Captain, there are literally thousands of these tunnels in this general area alone. Far too many to be cut by the one creature in an ordinary lifetime.
Then we're dealing with more than one creature, despite your tricorder readings, or - we have a creature with an extremely long lifespan.
Or, it is the last of a race of creatures which made these tunnels. If so, if it is the only survivor of a dead race, to kill it would be a crime against science.
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