Now we know where giraffe spots come from

Like mother, like baby.
Like mother, like baby.
Image: AP Photo/Richard Vogel
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Fifty years ago, biologist and giraffe expert Anne Innis Dagg had a theory: the distinctive geometric shapes of a giraffe’s fur coat were not random, but an inheritable pattern passed down from parent to offspring.

But the unusual print of a giraffe’s coat—a design like cracked dry earth, with tawny lines running between patches of russet brown—is a tricky thing to study. Measuring and quantifying the minute differences in giraffe coats in the wild proved a challenge, and without measurement, there are no data.

But now, half a century after Dagg’s pioneering work, researchers have validated her theory with the help of digital photography and pattern-recognition software. A Pennsylvania State University research team has found that a giraffe’s spot pattern is in part inherited from its mother, and that certain patterns may actually improve a baby giraffe’s chances of surviving infancy.

Between 2012 and 2016, the team documented 31 mother-calf pairs of Masai giraffe in the savannas of northern Tanzania, as detailed in a new paper published in the journal PeerJ. When they analyzed photographs of the pairs’ coats, the imaging software found significantly more visual similarities in the spot patterns of related giraffes.

If spot patterns are an inherited trait, the researchers wondered, what advantage might certain patterns serve? To answer that, the team looked at the survival rates of 258 giraffe calves in the wild between birth and four months of age. A distinct trend emerged: animals with larger and more irregularly shaped spots were 7.5% more likely than others to survive the first four months of life. Given that predators are the leading cause of infant mortality among Masai giraffe, it’s possible that spot pattern plays a role in camouflage.

“There are likely many reasons for why giraffes have spots,” says Derek Lee, associate research professor at Penn State and the paper’s lead author. “We were thrilled to validate the 50-year-old theory of Dr. Anne Dagg that calves inherit some of their spot traits from their mothers. This is how science works, by building up evidence over time. It just took us a long time to catch up to Dr. Dagg’s thinking.”

Camouflage is one of several potential theories biologists have pondered over the years for why giraffes look as they do: The spots may also help attract mates, regulate the animals’ temperature, or may simply be how the animals recognize each other. Spots may play a central role in how herds come together.

“At the heart of giraffe herds are relatives and peers, who seem to recognize each other from quite a distance away,” says Fred Bercovitch, executive director of the advocacy group Save the Giraffes and an adjunct professor at Kyoto University. If the spots do in fact indicate something about genetic lineage, says Bercovitch, it means that a giraffe’s patterning could potentially be a way it could “broadcast of information to other giraffes [about] not only who the animal is, but something about the ancestry of the animal.”