Rats like to have their bellies tickled, so they used that as basis for testing happiness in rats. They found out that the ears of rats undergoing tickling became droopier and pinker - subtle signs of being relaxed and happy.
It takes bald eagles about 5 years to obtain their white head. These pictures are of the same bird taken years apart, illustrating the difference between juvenile and subadult plumage.
Rats giggle when you tickle them. Their voices are so high-pitched you need special equipment to hear them, but when you do, their laughs are immediately evident.
Gibbons are one of the only non-human primates which practice monogamy. Both parents play a vital role in raising their young.
A sloth's claws work the opposite way that the human hand does. Their default position is a tight strong grip, and sloths must exert effort to open them up. This is why sloths don't fall out of trees when they're asleep.
6Chinese Water Deer
A newborn Chinese Water Deer is so small it can almost be held in the palm of the hand. When it matures, instead of growing antlers, they grow long upper canine teeth gaining them the name "Vampire Deer."
Red Pandas can stand on their hind legs to make themselves appear larger. They also have "false thumbs", which is an extension of the wrist bone, to aid them in grasping their food.
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King cheetahs are a variety of cheetahs with a rare mutation which is caused by a recessive allele. Their cream-colored fur is marked with large, blotchy spots and three dark, wide stripes that extend from the neck to the tail.
Tigers are carnivores but will eat fruits to aid and ease digestion.
10Male African Jacanas
Male African Jacanas are also known as “Jesus Bird” because they carry their chicks in their wings.