habitats, including areas of intense human development. Like the wolf, it is distributed throughout the majority of the Holarctic, but it has avoided extirpation. The wolverine (Gulo gulo) is a large member of the weasel family found primarily in the arctic and in boreal forests, ranging south in mountainous regions. It is distributed in such areas throughout Eurasia and North America. The moose (Alces alces) is the largest member of the deer family. It is found throughout most of the boreal forest through continental Eurasia into Scandinavia, eastern North America, and boreal and montane regions of western North America. In some areas it ranges south into the deciduous forest. The caribou, or reindeer (Rangifer tarandus) is found in boreal forest and tundra in the northern parts of the Holarctic. In Eurasia, it has been domesticated. It is divided into several subspecies, which are adapted to different habitats and geographic areas. The golden eagle (Aquila chrysaetos) is one of the best-known birds of prey in the Northern Hemisphere. It is the most widely distributed species of eagle. Golden eagles use their agility and speed combined with powerful feet and massive, sharp talons to snatch up a variety of prey (mainly hares, rabbits, marmots and other ground squirrels). The common raven (Corvus corax) is the most widespread of the corvids, and one of the largest. It is found in a variety of habitats, but primarily wooded northern areas. It has been known to adapt well to areas of human activity. Their distribution also makes up most of the Holarctic realm. Leptothorax acervorum is a small red Holarctic ant widely distributed across Eurasia, ranging from central Spain and Italy to the northernmost parts of Scandinavia and Siberia. Zygiella x-notata is a species of orb-weaving spider with a Holarctic distribution, mostly inhabiting urban and suburban regions of Europe and parts of North America. Origin The continuity of the northern parts of the Holarctic results from their shared glacial history. During the Pleistocene (Ice Age), these areas were subjected to repeated glaciations. Icecaps expanded, scouring the land of life and reshaping its topography. During glacial periods, species survived in refugia, small areas that maintained a suitable climate due to local geography. These areas are believed to have been primarily in southern regions, but some genetic and paleontological evidence points to additional refugia in the sheltered areas of the north. Wherever these areas were found, they