(Christian Science Monitor) December usually marks the start of humpback whale season in Hawaii, but experts say the animals have been slow to return this year. The giant whales are an iconic part of winter on the islands and a source of income for tour operators. But officials at the Humpback Whale Marine Sanctuary said they’ve been getting reports that the whales have been difficult to spot so far.

“This isn’t a concern, but it’s of interest. One theory was that something like this happened as whales increased. It’s a product of their success,” said Ed Lyman, a Maui-based resource protection manager and response coordinator for the sanctuary.

“What I’m seeing out there right now I would have expected a month ago,” said Lyman, who was surprised by how few of the animals he saw while responding to a call about a distressed calf on Christmas Eve. “We’ve just seen a handful of whales.” FULL REPORT