There is a moderate-sized red deer population living outside of our town.
The red deer venture closer to the town limits more rarely than, for example, the wild boar that also inhabit the rural regions (especially, riparian regions).
However, I have seen a herd of red deer approach the highway on the south side of the town but apparently they did not wish to cross.
There have also been observations of fewer red deer individuals on the east side of the town but not as close to intensely used human infrastructure (still within the agriculture-riparian forest-field forest patch rural landscape).
On the east side I have seen small groups of females (2 – 3), young males and some females with their young (on few occasions 1 female + 1 calf and on several occasions perhaps 2 or 3 females with their calves).
In distance, across vast fields and near a larger forest patch I have also seen a red deer stag who had reached full maturity.
These individuals and small groups do not, however, live close to town and they arrive from across fields or from across the same highway but along a more rural section of it.
However, last September in the very beginning of the rut season, I heard 4 red deer males who had apparently crossed the highway (3 on the more intensely trafficked side and 1 in the remote and rural section).
These males ended up on different parts of town outskirts where there are some smaller riparian forests and pastures.
One of them (and by the sound of its roar, it was a younger male), in fact, entered the town and spent a few nights in the green zone of the town (also, riparian forests).
This male came almost to our street (private housing area aka the suburbs) and one night I heard him bugling right outside my window but by the time I dressed, he was gone.
I began wondering what the message of these calls entitles.
Usually I had assumed that the stags roar to notify and to intimidate their competitors (other stags).
But these males had essentially entered an area which hosts no red deer population and the four males were bugling despite being rather far from one another (for example, 1 male was on the other side of the town and could not interact with the other three males at all).
I wondered whether these calls were used to:
- discover potential locations of other red deer in this new area (which would lead to finding females);
- to attract females.
I suppose the first assumption could be correct as the bugling males certainly heard one another and they could have estimated one another’s locations.
However, they were most likely alone and even in other areas where there are active red deer societies, locating males would not be very helpful because these males would already have gathered harems or they might not even have yet joined the female herds (the four males ventured into our town slightly before the peak rutting season).
Therefore, it might make sense to roar in order to find out whether there are red deer at all in the area and where approximately they are located.
However, roaring (if only soliciting response from other males) might not necessarily assist in finding and securing females (but it could allow for the stag to head in the direction of the local population in a new, unfamiliar area).
Also, the males never travelled in the direction of one another and the entire period they spent on this side of the highway (which was about 1 – 1.5 weeks), they each kept to their own bugling spot.
Thereby, I wondered if females in any manner respond to the roars and if they ever approach the roaring stags in order to join their harem.
It is known that females can change harems during the rut of their free will and the quality of the roar might attract females who are currently not satisfied with their harem stag.
I have seen mature, healthy red deer females in the countryside trotting about confidently in small groups (2 – 3) during the peak rut when harems must have been formed already without much concern that they should belong to this or that harem.
However, as I stated above, these ventures into the town outskirts happened slightly before the true formation of the harems and I do not suppose that they would have been directed at females who were already a part of a harem and who wished to change their harem.
I wondered whether the stags had travelled into unoccupied areas and begun bugling (upon having found what they perhaps deemed a suitable breeding habitat) in order to entice some females from the growing local populations to follow them into these lands open for colonization.
The mechanisms would thereby be different, i.e., the stags would not be attempting to outcompete other stags (by stealing their females) but they would rather be advertising a choice foraging and breeding ground attempting to lure some females out of the existing population to join them.
As the population has been growing while the forests are being cleared as we speak, I suppose there might have been females who knew they would struggle finding appropriate habitat (food and shelter for themselves and their young) during the forthcoming spring/summer/autumn.
Alternatively, there might be some type of responses that hinds give out as reactions to male roaring which could inform the male whether there are females at all in the area.
As the males did not approach other males (and they bugled quite intermittently throughout the active period), they might have been listening on for some responses by females in order to establish whether there were any females in the area (directly and not through first locating other bugling males).
I have not read anything about female rut calls and the overall impression is that the females care relatively little about the rut (although playful interactions with males can be observed).
According to these assumptions, it is unlikely females would respond vocally to the male’s roaring but, then again, the world is full of surprises.
Perhaps if a new male ventures into an area, the females might travel slightly closer to him in order ‘to check him out’.
The stag could then detect female presence through visual or olfactory cues establishing that are are, indeed, females in the area.
Perhaps these males applied both strategies (trying to detect female presence and trying to lure females out of the dense, suboptimal population to join him in colonizing the new breeding grounds).
As the males and the females do not use the same foraging grounds (and calf-raising grounds) after the rut, it is curious to think what parameters the stags based their evaluation of colonizable habitat on.
This leads me to the second part of the post which I wished to dedicate to the social group dynamics during the rut.
However, I would like to firstly end the story of the four venturing males by revealing that they probably did not find any mates, nor they were able to attract mates (if such mechanism is relevant in the species) and they disappeared from the outskirts of the town and back to the rural side of the highway.
Outside of the rut, the red deer population is mainly comprised of bachelor herds and family herds (hinds + their calves + probably younglings who are not mature yet, including young males although this might depend on population density and forage availability).
There might be other groups.
For example, I have observed small groups of females without calves, single females and even a pair of a female and a young male who apparently have separated from their main group to visit some less optimal habitats that could not possibly host the entire herd.
However, I would assume that the rutting begins by the stags approaching the matriarchal/matrilineal herds formed by the females and their offspring.
As far as I understand, these female herds (which might include some young males which are probably actively excluded by the dominant stag during the mating period) are composed of related individuals (mother and her older daughters who can all have had calves).
This probably results in the breaking up of the matrilineal herd as some hinds stay in the harem and others leave and join other herds.
At this point, it is interesting to address the issue of the impact of this break-up on the genetic diversity of the population.
If the stag approached only one herd and the herd remained together, this herd would be composed of closely related females who would all mate with the same male.
It is likely more beneficial for the herds to break up and mingle during the rut because this would ensure a greater genetic diversity on the population level.
While the red deer individuals perhaps do not consider the population benefits, they might attempt to avoid inbreeding as mating with several males by the same genetic lineage of females would ensure that at least some (if not all) of these females would not have bred with a related male.
Inbreeding avoidance is a behaviour actively applied by species.
The breaking up of the matrilineal herd would also imply that new female groupings are formed during the rut which are comprised of related and unrelated individuals as females move from a harem to a harem choosing the best mate and probably making decisions also based on the habitat that the male has secured during the mating season (red deer are capital breeders which means that their reproductive success is based on the body condition that they acquire over time until birth and therefore the females invest timely in their fitness).
The habitat aspect in the female choice might additionally imply that perhaps the male is not the only one who makes active decisions regarding the herd structure.
For example, if a less appealing male approaches a herd of related females and if this male is not deemed worthy (but the habitat that the herd currently occupies is highly optimal), the females may wish to stay on their range in order to ensure proper foraging and they might chase off the undesirable mate (rather than simply letting the male stay and emigrating themselves).
It is also curious what happens with the calves of the year who are not sexually mature yet and do not partake in mating decisions (and who are not mating candidates, not competitors with respect to the stag).
It is known that calves remain with their mothers also as yearlings (and female offspring might stay permanently in her mother’s group).
Do they temporarily separate from their mothers during the rut? Do they form their own herds of young ones? Or do only young males separate while juvenile females follow their mothers if the mothers decide on changing the harem?
I find it less probable that the young ones would entirely separate from their mothers because they are still at a vulnerable age when predation risk is rather high.
If the mother has invested in raising them until the rut and if she continues accepting them (and possibly investing in their education and protection) throughout their yearling stage, would she easily abandon them for 1 – 2 months when predators have become mobile looking for vulnerable prey (and having a hard time finding any because the summer has nourished the ungulates who are yet strong which is why the predators would likely focus on the younger, inexperienced individuals).
Regardless of where the juveniles end up during the rut, I find it interesting to imagine the social dynamics and habitat exploration that should occur on occasion the harems are not comprised of the same female individuals as the matrilineal herds during summer.
Apparently the herds reunite after the rut as there would have been no detection of matrilineal societies if they did not.
But if the females travel from harem to harem according to their preferences of mates and foraging grounds (and perhaps some additional considerations), it would imply that during the rut they mingle with unrelated females and they might visit and experience other foraging grounds.
This could be especially true of the younger, less dominant females if the dominant females sort of defended their preferred foraging grounds against undesirable mates thus exerting their mate selection not through emigration but through forcing the unwanted male to emigrate.
Mingling might provide important social experience for the females (and juveniles if they, indeed, followed their mothers).
Females of dispersing age might survey the social grouping prospects, population density and available, profitable ranges.
Other females, especially, younger ones might gain new skills by observing the behaviour of other females who do not belong in their social group.
This could be a significant educational opportunity for females who otherwise tend to remain in their natal group (unlike males who later join mixed bachelor herds where they can learn from other, unrelated males).
I wonder if some females might make their harem choice not based on the habitat, nor the male but on the composition of the harem female group (in terms of gaining knowledge and experience as well as getting along).
Additionally, as the females perhaps move outside of their typical range, they might access new types for forage and they might explore new habitats.
While most females apparently later return to their pre-rut home range, these experiences might be remembered and applied later in life or herds might even alter their habitat use based on the new experiences.
It would be interesting to study whether the use of habitat as well as some social interactions (or other representations of the education obtained during the social mingling) change after the rut and whether foraging choices or social interactions observed previously in one herd but not in others become transferred to other herds.
As the tenure of the herds is probably quite stable, these alterations might be best observed in younger females who have not yet experienced many years of interactions with other nearby female herds.
Perhaps some individuals might even form bonds with other herds (or they might favour the new foraging grounds) and decide to join them over their natal group.
I find it interesting to determine to what extent the stag is the one who forms the harem and to what extent those are the dominant females who have their own habitat preferences and who impact the location of harems.
The stag might be proven a joiner-in rather than a true harem establisher, permitted by the dominant females to stay on their ranges if he is deemed fit.
Harem formation by the stag himself might be more explicit if some of the females ventured out of their typical ranges and joined the stag ‘on his turf’ (the grounds normally used by the bachelor herd).
These habitats would be less familiar to the females and there might not be any ‘core group’ of females who have been using the range all the while.
Such harems might be more reliant on the stag but also perhaps sometimes less profitable for the hinds as the stags tend to occupy less optimal habitats during summer focusing on bulk intake rather than forage quality.
Thusly, the dominance and experience of females might, once more, become a strong factor in determining the harem formation based on considerations entirely different than the actual mate choice.
The rutting season might be a time of adventure for the younger hinds while the older hinds might assert their dominance even over the males.
If females are less likely to venture out on the foraging grounds of the bachelor herds (due to suboptimal foraging opportunities), these factors might also influence the harem composition and location as the best fit stags might attempt to approach the matrilineal herds (and thereby the dominant females might not have to chase them off because they are already the fittest among them all) while the less fit males might expect until some females who find no place in the existing harems agree to join them in the former bachelor ranges.
This, however, would segregate dominant stags and dominant hinds from less dominant stags + hinds.
The four ‘colonists’ I observed near my town might represent a third scenario whereby some males emigrate from the typical ranges of both females and males.
It is not clear whether their emigration was aimed at discovering local female populations (I do not suppose it was because they must have noted early on that there were no females and that the ranges on this side of the highway were limited, not suited for accommodating large red deer populations) or it was aimed at finding suitable breeding grounds and luring out hinds from the increasingly dense population.
It might also be worth asking whether the colonizing attempts by these stags were based on their understanding of what constitutes good breeding grounds.
If females base their breeding choices both on the quality of the male and quality of the habitat (as capital breeders should in order for their fitness status not to deteriorate prior to winter), this might mean that the male, upon establishing an entirely new spot for a harem, should select optimal grounds for the female’s foraging requirements.
Otherwise, the male might not attract any females at all or he might attract ‘poor quality’ females who are, for some reason, excluded from the better grounds.
On the other hand, kin loyalty might grant high quality mate access to ‘lower quality’ females (in poorer condition) if these females remain in their mother’s (/grandmother’s) herd which, due to its high range quality, only tolerates high quality mates because poorer quality mates are excluded.
One of the males who arrived to our town in September was, by the sound of his vocalizations, a mature if not older male.
He sounded very ‘convincing’ and I find it difficult to assume that he was simply a non-dominant, weaker male who had been pushed out by other dominant stags.
It seemed to me that he was deliberating his chances and that he had discovered a relatively optimal habitat (which was perhaps at the time even better than the habitats in the rural area which have been subjected to intense management).
Thereby, I wonder if he had intended to attract ‘high quality’ females who might have dispersed from their matrilineal herds due to incompatibility with the stag holding harem there or who might have sought to use this period for dispersal in general.
All in all, I hope red deer might establish a small subpopulation nearer our town where I could observe them more regularly.
They appear to be attempting to join the two subpopulations that both reside on the other side of the highway but that are separated and likely attached to different landscape features.
Curiously, the populations can apparently become best joined through incorporation of the outskirt areas of our town.
***
The autumn rut and the potential mingling between the summer social groups might also promote the winter herding behaviour at a later time when smaller social units can associate (temporarily) or disassociate.
A degree of former familiarization with individuals from other social groups might reduce tension and encourage cooperation during the winter aggregation period.
Notes by Ieva 