Why Do Deer Fight?
In a nutshell: deer fight to gain, or retain, dominance.
Both Sexes Fight
Although mainly associated with aggressive bucks that are pumped up with burgeoning levels of testosterone, fighting is not restricted to bucks; female roe deer also engage in battles with others of their own kind too, albeit, less frequently than the bucks. But the different sexes tussle for different reasons.
A Last Resort
An animal that is as ancient as the roe deer, would not have lasted as long on Earth as it has if it was predisposed to rush head long into a fight at the slightest of opportunities.
Instead, roe deer use scent marking and threatening body language, to avert heavy, physical contact between themselves and a rival. That’s because engaging in physical conflict is costly in terms of energy and risky with respect to picking up a life-threatening injury, or even dying.
Certain injuries such as a major trauma to the skull, or the rupturing of an important artery, will bring death very swiftly and deer will pay ultimate price. But the seriousness an injury incurred as a result of body-to-body combat is not always obvious.
The antlers of roe deer can be quite sharp, and they are capable to delivering a serious gouge to the unfortunate recipient. An incision to leg muscle can mean that the victim may not be able to walk properly for a short, or long period of time, which will restrict its movements, making it more susceptible to being hunted by a natural predator, or shot by a human.
It will also mean the wounded deer would not be so able to flee from frightening situations, which will stress the animal, exposing it to all the negative health effects of stress, such as an increase in the likelihood on contracting disease, etc… (although, wild roe deer are, in general, very healthy).
In certain situations, the deer’s injury may affect its ability to feed, leading to an increased possibility of starvation, if food resources are scarce.
Which leads us onto the next reason why fighting is a last resort for a roe deer; the energy demands are very high.
Roe deer do not carry a large amount of body fat, never getting significantly above 10% and 9% for an adult buck and doe respectively or 5% for fawns. So, using a large quantity of energy by engaging in physical conflict and picking up life diminishing injuries, needs to be balanced by what is to gained by being able to pass on their genes (mainly relevant to bucks) and the ability to raise their young (only relevant to does).
Whether or not a deer does, indeed, actually take on a rival, is not determined by rational thought, of course, but is driven by ingrained instincts that have been responsible the success (or otherwise) of a particular lineage of roe deer.
I have anecdotally observed a noticeable variability in adult males of approximately the same age, in the same environment, in their ‘willingness’ to engage hostilities with other roebucks. A pattern that has, to some degree, being reflected in their (probable*) male descendants.
Three days ago, on cold December morning, I watched a six-and-half-month-old buck fawn, descendant of an especially feisty male*, rush over to an eighteen-month-old buck and go head-to-head with him for a few seconds. Interestingly, the elder had just cast his antlers (and his new ones had just started to grow) and the youngster had just button antlers.
The size difference between the pair was significant, and it was the smaller of the two deer that aggressively approached the other. The approach was probably playful, but bearing in mind how infrequently I have seen this behaviour, it could indicate a possible character trait of the individual deer as he matures.
It must be remembered though, that these are purely my observations and I don’t intend to make any assertions that in any way constitute some kind of ‘rule’, or scientific fact.
*It’s very difficult, if not impossible, to state with certainty, the identity of the father of a particular fawn. But certain ‘local’ factors (such as the number of other males around during the time when the doe was made pregnant) can reduce the chance of making an identification error.
Reasons for Deer Fighting
Essentially it all comes down to making sure a buck is able to pass on his genes to the next generation. And he does this by staking out the best territory in the area and defending it against all roe antlered intruders.
As previously mentioned, the territorial male will scent mark his domain and attempt avert deer-to-deer physical contact by using threatening body language. But if neither roebuck backs down, hostilities will commence.
By expelling competing males, the buck’s aim to make sure he’s in prime position to mate with the in season does that enter his territory, during the rut.
I have not known females fight over the right to mate with a particular male, but instead to tussle to maintain her ‘rights’ over a particular area. They do this to preserve a domain with plentiful food and cover to successfully raise her young.
One particular instance comes to mind:
Towards the end of one winter, there were two does of the same age, both raising twin bucks, in respective domains where their home ranges overlapped slightly.
During the winter, with a dearth of rich food sources around, one of the does could frequently be seen aggressively posturing towards the other mother when she intruded into a core area of her territory. Short chases often ensued as the dominant doe forced the intruder off her patch.
In and around the bush-lines of the area I had a number of camera traps set up to record activity in some of the woody areas, frequented by the roe. And on checking the results one day, I could see that the camera had taken a sequence of shots recording a head-to-head tussle between the two does, just like that is observed between two bucks, when they battle (minus the use of any headgear, of course).
The photos were of poor quality, but nonetheless showed an uncommon fight between two adult does, outside the breeding season.
Most of the time, ‘fight’ is not the right term to use to describe conflict between two female roe deer.
Instead, what I have seen on a number of occasions is an expectant mother doe, aggressively butt a ‘clingy’ daughter in the ribs, or at base of her neck, to break the bond with the yearling**; in order to secure isolation in her fawning area, just before and after the birth of her new fawns.
**Buck fawns break the bond with their mother well before the next fawning season draws near.