Narwhals, also called Arctic unicorns because of their distinctive solo tusk, wait for the summer ice melt to travel to the Arctic. Swimming the 600 miles north to reach rich fishing grounds is treacherous. Â Narwhals must follow circuitous paths or leads in the ocean created by melting sea ice. Passages which are choked with ice either force the narwhals to stop and wait or dive under the ice. Since they are air-breathing mammals they break open breathing holes with their tusk. If the temperature suddenly dips to freezing, they could become trapped under the ice and die from lack of oxygen.
