In more recent times we could ask the same questions about the Quebec caribou herd. I hunted NW Quebec in 2002 and 2003. Herd was estimated at 1.2 million head. We saw thousands. By 2017 the estimated herd was 200,000 or less and sport hunting stopped. Sport hunting had been taking less than 10,000 a year, native winter hunting somewhat more. I saw a place on Lac Minto where hundreds had drown and washed ashore so nature had an impact too. I believe it is never one thing but an overwhelming combination of factors. Migrating herds do so to avoid over grazing a single area. Snow geese eat the same lichen as caribou in their nesting area and their populations were expanding at the same time as the caribou. The lichen grows very slowly. I think available food became a problem and led to fewer calves and diseases. Similar to the buffalo? Maybe. Easier to just blame climate change or hunters.
