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Science Square (Issue 99)
May 1, 2014

Elephants can distinguish human languages

Elephants can determine ethnicity, gender, and age from acoustic cues in human voices. McComb et al. February 2014, PNAS.

African elephants (Loxodonta africana) are the largest land animals on Earth and they have been facing the danger of extinction due to habitat loss and illegal hunting for their ivory tusks. Elephants are also known to be very intelligent creatures and a recent study showed that they can even differentiate between human languages. Researchers at Amboseli National Park in Kenya played two different recordings of human voices for elephants. One group of voices belonged to local Maasai men, who happen to have violent encounters with elephants from time to time while herding their cattle. Other voices belonged to Kamba men, who are farmers or employees of the national park, and usually pose no threat to the elephants. In both cases, researchers played the same phrase, "Look, look over there, a group of elephants is coming," in two different languages. When elephants heard Maasi voices, they demonstrated defensive behaviors, such as gathering together, investigative smelling through their trunks, and moving cautiously away from the stimuli. Interestingly, elephants showed a greater reaction to the voices of Maasi men than Maasi women or boys, suggesting that they can even differentiate the gender and age of humans. In contrast, when they heard Kamba voices, of any gender or age, they did not show any concern. Ability to recognize predators is a crucial skill for many animals, and elephants seem to be capable of pinpointing the ethnicity, gender, and age of a potential predator, perhaps through recognizing acoustic cues in human voices. This ability serves as an early warning system for elephants and it could become very useful, especially when the predator is out of sight.

Set your alarm early to control weight

Timing and intensity of light correlate with body weight in adults. Reid JK et al. February 2014, PLOS ONE

Early sunlight exposure in the morning has been found to lower a person's body mass index (BMI). A recent study showed that 20-30 minutes of morning light controls approximately 20% of the variation in a person's BMI. This effect was independent of physical activity, caloric intake, sleep timing, age, or season. Our bodies have an internal body clock called the "circadian clock." It roughly controls 24-hour cycles of physical, mental, and behavioral activities. Light is the most potent regulator of our circadian clock. It sends strong signals to our brain and body, which in turn regulate our energy balance and metabolism. Previous studies showed that animals with an altered circadian clock gain weight even though they don't eat more. Similarly, new research with study subjects showed that missing out on the early rays of sun shifts our circadian clock and alters our appetite, satiety, and even the way that our body processes food, which ultimately leads to weight gain. In modern times, we live and work indoors, thus are often not able to get enough light in the morning. While the daylight is the best source, experts think that standing by the windows or even using a strong desk lamp would be sufficient to properly synchronize our circadian clock in the morning.

Mystery of zebra stripes solved

The function of zebra stripes. Caro T. et al. March 2014, Nature Communications

The black and white stripes of zebras have intrigued people for centuries. Scientists have speculated many hypotheses for the purpose of these stripes, such as camouflage, heat management, social implications, etc. A new systematic study analyzed 7 different equid species with stripes on their bodies and mapped their geographic locations. Then, researchers generated a statistical model by comparing the stripe patterns of these animals and their environmental conditions. Strikingly, they discovered a clear overlap between the range of striped animals and where biting flies, like horseflies or tsetse flies, are highly populated. Scientists noticed greater striping among animals in regions where there were more flies. These results suggest that having stripes may protect zebras from biting flies. Zebras, unlike other African hooved mammals living in the same area, are particularly susceptible to biting, as their hair is shorter than the pinchers of the biting flies. A separate work has shown that some flies tend to avoid black-and-white striped surfaces, supporting the hypothesis that biting flies may avoid the striped surfaces of zebras. As much as these results are encouraging, no one actually observed zebras in the wild to see if biting flies avoid landing on them, in part because it's almost impossible to stay that close to zebras. The next challenge for the researchers is to observe this phenomena live in the wild.