We're all familiar with the idea of a sleep cycle. For people, sticking to a schedule helps our internal clock stay accurate, letting us sleep when it's time for bed, eat at mealtime and stay awake during the day.

Those of us who have hopped on a red eye or international flight know how jet lag can mess that inner clock up. As it turns out, according to a study published Monday in the journal Frontiers in Psychology, giant panda bears are familiar with the pitfalls of jet lag as well.

Giant pandas living outside of their natural habitat in China can and do experience disruptions to their circadian rhythm, or internal clock, found the research. As with the rest of the animal kingdom, pandas rely on environmental cues, including light and dark cycles, food and shifts in temperature, to regulate their body's rhythm and navigate everyday life.

Living in environments unlike those they evolved for in the wild has implications for pandas' overall well-being, found the study's authors. Those living outside of their natural latitudinal ranges experience changes not only to the natural stimuli around them, such as seasonal weather, but learn to respond to stimuli that is entirely man-made as a result of living in captivity.

As a result, some pandas observed in the study were seen performing fewer activities and displaying some inconsistent or abnormal behaviors.

“Animals, including humans, have evolved rhythms to synchronize their internal environment with the external environment,” Kristine Gandia of the University of Stirling and lead author of the study said in a statement. “When internal clocks are not synchronized with external cues like light and temperature, animals experience adverse effects. In humans, this can range from jet lag to metabolic issues and seasonal affective disorder.”

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Why pandas?

While the study's authors indicated that these results could apply to any animal held in captivity, giant pandas were selected because their lives in the wild are highly dependent on seasonal changes.

The migratory season for pandas in nature is triggered during spring, when new shoots of the bamboo they love to eat begin to emerge. This is also when breeding occurs, as finding mates is easier when eligible suitors are sharing the same foraging path to locate their favorite bamboo roots.

They are also very popular animals in zoos around the world, which made it easier for researchers to capitalize on existing means of monitoring them.

“Pandas are very good animals to focus on,” said Gandia. “They are very popular in zoos and there are a lot which have ‘panda cams’ (webcams from the animals’ enclosures), so we can see how their behavior changes across different latitudes.”

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What did they study?

A team of 13 observers participated in the study, watching 11 giant pandas born and living in captivity at six zoos around the world. Some of these zoos were located inside the pandas’ natural latitudinal range and others outside.

Using webcams, the team observed the pandas using hourly focal sampling, which entails watching one animal at a time for a specific length of time and recording everything that animal can be seen doing.

Each month for the 12 months, the team completed one day's worth of the sampling, which was later compared against the rest of the data to see how behaviors changed between observation days and over the course of the year.

The researchers recorded three main categories, which were general activity, sexual behavior, and abnormal behavior.

What they found

Daylight and temperature cues were found to have the largest impact on the pandas.

Those housed in latitudes that matched natural conditions in China had general activity most closely reflecting behavior in the wild, including three peaks of activity over 24 hours. Adult pandas only displayed sexual behaviors during daytime, which could be because it is easier to find mates in the wild during daylight hours.

Those living outside of their natural latitudes, however, were overall less active and showed different behaviors from those in matched latitudes.

“When giant pandas are housed at higher latitudes — meaning they experience more extreme seasons than they evolved with — this changes their levels of general activity and abnormal behavior,” said Gandia in a statement.

All of the pandas responded to zoo-specific and human-created cues, such as becoming very active early in the morning in anticipation of keepers arriving with breakfast.

All of the pandas also showed abnormal and sexual behaviors fluctuating at similar points. The researchers believe these could stem from an inability to pursue natural migration and mating rituals, causing frustration. Pandas who lived outside of the natural latitude range actually participated in fewer abnormal behaviors, which the team suggested could be due to lack of cues for the mating behavior to begin.

Giant pandas are long-time members of the endanger species list, with only about 1,800 left in the wild. They currently have been upgraded to "at-risk" status, thanks to concerted efforts to preserve their environments and keep and breed them in captivity.

Understanding how the pandas function when in human care is important to their preservation, said the study.

“To expand on this research, we would want to incorporate cycles of physiological indicators,” said Gandia. “Importantly, we would want to assess sexual hormones to understand the effects the environment may have on the timing of release. This could help us further understand how to promote successful reproduction for a vulnerable species which is notoriously difficult to breed.”

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