The Sierra de Guadarrama National Park and its Peripheral Protection Zone host 135 avian species having a regular presence sometime in the year, whether they are summer, wintering or standing species. The preservation actions on this fauna group have been noticeable particularly from the approval of the 79/409/EEC Directive on the conservation of wild birds and their habitats. Without this directive, the wide diversity of species living in the National Park and its Peripheral Protection Zone would not have been acknowledged.

The Directive and its implementation in Spain have resulted in the creation of a number of “Birds Special Protection Areas” (SPAs), which sole aim is to preserve the classified bird populations and their habitats. In the National Park and its Peripheral Protection Zone; this status protects a surface over 52.589 ha; 44.723 ha belong to the Sierra de Guadarrama SPA -ES0000010, in the province of Segovia, and 7.866 ha belong to the Alto Lozoya SPA -ES0000057, in the province of Madrid.

In the Sierra de Guadarrama National Park and in its Peripheral Protection Zone, there are 61 species of mammals. Six species are Iberian endemism (the Iberian hare, the Lusitanian pine vole, the Iberian shrew, the Iberian mole, the Pyrenean desman and the Cabrera’s vole). The Mediterranean mountains as the Sierra de Guadarrama are critical areas for the preservation of diversity and wealth regarding fauna in general and mammals in particular.

The cooling and the intensification of precipitation due to the height, make them islands having distinctive bioclimatic characteristics from the surrounding plains, very conducive for the reception of typically Euroasian species, such as the Pyrenean desman, the pygmy shrew, the common vole or the snowy vole. In addition, its relief and its wilderness areas have enabled the preservation of great sized species not finding adequate shelter in other areas, such as the European roe deer, the wildcat, the Euroasian otter or the European badger.

The amphibian inventory of the National Park and its Peripheral Protection Zone is made up of 15 species, of which 5 are Iberian endemism. Several studies on the areas of interest for the conservation of amphibians in the Iberian peninsula, have pointed out the Sierra de Guadarrama importance, and particularly the Peñalara Massif, in a number of species preservation.

This environment has a considerable diversity of species. Only in the Peñalara Massif wetlands, included in the RAMSAR list, there are usually nine species: the Common salamander (Salamandra salamandra), the Marbled triton (Triturus marmoratus), the introduced Alpine newt (Mesotriton alpestris), the Common frog (Hylo molleri), the Common toad (Bufo spinosus), the Natterjack toad (Epidalea calamita), the Common midwife toad (Alytes obstetricans) and the European tree frog (Hyla molleri). Some Iberian painted toad (Discoglossus galganoi) samples have also been detected.

24 species of reptiles are inventoried in the Sierra de Guadarrama National Park and its Peripheral Protection Zone, giving an idea of the crucial role the Sierra de Guadarrama plays in this fauna group preservation. Various directories focussed on the Iberian herpetofauna conservation critical zones, show the significance the Peñalara Massif and the Upper Manzanares Basin have. To some extent, both enclaves are river headwaters zones and they have stayed long time under different regional protection modalities, so they have maintained environmental conditions conducive to the conservation of these species ecosystems.  Some taxa specimens flourishing populations, together with the existence of many endemism, uphold these territories wealth, not only ato the regional level, but also to the national and European scale. The Sierra height and topographical features result in a progression of the temperature/rainfall ratio, enabling a great variety of biotopes which are optimal for the presence of reptiles.

Among the 23 mentioned species, the Iberian rock lizard, the Iberian emerald lizard, and the Common wall lizard distribution areas are limited to mountain environments. In the National Park, the highest species wealth appears significantly at intermediate altitudes, between 1,000 and 1,650 m, being undermined by the higher or lower altitude. This proves the importance of preserving the mid-altitude sites, that is to say the Sierra de Guadarrama slopes, which are conducive to the reptiles’ distribution.

There are inventoried 18 fish species in the National Park of the Sierra de Guadarrama and in its Peripheral Zone of Protection. Overall, the Sierra de Guadarrama has some biogeographic peculiarities regarding its ichthyofauna. For some species, such as the “Bermejuela” (Achondrostoma arcasii) or the “Lamprehuela” (Cobitis calderoni), the Sierra de Guadarrama constitutes their southern limit of distribution. On the other hand, for several other species, such as the Iberian barbel (Barbus comizo), it marks their northern border. As in most of Spanish rivers, there have been several fish species introductions in these water streams. Among the ones that occurred in the limits of the protected space, the Pumpkinseed (Lepomis gibbosus), the Iberian gudgeon (Gobio lozanoi), the Common Carp (Cyprinus carpio) and the Goldfish (Carassius auratus), are particularly noticeable.

The Sierra de Guadarrama spills its waters on its Castilian-Leonese side only to the drainage basin of the Duero, while the Madrid area is part of the Tajo basin. The comparison between the fish community of the Duero basin (Segovia) and the Tajo basin (Madrid) reveals a noticeable difference, with a fish community less rich in the Segovian slope, although better preserved, since there are fewer introduced or exotic taxa.

The invertebrates are the group having a species highest number in the Sierra de Guadarrama National Park. Its high diversity and adaptability to the environment climatic conditions -low temperatures, high snowfall and rainfall, strong winds and high solar radiation - shorten its biological cycle. These extreme variables have led to fundamentally different adaptive strategies in insects, from singular shapes and reduced sizes to the most diverse range of colors, such as the ornamentation of coleopteran elytra or the striking chromatism of butterflies.

In the National Park, spring and summer are time par excellence for a show: a period when insect larvae, after spending winter under the ground, snow and ice, emerge in their adult stages. This metamorphosis process all insects share, causes an explosion of life and triggers a race against time to ensure descent in years to come.