Wolf (Canis lupus) litter size in Spain

Reproductive variables constitute a key information to assess population dynamics and inform wildlife management. We estimated wolf (Canis lupus) litter size and reproductive phenology in Spain between 1987 and 2015 based on foetus or placental scar counts on 75 females. Three out of twenty-five subadults (12%) and 32 out of 41 adults (78%) were classified as reproductive females. The mean litter size was estimated in 35 females, being 5.67 in subadults, based on placental scar counting, and 5.54 to 6.00 in adults, estimated by foetus counting or placental scar counting, respectively. Pregnancy was observed in 13 adults, which were sampled in April (N = 7), May (N = 4) and June (N = 2). Hence, the main mating season was estimated to occur between February and March. To our knowledge, the referred data constitutes the most extensive and updated information available on wolf reproduction in Spain until today.