Medical News Today: Why are baby pandas so small? Study explores

An unusual study explores a question that has puzzled researchers for a long time: Why are giant pandas so tiny when they are born?

baby pandaShare on Pinterest
Baby pandas only weigh about 100 grams at birth.

Kathleen Smith, a biology professor at Duke University in Durham, NC, and her former student Peishu Li, conducted the new research, which appears in the Journal of Anatomy.

There are a lot of intriguing — and somewhat endearing — facts about baby pandas.

For one thing, the giant panda newborns are particularly "helpless." They are born blind, pink, and hairless. They do not open their eyes until they are 6–8 weeks old, and they cannot move before the age of 3 months.

The cubs do not leave their mother's side until they are between 1.5 and 3 years old — out of a lifespan of about 20 years.

Furthermore, giant panda babies are 900 times smaller in size than their mothers. They only weigh about 100 grams at birth.

With the exception of opossums and kangaroos, giant panda newborns are the smallest mammal babies compared with their mother's size.

But why is that? To find out, Smith and Li examined skeletons from baby pandas that had been born at the Smithsonian's National Zoo in Washington, D.C.

Studying pandas' skeletons

The prevalent theory for explaining small birth size relies on the fact that pregnancy occurs at the same time as winter hibernation in some species.

During hibernation, pregnant mothers rely on fat reserves to survive, so they do not eat or drink. They also break down muscle mass to feed protein to the fetus.

However, such a process can only be short-lived before it poses a threat to the mother's health. In other words, the energy resources are limited, so the babies must be born prematurely, resulting in small cubs.

Although pandas do not hibernate in winter, those who support this theory contend that small birth weight is a common trait that genetics predetermines in the so-called Ursidae family — a family that comprises eight species of bears across five genera, ranging from brown bears to giant pandas.

To test if this theory was correct, the authors of the new study set out to compare several species.

Giant pandas' bones not mature enough

The researchers took micro-CT scans of giant panda babies, as well as other related animals, including baby grizzlies, sloth bears, polar bears, red pandas, domestic dogs, an African wild dog, and an arctic fox.

They then used the micro-CT scans to create 3D digital models of the animals' skeletons. The researchers looked at how much of the skeleton had ossified before birth, whether teeth had started to erupt, and examined the fusion between the neural arches, that is, the bony plates that make up the skull.

Even though Smith agrees that the prevalent theory is "an interesting hypothesis," the researchers' findings did not seem to support it.

The scientists failed to find any differences between hibernating bears and their nonhibernating relatives when it came to bone growth. Despite the small size, most bear skeletons showed a similar degree of maturity at birth as their relatives, with giant pandas being the only exception.

Full-term baby pandas resemble a "28-week human fetus" in terms of bone density and maturity at birth, says Smith.

'Development is just cut short'

The scientists do not yet know the answer to this question, but they do know that baby pandas seem to mature at the same pace as other mammals, at least judging by their skeletons.

The only difference is that "Development is just cut short," according to Smith. Giant pandas' relatives gestate for 2 months after the egg's implantation, whereas panda bears only do so for 1 month.

"We really need more information about their ecology and reproduction in the wild," the author adds, pointing out that their findings only involve the bones. Looking at other organs, such as the brain, might reveal new and different theories.

Original Article

Medical News Today: For rats, empathy may be a survival strategy

New research suggests that a rat's experiences may act as an early warning system to its fellow rodents.

rats munching on booksShare on Pinterest
New research sheds light on the mechanism of empathy in rats.

Empathy is the ability to understand someone else's emotional experiences. Typically, we think of empathy as a noble quality that we relate to compassion.

However, a new study from the Netherlands Institute for Neuroscience in Amsterdam suggests that for rats, being able to detect another's feelings may be a vital survival tool.

"What our data suggest is that an observer shares the emotions of others because it enables the observer to prepare for danger. It's not about helping the victim but about avoiding [becoming] a victim yourself."

Valeria Gazzola, senior author

The research suggests that empathy tells a rat what lies ahead; another rat's fright or pain may serve as an early warning, while their happiness could suggest the "all clear."

The new research appears in the journal PLoS Biology.

The experiments

The authors of the study examined empathy in a series of experiments and drew several conclusions about the manner in which rodent empathy works.

The researchers were also interested in ascertaining the factors that might create greater empathy.

The experiments positioned pairs of rats face-to-face. The scientists designated one rodent as the "demonstrator" and the other as the "observer" or "bystander."

In each round, the demonstrator was startled by the brief application of electrical current to their front paws as the observer watched.

"The first thing you see is, upon witnessing its neighbor jump, the bystander suddenly looks scared as well. The bystander catches the fear of the demonstrator," according to author Rune Bruls.

"Fear just jumps from one rat to another," Bruls adds, and the fear also jumps back. The researchers saw that the observer's reaction also affected the demonstrator's feelings about the electrical current.

The suggestion is that the observer's level of fear provided a clue to the demonstrator — the rat that had experienced the shock firsthand — how to feel.

If the observer did not seem that scared, then neither did the demonstrator. If the observer was terrified, so was the demonstrator.

How familiarity, experience affects empathy

People may assume that the closer they are to another, the more readily empathy will occur. It turns out this is not the case, at least for rats.

By comparing the empathetic responses of rats that had never met before against other pairs that had shared a living space for 5 weeks, there was no difference in the speed or intensity of the emotional contagion, according to the paper's authors.

Gazzola considers this finding as supportive of the empathy for survival hypothesis: If survival is a rat's main concern, the relative familiarity of a partner would be of little consequence.

One factor that did have an impact on empathetic response was an observer's own previous experience with electrical shocks.

Observers unfamiliar with the experience were less likely to react to a demonstrator's plight in a big way.

Efe Soyman, another of the study's authors, suggests: "Rats are like humans: The more our experiences match those of the people we observe, the more we can empathize with what they feel. It takes one to know one!"

Rats vs. humans

The research team was able to use the rat experiments to make a connection with the brain area scientists associate with empathy in humans, called the anterior cingulate cortex (ACC).

To see if the rats' ACC was similarly involved in empathy, the researchers introduced a drug that temporarily reduces activity in the area.

"What we observed," says Prof. Christian Keysers, lead author of the study, "was striking."

"Without the region that humans use to empathize, the rats were no longer sensitive to the distress of a fellow rat. Our sensitivity to the emotions of others is thus perhaps more similar to that of the rat than many may have thought."

Christian Keysers

After all, rats are not the only species that wants and needs to survive.

Original Article