To learn more, see the original posts:

• 10 Animals Heart Facts for Valentine’s Day
• Valentine’s Day: Some Animals Really Have Heart

Update: The image above has been updated with the correct silhouettes for the blue whale and cheetah.

The Fastest Swimmers

The sailfish is considered the fastest swimmer among fish, often reaching 70 mph. Although a black marlin was recently clocked at 80 mph so the sailfish record may fall to its cousin.

The fastest swimming mammal is the orca (often called killer whale) which can swim over 55 mph but the Dall’s porpoise of the north Pacific has been clocked at the same speed.

We all know that birds can fly fast.  In flight, the fastest bird is the spine-tailed swift of Siberia which can reach speeds in excess of 100 miles per hour, but the fastest bird in the water is the Gentoo penguin, which swims at about 22 mph. (Watch this video of a Gentoo swimming madly to avoid a pod of hungry orcas.)

The Gentoo’s speed is about the same as the fastest sea turtle, the leatherback.

Using a different mode of movement, squid can achieve 25 mph through a form of jet propulsion.

The Deepest Swimmers

Scientists once thought that the deepest parts of the ocean were too dark and cold to sustain life.  But they have been discovering that the deep ocean holds a rich ecosystem of many living forms.

For example, they have recently found a type of snailfish that lives happily nearly five miles down where the water pressure is almost unimaginable. (Watch this video of these true denizens of the deep.)

People are also often amazed to learn that whales once lived on land and liked swimming so much that they went back to living in the sea.  These sea-going mammals can dive down to some of the deepest parts of the ocean.  The sperm whale routinely dives to depths of 10,000 feet (about two miles) to hunt for giant squid.

Slowest Swimmer

Scientists believe that the sea horse is the slowest fish in the ocean.  It moves along at about 0.01 (one hundredth) mph.  (Watch this video shows how the sea horse swims.)

Largest Swimmers:

The whale shark is the largest fish in the sea.  One was measured at 41 feet in length and weighed over 35 tons. This (Watch this video of divers swimming near a whale shark.) However, the blue whale (a mammal) is the largest living creature.  Adult blue whales can reach 100 feet in length and 200 tons in weight.

The largest giant squid ever recorded was captured in the North Atlantic in 1878. It weighed 4 tons and its tentacles measured 10 m (35 ft) long.

The heaviest crustacean ever found swimming along the bottom was a lobster weighing 42 lbs, caught in 1934.

Secret Swimmers

Some animals have reputations for not being able to swim or being afraid of the water.  Take cats, for example.  The truth is cats can swim. Some cats, such as the jaguar of South and Central America are excellent swimmers.  Tigers are good swimmers too as it turns out.

With primates, most indications are that gorillas do not swim but that chimpanzees are swimmers, if reluctantly.

Other animals that are identified as not being able to swim range from camels to armadillos (although the long-nosed armadillo of South America is an armadillo species that can swim).

Unconventional Swimmers

Some fish swim vertically.  The sea horse is one example but there are many others in the fish world including the razor fish or shrimp fish, that swim a vertical position.

Many fish can swim backwards.  Eels are best known for this.

Anadromous species, such as salmon and shad, live in the ocean and travel up rivers to spawn.  These fish know to return to the same place from which they hatched.

Just Plain Different

Once in a while, something unexpected will happen.  Forget about the Loch Ness monster.  One time, in 2007, a deer was sighted miles from the shore in the Chesapeake Bay.  The fisherman who saw the deer took her on board his boat and released her safely on shore.

Another animal that is simply fascinating to watch in the water is the elephant.  (This video shows elephants swimming in deep water from an underwater perspective.)

Polar bears are also champion swimmers.  Recently, however, a lack of ice in the Arctic Ocean forced a particular polar bear to have to swim 426 miles over nine straight days to reach an ice flow.  The bear lost 100 pounds and a cub, and reminds us, during National Wildlife Week, of how important it is to protect natural environments worldwide – especially those of champion swimmers.

But how does a healthy human heart—a hollow ball of muscle about the size of a clenched fist that beats around 72 times a minute when at rest, pumping the body’s 8 to 12 pints of blood (depending on age, gender and size)—stack up against other hearts in the Animal Kingdom? Would you be offering your loved one something far more exceptional if, for example, you were a blue whale?  Or a cheetah?

Let’s take a quick look at some alternatives to Valentine’s Day’s favorite human organ.

A ruby-throated hummingbird near Blackhawk, Colorado, hovers on high-speed wings.

Hummingbird hearts, depending on species, beat in excess of 1,000 times a minute. This rapid beat keeps blood flowing to the wings, which, in the fastest, smallest hummers, can hit around 100 beats per second (6,000 per minute; don’t try this with your arms). The energy required for this feat comes from a steady diet of insects, spiders and—most of all—flower nectar, of which the birds eat in excess of their body weight daily. To save energy at night or when food is scarce, hummingbirds sleep deeply, a form of torpor during which the heart rate slows to a paltry 50 to 180 beats a minutes.

The hearts of some shrew species—among which is the smallest known mammal (the pygmy shrew; it can fit on your thumbnail, if you’re an adult)—purr along at around 1,300 beats per minute. Shrew metabolism is so high that some shrews eat about three times their body weight every day (which means they sleep only a few minutes at a time) and starve to death after an hour without food.

The blue whale—which probably grows in excess of 100 feet long and 150 tons, making it the largest animal that ever lived—has, as you might imagine, a lotta heart. In fact, about 1,300 pounds of heart, an organ in which you could park a small car. This mass of muscle pumps the whale’s estimated 7 tons of blood—roughly 40 percent greater than the weight of an adult African elephant—through an aorta more than 9 inches in diameter, but it beats only about seven times a minute.

In adult Asian elephants, the heart weighs 40 to 60 pounds and beats on average around 30 times a minute at rest—less than half the human rate.  Which suggests something of a rule of nature—the larger the animal, the slower its metabolism is likely to be.

Giraffes stand upwards of 18 feet tall with necks 7 feet long. Their problem: how to get blood all the way up that neck when the animal is standing erect and yet keep the blood pressure from blowing out the giraffe’s brains when the animal lowers its head, for example to drink water. After all, the giraffe’s 20-pound-plus heart pumps blood under the highest known pressure of any mammal—280/180 millimeters of mercury, more than twice the pressure in a healthy human. The solution—the giraffe has a system of valves in the blood vessels of its neck that regulate the flow to the noggin, reducing pressure when the animal dips for a drink or any other purpose.

It’s all well and good to be lionhearted—brave and bold and such—but consider the cheetah, whose heart is a sprinter’s dream. The cheetah heart can go from a resting low of 120 beats per minute to perhaps 250 within seconds during a hard run and also is relatively large, so it can really pump out blood when needed. With that heart (plus a spine like a coiled spring and powerful lungs), a cheetah can break from 0 to 60 miles per hour in 3 seconds.

But let the lowly human heart not despair. It does a fantastic job in meeting our needs. During an 80-year lifespan, your heart will beat perhaps 2.8 billion times—that’s 100,000 times a day, 36,000,000 times year—if you spend your whole life sleeping. If you actually get up do something, the heart will be faster and rack up a much larger score.

Want more info on animal hearts: hit it.  Something about animal love fests: do go on.

Happy Valentine’s Day.

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More Valentine’s Day Fun:

• Animal Valentines: Trickery, hermaphroditism and scented dung: For these species, courtship is hardly a long walk on the beach.
• Seabird Love: Read how seabirds send “love letters” to their potential mates.
• Kid-Friendly Nature Crafts: Show love for the people—and birds—in your life with bird- and mouse-themed Valentine’s crafts.

Hope everyone has a wonderful Valentine’s Day. (Believe me, this beats (ha!) me showing you some exposed wildlife hearts which I considered doing)

ADVISORY: The following facts make great date conversation.

1. The heart of a blue whale is as big as a car.
2. Frogs and lizards have three chambers whereas birds and mammals have four.
3. The human heart beats roughly 35 million times a year.
4. Octopuses have three hearts.
5. Dogs have a larger heart to body mass ratio than all other mammals.
6. Scientists have re-created the heart of a rat and it even started beating!
7. Pythons grow bigger hearts at mealtimes.
8. A blue whale’s heart beats six times a minute (next to a human’s 70 times)
9. A manatee‘s heart rate slows down by half during a long dive.
10. A giraffe depends on it’s powerful heart that weighs up to 12kg so that it can fight the force of gravity up that long neck to the head.