The beautiful mottled patterns of a giraffe’s coat work as more than camouflage – the size of the spots seems to be linked to how well the animals survive during unusual temperatures.
Every giraffe has a unique array of spots. Patterns with larger and rounder spots can increase the chance of a baby giraffe surviving its first four months, because they help them blend into the background in the dappled light near bushes. But because the spots are darker than the rest of the fur, it is also thought they might affect how giraffes handle temperature.
To investigate, at the University of Zurich in Switzerland and her colleagues studied 810 wild Masai giraffes (Giraffa camelopardalis tippelskirchi) living in the in Tanzania.
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Because of their unique spot patterns, the researchers could identify which individuals they saw in three surveys each year from 2012 to 2020.
Overall, they found that calves with small, lobed spots and adult males with small, lobed or large, polygonal spots were more likely to survive.
Yet, when average seasonal temperatures got to a degree or two above or below the seasonal mean, the picture changed.
Survival of adult male and female giraffes was lower at these times. However, the calves and adult males with larger spots were more likely to survive when the temperature was anomalously low, and those with smaller spots had higher survival chances when the temperature was very high. Spot patterns had little effect on the survival of adult females though.
“Camouflage may be important, but there’s a lot more going on with this pattern than just trying to match the dappled light,” says at the University of Bristol, UK.
The spots do help in terms of camouflage by breaking up the image of a young giraffe that a predator is looking for, says team member at the University of Zurich. But adult giraffes are less likely to become prey for animals like lions because they are so big, she says. Any advantage from spots later in life may be down to .
“Giraffe spots have an underlying dense network of blood vessels, and it is thought the animals can constrict those blood vessels to conserve heat when it’s cold or expand them and release more heat when it’s hot,” says Bond.
That might explain why bigger spots are leading to better giraffe survival in colder temperatures.
However, the spots are also thought to absorb more of the sun’s heat than lighter regions of fur because they are dark, so reflect less light. This means when temperatures get too high, the heat absorbed from sunlight by larger dark spots may exceed the capacity to dissipate excess heat, making the spots disadvantageous and exposing individuals to hyperthermia, says Mouchet.
But why would the spots be more influential for adult males than females? “Females mostly stay in groups with their calves and they are more sedentary than males, which are larger and tend to roam between the female groups to search for sexual partners,” says Mouchet, so the males may be more exposed to the elements than females.
“We shouldn’t take it for granted that we’ve got the story of camouflage nailed,” says Caro. “Perhaps we have to be thinking about other animals like leopards in a different way, too.”
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