Narwhals may not be much good at hunting in summer, according to new research that warns the unicorn-tusked whales may be dangerously reliant on their ice-bound winter habitat that could “disappear” with climate change. Scientists studying the mammals in the fjords off the eastern coast of Greenland during the summer found narwhals were largely unsuccessful at capturing prey. “(This) suggests that they could actually rely on the wintering grounds to build up sufficient body reserves and energy stores to sustain year-round activities,” said Philippine Chambault of the University of California Santa Cruz, co-author of the study published in the journal Biology Letters on Wednesday. Nicknamed the “unicorns of the sea” because of their long head tusks, narwhals live in the Arctic waters off Canada, Norway, Greenland and Russia. Although they are not endangered, there are growing concerns about the whales as the planet warms and ice melts in their Arctic habitat. Researchers believe most narwhals spend their winters feasting on fish and squid under sea ice off the coast of Greenland, but Chambault said this cold-water habitat may essentially “disappear” because of climate change, with expected increases in ocean temperatures driving ice melt and potentially causing prey to relocate.