The Narwhal's Tusk

The narwhal is a strange, strange beast -
Quite fabulous, to say the least,
For, unlike any other whale,
A tusk adorns the narwhal male.
That tusk, a strange, elongate prong,
Which sometimes grows to nine feet long,
Caused folks to ask, since days of yore:
What is its use? What is it for?
One thought: The tusk's a mere device -
The narwhal's way to break the ice.
It's been suggested - never found -
The tusk's involved in sending sound.
And further, it is now quite clear
Its tusk is not a simple spear
For fencing, or for piercing ships,
Or spearing fish on Arctic trips,
Nor to gain social dominance.
What use, then, this odd prominence?
Good news! At last we know the truth,
The purpose of the narwhal's tooth.
A clever scientific sleuth
Has tracked the nerves from brain to tooth.
Thus, tooth, with all those nerves supplied
Is narwhal's link to what's outside.
He checks the water: cold or warm?
That tusk, held high, might sense a storm.
The narwhal, freak of history,
With tooth a thing of mystery -
At long last, truth: facts commencing.
We now know that tusk's for sensing.