Roe deer mating behaviour and rut, part 2
The females’ roe deer's home range and the rut
Apart from the courtship and mating during the rut, females live a life independently away from the males, and that includes the raising of young; male roe deer play no part in the rearing of fawns.
They are solitary for most of the year and the location of their home range is independent of the males’ domain, although they are approximately the same size. And because they don’t engage in aggressive behaviour with a frequency anywhere near than that of the males, they do not extensively mark their home range, like the bucks mark their territory.
The independence between the sexes means that the females’ home ranges normally overlap some of the resident’s bucks’ domains.
When do roe deer rut?
Remember, the rut is the deer's breeding season.
Now, when people talk about the rut, what they’re normally referring to is the peak of the rut i.e. the peak of the breeding season. And, as far as we’re concerned with here, the peak of the rut is defined to be the date when the number of matings per day, reaches a maximum.
This usually occurs sometime between late July through to the middle of August. The exact timing for any given locale varies from year-to-year, but there is some degree of a latitudinal and longitudinal variation; with the southern locations starting before the northern areas and western populations commencing before the eastern communities. Local climate is probably the crucial factor, explaining why there are many exceptions to this ‘rule’.
Even though the vast majority of roe deer mating takes place in July and August, males do have stores of viable sperm available from March through to October. However, the females are only able to conceive when they’re in oestrus, which occurs during the July / August window.
But there is one possible notable exception…
The ‘false rut’
This is an event that occasionally occurs in the autumn, when there is a very brief resumption in rutting behaviour.
This behaviour has not been extensively researched, but it is believed that some of the adult females could experience another oestrus cycle of the year, having not been fertilised during the main rut.
This excites the resident males and they can become aggressive once again (territoriality would have been abandoned by this time of the year), and they can be seen courting some of the aroused does, as well as chasing and tussling other males.
The few false ruts I have observed only lasted one or two days, and although courtship was seen to take place, as well as one full-on battle between two yearling bucks, no mating was observed.
When it comes to new pregnancies, I would expect these to be few and far between because stores of viable sperm will be low. In fact, I haven’t known any new pregnancies at this time of the season.
Any males that could still be fertile this late in the year are most likely going to be yearlings, as a result of their slightly delayed commencement of sperm production compared the older males. It could be possible for a master buck to fertilise an ovum at this time, if they will have a small amount of sperm stored in a duct behind the testes, but this is unlikely.
What happens during the rut?
We’re now talking about the main summer rut, not the ‘false rut’.
At this time, the adult roebucks seek out all non-fawn females when they come into season.
In the days leading up to the peak of the rut, the females will become restless and more wide-ranging in their daily movements; does with dependent fawns will sometimes leave them alone in their principal range as she searches for suitable mates.
The does ‘advertise’ their hormonally driven state by scent released when she urinates. Bucks can detect her scent from hundreds of metres away, and he will approach the receptive doe.
As they get closer, the doe will lower her head in a submissive manner. At this point, the buck will often stop, raise his nose into the air and fully dilate his nostril openings, as well as rolling back his upper lip to maximise the intake of her scent and pheromones. This action is called the flehmen response.
Once they are within a couple of metres of each other, she will suddenly wheel-away and emit high-pitch squeaks, encouraging him to give chase.
Does are selective in their choice of mate and one of the physical attributes common to successful bucks is strength and endurance.
So, what happens next is that over the next few days, their courtship will consist of the doe using a combination of an alluring scent (emitted by frequent urination), proximity and squeaky calls to encourage the virile buck to pursue her across his territory, and beyond.
This can continue day and night, and the frantic chases are broken by frequent rests and time for the doe to nurse to her beleaguered fawns.
Continuing for a number of days, initially the chases are at high speed, but as she approaches oestrus, the pace drops to a more of a trot, often around in circles, or in a figure-of-eight shaped path. The vegetation getting repeatedly trodden and worn away by this action, and produces discernible paths on the ground; these are called doe-rings.
Although she will be receptive to his advances for a period of time from 2 to 6 days, she will only be fertile for about 36 hours.
When she is ready for him to mate with her, she will standstill as he approaches, allowing him to mount her.
Once the initial copulation has taken place, many more will follow in the next 24 to 36 hours. Although an hour to 2 hours between couplings is normal, time intervals in the order of minutes are not uncommon either.
Roe deer are mono-oestrus (although there is not 100% agreement with biologists about this), therefore it’s important that once the annual fertile state has been reached, she will be persistent in her need for egg(s) to be fertilised. So, once a mate has been selected, the doe will not necessarily maintain fidelity. If the pair get separated for any reason, the in season doe will mate with any other suitable partner, without further courtship.
Why is roe deer courtship so long?
It is to do with the fact that most, of not all, roe deer are mono-oestrus, meaning that they only have one chance to become pregnant during the year. (Although it has been suggested that the ‘false rut’ can be due to females that have not be fertilised in the summer experiencing a second oestrus. But the lack of extensive reliable mating observations at this time of year, does cast a shadow of doubt over this. Further research in this area will needed for confirmation.)
As you know, roe deer are a solidary species (at least in the summer), therefore, it is quite possible that when the female comes into oestrus, she could well away from any fertile males.
So, what happens is...
To make sure that she has a suitable mate in close proximity for when her egg(s) are ripe, she extensively wanders around in her normal range, and beyond, giving off a strong scent; pulling in a virile buck, like an iron filing to a magnet.
And by keeping him ‘on the run’, she not only tests his physical ability (a sign of good genes), but it also keeps him close for when the crucial, oestrus time comes. Frequent copulations then maximise the probability of fertilisation.
Once the oestrus passes, both individuals lose interest in each other. The does will return to paying more attention to her fawns and the buck will search for another receptive female.
Since the females’ home range is independent of the males’ territories, in areas of reasonably high roe deer density, it’s likely that a doe’s residence will encompass more than one buck’s domain. When this happens, she will normally visit the neighbouring males throughout her courtship and oestrus period.
Working independently, researchers Liberg and Anderson, found that up to half of the rutting does in their study areas moved extensively, travelling through a number of males’ domains, to be serviced by a particular buck that was well outside of their normal living range.
And this may explain something I’ve observed with roe deer I’ve been studying; every summer, a couple of the does ‘vanish’ from the range for protracted stretches of time during the rut.
Despite my best efforts, I simply cannot locate them. Of course, I don’t have the benefit of radio collars that Liberg and Anderson had, but if I did, I suspect I would have located them with a master buck in a prime territory a few kilometres away.
Biologists also found that as well as being attracted to certain males, they actively avoided the attention of ‘inferior’, non-territorial bucks during their excursions.
Remarkably, researcher Hennig as far back as 1962, reported that does vocally protested to attention they received from ‘unfavoured’ males, which in turn prompted the intervention of the dominant beast.
So, with the amorous does traversing several domains of ‘perfectly good’ bucks in favour of consorting with one particular male, the females are showing a considerable degree of selection in their choice of father to their fawns.
But, of course, it not as one dimensional as preferring one male over another; the selection process takes into the account the quality of the territory in which the males live, too.
High quality territories are preferred
High quality simply means that a given area of habitat contains plenty of disturbance free cover, shelter from adverse weather conditions and an abundant supply of nutrient dense food.
And for those reasons, in season does have shown a tendency to select breeding mates based on the domain in which they reside.
Agneta Johannson in her PhD thesis at the Stockholm University, reported that does in oestrus exhibited a distinct preference for bucks inhabiting territories containing rich, agricultural crops.
The superior quality of the bucks’ food intake positively affects the quality of the males’ sperm and his overall physical condition.
With one or two bucks being favoured by the females over all the others, this can lead to competition between females to mate with the master buck. In this situation, minor hostilities have been known to break out between the does, normally in the form of a short charge, occasionally butting a competing female in the neck.
For these reasons, the prime buck in the range will consort and mate with several does over the course of the rut. Indeed, in a good roe community, the dominant beast can mate with up to 5 or 6 females, and multiple does can be present within his domain at the same time, as they’re waiting to be serviced by the master.
In this not uncommon scenario, master buck will be at different stages of the mating cycle with different females i.e. he maybe in the process of courting one female, but then during ‘rest’ periods, copulating with the other does that are oestrus.
Why are some bucks more successful at mating than others?
As we’ve said above, the territory has a significant influence. Not only on the physical condition of the buck himself, but also the quality of sustenance available for the doe.
In the case where a doe has consorted with a male in a prime territory, there is an increased probability that she will reside in that same domain when the oestrus has passed.
Because of the territorial dependence on the roe deer’s mating strategy, it is not surprising that non-territorial males are not a successful at mating as those bucks retaining a prime domain.
In fact, my own limited observations are very much in-line with the findings reported by field biologists, where they say nearly all consorts by rutting pairs, occur with territorial bucks. Although I have observed yearlings courting and mating with a 3-year-old doe, this is an unusual occurrence and is not widely reported in the scientific journals.
Subadults are more likely to find a mate, providing they have a territory – but again, unless there is a dearth of adult bucks, this is not the normal sequence of events.
It turns out that one of the most important attribute of a buck that will make him successful is his age; 6 years being the prime age.
Possible reasons for this include:
1. Males of this age are in their physical prime, so their combative ability will be at an all-time high.
2. Since he’s lived for longer than average, there’s a good chance of possessing good genes.
3. And linked to the above, his relatively long life experience, antlers being in ‘hard horn’ before any of his competitors and possessing a favourable physical stature (giving him a superior fighting ability), he’s likely to occupy the best territory in the area; territorial occupation is crucial to sustained mating success in the world of the roe deer.