Lady Meerkats Make More Testosterone Than Males

Two female meerkats, mid-beef. Image Credit: Charli Davies, Duke University

They’re unpleasant. They’re uncooperative. And they’re unwilling to share.* Testosterone-fueled bad behavior is as common in meerkats as it is among other animals. But there’s one major difference: In meerkat society, scientists say, it’s the females doing the misbehaving. A report on their misconduct, and its implications for their health, was published in the journal Scientific Reports.

Meerkats are intensely social animals. They live in tight-knit groups of up to 40 or 50 animals and do everything collectively, from hunting and sleeping to raising pups. They maintain order through a strict hierarchy led by a fierce matriarch and her subordinates. Meerkat matriarchs are notoriously self-involved, but other females are not much sweeter. They, and not the males, are the growlers, the biters, the brawlers, the food-swipers, and the warmongers—all identities traditionally associated with high levels of testosterone.

To find out if the females’ bad attitudes were linked to this so-called male hormone, researchers collected blood and poop samples from 93 wild meerkat males and 91 females on the Kuruman River Reserve in South Africa. The meerkats there are habituated to scientists, which made it no big deal for the team to catch them, anesthetize them, and take a little blood. They’re also clearly tagged with individual dye markings, which made it easier for the researchers to tell who was chasing (or being chased by) whom.

They're going to a rumble. (No, really. They are.) Image Credit: Kendra Smyth, Duke University

As anticipated, the blood tests showed a stark difference in hormone levels between male and female meerkats. The females’ blood boasted much more testosterone than the males’ blood did—in some cases almost double. Levels of testosterone and related hormones in females were closely linked with their place in the hierarchy. This was less true for males, whose hormones were more likely to fluctuate during mating periods.

A testosterone-charged life doesn’t come without its costs. For meerkats, as with other animals, this may mean a compromised immune system. They combed through the meerkats’ feces and counted the number of parasite eggs they found in each sample. The higher a female’s testosterone level, the higher her parasite count—and the weaker her immune response.

Riding high on testosterone may not make a lady meerkat popular, and it may not make her healthier, but all that jerk behavior could just give her—and her kids—a competitive edge.

*National Geographic appears to have gone for a slightly different tagline.
Know of something you think we should cover? Email us at

These Sparrows Have Been Singing the Same Songs for 1500 Years

Swamp sparrows are creatures of habit—so much so that they’ve been chirping out the same few tunes for more than 1500 years, Science magazine reports.

These findings, published in the journal Nature Communications, resulted from an analysis of the songs of 615 adult male swamp sparrows found in six different areas of the northeastern U.S. Researchers learned that young swamp sparrows pick up these songs from the adults around them and are able to mimic the notes with astounding accuracy.

Here’s what one of their songs sounds like:

“We were able to show that swamp sparrows very rarely make mistakes when they learn their songs, and they don't just learn songs at random; they pick up commoner songs rather than rarer songs,” Robert Lachlan, a biologist at London’s Queen Mary University and the study’s lead author, tells National Geographic.

Put differently, the birds don’t mimic every song their elders crank out. Instead, they memorize the ones they hear most often, and scientists say this form of “conformist bias” was previously thought to be a uniquely human behavior.

Using acoustic analysis software, researchers broke down each individual note of the sparrows’ songs—160 different syllables in total—and discovered that only 2 percent of sparrows deviated from the norm. They then used a statistical method to determine how the songs would have evolved over time. With recordings from 2009 and the 1970s, they were able to estimate that the oldest swamp sparrow songs date back 1537 years on average.

The swamp sparrow’s dedication to accuracy sets the species apart from other songbirds, according to researchers. “Among songbirds, it is clear that some species of birds learn precisely, such as swamp sparrows, while others rarely learn all parts of a demonstrator’s song precisely,” they write.

According to the Audubon Guide to North American Birds, swamp sparrows are similar to other sparrows, like the Lincoln’s sparrow, song sparrow, and chipping sparrow. They’re frequently found in marshes throughout the Northeast and Midwest, as well as much of Canada. They’re known for their piercing call notes and may respond to birders who make loud squeaking sounds in their habitat.

[h/t Science magazine]

ZUMA Press, Inc., Alamy
5 Fascinating Facts About Koko the Gorilla
ZUMA Press, Inc., Alamy
ZUMA Press, Inc., Alamy

After 46 years of learning, making new friends, and challenging ideas about language, Koko the gorilla died in her sleep at her home at the Gorilla Foundation in Woodside, California on June 21, 2018. Koko first gained recognition in the late 1970s for her ability to use sign language, but it was her friendly personality that made her a beloved icon. Here are five facts you should know about the history-making ape.


Francine "Penny" Patterson, then a graduate student at Stanford University, was looking for an animal subject for her inter-species animal communication experiment in the early 1970s when she found a baby gorilla at the San Francisco Zoo. Originally named Hanabiko (Japanese for "fireworks child," a reference to her Fourth of July birthdate), Koko took to signing quickly. Some of the first words Koko learned in "Gorilla Sign Language," Patterson's modified version of American Sign Language, were "food," "drink," and "more." She followed a similar trajectory as a human toddler, learning the bulk of her words between ages 2.5 and 4.5. Eventually Koko would come to know over 1000 signs and understand about 2000 words spoken to her in English. Though she never got a grasp on grammar or syntax, she was able to express complex ideas, like sadness when watching a sad movie and her desire to have a baby.


Not only did Koko use language to communicate—she also used it in a way that was once only thought possible in humans. Her caretakers have reported her signing about objects that weren't in the room, recalling memories, and even commenting on language itself. Her vocabulary was on par with that of a 3-year-old child.


Koko was the most famous great ape who knew sign language, but she wasn't alone. Michael, a male gorilla who lived with Koko at the Gorilla Foundation from 1976 until his death in 2000, learned over 500 signs with help from Koko and Patterson. He was even able to express the memory of his mother being killed by poachers when he was a baby. Other non-human primates have also shown they're capable of learning sign language, like Washoe the chimpanzee and Chantek the orangutan.


Koko received many visitors during her lifetime, including some celebrities. When Robin Williams came to her home in Woodside, California in 2001, the two bonded right away, with Williams tickling the gorilla and Koko trying on his glasses. But perhaps her most famous celebrity encounter came when Mr. Rogers paid her a visit in 1999. She immediately recognized him as the star of one of her favorite shows, Mister Rogers' Neighborhood, and greeted him by helping him take off his shoes like he did at the start of every episode.


Koko was never able to have offspring of her own, but she did adopt several cats. After asking for a kitten, she was allowed to pick one from a litter for her birthday in 1985. She named the gray-and-white cat "All Ball" and handled it gently as if it were her real baby, even trying to nurse it. She had recently received two new kittens for her 44th birthday named Ms. Gray and Ms. Black.


More from mental floss studios