Giraffes are the tallest living animals in the world, ranging from 16 to 19 feet tall. They can weigh up to 2,800 pounds and on average live until age 25. They tend to live in groups of 12–15 members, led by an older male, and this group is termed a tower of giraffes (yes, really). Just like human fingerprints, each giraffe has a unique coat pattern—no two giraffes' coats are the same. And giraffe tongues are black and prehensile, meaning that they're capable of grasping or holding objects.

We know a lot about giraffes, on the surface of things, but there's still so much left to learn about these fascinating animals. In the past couple of years, scientists have made great strides toward understanding giraffes, from the sounds they make to their genetic makeup.

Giraffes are huge but efficient

Giraffes are known for their long necks, but their legs are nothing to scoff at. A giraffe's legs alone account for 6 feet of its height, and their feet average about 12 inches across. These long legs allow giraffes to run as fast as 35 miles per hour over short distances and 10 miles per hour over longer distances. Not only that, but they also sleep less than 20 minutes per day total, spaced out over the course of the day in quick little naps. No being snuck up on by predators for these gentle giants.

Giraffes eat hundreds of pounds of leaves per week and can go without drinking for weeks at a time thanks to the moisture they get from all the plants they eat. This is probably an important evolutionary trait, as giraffes need to splay their legs and bend down in an awkward position in order to drink from a watering hole, and that makes them vulnerable to predators. Not having to drink as often means not putting themselves at risk as often. When they do drink, they drink up to 10 gallons at a time.

So I suppose it wasn't just the long necks that made scientists of yesteryear think giraffes were related to camels.

Giraffes hum at night

Until recently, it was thought that giraffes communicated through low-frequency rumbles that were inaudible to the human ear. A recent study in BMC Research Notes, however, recorded nearly 1,000 hours of audio to find that giraffes make low-frequency humming noises at night, none of which were below the normal hearing range of humans. (You can listen to some audio clips here or check out the video above—they sound kind of otherworldly. If I didn't know that giraffes hardly ever sleep [see above], I might think they were just snoring.)

After analyzing data both day and night, the researchers were surprised to find that giraffes only hummed at night—never during the day. The only sounds giraffes seem to make during the day are infrequent grunts, snorts, and bleats. The researchers don't know yet if the humming is being used by the giraffes to communicate with each other, and if so, they don't know why the giraffes don't do so during the day as well.

(Editor's note: Caution to the squeamish—the following video includes giraffe autopsy imagery.)



Giraffe necks have a long history

Despite having the same number of bones in its neck as a human does, a giraffe's neck is 6 feet long and weighs about 600 lb. The long neck is probably the characteristic most well known about giraffes, but until recently scientists didn't know all that much about it, evolutionarily speaking. A 2015 study in Royal Society Open Science found that the elongation of the giraffe neck occurred in at least two stages: first the cervical vertebrate stretched toward the head, and second, millions of years later, it stretched toward the tail.

The researchers analyzed and compared 71 vertebrae from 11 species in the family Giraffidae: nine extinct and two living members. What's interesting is that the giraffe's ancestors started off with a slightly elongated neck: the neck lengthening started 16 million years ago, long before the giraffe family was even created. This means that neck length, despite being a giraffe's most distinguishing attribute, is apparently not a defining feature of the family.

There are four species of giraffe

Until about 6 months ago, the world thought that all giraffes belonged to one species—Giraffa Camelopardalis—with nine subspecies categorized based on coat patterns, horn structures, and geographical distribution. Scientists in Current Biology revealed last fall that there are actually four genetically highly distinct groups of giraffe—so distinct that these species don't even mate with each other in the wild. They are the southern giraffe (Giraffa giraffa), northern giraffe (G. camelopardalis), reticulated giraffe (G. reticulata), and Masai giraffe (G. tippelskirchi).

To make this discovery, the scientists performed genetic analysis on 190 giraffe skin biopsy samples from each of the previously recognized giraffe subspecies, collected over the course of a decade. The genetic diversity reveals that all four new species had a common ancestor between 0.4 and 2 million years ago.

Giraffes need our help

Now that we know that there are actually four different species of giraffes, more-accurate estimates about their biodiversity levels can be made. Approximately 40% of the giraffe population has disappeared in the last 15 years, and because the species don't interbreed, population numbers for all African giraffes won't accurately represent whether each group is doing well.

Humans hunt giraffes for their beautiful pelts and also for their tails, which are prized in some cultures. As our population grows, we also contribute to their habitat loss, forcing these natural nomads into smaller and more fragmented areas.

So how can you help? Well, for starters, you can donate money to conservation efforts and foundations. You can "adopt" a giraffe, donate tree seedlings to help with reforestation efforts, or volunteer some time to help wildlife foundations. Easiest of all, you can spread the word to your friends and family—let them know how interesting giraffes are and get them involved in the cause. (And while you're at it, maybe spread the word about pandas, too!)