6 Pigeons, both male and female, produce milk to feed their hatchlings. 

The milk produced by pigeons and doves is known as “crop milk,” and unlike mammalian milk, it is a pale-yellow, semi-solid substance. Crop milk is extremely high in protein and fats, more than the amounts seen in cow or human milk. But, just like mammalian milk, contains antioxidants and immune-enhancing factors.

During the first week, the adults stop feeding to keep the milk free from seeds which the squabs or baby pigeons or doves won’t be able to digest. In the second week, the parents introduce a small portion of seeds softened by crop milk, and by the third week, completely softened, adult food is introduced. Flamingos and penguins also produce a substance similar to crop milk to feed their young. (source)

7 Humans used to hunt animals by simply chasing them until they were exhausted. Humans are the most efficient endurance runners in the world and can outrun any animal given enough distance. 

Though most animals can run faster than humans at short distances, using endurance running or long-distance running as a hunting strategy is only seen among humans and a few animals such as grey wolves, African wild dogs, lungless spiders, and spotted hyenas.

Running expends a lot of energy and also increases body temperature. But, in order for the body to function normally, it needs to lose the heat that animals do by panting and humans by sweating. Sweating, and having relatively no hair on the body, acts as an effective means for thermoregulation and gives humans an edge over animals while running, with the exception of horses.

Persistence hunting is still practiced by hunters and gatherers in Sahara Desert, Kalahari Desert, and Northwestern Mexico. Scientists hypothesize that bipedalism in humans was a result of endurance running by hominins who would have found it difficult to catch prey over only short distances. (source)

8 The largest star’s radius is about the same as the distance from the center of the Sun to Jupiter.

The pulsating, red, hypergiant VY Canis Majoris was first observed on March 7, 1801, by the French astronomer Jérôme Lalande. Further observations found that the star has been dying since 1850 and so was described as the “crimson star.” With a radius between 1,800 to 2,100 times that of the Sun and almost 500,000 times the luminosity of the Sun, it is one of the most luminous and largest stars ever discovered up to now. The star is so massive that if it was put at the center of the Solar System, its outer surface would extend beyond the orbit of Jupiter and even Saturn according to some estimates. (1, 2)

9 A quarter of all animal species are beetles.

While there are over 36,000 species of vertebrates including the 9,040 species of birds and 4,000 species of mammals, scientists believe there are as many as 1.5 to 10 million species of invertebrates with some estimates reaching even 30 million. Of all the animals species, 75% are insects. With 400,000 to 500,000 species, the beetles make 40% of all known insect species and 25% of all known animal species. (1, 2)

10 No one can actually determine the length of any coastlines because as the unit of measurement gets smaller, the length becomes infinite. 

Also known as the coastline paradox, the phenomenon was first observed by Lewis Fry Richardson, an English mathematician, physicist, and psychologist, who decided to find out a relation between the probability of two countries going to a war and the length of their border. However, when he collected the data, he found that there is considerable variation between each published length.

As can be seen from the above image, the length of Britain’s coastline increases as the length of the ruler decreases. It is easy to suppose that at some point it would stop and that you could measure the true length of the coastline, but Richardson proved that the measured length of coastlines, or any such natural features for that matter, increases as the unit of measurement becomes smaller because of their fractal-like properties.

Fractals are curves that increase in complexity as you look closer, and their “true length” always goes to infinity. They are found everywhere in nature, and some of the examples include river networks, snowflakes, mountain ranges, animal color patterns, ocean waves, blood vessels, and flowers. (source)