Impact of Buck to Doe Ratios on Whitetail Fawning Dates

I’ve discussed buck to doe ratio more than once, but today we are going to talk about how buck to doe ratios impact subsequent fawning dates and recruitment of fawns into your white-tailed deer herd. Many factors can impact rutting or breeding activity, but most of the breeding takes place over a relatively short time in healthy deer herds. Timing, of course, depends on latitude, local conditions, and a host of other factors, but year-in and year-out most of the rut takes place more or less over the same time each year in a given area. Though often overlooked, buck to doe ratio should be an important deer management consideration on your ranch. 

In the previous sentences, I was talking about a “healthy” deer herd and said “most” of the breeding takes place at the same time, but what exactly does that mean. Well, a healthy deer herd would be one that is at carrying capacity for the habitat, has a buck to doe ratio of no fewer than 1 buck per 3 does, and all animals are in good body condition. With that said, most of the breeding would happen over the course of a 10-day period or less.

Why? Well as deer have evolved, the timing of deer breeding/rutting as become more constricted. A properly timed rut results in a high fawn survival rate and ultimately in the survival of the species. In some areas at northern latitudes, climate conditions can be extreme — so deer have adapted to a narrow fawning window. If fawns are born too early, it can still be too cold. If too late, they may not have enough time to build up the needed body mass and energy needed to get through the winter. At southern latitudes, temperature is not as much of a factor, but it still plays a role on those born way too early or late.

So without getting into all the factors that can impact fawning dates today, let’s talk about buck to doe ratios and how that effects the fawning season. White-tailed does come into estrus for only a day or two — usually in high numbers as if someone hit a switch. If they are not bred within that time, they will come back into estrus 28 days later. If there are not enough bucks to service all the does in an area, those does will not get bred until about a month later. If they aren’t bred then, it’s another 28 days. This explains what some people refer to as the “late rut.”

At this point you may be asking yourself “what’s the problem?” Well, it’s true that deer populations with a high number of does per buck still have high breeding success (number or percent of does bred), but those deer herds don’t necessarily have good recruitment of fawns into the adult population. One reason can simply be because of habitat conditions. If it turns out to be a dry spring, being born just one month later may have serious consequences with regards to the food sources available for a doe to maintain herself and raise fawns. If that’s two months later, that may be well into the summer season.

In short, make sure you have a proper buck to doe ratio in your area and it will most likely increase both breeding and fawning success. In the future we will discuss some of the other factors that impact fawn survival and recruitment.