Beaver dams as signals demanding respect?

I have been looking up some beaver-related videos.

Accidentally, I noticed the title of a CNN video that popped up on the suggestions column.

Certainly, CNN videos do not make trustworthy claims about wildlife behaviour but this one caught my attention.

The title itself was curious (if there could be any truth to it) because I have never read about beavers using structures like dams or lodges for territorial purposes (to advise other beavers).

They use scent-mounds instead (more densely along the territorial boundaries but possibly also within the territory, especially, while overmarking scent-mounds left by floaters aka dispersing or exploring beavers).

Dams would be an ineffective structure for signalling territoriality with respect to other beavers because when a strange beaver encountered a dam, they would have already managed to trespass considerably in the beaver’s territory (dam is usually a within-territory object) and the beaver’s primary interest would be to keep any trespassers outside of their territory.

However, there was something about this video that prompted me to watch it anyway and to entertain the propositions made by the wildlife rescue centre lady who had raised the beaver (whose behaviour was being discussed) since infancy and thereby, she should be somewhat familiar with its motivations, emotional states, habits etc.

Wildlife rescue centre workers, normally, should also be informed on wildlife basic facts (and frequently they have had a much more advanced training).

The wildlife rescue centre caretaker claims that the female beaver began building a dam after another female (whom she had not been on agreeable terms with) had been eventually resettled in another enclosure.

The caretaker interpreted it as a behaviour securing against the return of the other female beaver (the dam serving as a territorial object according to her).

I believe that the behaviour itself could be explained otherwise such as release from stress.

Perhaps the female beaver would have begun building dams prior to the disappearance of her ‘competitor’ but she had been kept under stress imposed by the presence of the other female restricting her from engaging in natural behaviour.

This could especially have some truth to it if this particular little female had been intimidated by the other female.

In the beginning of the video, some conflict behaviour has been recorded.

If I am not mistaken regarding the colouring differences between the individuals, the female who later built the dam, appeared to be rather intimidated by the aggressive behaviour of the other female.

Many facts have not been stated, e.g., whether the other female had been brought in at an older age (not raised up as a baby in the centre).

In the video, I do not see that the other female was overly aggressive in particular toward the resident.

It rather seems she was in a new place and her ‘aggressive’ behaviour was instead defensive – a reaction to novel conditions rather than displacement behaviour, competitive behaviour etc.

If she had grown up in the wild (unlike the focal female), she might simply not have enjoyed being approached so closely and so bold by the resident (who had been conditioned to the smells, sounds and interactions of the wildlife centre settings).

The captive beaver, meanwhile, would have had a difficult time identifying with the other individual in order to understand how the centre (where she herself had grown up with) could trouble and upset a non-captive beaver.

This might not have been territorial behaviour at all because at least the residential beaver was 5 months old and most territory defense is performed by dominant adults (and to a lesser degree, subordinates that are > 1 year old).

It has not been mentioned, either, whether the female used to build dams frequently before or only started building them after this incident.

The female appeared rather large (5 months as stated by the reporter) and young beavers might presumably begin helping their parents from the first autumn already as the parents are fixing any leaking structures or building new ones.

For such a large beaver, it even appears odd she would not have been building dams before if out of boredom.

If this was her first dam, the conflict itself may have triggered maturity in the female beaver that stayed behind.

And the exposure to another female may have made her realize she was not a baby anymore motivating her to take on adult tasks.

However, it seems that she had been building dams before (the reporter mentions that dam building behaviour would be triggered by sound of rain or running tap water and it appears that she refers to this particular female’s triggers although they are, of course, more general to the species).

Additionally, if this female had been kept alone in the centre facilities and the other female suddenly showed up but then was removed from the area, the first beaver might have perceived it as a victory (her first and successful territorial experience but see below for my interpretation of territoriality in this case).

She might have thought she evicted the other female and this could have caused her to feel she had claimed the territory.

The sense of being a territory holder might have similarly encouraged her to modify her habitat to her liking.

Namely, the fact that she built the dam across the doorway might not necessarily imply she was trying to block the entry.

It might simply have been a manifestation of her new sense of ownership and leadership regarding what she now perceived as her home.

This could have been the shift in the attitude that the rescue centre worker noted, and the maturity would have been not that of defense but that of ownership.

This new attitude could have become felt by those who had known her in the beaver female’s usual dam building habits.

The doorway might have been selected simply because it is a definite and narrow ‘channel’.

Beavers build dams across relatively narrower rivers and I have seen other video in which a captive beaver has build ‘dams’, e.g., across a hallway.

Doorways and hallways might appear narrow enough and they might resemble a channel more closely than open wide spaces.

They might be the natural choice (substitute channel) for dam building activities (rather than attempting to build in the middle of the room).

However, I still did not want to dismiss the rescue centre worker’s perception of this behaviour as somewhat… imposing.

And the female beaver, indeed, opted to pile the branches across the doorway leading not to other rooms (relatively safer space inside of the facility) but to the yard.

Perhaps the behaviour was not meant to keep out the other female who was now happily gone.

Maybe the female beaver started feeling possessive of the centre and its ‘family’, and she thought if she had suceeded in forcing the other female out, she might stop other annoyances, as well, e.g., visitors to the centre (human and otherwise).

It is possible that she had been slightly traumatized by the incomprehensible (to her) responses and actions of the other beaver.

She had grown up in the centre and it would be difficult for her to understand how another individual finds it a place inducing anxiety.

This might have been her first encounter with an animal that is distressed but also healthy enough to make a fuss about it.

Thereby, I find it not entirely unlikely that the resident female beaver wished to secure against future threats and that she had developed a sense of her world open to being compromised.

This new awareness of her as the territory holder (confidence, proactive stand, leadership) might have interacted also with her new anxieties.

As I mentioned before, if she had been concerned about the other female in particular, she would probably have scent-marked a mound and not built a dam (although I am not aware at what age precisely young beavers begin scent-marking and at what age they can physically produce scent from the glands).

But dams can pose obstructions to some species other than beavers and while I have never heard of dams being used as territory boundary signaling structures (against conspecifics or against other species), beavers may have noticed that dams can temporarily stop or halter other freshwater inhabitants (e.g., mink, otter, fish etc.).

Or rather that these inhabitants respect the beaver dam and are aware that there is a beaver around when this object is visible.

Thus, within the beaver’s territory, objects like dams or lodges could serve some type of territorial purpose not against other beavers (because scent-mounds are used along boundaries to warn other beavers) but to have other species respect the beaver’s presence.

I have thus far found zero studies regarding beaver interactions with other species that are not predators (outside of indirect facilitation through creation of habitats).

But I have observed that where I live beavers sometimes slap their tails when they are annoyed by ducks, roe deer (that cross the river) etc.

It is possible that other species have learned to mind the beaver’s presence nearby a beaver’s structure (beaver being a large animal with sharp teeth), and the beavers know it.

Therefore, I thought perhaps this beaver, having conquered one ‘foe’ (having overcome one situation of adversity and anxiety), proceeded to attempt to demand some respect from the incoming, outcoming flows of humans by building the dam as an object stating her presence which should announce to other species that this was actually her territory.

She would not prevent them from passing through but she was to be recognized as the boss there (or at least as an equal).

One of the top comments I saw below the video also shared a story which I cannot fully trust but which I thought was not made-up.

It stated that this author had friends who had tried to tear down a beaver dam several times (please, never do that!) and that the beaver had dammed up their footpath instead.

(It is possible that the humans, in fact, due to bad conscience, perceived beaver-felled trees that had fallen cross their path as a structure-building or rather obstruction-building activity while it had simply been a foraging effort.)

Once again, this had been perceived as a territorial behaviour but I think (if it were deliberate at all) it could have been a warning behaviour that beavers might use not toward other beavers but toward other species within their territories (and not on the bounds of their territories).

I believe, in wildlife biology the term ‘territory’ is sometimes not understood completely and that wildlife species are territorial in ways that do not entitle conflict with other individuals or social groups of their own species, nor it involves exclusivity.

I simply suppose that large, long-lived, highly territorial and mostly territory-loyal species like beavers become attached to their homes and they are frequently the dominating species there that outlive many other ‘transients’.

This could involve a sense of hierarchy that is not exclusive of space and resources but that is still somewhat territorial (in the same manner landlords would be ‘territorial’ with their tennants or we would be ‘territorial’ with one another in our common kitchen regarding our routines, habits, ownership of mugs, replacement of exhausted food resources etc.).

It is not really about who may or who may not access something.

It is about respect.

And I believe the demand for respect was likely what the rescue centre worker sensed in the female beaver’s new attitude while dam-building (which must have otherwise happened before).

It might be important to distinguish between these types of territorial behaviour because the little female beaver may have been too young to experience actual territorial defense instinct (in the sense in which it is experienced by adults that hold territories).

But she could have been old enough to experience a sense of territoriality that comes with belonging to a home and wishing for it have its ‘good order’ and participating in its maintenance.

If there was any defense or aggression, I do not believe it was directed at ensuring territorial exclusivity but rather at ensuring peace and order at one’s home.

I think that the instinct that was triggered, was not that of home ownership but that of home partnership, i.e., the young beaver realized she had a home and wished to be an equal and operative, participating member in it.

This could have changed the motivation behind previously rather automatically executed behaviours.