It’s the start of humpback whale season in Hawaii, but they’re nowhere to be found — and this might not be a bad thing for the species.

Experts were surprised at the low level of sightings so far this season, which begins in November when the humpbacks make their annual trip from their feeding grounds near Alaska to their breeding grounds in the warmer waters of Hawaii, according to an SFGate.com report.

About 10,000 whales make the long journey each year, but those numbers are way down around Hawaii. Where have they all gone?

While it’s not quite certain why this is, scientists have some ideas, and it’s actually good news for the whales.

One possibility is that El Nino is resulting in warmer temperatures in the Pacific Ocean that could be delaying the whales’ migration.

A second possibility is that the delay in the whales’ arrival is because their population has grown much larger, and therefore the whales have to spend more time competiting for food to fuel their long journey to Hawaii. That would certainly be a good sign that shows the whale population is thriving, not dwindling.

Still, it’s not an easy thing for the local tourism industry, which relies heavily on humpback whales. The giant mammals are famous this time of year for being visible slapping the surface, breaching, or blowing out water as onlookers gape.

The humpback whale is certainly one of the most famous species of marine mammal. They can grow to a length of 52 feet and weigh up to 79,000 lbs. They have a distinctive appearance, with long pectoral fins and its signature knobbly head. Its tendency to breach and play on the surface is what makes it a popular species with tourists and whale watchers. They also have a long, complex song that can last up to 20 minutes, which is often repeated for hours. Humpback whales are found all around the world, and its population has rebounded after it was hunted nearly to the brink of extinction in the 20th century.