Maybe, maybe not. I know nothing about this, but here's something to consider from a participant on Gary Reeder's site (an American gunsmith):
Lightning is a part of the E3 (Environmental Effects) area of Electromagnetics that I worked in for over 48 years and I have never seen a strike foot print with the number of leaders that would be required to be present to cover such a wide area. The normal strike cross sectional diameter of a normal 1.5 megavolt 25000 amp strike is about 6 inches. I would be more inclined to look for some sort of disease that strikes fast and would kill a lot of these ungulates rapidly. Perhaps anthrax or some other disease that would act within a few days. The bellies are well swollen in the picture so I suspect that they have been dead over a period of several days. Long enough for a disease to have killed that many raindeer. Just my opinion in the for what its worth department.