1. Orcas aren't whales.
Orcas are often called killer whales — and they are indeed enormous like whales — but they're actually the world's largest species of dolphin.
2. Orcas are the only known non-human animal to have evolved based on culture.
In a recent study, the genes of different orca pods were analyzed, and researchers found that distinctions in genes coincided with distinctions in culture.
"Foote's team looked at the genomes of two killer whale cultures in the Pacific Ocean and three cultures in the Antarctic Ocean. The genomes were shown to clearly fall into five different groups, which just happened to coincide perfectly with the cultural distinctions," we reported in early June. "It's not easy for these distinct groups to mingle; they hunt different prey, have different techniques, and even have different languages. So they also rarely breed, which eventually leads to distinct genomes."
Only humans are known to have evolved based on culture, so this is a big deal for orcas — and for science.
3. Orcas are one of only 5 animal species on the planet to go through menopause.
All other animals continue to have the ability to reproduce until their deaths, but orcas, humans, short-finned pilot whales, narwhals and belugas stop reproducing at a certain point, and continue to live on for many decades. Why would a species evolve to stop reproducing mid-life? National Geographic shares a theory:
"One of the most compelling explanations is called the grandmother hypothesis. Proposed in 1966, it suggests that older females forgo the option to bear more children so they can support their existing ones. By helping their children and grandchildren to survive and thrive, they still ensure that their genes cascade down the generations."
But there's more to this question of why menopause happens. Because both sons and daughters remain in the pod throughout adulthood, the older females are increasingly related to everyone in the pod. Because she shares genes with so many of her pod members, it's a good reason to stop breeding and instead focus on supporting, guiding and teaching her children, grandchildren and great grandchildren.
4. Orca groups are divided into pods, clans and communities.
The distinctions between different pods and clans are based on language. A single clan is comprised of several pods or family groups. All of the pods speak the same language, but each pod has its own accent. It's much like English speakers might have a Cockney, Midlands or West Country accent.
Meanwhile, clans speak completely different languages. Clans coming together for a chat would be like an English speaker, Russian speaker and Chinese speaker trying to have a conversation.
Communities are made up of clans that regularly cross paths or have territories that overlap.
5. Orcas are the most widespread mammal besides humans.
The species ranges from the Arctic to the Antarctic, and are found everywhere from the freezing waters of the north and south to the warm waters along the equator, including around the Hawaiian Islands, Galapagos and Gulf of California. They're second only to humans and perhaps the brown rat for global distribution (though humans can take credit for helping the brown rat's spread).
Not only have orcas been spotted in all of the world's oceans, but sometimes they have been spotted in freshwater rivers, including the Rhine, Thames and Elbe rivers. An orca was even spotted more than 100 miles up the Columbia River as it hunted fish.
Editor's note: This story has been updated since it was published in June 2016.