The majority of the 19 amphibian species native to Bavaria spend most of their time on land. For their reproduction, however, all of the species – with the exception of the alpine salamander (Salamandra atra) – are dependent on the availability of suitable spawning sites. Eight of the amphibian species occur most often on sites in the forest or on the edge of the forest. The forest thus plays a significant role here as a habitat.
Amphibians - between water and land
Amphibians live in different habitats over the course of the year: In the winter months – from around November to February – they seek out frost-free winter quarters (e.g. mouse tunnels or other small hollows in the ground or under lying deadwood), because as ectothermic (cold-blooded) vertebrates, they cannot regulate their body temperature themselves. When they emerge from hibernation in spring, the breeding season begins for the sexually mature animals, and they migrate to suitable spawning sites to mate and lay their eggs. It is often only at this time, when they set off en masse to migrate to their spawning sites, that they become visible for us humans. After mating, they move to suitable summer habitats e.g. into forests. To escape drought and rising temperatures, the amphibians seek out hiding places in the soil or under logs or stones during the day, and only go looking for prey during wet weather or at night.
Fig. 1: Water bodies in the forest are important for the reproduction of our amphibians. A rich range of structures along and near the banks, thanks to deadwood and an abundance of woody plants, offers plenty of places for amphibians to hide and spend the winter (Picture: Christine Franz).
The forest as a habitat
Fig. 2: Yellow-bellied toad (Bombina variegata) (Picture: Boris Mittermeier)
Fig. 3: Fire salamander (Salamandra salamandra) (Picture: Gero Brehm, AELF FFB)
Fig. 4: Northern crested/great crested newt (Triturus cristatus) (Picture: H.-J. Fünfstück/ www.5erls-naturfotos).
Fig. 5: Alpine salamander (Salamandra atra) (Picture: Kathrin Weber).
The forest serves many of our native amphibian species as a habitat. Typical species to be found in the forest are the fire salamander, the yellow-bellied toad, the northern crested newt, the alpine salamander and several other species. They use wet areas of the forest – waterlogged hollows and depressions under upturned root plates, for example, and small pools – for reproduction in spring and as somewhere to live in the summer and winter months. Bodies of water like this in the forest are often very shallow, free of fish, and low in the number of other natural predators that might prey on the spawn and larvae. But ditches along forest and agricultural tracks, as well as the ruts left by vehicles and skidding during forestry operations, which temporarily fill up with water and then dry out again, also offer the ideal conditions for reproduction of some pioneer species such as the yellow-bellied toad. In addition to spawning sites, the adult amphibians and juvenile animals also require suitable terrestrial habitats – within reach of the water body because of the animals’ limited mobility on land.
In forests managed using a close-to-nature style of management, amphibians will find a diverse range of places to hide – in mouse burrows or under root stocks, lying deadwood, or piles of branches or stones. Structures like this are comparatively moist and, in combination with the shade provided by the tree canopy, protect the delicate skin of the amphibians from drying out in the dry periods of the summer months. Thanks to their stable microclimate, these refuges are also frost-free places to spend the winter. Sometimes natural ageing or decaying processes and/or the targeted removal of individual trees create small gaps in the tree canopy. This promotes the development of herbaceous and shrub vegetation and can thus benefit amphibians.
However, not all forests are equally suitable as habitats. In pure coniferous stands, for example, there is often a shortage of suitable ground vegetation, and a thick carpet of needles is not a good habitat for insects such as isopods, mosquitoes and beetles, or for snails and worms, all of which are an important food source for amphibians.
Protective measures
Comparatively simple measures can be implemented to protect and thus ensure the long-term survival of amphibian populations in the forest. The conservation or creation of new bodies of water in the forest and provision of structurally rich terrestrial habitats around them play a crucial role in this.
- Conserving and maintaining forest water bodies
Existing small bodies of water in the forest should be conserved and maintained. Less crucial than the size of the water body is its condition and the structural variety around it. Forest streams and ditches should also be maintained. Here it is important to keep the waters as far as possible free of fish. Along forest roads, care should be taken to maintain ditches and banks in such a way that the impact on amphibians is minimised (mulching and ditch-clearing only outside the breeding season, etc.).
- Creation of new small bodies of water
Artificially created wetland biotopes are another way to promote amphibians. In order to keep the costs of creating them low, it makes sense to create hollows and depressions primarily on waterlogged soils or those close to the groundwater level. Bodies of water created in this way should be shallow enough to dry out periodically and remain free of fish.
Fig. 6: Small bodies of water can be established with little effort, e.g. by giving roadside ditches cascade-like profiles (Picture: U. Messlinger).
- Conservation and promotion of terrestrial habitats
Amphibians require suitable terrestrial habitats in the vicinity of their aquatic sites. A close-to-nature style of forest management is beneficial for amphibian populations. Stands rich in deciduous trees and with plenty of ground vegetation offer an ideal range of food sources and places to hide. The creation of sparse structures allowing light on to the water body and its immediate surroundings is good for the warmth requirements of many amphibians and encourages the growth of the layer of herbaceous plants and shrubs they require.
Wide, structure-rich forest edges and forest-internal transition zones along tracks and around clearings should be conserved and promoted. These are important structures connecting adjacent terrestrial habitats such as wet meadows, fallow land and fields.
Deadwood around bodies of water offers safe places to hide during the day and to spend the winter. The supply of deadwood should thus be improved by leaving rootstocks, piles of branches or the trunks of dead trees in the forest. Beaver dams and lodges are also excellent hiding places.
Fig. 7: An enriched supply of deadwood offers many amphibians valuable daytime hiding places and winter quarters (Picture: Kathrin Weber).
Fig. 8: Beavers not only create new wet habitats; their dams also provide excellent daytime hiding places (Picture: Christine Franz).
- Leaving of vehicle and skid tracks
For some amphibians, especially for the yellow-bellied toad, vehicle and skid tracks filled up with water are important and often the only spawning sites available in the forest
