Dean Cluff necropsied Brutus last week and learned that:
1. The hole in his rib cage was the result of a scavenger, probably a raven.
2. The carcass was emaciated, with no fat even in the femur bone marrow. Fat there is the last to be used, so when it is gone, the animal dies.
Thus we conclude that Brutus died of starvation. Why he starved is unknown. The last time we know he was with the pack was March 29 (see April 29 blog). He could have been in marginal condition then, which we could not have detected from photos.
He traveled straight-line distances of 110.5 miles (176.8 km), or an average of 9.2 mi (14.7 km)/12-hr period from March 29 to April 4 when he then remained in a single location for at least 36 hr. We presume this indicates a kill. After leaving that on April 6, he traveled a straight-line distance of 70.9 miles (113.4 km), or an average of 5.9 mi (9.4 km)/12-hr period before reaching the location where he died, sometime about April 13-15.
A rough and very preliminary examination of all Brutus' location data from October on suggests that the pack's rate of kill was similar from October through January. However in February it dropped by 45%, and in March by 65% from the Oct.-January period. Had the pack killed most of the vulnerable muskoxen by then?
Was Brutus' kicked out of the pack after the last kill on April 5-6? Was he too old or weak then to compete for food at that kill? Was the kill only a muskox calf from last year that had too little food on it to feed the whole pack? Wolves can eat 22 pounds (10 kg) at a sitting, so a calf would not fully feed all 20 wolves.
Brutus' death raises this and many other questions.
Most of them will remain unanswered, but they help feed our motivation to learn more about this pack and its ecology and behavior. Hopefully this summer we will collar more wolves and thus continue to discover much more. We also will begin analyzing the data from Brutus. So, please check back with us periodically.
Thanks for your continuing interest.