There are very few scientific materials dedicated to beaver vocalizations and beaver sound perception.
Mostly it is assumed that beavers (apart from tail-slapping) are quiet animals (e.g., Novakowski, N.S., 1969) and that most vocalizations occur in close quarters between the beavers and are rather soft.
This makes sense because beavers have ‘busy mouths’ and spend a lot of their time either gnawing or swimming (which is not very conductive to vocalizations, either).
Their strategy appears to be elusiveness (going by unnoticed) that is enhanced by moving around quietly and not drawing much attention.
It is one of the reasons why beaver vocalizations in the wild are difficult to study.
Many vocalizations occur, e.g., in the den where they cannot be easily recorded, and they are relatively quiet.
I have not yet encountered publications regarding bear audial perception although I have seen mentions of their excellent hearing which is probably a great anti-predator strategy while foraging/acquiring materials above the ground.
Thus, it is possible that beavers, while themselves using the loud tail-splash signalling, might be sensitive to loud noises because they have honed their skills to listen in and most of their vocal communication occurs in close proximity to one another and at low sound level.
If beavers themselves do not produce that many sounds for communication or they mostly produce them when feeding nearby or inside of the den, they are likely adapted to use their hearing in order to perceive other sounds in the environment.
Namely, they are not listening on for other beavers but they are using their potential to listen in on predators, other disturbances etc.
This is of psychological relevance because listening in to detect predators and not being surrounded by many sounds of conspecifics might contribute of a certain sound perception where noise is associated with potential danger and not with potential ally.
This will be relevant to the following discussion.
Perhaps different types of sound have varied effects, e.g., water can be rather loud, as well, although beavers do not locate themselves near shallow rapids but rather construct deep and still water habitats.
I was searching for information on beaver vocalizations and I came across this YouTube video where a beaver kit has been fed sweet potato and it is reacting with increasingly frustrated (angry – as characterized by the video author) vocalizations that the author of the video attributes to the feeding situation (protectiveness over the food resource?).
This will be a subjective impression but it appeared to me, personally, (and I mean no disrespect to the lady in the video who seems to be a nice and kind individual) that the beaver was reacting to her loud voice and not to the feeding circumstance.
This made me wonder on beavers’ hearing.
Perhaps it is very sensitive and perhaps the beavers have not evolved louder vocalizations because they do want to expose themselves to disturbing sound types or levels.
I have observed rather loud vocalizations by beavers (e.g., this YouTube video by Holley Muraco and her rescued beavers) and if they produce tail-slaps, they are not altogether harmed by loud noises.
But I suspect there might be certain pitch or vibration that is very unpleasant to the beaver and that the beaver does not wish to incorporate in its own vocalizations, nor it wishes to be exposed to it in close quarters.
I even tend to consider vibrational effect over pitch etc. because baby beavers produce high pitched squeals which the parents tolerate.
Beavers spend a lot of time in the water where sound travels differently and impacts as vibrational force.
If beavers have excellent hearing and their hearing is also adapted to underwater environment, there might be sounds and noises that are unpleasant to them for some physical reasons.
Beavers can close their ears while swimming underwater which could contribute to the vibrational effect of any sound.
The valve might act as a membrane that reverberates upon meeting sound waves and thus sound perception would always be slightly vibrational when underwater.
When above water, the valve would be open but the general sound perception (both in and out of water) might have been ‘irreversibly’ altered due to the sheer amount of time spent in the water medium.
Beavers might have been adapted to use these vibrations underwater to enhance their sound perception.
When out of water or above water, beavers might still react to vibrations because it has become a part of their sound perception.
Similarly, water medium alters how sound travels and sounds might be able to reach beavers from afar while simultaneously changing how ‘things sound’ nearby.
Beaver sound perception might have evolved to be different from that of terrestrial rodents/mammals even when the hearing is used outside of the water and with valves open.
I believe not only would it be curious to study how beavers perceive sound but it might also be important because beavers might be vulnerable when exposed to certain types of sound stimuli and thus, in order to protect their habitats, these stimuli should be limited near active beaver colonies.
Notes by Ieva 