As I have been observing the 6 – 7 beaver families (colonies) that inhabit the river in the sectors which I can access, I have attempted to determine their composition, territory size, foraging patches etc.
Most of the families appear rather conventional and they would forage near the shore bringing the branches close to the water and rarely venturing further than 20 metres from the bank.
They also have dens on the side of the river which does not have active trails used by people although I believe that one den is located on the hayfield side of the river which is more greatly prone to disturbance although not overly so.
Additionally, there are some trees growing right on the bank which is steep and I think this spot makes for a suitable denning location because the roots provide structural support while the steep bank provides space for the den chambers as well as proper beaver ‘chimneys’ (ventilation holes).
Two of the families seem to have very large territories (compared to others) and I assume they might have been among the first settlers (or the heirs to the first settlers) as they also have choice foraging grounds.
It is known that the first settlers tend to have larger home ranges than latecomers although later the population dynamics usually even out the disproportionate land tenure (see, e.g., Campbell, R. et al., 2005).
One of these families, however, has suffered significant alterations to their range (clearance of riparian shrubs in some sectors) and perhaps, as a result, they have begun foraging along a ditch that extends along a hayfield.
I find it interesting that two of these families seem more adventurous than others.
Both might have been prompted to more daring foraging feats by human disturbance to the vegetation (one more than others because this family barely has any decent riparian sections with lush shrubs and riparian forests and, consequently, they have to resort to more extraordinary means of provisioning.
These families live adjacent to one another (at least according to my assumptions) and I have described some of their ‘stranger’ foraging behaviour in two earlier posts (Beaver observations – Feb 9 and 10, 2024 (exemption to central-place foraging); Beaver observations (Feb, 2024) – keeping watch / mate guarding behaviour?).
One of these families (the one with the better quality territory which is more secluded, less disturbed and which has riparian shrubs and forests but which has been supplemented with ditch-side foraging as well as some foraging on steep slope without apparently returning to consume the branches down by the water due to the travel expenses in terms of energy) might have been among the earlier settlers.
Their territory is rather big and it is more remote and ‘wild’ than many other beaver territories on our river.
The other family lives a bit upstream and their territory used to be quite optimal but it has suffered a lot of disturbance (tree cutting, clearing of riparian shrubs, cattle grazing, cattle fences, pedestrian trails, dog playground).
Its range might be of the same size or smaller.
I do not believe that they have arrived significantly later than the first family but, over time, their ‘usable’ range has shrunken considerably while the beaver population density has grown and thereby they have not had the chance any longer to expand and to adjust to the new conditions.
Consequently, they have resorted to foraging large distances offshore (e.g., > 40 metres) and I believe this is the family that has demonstrated what I find highly extraordinary behaviour.
Since late last autumn they have travelled about 300 – 400 metres across land (through a partly felled riparian forest where mostly only mature trees that might be alders remain).
Then they have proceeded to climb up a very steep slope (> 70°) ending up in some private garden allotments of which some are abandoned and overgrown with tall forbs and grasses, one is overgrown with small pines and birches but some are also being managed (although unfenced).
They have crossed these allotments (ca. 100 m) where they have foraged some on this side of the road between the allotments (mainly on cherry plums, plums but also some smaller native deciduous species) but they have also crossed the road to forage on the cherry plum hedgerow and they also seem to have travelled along the road (which I cannot state firmly because I cannot be certain whether they always ascended the slope in the same location which shows their trail) for about 50 metres in both directions exploring.
They do not seem to have dragged larger trees down the slope and they have mostly felled medium-sized trees to obtain the branches or they have taken the lower branches of the hedge (that are accessible without felling the entire tree).
Some of the branches might have been dragged into shelter or down to the river although I found none on the slope itself.
Some of the branches have clearly been consumed on the spot (even near the road and almost on the road).
The road, of course, does not receive almost any traffic at night.
These feats have not been achieved by a dispersing beaver which perhaps has ventured overland as the river has dense colonies and might not be easy to travel.
The foraging has occurred regularly (in warmer periods).
The beavers in this unfortunate family who has lost 60% of their formerly suitable range have essentially travelled at least 400 + 200 (slope) + 100 metres = 700 metres to forage in a highly perilous circumstance.
It is curious that they have not stopped in the riparian forest which despite having been cleared quite intensely, still has some shrubs and alders and probably other tree species.
It is, however, significant perhaps that they appear to have travelled through the forest rather than crossing the open hayfield.
It seems that they might have been looking not merely for ‘something to eat’ but for specific nutrients that are perhaps obtained from the fruit trees rather than the alders.
I believe that it is the access to these nutrients the beavers have been seeking rather than access to any kind of palatable woody plants.
The courage of these individuals appears stunning and I hope that people recognize this family is not raiding their orchards because they have nothing better to do but because all along their territory they have suffered losses of resources that have driven them to apply novel solutions.
One of the reasons why they might have ventured thus far during the cold months while ignoring some of the riparian native species could be related to strategic planning.
The beavers know that during spring and summer they will not be able to invest into such ‘adventures’ and they will be in need of resources closer to home in order to nurse, feed and protect their kits.
Also, perhaps the older beavers (or subordinates aka older siblings) might have tested their chances so that the kits of the previous spring can forage on the limited vegetation near the safety of the water and the den.
Additionally, spring and summer are the seasons when humans visit their allotments frequently and the disturbance would be too great for the beavers to tolerate.
These two families have demonstrated boldness, adaptability and perhaps a slight touch of being adventurous, innovative and non-conventional – traits that I have not observed as greatly in other families.
Other families, too, have been flexible and some have ventured upslope (but they have always been under cover of shrubs and trees and they have had pools or water or deep ditches close to the foot of the slope etc.) and some have crossed walking trails to access trees ca. 15 – 20 metres from the shore.
However, none of these other families have professed comparable daring.
It makes me wonder whether:
- any beaver family would demonstrate similar adaptability under similar conditions;
- the two extraordinary beaver families might be related.
I have entertained the latter assumption quite greatly because the territories are adjacent and they might have been established not long one after another (e.g., one of the first dispersing generations produced by the first colonizers).
I also wonder about the nutritional merits of different woody plants and how they related to individuals who attest to different traits and behaviours.
For example, if these individuals are genetically more inclined to be explorative, adventurous, bold and curious (possibly, long-term schemers), their energy and nutritional needs might differ from other individuals who are more contended with a ‘simpler life’.
Thus, the behaviours observed might not only be the result of suboptimal range and lack of available forage near to the river but they could also be the cause of these behaviours themselves.
It is a strange statement and what I mean to say is that the genetic traits that prompt the individuals to seek novel solutions, to explore, to challenge themselves might cause behaviours that result in energy expenditure and metabolic requirements which differ from those of more conventional beavers.
(Similarly to how perhaps humans who predominantly work in an office using their intellectual capacities vs. humans who mainly invest emotionally vs. humans who perform largely physical labour might end up needing different type of food, rest and exercise.)
Thusly, the behaviours caused by the traits inspire additional behaviours which are already carried out in order to fuel the behaviours themselves (as expressions of the traits).
For example, if these families are more exploratory in nature, they might have a need to discover what else lies on their range.
While the loss of habitat is certainly a factor of utmost influence in the case of the second family, the loss of habitat might have additionally resulted in a loss of space to explore and to study.
Accordingly, the driving motivation behind these inland ventures might have been both food acquisition and the satisfying of the need to learn, to discover which cannot be fulfilled in the depleted sections of their range that have become poor not only in food but also in exploratory stimuli.
It cannot be known whether the beavers in this family were driven to venture ca. 700 m through difficult and dangerous terrain to attain some branches of plum trees by:
- hunger and lack of palatable food near home;
- the need to explore and to satisfy curiosity;
- the need to acquire nutritional resources that are somehow better or better fitted to the character of these individuals.
For example, I believe that mental investment might call for different nutrients and also, combined physical and mental investment might increase the overall energy demand.
Beavers who lead a more typical lifestyle might not be in need for greater energy levels, nor ‘special foods’ and perhaps they would not take such extraordinary measures – under the same circumstances – due to their character (genetic traits).
Character might determine the behaviour of the beavers to an extent that some families might find their homes suboptimal to a greater degree than others upon losing parts of former range or being forced to settle in poor habitats.
These beavers might, at the same time, be more adaptive (coming up with innovative and courageous solutions) and less adaptive (not being able to cope with what is available) than more conventionally ‘geared’ beavers.
Thusly, in nature conservation, the optimal conditions should also be viewed from the perspective of the character of the individuals because some individuals might be more contended in less optimal conditions than others and the mental health requirements might be closely intervowen with the physical requirements.
I even believe there might be differences in the types of beavers who settle in habitats during early colonization vs. during the period when the resources are somewhat depleted and regenerating.
Bold, adventurous individuals might be better adapted to travel further and to seek unoccupied habitats or optimal habitats with breeding vacancies in order to satisfy their high and specific demands both in terms of food and opportunity to express their character traits.
Meanwhile, less adventurous individuals might be the more appropriate for taking care of territories which are not as optimal because they are yet optimal enough for them.
References
Campbell, R. et al. (2005). Territory and group sizes in Eurasian beavers (Castor fiber). Behavioral Ecology and Sociobiology. 58. 597-607. 10.1007/s00265-005-0942-6.
Notes by Ieva 