 As for the types of habitats, two forests dominate the landscape. Holm oak groves occupy sunny terrains with scarce soil where this type of oak (Quercus ilex) can thrive in better conditions than other species. In general, the holm oak grove is quite understocked, although one can find somewhat thicker patches. Occasionally, there are clearings in the forest, giving way to different types of bushes (juniper bushes) and mainly to wasteland and xerophyte pastures.
Gall oak (Quercus faginea) groves occupy the areas with the deepest soils, mainly on the northern slopes and the bottoms of some small valleys on the meridian. In general this forest is in a juvenile state, constituting phases of natural regeneration has from fires that in the past have burnt down this area. Concretely, patches with more mature trees are scarce and concentrated in the fresher areas of the space. The gall oak groves have many less clearings than the holm oak groves, in which juniper bushes and pastures are predominant.
 In spite of the juvenile state of most of the forests in this area, the presence of three species of coleopters included in the annexes of the Directive that need well-conserved forest habitats is quite surprising. Concretely, there is a known presence in these masses of the stag beetle (Lucanus cervus), the longhorn beetle (Cerambyx cerdo) and the Osmoderma eremita cetonide. The presence of this latter species has only been recently known and it constitutes, for the species, the first known emplacement of European Community Interest within the Autonomous Community of the Basque Country. Although it has an ample distribution in the rest of the European Union, in the Iberian peninsula it is restricted to the Pyrenees area and the Cantabrian cornice, where it is very localised.
As for vertebrate fauna, it is important to point out the strategic situation of this small mountain chain between the Ullibarri-Gamboa Reservoir and the valleys of the Barrundia and Zadorra rivers, makes it especially interesting for certain birds of prey like the booted eagle (Hieraetus pennatus), the short-toed eagle (Circaetus gallicus) or the black kite (Milvus migrans) which, although they hunt in open areas, need tree-covered environments in which to install their nests.
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