Latest facts
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Episode 01
Sea otters have fur with up to 1,000,000 hairs per square inch, the densest fur of any animal. A person has about 100,000 hairs on their whole head, so one square inch of otter fur is about 10 human heads of hair. No blubber: a trapped layer of air in the fur keeps cold water off their skin.
Source: U.S. Fish & Wildlife Service
Episode 02
Earlier generations finish their whole life cycle in about four weeks. The last generation of the summer, the monarch “super generation”, can survive up to eight months. Eastern monarchs of that generation fly up to 3,000 miles to Mexico, where most spend the winter in fir forests high in the mountains, guided by the sun and powered by stored fat.
Source: USFWS: monarch migration · USFWS: monarch species profile
Episode 03
The humpback is called the “singing whale”. A male’s song may be as long as half an hour and changes from year to year. Some populations swim 5,000 miles between feeding and breeding waters.
Source: NOAA Fisheries: fun facts about whales · NOAA Fisheries: humpback whale
Episode 04
An octopus has three hearts. Two of them move blood past the gills, and its blood looks blue because of a copper-based protein. The oldest known octopus ancestor lived about 330 million years ago.
Source: Smithsonian Magazine: ten wild facts about octopuses
Episode 05
An Anna's hummingbird weighs about two pennies. In flight, a hummingbird's heart rate can jump to 1,220 beats a minute, wings beat 12 to 80 times a second depending on the species, and on cold nights the heart rate can dip to 50 beats a minute in torpor.
Source: U.S. National Park Service: Anna's Hummingbird · Smithsonian's National Zoo: Hummingbirds
Episode 06
A bald eagle's eyesight is at least four times as sharp as a person's with perfect vision. Some nests can weigh two tons, and a bald eagle's white head doesn't appear until it is four or five years old.
Source: U.S. Fish & Wildlife Service: Eagles Across America
Episode 07
An African elephant's trunk has no bones, but it has more than 150,000 separate muscle units. Adults need to eat about 350 pounds of vegetation a day, and herds are led by the oldest female, called the matriarch.
Source: Smithsonian Institution: Africa's Elephant Kingdom educator guide · Smithsonian's National Zoo: Asian elephant
Episode 08
A jellyfish has no brain, no blood and no heart. A simple nerve net lets it smell, detect light and respond to other stimuli, and jellyfish are about 95 percent water.
Source: NOAA National Ocean Service: What are jellyfish made of?
Episode 09
African penguins appear to recognize their mates by the spots on their chests. The spots start at about three to five months old and regrow in the same places each year. The species is listed as critically endangered, with about 19,800 mature adults.
Source: Smithsonian Magazine: African penguins tell each other apart by their polka dot patterns · IUCN Red List: African Penguin
Sources
We keep the wording no stronger than the source: “up to”, “about” and “may” stay exactly as the source says them.
U.S. Fish & Wildlife Service: Sea otters are unlikely helpers in our fight against climate change
U.S. Fish & Wildlife Service: The monarch super generation and their phenomenal migration and Monarch butterfly species profile
NOAA Fisheries: Fun facts about wonderful whales and Humpback whale
Sources: Smithsonian Magazine: ten wild facts about octopuses
Sources: U.S. National Park Service: Anna's Hummingbird and Smithsonian's National Zoo: Hummingbirds
Sources: U.S. Fish & Wildlife Service: Eagles Across America
Sources: Smithsonian Institution: Africa's Elephant Kingdom educator guide and Smithsonian's National Zoo: Asian elephant
Sources: NOAA National Ocean Service: What are jellyfish made of?
Sources: Smithsonian Magazine: African penguins tell each other apart by their polka dot patterns and IUCN Red List: African Penguin
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Natural History Daily makes short videos about animals and nature. Each one is built on one fact that we can point to, and the source goes in the description and on this page.
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