Sometimes I can observe beavers (European beavers, Castor fiber) early in the morning (before sunrise) in a relatively remote riparian (agricultural) area where several beaver colonies (families) live (although they are separated from one another by a decent distance of several kilometres).
I go there with my dog and the beavers have become somewhat accustomed to our presence (not habituated but simply not minding us much because they have learned that we just sit quietly by the river and do not bother them).
This has enabled me to observe some of their behaviour which is not an immediate response to our presence (also because we tend to stay for longer periods which causes the initial disturbance of us passing by to become ‘forgotten’).
I used to think that splashing (slapping) the tail against the water surface only served as a warning / alarm signal mostly intended for other beaver’s family members to notify them of a possible danger (e.g., someone approaching) or to react to disturbance.
I had also observed that larger beavers splashed their tails more often while smaller ones rather dived under water and tried to sneak away unnoticed by us (? validation needed).
But over a few mornings, I have heard the beavers splashing their tails in a communicative situation which I could not interpret as related to danger or to our presence, or any other type of external disturbance.
Question: Do beavers use tail slapping against water as a communication signal outside of warning / alarm situations?
For example, could this signal sometimes serve to exchange information among family members on where they are feeding (to be able to locate one another) etc.?
The setting was quite similar in all the mornings when I observed the activity which is why I will describe just one of the situations.
We had been sitting very quietly by the river for about 15 – 20 minutes already (wintertime, about 5 am).
We had passed the beaver ‘hotspots’ and settled in a good observation spot which is far enough from the beaver most active feeding sites but close enough to sometimes see them swimming buy or foraging on the opposite bank.
It was dark and I do not suppose we were very visible against the shoreline vegetation. And even if we were, beavers had swum right past us in similar settings on other mornings without paying any heed to us.
There was no wind to carry the scent but perhaps the beavers could catch our scent anyway.
One of the beavers was feeding in its usual spot (this beaver is larger than the others and could be the dominant male).
This beaver’s favourite feeding spot is relatively further from where we were sitting (about 30 – 40 metres upstream).
Also, the river is meandering there with riparian groves of Salix which made us even farther separated from the beaver.
(Previously I had observed that this same beaver only splashed at us if we approached very near, e.g., a few metres from the beaver itself. Not very jumpy, that one.)
But as we were sitting quietly and not moving, not standing up, nor walking in its direction, the beaver suddenly splashed its tail and due to us being so far away and having not stirred for a longer while, I could not see how this was connected to our presence.
There were no other animals around, either.
Generally, this is an area where adult beavers do not have natural predators (perhaps apart from stray dogs although I have never seen a beaver killed by a dog by our river or heard of such a sad event, and the dog-keeping regulations in Latvia are moderately strict which means that there are not many free-ranging dogs near towns).
Later when we were walking back, I also allowed my dog to sniff around by the bank where the beaver had been feeding (the beaver had left already).
I let her sniff nearby the beaver’s feeding site in order to see if she discovered fresh tracks of another animal which might have caused the beaver to react in alarm (or irritation) but the dog sniffed at nothing at all so I assume there had been nobody else on the respective bank recently.
On other occasions, I have seen beavers react to ducks but this was not a spot where the ducks were gathering (the respective ‘duck area’ being rather upstream).
There could have been other more aquatic causes of disturbance (fish? mink?) that did not bring their traces ashore.
Returning to the story, the beaver splashed from its feeding spot presumably at nothing.
About 5 minutes later I heard another splash, this time closer to us but in the middle of the river (it was flooded and wide at the time which might be relevant because the usual layout of the riparian area had been substantially altered for several weeks and it could have impacted the beaver routines and familiarity with the site).
This second splash could have been directed at us (because it was nearer to where we were sitting) but I also find it hard to believe because a bit later the very same beaver almost climbed ashore right in front of us and when it became aware of our presence, it simply returned to the water without any splash and no reaction.
(This beaver appeared smaller and was perhaps the dominant female or a subordinate.)
Due to the aforementioned reasons and our stillness, I conclude that the second beaver had not splashed specifically at us, either, because it had not noticed us.
At first (just after hearing it) I thought that the second splash belonged to the same beaver which had splashed before.
But in about 10 more minutes, the former beaver splashed again from its old spot while I had seen other beaver (the one that gave the second splash) swimming off in the opposite direction.
Thus, I assume that the first splasher had never left its feeding spot at all and the second splash had been given by another beaver (family member – as concluded due to close proximity).
This might sound subjective but I did not feel included in this communicative exchange.
I cannot see how it was concerning us because on all three occasions, the beavers were far from us and usually, they only raise alarm if we, so to speak, lack the manners and almost step on them, not much sooner.
This is a species-poor habitat and there are not many other animals around to have spooked the beavers.
Also, as I said, we investigated the shore.
The beaver which splashed closer to us (the second splash), was in the middle of the river which was flooded extensively resulting in a very wide stretch where not even a wolf could get at the beaver easily (and I believe the beaver knew that).
It made me wonder whether these beavers could have been communicating something other than alarm.
I was wondering whether beavers ever splashed their tails in order to use the sound as a communication signal to locate other family members or simply to bond with them during separation (like we would holler to one another if walking separate trails in a forest etc.).
***
In July, 2023, I have observed another interesting tail-slapping behaviour.
It occurs on the same river but an entirely different stretch which is still bendy but it has a bit more of riparian forest.
For several mornings, I have heard a beaver slapping its tail downstream (the beaver cannot possibly have heard my arrival there and this is not related to my presence).
Curiously, the slapping activity seems to happen at about the same time every morning (I do not carry any devices that can tell time but it is slightly before dawn and during dawn).
It also happens in about the same spot.
There are no predators for adult beavers there and in July the beaver kits are too large to be taken by foxes.
Also, this behaviour is not protective of beaver kits because it occurs relatively far from the active den (almost 1 km downstream).
This could be a reaction to some nuisance (e.g., roe deer frequently cross the river thereabouts and there are ducks swimming there).
I do not suppose it is a behaviour of being startled because, as I mentioned before, this happens with quite some regularity and even if the beaver has not memorized the cause to becoming startled, I assume that the beaver’s body has acquired a sense of ‘premonition’ around that time.
One morning, I truly heard a roe deer barking right around the time of beaver’s splashing (unfortunately, I was not attentive enough and I cannot recall which came first).
The other mornings, there is no other sound to suggest what has been happening but sometimes the roe deer cross the river rather quietly and I could have missed out on additional cues.
However, it seems almost as if there was a certain routine.
This is strengthened by my observations nearer the den.
The adults are mostly foraging elsewhere during pre-dawn hours and returning slightly before dawn.
The beaver kit seems to have some entertainment and a meal around 3 am – 4 am and then disappears for about half an hour or an hour (from 4 am to 4.30 or 5 am) – presumably for a nap.
Sometimes this disappearance is accompanied by the return of the adult but, in order to avoid disturbing the family, I locate myself in a way that makes it difficult to always catch the movement by the beavers in the stream.
I could have not noticed some of the traffic.
This slight regularity of some morning ‘rites’ has made me presume that the slapping beaver downstream also communicates something that is related to their routine.
The lack of predators does not predict much danger while the effect of nuisance / disturbance is less plausible due to the regularity of the sound-making.
Also, I am not sure if signalling alarm would be effective in this situation because many times the other beavers are very far from the tail-slapper (see below) and any incident unfolding downstream would be rather unlikely to affect the upstream foragers.
On some occasions, I have observed another adult beaver upstream (also about 1 km from the tail-slapper but above the den).
There is no apparent response that I can hear (no splashing in response) although I cannot attest to behavioural and quiet responses (such as changing activity or returning to the den).
However, it seems that the tail-slapping almost announces some shift in the schedule, ‘Soon I am coming home’ or ‘I am coming home now.’
The beaver kit’s naptime does not follow the slap precisely, nor the return of the adults that I have explicitly observed are immediate to the signal.
There might be some lag, nevertheless, i.e., the signal communicates, ‘Let’s wrap it up’ and the beavers gradually abandon their activities to commune.
Notes by Ieva 