Minimum average pack size in Iberian wolves

We present information on the minimum average number of wolves per pack in late summer derived from fieldwork activities during the last three decades in north-western Spain, and on the mean minimum number of wolves travelling together in winter in the Cantabrian Mountains. The minimum average litter size observed between August and October (when the pups are between 3–6 months old) was 5.15 (CI 95%: 4.50–5.85); whereas the minimum mean number of adults/subadults observed was 3.85 (CI 95%: 3.30–4.45). Combined, the estimated minimum average pack size in late summer was 8.95 wolves (CI 95%: 8.10–9.80). In winter time (December-March), the mean number of wolves observed travelling together was 3.44 (CI 95%: 3.23–3.68). When using the average minimum pack size to convert wolf reproductions into an estimated number of wolves in late summer, an estimated number of wolves not linked to breeding packs should be also considered, which, in northern Spain, has been estimated between 16 and 25% of the total number of wolves at this time of the year.