I would like to write down the conclusions drawn over many observations of roe deer in my area.
I would also like to note that I made most of these observations prior to discovering the scientific article which led to assumptions that two roe deer species (the European and the Siberian roe deer) might, indeed, cohabit in the Baltic region (at least in Lithuania; moreover, in a region which is not far from Dobele Municipality where I live in Latvia).
I have addressed these roe deer species issues in another post – Siberian roe deer in the Baltics – an additional cervid species in the European Union?
I cannot say whether the two types I believe I have observed (and which I had begun to distinguish between prior to finding information of a possible species division) are the result of environmental adaptations (ecotypes) or if they are the result of some genetic expressions (genotypes or even separate species).
However, I have noticed that these two types attest to slightly different habitat choice and behaviour although some attributes remain strikingly similar despite the potential benefits of introducing behavioural modifications.
Firstly, I have noticed that some roe deer who mainly live further from the immediate riparian areas and whose available forest cover is frequently not very extensive while the agricultural lands (crop fields) take up hectares of space in the landscape that they inhabit, have little worry over crossing large open areas without immediate proximity of tree cover.
Meanwhile, the other type appears concerned if the field is too large and they hesitate when they have found themselves too far out in the open.
They seek to travel along tree lines and they would not run across a several hectare open field but they would rather turn back or aside after about 200 – 300 metres in order to reach tree cover.
The former (open habitat type) roe deer can also live close to massive forest stands and some of these forest stands are even larger than those utilized by the forest type roe deer.
The forest type roe deer, however, seem to stick close to riparian forests in particular and they appear to enjoy a mosaic of habitats wherein none of the patches (not even the forest patches) are not too large.
However, I would say that there is some minimum riparian forest tree cover that these roe deer need.
They probably prefer edge habitat (ecotones) and therefore they might not feel as comfortable in denser forests but they are less likely to be observed near very narrow strips of trees or small forest patches in the middle of the agricultural field where the open field type can be seen.
Perhaps 30 – 50 metres is the minimum riparian woodland width that these forest type roe deer tolerate (granted that the band reaches along the river far enough to form a significant total area of tree cover).
Meanwhile, the open field type roe deer can run across several fields and roads perhaps over the total distance of nearly 1 km without turning for tree cover (although they do run to the tree cover).
I think that these bands of trees are used by the roe deer to travel and that they prefer a situation where they can hide in the relative density of the trees (closer to the water) but where they mostly can move along the edge keeping an eye both on their shelter/forage (forest) and forage (small open area) habitats.
They probably forage out in the open only when the tree cover is near and when the tree cover can be used as the main travel route crossing as little space as possible out in the open.
I should say the forest type roe deer prefers wetlands and wetland forests while the open field roe deer mostly focuses on tree cover as such irrespective of whether it has significant water resources or is simply surrounded by an irrigation ditch.
The riparian forests are characterized by ecotones on both sides because rarely the trees reach down to the very riverside and thus the riparian forest on the side of the river is, too, concluded with strips of grasses, forbs and shrubs maintained by flood activity, beavers etc.
I am not certain which type actually dwells predominantly in large forest massifs.
I believe it might depend on the surrounding matrix (whether there are large open fields nearby or smaller open habitats) as well as on the presence of a river or another larger, more influential body of water (that is not a small pond or a ditch).
The forest type roe deer appear to mingle quite closely with the open field type roe deer and I believe I have seen them foraging on the same crop fields (but mainly on the forest type roe deer side of the habitat).
The open field type roe deer are perhaps better capable of crossing roads while the forest type roe deer cross rivers to reach new/shared habitats.
The extent of mingling and joining of one type of roe deer of the groupings of the other might be limited by the forest type roe deer which cannot follow the open field type easily (see also Roe deer observation – Feb 8, 2024 (winter habitat use, anti-predator behaviour)).
I am currently not certain if the open field type roe deer are limited in joining the forest type roe deer.
They might if they are larger (see below), less ‘bouncy’ and if they have adapted to consuming cereals at greater rates (it might be difficult for them to sustain themselves on browse alone).
The open field roe deer occasionally (but not always) seem larger than the forest type roe deer.
In fact, when observed in twilight, they are sometimes difficult to tell apart from red deer hinds (in areas where both deer species are known to occur and therefore I am confused over who I am seeing).
They are not huge and the difference is not overwhelming but they might, in some places, reach perhaps a size by 20% larger than that of the other ecotype/genotype.
They are often darker brown/reddish, too, while the forest type roe deer can be more sandy but I am not superpositive regarding this assessment.
They seem to exhibit less of a ‘bouncy’ trot and more of an ‘even run’ compared to the forest type.
It is usually possible to tell apart red deer hinds from roe deer by the manner in which they run.
Red deer run more smoothly while roe deer bounce (more resemblant of perhaps goats).
I suppose the bouncing trot is an adaptation to running in a habitat with many obstacles (such as a riparian forest).
On open fields, the ability to run fast in a straight line without investing into bouncing (because there are few obstacles in such habitats) might be beneficial and these open field type roe deer, indeed, seem to run more smoothly contributing, once more, to the difficulty of telling them apart from the red deer.
However, as I have stated in the opening of this post, the open field type roe deer do not appear to gather in larger herds than the forest type roe deer (during winter).
They perhaps gather in herds earlier than the forest type roe deer and perhaps more often (Fawns following female roe deer also after rut and roe deer winter grouping behaviour) but the herds are not necessarily larger which suggests that the roe deer density is probably determined by the access to tree cover (shelter) also on the open fields and there are not vastly great numbers of roe deer on large open fields if the shelter habitat is limited (which it mostly is).
Aggregation of larger groups in open areas is a typical anti-predator strategy in many species (including, e.g., the red deer and probably also including roe deer during winter) but the open field type roe deer apparently do not attempt to form very large herds and this could suggest that they main strategy has not altered from that of the other type.
Namely, they rely on tree cover and while they are more comfortable at crossing larger open areas, they try to stay close to the trees (however, they might also use mere ditchside shrubs and few square metre tree patches in the middle of the field that the forest type roe deer would likely deem unfit for ensuring their safety).
I believe the main difference might be that of their dominating travelling mode (using riparian forests to move around or cutting across fields) but also there could be major diet adaptations resulting in different physiology and maybe phenology.
It is also curious how the open field type roe deer resolve matters such as finding fawning sites (many of them rely on very scarce tree cover and frequently, long grasses or ferns such as can be found in riparian areas, are not available to them) and how the males defend territories during summer when they travel greater distances altogether and a large part of their habitat might be of low protective interest and entirely unrelated to where the females would be most often found during late summer.
The forest type roe deer during summer seem to stick more closely to their riparian shores and their foraging sites overlap with their shelter/fawn raising sites.
Meanwhile, the open field type roe deer probably do not have sufficient amount of forage in the sites where they seek shelter and while the density on the fields might not be higher, the density in the cover habitats could be slightly greater than that of the forest type roe deer.
The open field type roe deer might be more ‘cramped’ in their refugias while unable to avoid each other during foraging, either (additionally, there might be a need to make slight aggregations during summer on the open fields to avoid predation).
Perhaps the social structures and territorial behaviours in these types are not identical although not extraordinarily diverged either.
The open field type roe deer might be more tolerant of one another allowing for reduced spacing out and some of their summer foraging behaviour might be similar to their winter foraging behaviour from the social perspective.
I hope to observe these behavioural details more closely in the time to come.
Notes by Ieva 