Year‐round variation in monthly and daily group size estimates of barren‐ground caribou in east‐central Alaska

Abstract Sociality plays a major role in an array of factors critical to the ecology of many species, including sexual selection, migration, habitat selection, predation risk, and parasite infection. Group size is a fundamental metric used to assess sociality in many species. While barren‐ground caribou ( Rangifer tarandus ) are highly social, there is little quantitative documentation of the patterns in their year‐round group sizes. I report the daily and monthly average group sizes of the Nelchina Caribou Herd in east‐central Alaska. Group sizes were small not only in winter and late summer but also during calving. Group sizes increased post‐calving and reached their maximum during the peak of insect harassment in July. The largest single group observed was >30% of the entire herd. July was the only month where the average group size was more than 1% of the size of the herd. Group sizes were relatively large during migration but larger during fall migration than spring, which may reflect the importance of sociality during the rut and/or the dispersed nature of barren‐ground caribou during winter.