In the morning of June 20 (2024), we (my dog and I) were idly observing a roe deer male foraging on a hayfield.
The hayfield is mature.
The grasses and some of the forbs were taller than the deer himself, and the deer knows how to use them as cover which is interesting because I believe this behaviour has been appropriated by the adults through the use of memories of the time they were yet fawns.
Namely, before the habitats became more open and the roe deer were, essentially, driven out of the forests / forest edge environment and onto larger fields, they must have altered their anti-predator strategies.
In the forest, adult roe deer do not always attempt to hide behind vegetation but they rather stand still where they are at the moment as the forest itself conceals them well enough with its distribution of shrubs, saplings and taller trees the trunks of which confound the eye and are of the same colour as the roe deer.
Certainly, they might take cover in shrubs but this behaviour is mostly observed when the roe deer are already out in the open (e.g., on a field with shrubby groves).
When spotted in a forest, meanwhile, they ‘freeze’ quite instantly because, I suppose, the predominant strategy (when already inside of a forest) is to move as little as possible rather than to move toward a better cover.
In fact, even when on the forest edge (with the forest as the background), the roe deer tend to freeze first and only later (if all fails) to run into the forest itself.
They have evolved alongside shrubs and trees, and the woody plants, their height and their colour are sufficient to hide the roe deer almost wherever the individual deer stand at the moment.
The roe deer are not taller than most forest undergrowth shrubs/saplings and the roe deer are, additionally, not too tall to reach many of the more mature canopies (whereby the brownish/greyish trunks are the natural background and not the green leaves).
Meanwhile, out in the open, the roe deer choose to, first, evaluate the situation which is rather different than ‘freezing’ because they seem conscious of having been easily noticed and therefore they only apply the forest ‘no movement’ strategy if they are far enough and perhaps if it is dark enough.
Otherwise, they assess the situation and this occurs in a slightly different manner. While the roe deer still do not move, they are more conspicuous in their stance.
It is difficult to explain what constitutes the contrast between a ‘frozen deer’ in the forest vs. out in the open.
It is almost as if, in the forest, the deer somehow disengage their presence, as if they become the forest itself while, out in the open, the roe deer are themselves and the processing of the situation draws attention to them.
I would even say that the way the roe deer think in the forest is dis-associative from their bodies while, out in the open, they clearly perceive stimuli directly.
Namely, in the forest, the deer might not try to perceive the threat directly as many animals have this ability to suspect that someone is watching them, someone is listening in for them etc.
Maybe, in the forest, the deer are perceiving the threat through the sounds, shadows, scents that are mediated by the forest itself.
For example, rather than paying direct attention to someone’s visual shape, they might be looking at the shrubs, at patches of light and shade, listening not to the sound produced by the subject but by the sound produced by the impacted objects (which is very similar but it retrieves the focus from the subject and onto the environment that can be perceived safely), and evaluating the changes that the presence brings upon the forest rather than the presence itself.
Out in the open, such mediation might not be possible as the landscape structure is generally far more simplified.
Nevertheless, the roe deer still attempt to avoid movement, especially, if not at close quarters.
On the hayfield, meanwhile, the male has several times demonstrated the strategy of retreating into taller grasses.
The hayfield is a heterogeneous habitat where some patches of grass/forbs are taller than others, and the male seems to be perfectly aware of the distribution of such patches.
When he becomes more alert, he transitions toward the taller grass patches where he is almost entirely concealed but, during low vigilance periods, he does not seem to mind much how tall the vegetation is.
I even believe that one time (while the hayfield vegetation was yet comparatively low of growth), the male lay down not to rest but to be concealed by the grasses and forbs.
This behaviour is different than the prescribed adult roe deer response pattern.
It involves movement rather than freezing and it involves finding a place to hide on the grassland and not running for the nearby tree/shrub habitat patch.
It rather reminds the behaviour of fawns in the birthing sites where they find tall herbaceous species to conceal themselves in and, typically, also lie down.
The fawns do not leave the habitat patch but they find the suitable cover within it.
The adult male does not lie down (I have not observed it more often than once) but he, too, moves within the habitat to leave the open areas and to find the taller grasses.
I think, when the roe deer came to utilize grassland habitats, they might have readjusted the behaviour they learned yet as fawns which, thence, served them during their adult life stage.
However, it is also interesting that the application of this behaviour does not render the individual more timid (the way it would be assuming the adults are, essentially, mimicking fawn behaviour) but rather the individual becomes bolder as this male frequently does not freeze at all (not even when he is aware we are present) and he is perhaps even less alert and easily spooked than in other types of situations (e.g., by the forest edge, in the forest, in an orchard).
I wonder what psychological effects might be at play here.
A fawn might be worried if the patch of herbs it is hiding in, is very limited in size as the predator is then quite close at all times.
The sheer expanse of the grassland cover might evoke some type of psychological impression that the predator can never find the individual in such vastness and perhaps, as the behaviour is executed, it gives the impression that the individual is a very, very small fawn in a very, very large forest.
Forests, normally, do not offer such extensive herb cover and a forest which does must be enormous but the psychological association between hiding in herbs and being in a forest, might be strong enough to trick the mind into forgetting that the habitat is open).
Perhaps the individual then feels quite secure of itself as they might somehow imagine they are in a forest (because fawns are born in forests) and the threat is very far.
Accordingly, as adults, the roe deer might not respond to threat because it is not close enough with regard to ‘forest standards’.
In a forest, the threat is probably not responded to unless it approaches to a certain distance because otherwise the roe deer would be constantly spooked as the forest is a relatively rustling environment with many events happening.
Also, in a forest, many trees would stand between the roe deer and the threat at such distance as on a hayfield, and these trees would conceal the individual well enough.
There are, of course, no trees on a hayfield of this sort but the bodily associations of being a fawn and hiding in herbs + being a fawn and growing up in a forest (hence, being in a forest when hiding in herbs) + the threat being far relative to forest standards + the forest having many trees between the threat and the individual -> might lead to a psychological impression of being quite safe.
In my experience, roe deer are rather curious and, in this open situation, the roe deer might be enjoying the perceived sense of safety combined with a scope to use their vision to study the circumstances (which is not always possible in the thicket-type habitats).
I have sometimes also wondered about the distance at which a sound is perceived as a threat and perceived in the first place.
Namely, in species which dwell in forests and other habitats which can be rather noisy, it might be unprofitable to react to every single noise.
Some noises are, of course, more threatening than others (e.g., voices, howls, barks etc.) but, overall, the snapping of twigs, the rustling etc. might not be perceived as a threat and watched out for unless specific conditions apply (nearness being one such measure).
For example, I have noticed that it is possible to sneak up on the roe deer quite closely without them becoming alerted but then, at a certain distance (which is perhaps that of 50 m), they are suddenly all ears and nothing passes by them.
Perhaps prey species have learned to filter sensory signals related to threat in order not to be in a constant state of alertness.
This could also imply that prey species, curiously, might have worse hearing (not bad hearing, mind you) than, for example, predators because the predators are listening in on sounds near and far and it is profitable for them to hear at a great distance.
Meanwhile, prey species might expend too much energy responding to every noise, especially, in ‘noisy environments’ and they might have reduced their hearing only to a certain scope which helps them avoid threat while enjoying some peace of mind.
Even on the hayfield, however, the roe deer prefer trees to grasses, and while there might be some brazen spirit exhibited during the foraging process in tall herb patches, they tend to move from one woody plant patch to another and, if possible, forage near or under tree cover.
Thusly, for example, on the small hayfield, the deer tend to keep at < 10 m distance from the forest edge.
On this large hayfield, the male buck tends to move from the riparian tree grove toward some apple trees in the middle of the field and back.
While traversing the relatively vast field, however, the male is behaving differently than roe deer in/near treed environment as well as roe deer on open fields where the vegetation is quite short (e.g., wheat fields).
Notes by Ieva 