Table 2. Availability, use and selection of major food items (>1% of the diet) consumed by lemmings in winter.

Food item	Availability	Use	Selection ratio (wi)	SE of Selection ratio
(a) Collared lemming
Vascular plant families 1
Fabaceae	0.013	0.003	0.2	0.5	(−)
Juncaceae	0.113	0.018	0.2	0.1	−
Poaceae	0.054	0.124	2.2	2.4	0
Rosaceae	0.043	0.005	0.1	0.2	−
Salicaceae	0.713	0.839	1.2	0.2	0
(b) Brown lemming
Vascular plant families 1
Fabaceae	0.013	0.010	0.8	1.9	0
Juncaceae	0.113	0.029	0.3	0.2	−
Poaceae	0.056	0.091	1.6	1.7	0
Polygonaceae	0.008	0.049	6.5	19	0
Rosaceae	0.043	0.048	1.1	1.7	0
Salicaceae	0.713	0.727	1.0	0.2	0
Saxifragaceae	0.004	0.036	8.4	33	0
Moss families 2 , 3
Aulacomniaceae	0.027	0.334	16.1	28	0
Dicranaceae	0.015	0.062	4.1	8.3	0
Polytrichaceae	0.267	0.501	1.9	0.8	0

Availability is based on biomass of vascular plants and mosses sampled in stream gullies and mesic tundra in August 2010, at peak growth (n = 16 plots). Both availability and use are presented as proportions. Selection was analyzed separately for vascular plants and mosses and availability and use sum to 1 within each of these taxonomic groups (0 = no selection, + = positive selection, − = negative selection; based on 95% confidence interval; signs in parenthesis indicates selection ratio based on 90% confidence interval).

¹ Ericaceae, which accounted for 58% of all vascular plant biomass, was excluded because it was not consumed by either lemming species.

² Selection could not be calculated for Bryaceae, Grimmiaceae and Timmiaceae because these plants were not found that year in our availability sampling plots.

³ Other important moss families present at the site and not consumed by lemmings include Scapaniaceae (availability = 0.228), Amblystegiaceae (0.195), Hylocomiaceae (0.193), Ptilidiaceae (0.043) and Ditrichaceae (0.019).