A calf sighting far from its usual habitat has sparked hope for one of the world’s most endangered whales.

Last week the Guardian reported the sighting of a North Atlantic right whale calf near the Spanish island of El Heirro in the Canaries, thousands of miles from the species’ usual habitat, along the US and Canadian eastern seaboard. Once feared to be the first great whale that would become extinct in modern times, this incredible discovery offers a spark of hope for its survival.

To mark the encouraging find, here are 10 things you (probably) didn’t know about right whales:

1. Their name has an unfortunate origin
Considered enormously valuable for the many uses of their oil and baleen, whalers identified the species as the “right” whale to kill on a hunt. It also helped that their thick blubber caused their carcasses to float.

2. Their ‘white’ callosities are actually grey
Right whale callosities, the patches of raised tissue on their heads, are dark like the whale’s skin, but infested with millions of light-coloured syamids (whale lice), providing contrast against the skin. Their placement and pattern is unique to each whale.

3. They are one of the heaviest whale species
Growing to an average length of 18 metres (60 feet), they are typically shorter than sperm and fin whales, but their excessive blubber means they can sometimes weigh over 100 tons, second only to the blue whale, known to weigh upwards of 173 tons.

4. They are drawn to the sound of sirens
Northern right whales ignore most man-made noise, including passing vessels, but have been known to respond to sounds like the sirens used by emergency services.

5. They might live to be 100
Closely related species have been known to live more than 100 years, though data on right whale lifespan has been historically limited. Modern techniques include using ear wax to estimate age, which has suggested they can live for at least 70 years.

6. They have inspired whale watching hotels
The Windsor Hotel in Hermanus, South Africa, attracts whale watchers during the Southern right whale breeding season, between July and November. The town even boasts its own “whale crier”, who blows a horn to alert tourists and locals to whale sightings, issuing a unique blow for the Southern right.

7. They eat around 2,000 pounds (900 kg) every day
Right whales mainly feed on tiny crustaceans called copepods. Warming oceans have forced copepods to migrate north, so North Atlantic right whales travel outside of protected areas to sate their enormous appetite, making them more vulnerable to vessel strikes and fishing gear entanglement.

8. They are among the slowest swimming whales
Right whales swim at about 1.3 km/hr on average, though they can reach up to 15km/hr in short spurts. Despite their slow speeds, they are acrobatic mammals, often seen breaching, lobtailing and flippering.

9. They are among the world’s rarest marine mammals
Both North Atlantic and North Pacific right whale populations are thought to be in the mid-to-low hundreds, though southern right whale numbers are more promising, estimated at 12,000.

10 …But there is hope for their survival
In addition to encouraging sightings like the El Heirro calf, there is hope for right whales in the form of human behavioural change. Whaling is no longer a serious threat, seasonal vessel speed limits have been put in place in migration, calving and feeding locations, and research is underway to develop fishing gear that will prevent entanglement.

^{Sources: BBC News, Eden Killer Whale Museum, Encyclopedia of Marine Mammals, National Center for Biotechnology Information, National Geographic (1) (2), New England Aquarium [archived], NOAA (1) (2), SA Venues, Smithsonian, Wildlife Trip, Windsor Hotel}