Mankes had a reputation as an ascetic living in a kind of self-chosen isolation in De Knipe, Friesland, far from the heart of the country's culture.

A progressive Protestant, in 1915 he married Anne Zernike, the country's first female minister with a doctoral degree.

[1] Zernike was a Mennonite; a drawing of her, made by Mankes in 1911, is in the collection of the Fries Museum in Leeuwarden.

[1] Mankes studied and then sketched his subjects (often birds and farm animals) "until he knew them by heart, and then painted them from memory".

Mankes used a glazing technique, in which a large number of layers of paint on an opaque base "lend a fairytale-like quality to the owl".