Amphibians in a blue-green infrastructure stream on the NMBU campus

Abstract

Amphibians are the most threatened vertebrate group globally, facing high rates of decline and extinction, with habitat loss and degradation being the largest threat. Infrastructure development and urbanisation is a large driver of this decline, destroying both terrestrial and aquatic habitats and changing catchment hydrology. Blue-Green Infrastructures (BGIs) reintroduce natural elements into urban environments and are increasingly used to mitigate these impacts. BGIs create habitats for a range of organism groups and might provide an opportunity to create habitat for species of conservation concern. The aim of my thesis was to investigate if blue-green infrastructures can support amphibian populations.

To this end, I studied the amphibians in a “blue-green stream” that was recently constructed on the campus of the Norwegian University of Life Sciences in Ås, Norway. Observational and trapping methods were used to identify resident amphibian species. Additionally, artificial macrophytes were constructed to test their suitability for oviposition by the smooth newt (Lissotriton vulgaris). Furthermore, water temperature was measured, and the crustacean community was sampled and analyzed to identify potential constraints on amphibian presence.

The common toad (Bufo bufo), common frog (Rana temporaria), and smooth newt were found to be reproducing in the stream system. No newt eggs were found on the artificial macrophytes, however larvae were found in one of the ponds. The resident species are generalists and none of the three red-listed species were found. Fish presence, water temperature and food availability might be limiting occurrence in some parts of the stream. The red listed species moor frog (Rana arvalis), great crested newt (Triturus cristatus), was absent and their occurrence might be limited by a lack of source population, suitable terrestrial habitat, migration barriers, and unsuitable stream design. However, the moor frog and great crested newt have been found in more urban settings elsewhere and therefore should be able to colonise blue-green infrastructures, provided they are suitably designed. The Norwegian population of the red listed pool frog (Pelophylax lessonae) is small (<50 individuals) and only present in a few ponds in close proximity in Agder county (approximately 180 km southwest of Ås). The species is therefore not relevant to this study.