The fox holes are small, but Karl is a small man. A small man with big ambitions and what he is striving for here is an empirical form of empathy. Rather than imagining what the animals hear, Karl wants to observe it himself.
We must take his obsession with the inside seriously and consider a surveillance system in which the recorders are disappearing into our bodies. They don't want to record what we are saying. They want to record what we are hearing.