The sheep are highly resistant to cold, and are generally left unshorn for the winter.

The Þoka (Thoka) gene is carried by some ewes, which may give birth to large litters of lambs.

[4]: 827 It is thought that the sheep were introduced to Iceland by Vikings in the late ninth or early tenth century.

[4]: 826 Breed numbers reached a peak in 1978, when there were approximately 891,000, or about four sheep for every inhabitant of Iceland.

[4]: 827  The wool of the outer coat has a diameter of about 28–40 microns or sometimes more, and a staple length of some 150–200 mm (5.9–7.9 in) the inner coat has a diameter of 19–22 μm (0.00075–0.00087 in) or sometimes less, with a staple length in the range 50–100 mm (2.0–3.9 in) The two types may be used separately, or spun into a single yarn, lopi, a soft wool which provides good insulation.