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Amphibians

General information

Amphibians are vertebrates that usually generate mixed or negative feelings among people. However, evidence proves more and more often that amphibians deserve our admiration: they appeared about 350 million years ago and although their body is not protected by feathers, scales or fur – only by permeable skin and its afferent substances – they managed to survive dinosaurs, major land movements and meteorite falls.  At present, there are over 6,500 species of amphibians all over the world.

However, amphibians have become the most endangered vertebrates in the world. The rate at which amphibian species become extinct is alarming, large populations disappearing over brief periods of time. The main cause of their extinction is human intervention – destruction of habitats, pollution, introduction of non-native species of animals (such as fish), over exploitation and so on.

We must also say that amphibians have certain features that make them vulnerable to becoming extinct if sudden changes occur in their environment. Two of those features are presented below:

  • Their life cycle makes them dependent of two living environments – water and land. Most amphibian species reproduce in water, having two aquatic development stages: eggs and larvae. The larvae go through a metamorphosis process consequently to which the terrestrial environment becomes essential. It is on the land that they disperse, migrate, feed or winter. Each year, adult amphibians migrate regularly between the two living environments. The destruction of the aquatic environment (drainage of wetlands, introduction of predators etc.) or of the terrestrial environment (deforestations, land burning, building driveways, extension of urban spaces etc.) and the interruption of the connection between the two environments causes the decline of the amphibian populations in the respective areas.
  • Their physiological features, such as the permeable skin that acts both as a respiratory organ (together with the lungs) and as an osmoregulator organ, make amphibians sensitive to changes in their microclimate. Amphibians prefer wet and chilly terrestrial areas (sometimes they live even in cellars!). Human impact usually results in local changes to the microclimate, which affects amphibians. As a consequence, amphibians become inactive, hide, do not feed and cannot accumulate the food reserves necessary for wintering and for reproducing in spring. 

Amphibians in the Breite Reserve

Eight species of amphibians inhabit the Breite plateau: the great crested newt (Triturus cristatus), the common newt (Triturus vulgaris ampelensis), the yellow-bellied toad (Bombina variegata), the common toad (Bufo bufo), the common spadefoot (Pelobates fuscus), the European tree frog (Hyla arborea), the agile frog (Rana dalmatina) and the European common brown frog (Rana temporaria).

The reserve is rich in terrestrial habitats suitable for amphibians, as the wetland vegetation and the forest are well represented. Amphibians use the temporary ponds for reproduction; the occurrence and success in the reproduction of various species depend on those habitats. The amphibian species that have long larvae stages use the habitats with prolonged aquatic periods for their metamorphosis. Observations made on the Breite show that the newt larvae develop well if the aquatic period of the reproduction habitats is longer than 90 – 120 days (90 for the common newt and120 for the great crested newt). In other words, the larvae of these species do not metamorphose if the habitat goes dry two months after inception. The larvae periods of the other species are: over 60 days for the common toad, the agile frog, the European tree frog and the common spadefoot, over 40 days for the European common brown frog and over 30 days for the yellow-bellied toad. Long term studies have shown that the species that have long larvae periods (over 60 days) are more likely to fail in reproducing.

Given the above, we may say that the species that have longer larvae periods are more sensitive to the factors that make the aquatic period of the reproduction habitats shorter. We must mention that the hydrological regime of the plateau suffered major changes due to the drainage ditches dug in the 80’s, which reduced the aquatic period of the wetlands. Nowadays, some of those ditches have the longest aquatic periods in the Reserve. So it is only natural that the amphibian species that have a long larvae period should reproduce more successfully in these ditches, and some of them should metamorphose exclusively here. However, in arid years all habitats go dry – for example, in 2007 the drainage ditches had water for a period of only 40 days on average! Recent studies have shown that ceasing grazing results in the excessive development of plants, which in turn causes the dramatic shortage of the aquatic period of temporary wet habitats through evapotranspiration (the aquatic period becomes up to 3 - 4 weeks shorter!). Controlled low-impact grazing is hence necessary in order to maintain the wet habitats in the Breite Reserve.

In conclusion, in order to ensure the continuity of the amphibian populations in the Breite Reserve, we must maintain a varied ensemble of wet habitats, from short-term to more permanent ones. The factors that affect the amphibians in the Reserve manifest through anthropogenic effects (grazing, drainage) and natural weather effects. The latter are amplified by human interventions, so it is very difficult to separate them clearly at present.

Conservation actions for the amphibians in the Breite Reserve

The Mihai Eminescu Trust undertook the following management actions aimed at protecting the amphibians in the reserve:

  • Ecological research (monitoring included). These studies began in 2003 and provided us important information regarding the species ecology, also representing an important reference point for future interventions.
  • Closing drainage ditches. This intervention began in 2007 and was an important step for balancing the hydrological regime of the reserve. It led to the creation of 6 new aquatic habitats, all of which are now colonized by various species of amphibians. In some areas, the increase in soil humidity brought about by this intervention encouraged the development of certain plant species along the ditches (e.g. Polygonum bistorta – the common bistort).
  • Introducing controlled grazing with sheep and goats (since 2009).
  • Experimental manipulation of vegetation (Juncus sp.) in the drainage ditches. This was aimed at increasing the spatial heterogeneity of reproduction habitats and at exploring the amphibians’ preferences in terms of microhabitats. The first results that we obtained are already promising. In the more superficial ditches, frogs agglomerate in the areas with less vegetation. On the contrary, in the deep ditches frogs prefer the areas rich in vegetation. In both types of ditches, newts are well represented in the areas where the vegetation was reduced experimentally.
  • Educational activities that involve the pupils from Sighişoara. These activities have already given good results. For example, two pupils from the Miron Neagu and Mircea Eliade high schools in Sighişoara won 1st and 2nd places at the National Contest for Scientific Communications in Biology, in 2007 and 2008 (2nd place – Adrian Boitoş and 1st place – Elza Sándor).

Tibor Hartel PhD

Custozi                                                                                                              Finanţatori

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