I doubt it would actually be a stethoscope then though. Maybe something to gather the sap or to see below the bark but a stethoscope wouldn’t help with that. (I’m not a biologist but I know that stethoscopes are used to make it easier to listen to things and likely require a proper contact which one wouldn’t get on bark.)
Wouldn’t the stethoscope have trouble actually bringing the sound to the ear pieces if the bark is as rough as in the image?