Rockface |Boulder | Steppe| Water | Timberline ecotone | Alpine habitat activity

The alpine zone offers different types of habitats for animals. Each habitat favors some special adaptation and houses a specific species composition. We will present and characterise the five main habitats. The classification is very rough and many subclasses of habitats could be made. To make comparisons between different mountains of the world possible, however, we have chosen the division of habitat at this low level.

The table shows the number of species that live in the habitats of the particular mountains.

The differences between the European Alps and the Ethiopian Highlands are clear. The European Alps are composed of a small scale mosaic of habitats. Factors like the directional exposure of a slope or precipitation play an important role in characterising a habitat. Accordingly, we find a homogenous distribution of animals in the different habitats. On the other hand, the Ethiopian Highlands show a more uniform development of the landscape. Large steppes shape the alpine landscape and the transition from the timberline ecotone to the steppes is less patchy than in the European alps. Boulder fields and open water are poorely represented and rock faces are very steep. As a result, we can see an accumulation of species in the two common types of habitats. The Snowy Mountains of Australia resemble the European Alps in their appearance.

In the following section we will present the five main habitats in the alpine zone. We will also enlarge our view to include organisms other than mammals in the description of habitats.

Rockface

Rockfaces are the habitat preferred by invertebrates and birds. These animals live on the rock surface, in crevices or caves. Birds prefer the rock habitat for safe nesting sites. Among birds living in the rocks, the insectivores dominate, since insects can be readily found in this habitat. But herbivores and raptors (e.g. bearded vulture (Gypaetus barbatus)) are also found to nest in the rocks. Among insects, predators like araneidae dominate. In addition, the rockface is a refuge for climbing animals (e.g. ibex (Capra ibex) and chamois (Rupicapra rupicapra) in the European Alps or gelada baboons (Theropithecus gelada) in Ethiopia), where they are protected from predators such as lynx (Lynx lynx) or leopard (Pantherus pardus) respectively.

Food on the rockface is very sparse, but there is a variable abundance of single plants, lichens and mosses. A special characteristic of rock habitats is the huge difference in temperature between night and day as well as between the ground and the air above.

Boulder

Boulders are formed by rock falls, weathering or are relicts of glaciation. So boulder fields consist of rocks of different granularity. Good cover is offered for animals that can not physically defend themselves against predators. The fauna in boulder fields includes small mammals as well as reptiles, ground nesting birds and invertebrates. Animals living in boulder fields also profit from the many different microhabitats the rocks provide (sun-warmed rocks, wind protected areas, shaded places, shelter from precipitation). Especially for poikilotherm reptiles, sun warmed rocks are of great importance. For small mammals and ground nesting birds, the most important feature of boulder fields are shelter and concealment from predators. Food supply for herbivores is sparse and comprises mostly lichens, mosses and some higher plants that are weak competitors and could not survive in closed vegetation.

Steppe

A great proportion of the alpine zone is steppe habitat, dominated by grassland. Steppe is sparsely structured and offers little cover from predation. Consequently, many small mammals living permanently in the steppe are burrowers, which create their own cover by digging.

Another large group of animals inhabiting the steppe are grazers for which this habitat offers a large quantity of food. scarcely any of the large herbivores permanently live in the alpine steppes. Most of them visit this habitat to feed and retreat into the timberline ecotone to rest.

A third group of animals for which the steppe is an important habitat is the invertebrates. As a result of the high phytomass productivity of steppes, the decomposers account for the largest part of invertebrates.

Steppes are an alpine habitat which is very often affected by human activities.

Water

In the alpine region we can find water in different forms. Typical bodies of water are springs, streams, ponds, lakes or fens.
In contrast to fishes and some insect larvae, the mammals live along the water and not in the water. Thus, the water performs different tasks: it can be a refuge or a source of food. The main advantage of the habitat “water” is its stable microclimate. Running water seldom reaches temperatures below 0 °C and even in lentic water some places remain favourable through local fluctuations of temperature. Fluctuation of water temperature between summer and winter is around 10 °C in contrast to land habitats, where fluctuations can reach 50 °C or more.

Timberline ecotone

The timberline ecotone is the transition zone between the subalpine forests and the alpine zone. It is characterized by a patchy distribution of open and closed vegetation. This mosaic is essential for the occurrence of some animals like the grouse. For other animals, the timberline ecotone serves as a refuge which provides cover and food.

The vegetation in this zone can vary in different regions of the world. In the European Alps, the timberline ecotone is dominated by spruce and in Ethiopia it is dominated by heather. However, the ecological function of each dominant vegetation remains the same.

29 August 2011
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