This autumn (late October/November) has seen high precipitation amounts which fell mostly during intense rain episodes that were, however, not scattered but followed one another rather closely.
As a result, water levels have risen in the river but also in other waterways such as agricultural ditches.
The rainfall occurred in autumn and, as a result, the water levels have not yet fallen greatly due to the cool weather (low evaporation and probably lower soil/root level water absorption rates).
Late spring/early summer, as well, were cool and characterized by rather frequent precipitation although water levels were not as high.
However, the rainfall was intense and regular and water levels were higher than usual.
Rain events also occurred before the summer heat period.
Thus, while vegetation might have been more active, evaporation rates were probably still low.
This is also the first year when I have observed beaver movement into new habitats:
- for occupation purposes;
- for foraging purposes.
In our area, I believe that the beaver population has been saturated or approximating saturation for at least a few years and I do not think that these colonization/forage seeking efforts are merely related to the occupancy of prime habitats and the beginning of settlement in suboptimal habitats.
Similarly, in the sites where I have observed beavers foraging deeper inland (while travelling along a ditch system or using temporary pond created by the rainfall), substantial changes in the availability of riparian vegetation cannot be detected.
Therefore, I assume that beavers have been using the sudden rise in water levels in the agricultural ditches (as well as the pond created in a natural hollow in the forest) in order to explore new habitats.
Water level rises at times in these ditches (that is what the ditches are for) but I suppose that rarely it has been kept as high for as long a period of time without falling to relatively shallow depth.
In two sites I have observed new colonization with settlement.
I cannot be certain when the settlement occurred precisely but I have not seen tree stumps indicative of old damage (felled last year or years ago) and I suspect that the settlement has been recent.
Although in one site, the beavers have attempted to dam up a culvert and the construction seems fundamental enough not to have been built over the past month.
Unfortunately, it is not accessible enough to investigate the freshness of the dam materials.
These particular beavers might have colonized the new site in spring/summer already.
They are inhabiting a very large ditch that runs between railway and an agricultural field.
The ditch is far from the actual river and thereby the beavers must have settled there permanently.
There are at least two beavers there.
It is difficult to say how they reached the site.
I believe they travelled along ditch systems that might be connected to the river at some point (I have not yet investigated where the ditch ends and these ditches do not show up on Google Maps).
However, the journey cannot have been short.
If the ditches are connected to the river as I suspect they are, these beavers would have travelled about 2 – 2.5 km.
Straight-line distance to the river would be ca. 1 km.
However, the beaver would have had to travel across land for most part of this journey conquering agricultural fields, possibly the railway and one country road).
I believe the beavers rather arrived along the ditches.
The same ditches might have been used by another beaver family which has settled in a pond amidst a clearing surrounded by vast arable fields.
The situation is rather the same – if the beavers travelled along ditches (and ditches are available there with few interruptions of small country roads), they probably journeyed more than 2 km.
Straight-line distance to river is < 1 km with one country road intersecting it.
However, the agricultural fields between the river and this beaver colony also include the danger of a household with active dogs that are not always restrained.
I believe there are also two beavers in this family, and this family, as well, might have settled during the late spring/early summer rainfall episodes.
Meanwhile, I have observed new foraging patches on the other side of the town.
In neither of these sites food availability has changed substantially.
In one site, there is a smaller ditch (which does not appear to be inhabited) connected to the river (ca. 500 m from the feeding site).
The beavers have travelled along the ditch and for the first time over past 6 years (since I have been living here), they have begun foraging on the willows that grow on the edge of a hay meadow.
The ditch separates the meadow from a slope that leads up to private gardens.
There are abundant willows (even a coppice) and beavers are apparently travelling along the ditch from their river home to forage.
The river itself is about 200 – 300 m from the coppice and the ditch.
I believe it would be inconvenient and dangerous for the beavers to travel across the hay meadow which is why they have discovered the willow resources only when the travel along the ditch became possible.
The ditch normally holds very little water (one can step over it in one large stride and the width of the water is only about 10 – 20 cm) and the ditch itself is narrow (ca. 50 cm – 1 m).
Currently, the ditch is full and overflowing and the water surface width reaches > 50 cm in most places (close to 1 m).
The river approaches the coppice more closely in one spot (only about 10 – 20 m) but it does not seem that the beavers have travelled overland there which is most curious.
They have begun foraging more toward the middle part of the coppice which suggests they use the ditch for the travel and they do not reach the coppice overland.
As the snow has fallen, I have not observed tracks across the dry land between the river and the coppice, either.
Beavers might have discovered these resources while travelling over dry land (foraging further from shore) but then they must also have discovered the ditch and its convenience as a travelling/transportation channel.
The other site lies relatively nearby (from a human perspective) although it is about 1 km downstream and the resident beavers form another family.
Here, a significant windthrow occurred during summer (in fact, about 30 – 50% of the trees fell or their tops were broken in the riparian woodland).
At first, I did not observe beavers utilizing these resources as they were rather inland (at least 20 m from the shore).
It is possible that beavers first used up the wind-fallen trees that had ended up right in the river or much closer to it.
However, this week (the last week of November) I walked through the small riparian woodland and I saw beavers debarking and debranching the dead trees deeper in the forest.
In that site, beavers travel between the river and the foraging patch directly.
But a pond has formed, as well, near the fallen trees.
The pond is not very large, nor it is very deep but it might allow for some ease to drag the materials and perhaps beavers simply feel safer near water.
I am not certain if beavers have started using this site because they depleted the shoreline windthrow and moved on to the forest patch, or if the formation of the pond somehow encouraged them (despite the low-level practical application of the pond structure itself).
But the use of this site began only after the rainfall events (although this could be coincidental).
Maybe beavers are able of detecting increased levels of organic nutrients incoming into the river from riparian groves after trees have fallen, and then they proceed to investigate.
As the trees had fallen in summer already, the high precipitation in autumn might have finally carried the organic flows into the river.
Thus, the pond itself might not have served as a feature of encouragement but rather its emergence is a token of the saturation of the local groundwater leading to overland flows that are reaching the river.
Previously (during summer and before the intense rainfall), the forest hollow might have soaked up and retained much of the organic matter.
Rainfall could also have facilitated decomposition contributing to the changes in the chemical composition of overland flows.
I have not encountered information, nevertheless, whether beavers have such fresh deadwood detection capabilities (sniffing or tasting the windthrows out from the river itself through the overland flows).
I simply wished to write down my observations during a year which saw two prolonged periods of high rainfall and relatively cool temperatures.
Notes by Ieva 