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Sixth scientific article: Frogs migrate during apricot blossom

Every year, thousands of amphibians are killed on Austria's roads. Amphibian protection measures are widely available, but need to be installed in time for migration. The University of Natural Resources and Life Sciences Vienna (BOKU), the Central Institute for Meteorology and Geodynamics (ZAMG), the Austrian Society for Nature Conservation and the Natural History Museum Vienna set the goal to better predict the start of amphibian migrations. The analysis of more than 11,500 observations over 18 years shows that the flowering dates of apricot and goat willow are good predictors of amphibian migration and can thus provide the starting signal for conservation measures.

Predicting amphibian migration - why is it important?

In order to mitigate the danger of roads for amphibians during their seasonal migration, temporary protection measures are used in Austria in addition to permanent facilities (so-called amphibian tunnels). For this purpose, protective fences are usually erected by volunteers along particularly endangered road sections and checked every day to see if there are any animals on site. Each animal is carried across the road by hand and released there. The challenge here is that the amphibian migration is weather-dependent and starts at different times each year, and the fences must be in place well in advance of the start of the migration. If the migration starts earlier than expected this means more amphibians killed, if the amphibian migration starts later than expected this means unnecessarily spent man hours for the volunteers. 

What do plants have to do with amphibians?

At first glance, amphibian migration has nothing to do with plants, but: amphibian migration is influenced primarily by temperature and day length, just like the flowering and leaf unfolding of plants. A team of researchers from the Institute of Zoology at BOKU Vienna, ZAMG, the Austrian Society for Nature Conservation and the Natural History Museum Vienna therefore analyzed the temporal occurrence of amphibian migration of grass frogs and common toads and the flowering and leaf development of seven plant species. For this, a unique dataset of a total of 11 569 observations from 18 years (2000-2018) from four Citizen Science projects was available.

This is what came out

According to statistical model calculations, the flowering of apricots and goat willows is particularly suitable for estimating the onset of grass frog migration. The earlier the apricot bloom the earlier the grass frog migration. In the years analyzed, the apricot flowered almost simultaneously with the grass frog migration, while the goat willow flowered about 20 days before. According to the model, the goat willow is also suitable for estimating the migration of the common toad. 

Gernot Neuwirth of Naturschutzbund Österreich: "Currently, the start of amphibian migration is estimated mainly by personal experience of people involved - so predicting the start of grass frog amphibian migration with the easily recognizable and common apricot or goat willow bloom could be especially helpful for volunteers with limited experience and for regions without past values." Amphibian migration could thus be estimated without technical effort, and protective measures could be established in a timely manner.

Data from Citizen Science

These results and conclusions could only be achieved with the help of the large amount of data collected by volunteers in the Citizen Science projects naturbeobachtung.at, Roadkill, Herpetofauna and Phenowatch. "Citizen Science makes it possible to investigate complex scientific questions that require data over long periods of time and from large study areas," says Florian Heigl, head of the Roadkill project and coordinator of Österreich forscht: "We would like to take this opportunity to thank all Citizen Scientists who made this study possible and invite all interested parties to participate in Citizen Science projects and actively contribute to science."

Studie: https://www.nature.com/articles/s41598-021-00912-4

The four Citizen Science projects:

naturbeobachtung.at (naturschutzbund Österreich) 

Phenowatch (Central Institute for Meteorology and Geodynamics Vienna) www.phenowatch.at

Roadkill (Citizen Science working group, Institute of Zoology) www.roadkill.at

Amphibians and Reptiles of Austria under Observation (Natural History Museum Vienna) nhm-wien.ac.at