Knoflookpad in Callantsoog Verspreiding, voortplanting en geografische herkomst

Distribution, reproduction and geographical origin of the common spadefoot at Callantsoog An illegally introduced population of, supposedly, common spadefoots (Pelobates fuscus) was discovered in the coastal dunes of Callantsoog in 2020. Additional research on the local distribution, reproduction and provenance has been conducted in 2021. The species’ distribution extended the range that was recorded in 2020 with one new square kilometre grid, totalling 6 grids. The total number of reproduction sites (chorus activity) was determined at 12 and successful reproduction (larvae) occurred in at least four of these sites. Successful breeding waters contained no fish, were clear and had roughly neutral pH values (6,1-7). A genetic study (mtDNA) revealed the spadefoots were indeed Pelobates fuscus but with a non-indigenous origin. Their haplotypes are known from Serbia (FUS5) and Austria, Hungary and Serbia (FUS6). Throughout the native range in the Netherlands haplotype FUS13 is present, with a single population additionally containing haplotype FUS14. The illegal introduction of herpetofauna is rather popular but is highly undesirable and comes with significant risks. Changes in Dutch legislation allows privates to keep and breed indigenous herpetofauna since 2017 which increased the risk of releasing of surplus stock. Because of the risks, including secondary distribution of introduced animals into native populations, elimination of introduced populations, despite possible species rareness, should be considered a real option In 2019 werd langs een amfibieënscherm tegen de duinen bij Callantsoog volstrekt onverwachts een knoflookpad in een valemmer gevonden. Een jaar later maakten gerichte luister- en zoekacties duidelijk dat zich hier een populatie gevestigd had. In 2021 is daarom aanvullend onderzoek uitgevoerd. Aandachtspunten daarbij waren de verspreiding, de voortplanting én de geografische herkomst (op basis van genetische gegevens) van de populatie. De resultaten zijn bijzonder en voegen wéér een extra dimensie toe aan de casus van deze illegaal geïntroduceerde maar sterk bedreigde dieren