Looks like 8 percent die of cars or disease, the rest are likely predation , by man or beast, or the good one, censored. I guess it would be hard to find the transmitter, as noted in some cases, could be underground, in a den. That number of predation is alarming. A decrease in predation sure could help our turkey numbers.
Those censored are the ones that died within a few days of being handled. A few always die within a few days of being handled from what is known as capture myopathy or undetected injuries. Handling wildlife is very stressful for them and there is always a level of risk to the species being captured and handled.
Yes predation is and always has been the leading cause of mortality for turkeys, as it is for most wildlife species. Wildlife species are just not likely to die of old age.
All the species, any species, have to do to keep their population stable is recruit two of their species back into the population during their entire life cycle.
Since a turkey typically incubates and hatches an average of about 10 poults per year it is pretty obvious to people who understand how nature is intended to work that the majority of the poults are not intended to survive long enough to reproduce.
Predation is just a part of nature and thus perfectly normal and acceptable.