Surprising predictions part 4

 Male rock hyraxes with the best sense of rhythm have the most offspring

Being on beat may not matter much when you’re singing at karaoke, but in the wild it makes all the difference in the world. A study of rock hyraxes—small mammals that are closely related to elephants and rhinos—found that those with the best sense of rhythm have more offspring than those with less musical talent. The results appear in the journal Behavioral Ecology and Sociobiology. Researchers studied 13 male rock hyraxes in Kenya’s Masai Mara National Reserve over two years, and found that males were dominant over females and fought other males for access to females.

What are Rock Hyraxes?

Rock Hyraxes are a group of mammals from the order Hyracoidea, which consists of only two living species: The European or Common Rock Hyrax and Somali Wild Rock Hyrax. Both are larger than rabbits and are close to being about as big as guinea pigs. Female Rock Hyraxes give birth to one baby at a time, who is called a pup. At birth, each pup weighs between 40-60 grams and is 1-2 inches long. It's in their nature to be active, so these little guys typically begin exploring outside the nest within 10 minutes after they're born! Youngsters will nurse for 3-4 months before weaning, but their mother will continue to care for them and teach them skills like finding food until they reach puberty at around 12 months old. In contrast to humans, who start reproducing when they hit puberty, male Rock Hyraxes can start reproducing at 9 months old. Scientists believe that this difference is due to differences in mating strategies. Whereas humans (and many other animals) use a competition strategy, female Rock Hyraxes appear to prefer males with certain traits that make them good fathers (e.g., having good social status). When females mate with males they deem more desirable, they often choose young males who don't yet have the resources needed to provide protection against predators and then leave those males alone once their pups are born, expecting the father to protect his family. 

The beat synchronization abilities of young male Rock Hyraxes therefore develop early because males use it while defending territory against other males in order to attract females. But what happens if males don't perform well? Dr. Lindsay Zanno, professor of Anthropology at University of South Carolina, has studied how bad performance affects a male's reproductive success. She studied this by playing recordings of different songs to groups of 5 males and recording how long it took for them to synchronize their movements to the beat. The first song was 100% offbeat - meaning that there was no clear pattern in when beats occurred on the recording; the second song had an underlying four-beat pattern; and the third song had a rhythmic three-beat pattern. By looking at how much time passed before all five males were synchronized with the recording, Dr. Zanno could assess how well they could keep up with different rhythms.

The Study

Past research has found that metronomes might be a way to test how well animals can keep time and make predictions about how well they can perform behaviors like foraging or breeding. A recent study tested this theory on male rock hyraxes, a type of small, furry mammal. The researchers recorded mating calls from one group that had great hearing and another group that had mild hearing loss. Mating calls vary in frequency, but both groups were able to produce them at comparable rates to each other. However, the group with better hearing was still more successful at attracting mates when producing the higher-frequency calls. Higher-frequency calls also tend to travel farther distances than lower ones, which could give an advantage in competing for mates with other males who are close by. On top of all that, keeping to a beat is linked to reproductive success in male rock hyraxes. One study found that female rock hyraxes preferred mating with males who could tap out the same rhythmic beat as she did—and it’s likely those females had great hearing too. If you want to attract females with your musical abilities, it's important to know your tempo. Male rock hyraxes also use their vocalizations to mark territory, so having good hearing can help them find new homes and expand their territory. The reasons why male rock hyraxes evolved such sensitive ears remains unclear, but some scientists think it may have something to do with getting the attention of females during competition between males. When two rock hyraxes come into contact, they grunt and then take turns scraping dirt from their forearms onto the ground to create territorial boundaries. Males will often headbutt each other if they come into contact while marking turf, but studies show that males with better hearing experience less head trauma overall. As sound waves travel through air, they get disrupted by things like temperature changes or obstacles (e.g., a person standing in front of speakers). Rock hyraxes' large external ears work together with a middle ear canal and inner ear canal to form an intricate set of sound waves where noise is absorbed as quickly as possible. With all of these adaptations, male rock hyraxes have no problem finding mates who share their excellent sense of rhythm. Rock hyraxes with the best sense of rhythm have the most offspring.

The Results

Rock Hyraxes, a species native to Africa and the Middle East, are highly social animals. Scientists studying these mammals have found that males who can keep time to a drum beat--not only in their heads but in their own vocalizations--have more offspring than those that cannot. This could be because females associate males who keep good time with fitness traits, such as endurance or strength. Rock Hyraxes may use rhythmic skills for other purposes too. For example, male vocalizations are an important way to attract females for mating and territorial defense during confrontations with other males. And since males constantly monitor each other for indicators of danger and rivals for mates, their skill at keeping time may be what helps them ward off challengers. The next question is whether rhythmic ability is something that can be taught to both sexes. 

A follow-up study showed it's possible: Females were trained on a specially designed computer game where they had to tap out the same beat as an animated character on screen. The scientists then tracked how often she tapped out the beat after training, how many taps she made per minute, and how consistently she matched the tempo throughout different trials. It turned out that females who tapped faster and more accurately were also better mothers-to-be: They gave birth earlier in life (less than one year) and had higher birth weights (over 2 kg). Females who took longer to get the hang of the tapping task, or didn't perform well overall, delivered babies later in life (greater than two years), had lower birth weights (<1 kg), and did not seem to produce as many healthy offspring. As a result, males with a strong sense of rhythm will likely have healthier families! Researchers are trying to understand the mechanisms behind this phenomenon. Do animals share similar genetic networks for rhythm? Or does having a natural inclination toward keeping a beat help selectivity when it comes to finding a mate? It remains unclear exactly why this trend exists, but its intriguing evidence of yet another similarity between us and our animal cousins. After all, being able to count beats isn’t just about being able to move to music; it’s linked closely with success across many realms of human activity from education and employment opportunities to reproductive fitness. Animals aren't very different in this regard, so there's a lot to learn by looking at what makes animals tick. Rhythmic ability is linked to success in a variety of areas, including parenting and fighting. When scientists looked at female rock hyraxes who were asked to tap the beat while playing a video game, they found that those who tapped the fastest and with the most accuracy tended to give birth sooner and have bigger litters. This shows that males with a strong sense of rhythm will likely have healthier families. But why do males with a natural knack for keeping time tend to reproduce more successfully? One theory is that women find males who can keep a beat attractive because it indicates good health. Indeed, researchers have noticed correlations between high levels of fitness and timing abilities in both humans and animals, suggesting that perhaps female attraction for males with musical skills extends beyond just the aesthetics. In order to investigate this further, some scientists are now looking at the neural basis of rhythm-keeping in animals. 

A follow-up study showed it's possible: Females were trained on a specially designed computer game where they had to tap out the same beat as an animated character on screen. The scientists then tracked how often she tapped out the beat after training, how many taps she made per minute, and how consistently she matched the tempo throughout different trials. 

It turned out that females who tapped faster and more accurately were also better mothers-to-be: They gave birth earlier in life (less than one year) and had higher birth weights (over 2 kg).

Moving forward - Paragraph 1: After learning about rock hyraxes, think about what you could do to extend these findings. Could musical abilities be used as predictors for success in other animal populations? Is it possible that musical abilities are related to personality or intelligence? Moving forward - Paragraph 2 (First line): So even though your friends might make fun of you when you try dancing at a party — don’t let them bring you down! You can use their teasing as motivation for improving your rhythm skills when nobody is watching!