Fawn survival and recruitment is the key to healthy mule deer populations, and it's not an easy thing to achieve in Idaho. Fawns have a rough time of it, and who knows what kind of a winter will be in store from year to year. Fortunately, we have had a mild winter so far. But just as challenging is the job of the wildlife biologists to predict survival, and then propose harvest limits for a specific management area.
Recruitment generally describes when a fawn has made it to its first birthday. Just getting there means that the mule deer has made it through two critical periods of life. The first critical period is generally June and July. Those are the first two months after birth when the little guys and gals are getting their feet wet, and are the obvious target for predators.
If they can survive those months, the next challenge they will have is late winter, generally February to April. This is when the fat reserves are put to the test. Fawns survive less so than more mature deer during this time period because adults are better able to put on fat during the summer and fall. Less fat means less energy, so malnutrition causes the fawns to become all the more vulnerable to predation and to the elements.
When comparing fawn survival rates between game management units, the big factors are habitat condition, predation, competition of feed, and herd density between those units. If the habitat can only feed so many mule deer, and the herd is too big for the habitat capacity, and the elk are needing the same feed, and the wolves are surrounding the camp - you have a recipe for disaster, and the fawns are the first to get left out.
The weather may be identical in another unit, but if the habitat is better, the carrying capacity isn't abused, and predation isn't as prevalent, the survival rates will be higher.
But from year to year in a given area, weather is the biggest factor. An unusually cold and wet fall and/or winter only brings on malnutrition quicker.
So how do Idaho's game managers set season harvest limits? First, they do what studies they can on particular mule deer populations, but by January, they have to propose something to the Fish and Game Commission. Season dates and harvest limits are then set in March. That means the dates and limits are set before the results of the studies can be observed in April, May, and June, as the fawns escape winter's clutches, or not.
Monitoring winter survival is tough, and the biologists do what they can with modeling, but nothing is perfect. It's not difficult to get mule deer populations in big trouble really fast. A couple years of too liberal harvest quotas, followed by a couple of years of drastic weather, and a particular population could be in big trouble.
It's a volatile situation for the fawns for obvious reasons. And it's volatile for the IF&G who has to answer to sportsmen and the public for any missteps.
