). Traps are placed in the evening and checked in the morning. This method is primarily used to catch Lissotriton and amphibian larvae. So very little data is collected with this method about eggs, frogs and toads.

1.203c listening routes Natterjack toad A fairly large area can be monitored in the evening to check for Epidalea calamita. An observer can visit various fixed locations by car or bike to listen for calling activity for 1 or 2 minutes. The period runs from mid-April to May and the aim is 3 field visits. Knowledge of the species is needed to predict which evenings are best to hear calling activity. Observations of other specimens are marked as invalid.

1.203d listening routes European tree frog A fairly large area can be monitored in the evening to check for Hyla arborea. An observer can listen for calling activity at fixed locations (near water). The period runs from mid-April to May and the aim is 3 field visits. Knowledge of the species is needed to predict which evenings are best to hear calling activity. Observations of other specimens are marked as invalid. This also applies to counting visits of juvenile species.

1.203e listening routes Garlic toad The Pelobates fuscus calls out under water. This can either be heard by ear or by hydrophone. An observer can listen along spawning waters to observe and note the number of callers. The period runs from mid-April to May and the aim is 3 field visits. Observations of other specimens are marked as invalid.

1.203f fixed transact Salamandra salamandra The Salamandra salamandra is monitored at night by walking along a fixed transact, preferably when it rains and the temperature is higher than 8 °C. In principle, field visits can be carried out year-round, although probability rates are higher in spring and autumn. Only adult and subadult animals are used in index calculations. Juvenile specimens and larvae are marked as invalid as per the protocol. This also applies to observations of other specimens.

1.203g monitoring Yellow-bellied toad The adult and subadult Bombina variegata is counted from June to August by inspecting banks of waters. Index calculations are made based on data collected by professionals in historical habitats and newly developed habitats (once it is established that the species maintains a population, so after about 5 years).

1.203h monitoring Common midwife toad Larvae of the Alytes obstetricans are counted and caught with a hand net from June to August. Index calculations are made with field data collected by professionals.

Dataset available via https://www.ndff.nl/english / serviceteamndff@natuurloket.nl

Positive observations without zeros

NDFF protocol 1.203 https://www.ndff.nl/overdendff/validatie/protocollen/1-203-monitoring-van-amfibieen-in-nederland-2015-2-3/