Copenhagen Zoo has released 116 captive-bred natterjack toads into an active NCC gravel pit in Denmark, and keepers report calling males as the fragile population slowly takes hold.
DR reported on August 24, 2026, that gravel pits may become an unexpected refuge for Denmark’s smallest toad species. The broadcaster followed 116 natterjack toads raised at Copenhagen Zoo‘s breeding center as they were released into a pit operated by the contractor NCC.
The natterjack toad grows to about eight centimeters and often carries a yellow stripe down its back. It lays eggs in shallow pools that must dry out roughly once a year, so fish and other predators cannot establish themselves. According to animal keeper and project leader Lene Vestergren Rasmussen, the breeding habitat is missing, and the species disappears as a result.
Such pools once existed on coastal meadows, but many have been drained or converted to farmland. Rasmussen appears in the DR program “Dyrenes Danmark”, hosted by biologist Vicky Knudsen. She told DR that gravel pits hold large potential for the species because they recreate those bare, shallow conditions.
Eddie Bach, project leader for the zoo’s national projects, said the toads were released last summer and that the recovery is moving forward slowly. Calling males have been registered at the site. There have also been problems with aquatic insects such as water striders and dragonfly larvae, which prey on the tadpoles.
The team has installed underwater fences to give the tadpoles protection. More toads were released this summer to test whether the animals can build a self-sustaining population. Per Bach, a drought or a very wet spring could cost an entire breeding season, which can be decisive for a threatened population.
NCC has its own biologist attached to the project, alongside periodic monitoring by the zoo. Bach noted that toads and trucks can share the pit because the amphibians are mostly active at night, when the vehicles are not running. Copenhagen Zoo, which has worked on conservation and habitat restoration for more than 20 years, hopes to set up similar partnerships at other gravel pits.
How the project started
According to a 2021 press release from NCC, natterjack toads were found breeding naturally in the Munke Bjergby gravel pit near Sorø in 2019. That discovery prompted NCC, Danmarks Naturfredningsforening and Copenhagen Zoo to dig new breeding ponds and keep a genetic backup of tadpoles at the zoo. A 2023 NCC release stated that the species was then known from only four localities on Zealand.
The local branch DN Sorø has reported that 100 adult toads were released into a permanent breeding pond, followed by 188 juveniles across three ponds in July 2024. The natterjack toad is protected as an Annex IV species under the EU Habitats Directive, meaning its breeding and resting sites may not be destroyed.
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