Table 3. Results from a linear mixed model on the effects of habitat (coastal or inland), age of animal (adult or juvenile) and tissue (fur, muscle and collagen) on the Euclidean distance to group centroids in a 2 dimensional isotope space formed by respective δ¹³C and δ¹⁵N values in Icelandic arctic foxes.

Fixed effect	DF	F	P
Habitat	1, 124	0.51	0.474
Age	1, 124	6.57	0.012
Tissue	2, 121	3.17	0.046
Habitat×Age	1, 124	15.41	<0.001
Habitat×Tissue	2, 121	1.95	0.147
Age×Tissue	2, 121	2.94	0.057
Habitat×Age×Tissue	2, 121	1.37	0.259

These distances can be interpreted as a measure of population wide isotope niche breadth.