One of the cornerstones of the SOS Guadarrama Amphibian Project is to recover the distribution of the Common Midwife Toad in the National Park. For that we need to find areas within the park that are favourable for the species, but also unfavourable for the development of chytridiomycosis. This is not easy, because while water bodies are ideal for toads they are also often the favourite sites for the chytrid fungus.
In the mountain areas the Common Midwife Toad needs permanent water bodies where their tadpoles can complete their long larval development. Low water temperature, and the scarcity of organic matter in these water bodies, further prolongs their development, so it is common for tadpoles to remain in the water for more than a year until metamorphosis. Unfortunately, the low water temperatures do not impede the growth of the fungus which weakens the immune system of the tadpoles making them more vulnerable to fungal attack.
Therefore, we must find places with permanent water bodies which are not too cold, and which are in an area with adequate shelter for adults where they can withstand the cold winter. An additional problem is that the water bodies must be deep enough so they do not freeze completely during the winter and wintering larvae can survive under ice. As you can see, this is easier said than done!
Last week we began to tour the areas on the map that may be suitable to accommodate new populations of the Common Midwife Toad. On the ground we do a thorough appraisal of the sites, assessing their suitability and taking into account the characteristics of the water bodies (depth, current, insulation, and temporary nature), the availability of shelters for adults, the terrain, etc. We also record which species of amphibians inhabit these places, which gives us clues about the environmental conditions.
This year we will start with reintroductions in the most favourable sites, but we will also monitor many other places in the long term. To do this we installed automatic devices to measure water temperature throughout the year, and we will visit the sites at the end of the summer to check that the water bodies do not dry up.