DYK #17: Animal ID

DYK #6: Jaws...

Though not as proficient as shown in movies, this water predator is known to have a keen sense for the red liquid that courses our veins. Parts per million (a.k.a ppm) is a commonly used unit of measurement. This is equivalent to one drop of water diluted into 50 liters

They have excellent hearing in the low frequencies and can pick out the sound of something thrashing around in the water well over 1,000 feet away. They're also outfitted with sensory cavities called the ampullae of Lorenzini, which register the faint electrical fields generated by living bodies. And then there's the shark's sense of smell, which though not quite as phenomenal as was once believed (you used to see a stat claiming that 70 percent of a shark's brain was devoted to olfaction, which seems to have been a real overstatement) is still plenty acute: sharks can detect some chemicals at concentrations of around one part per 25 million, and experts claim they've seen sharks go nuts over a single drop of blood in a 2,000-gallon tank.

Source: http://www.straightdope.com/columns/read/2781/shark-youre-whats-for-dinner

More facts on sharks senses:
http://www.enchantedlearning.com/subjects/sharks/anatomy/Senses.shtml

How sharks work:
http://science.howstuffworks.com/environmental/life/zoology/marine-life/shark3.htm

DYK #4: The criminal Koala

Even though humans are known to be known closely related to chimps, gorillas and monkeys, koala bears have identical fingerprints to the former.

It's not just that human fingerprints are roughly similar to koalas - they really are identical. A trained expert would have trouble telling human and koala fingerprints apart, even using a microscope. You can see a comparison of koala and human fingerprints on the left. While the two look quite similar in the larger view, it's under the even higher resolution of an electron microscope that they really look pretty much indistinguishable.

Source: http://io9.com/5798400/koalas-have-exactly-the-same-fingerprints-as-humans

Verification: http://naturalscience.com/ns/articles/01-04/ns_hll.html