All animals – including humans – have circadian clocks that are regulated by cues from their environment.
However, according to a recent study led by the University of Stirling in Scotland, animals in zoos can be exposed to highly different cues than their counterparts in the wild.
Since animals’ circadian clocks are tightly linked to their physiology and behavior, changes in these clocks can impact their welfare, which is crucial to maintaining captive populations at high risk of extinction in the wild, such as giant pandas.
To better understand this phenomenon, the experts examined how the “jet lag” of living in high latitudes may affect captive giant pandas. Since the animals did not evolve or live at high latitudes, their circadian clocks do not match their environment.
“Animals, including humans, have evolved rhythms to synchronize their internal environment with the external environment,” said lead author Kristine Gandia, a PhD student in Behavior and Evolution at Stirling.
“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.”
Since giant pandas have highly seasonal lives, they are an ideal case study for understanding how circadian clocks affect behavior and wellbeing.
Pandas prefer to eat specific species of bamboo and love new shoots, which triggers seasonal migration patterns as these shoots emerge in the spring.
Moreover, since finding mates is easier when all pandas follow the same nutritious shoots, the migratory season is also the breeding season.
Recently, pandas became so popular that many zoos housing them maintain public webcams, which makes it easier for behavior to be monitored around the clock.
In addition, since many pandas live in zoos located outside their normal range – where important cues such as daylight and temperature ranges are different from those in their natural habitats – zoos provide unique opportunities to understand why the circadian clock matters for their wellbeing.
According to the researchers, changes in the daylight and temperature ranges of the pandas could potentially leave them “jet lagged,” particularly since their circadian rhythms are highly dependent on seasonality. Moreover, pandas in captivity also appear to be frequently affected by anthropogenic cues, like zoo keepers’ regular visits.
For the present study, the scientists used webcams to monitor 11 giant pandas at six zoos located both inside and outside the animals’ natural latitudinal range.
Every month for a year, the researchers conducted a day’s worth of hourly focal sampling to understand how pandas’ behavior changed across a day, as well as how those patterns changed across a full year, by monitoring variables such as general activity, sexual behavior, and atypical behavior.
The investigations revealed that daylight and temperature were particularly important cues for pandas, being closely associated with general activity in latitudes matching their natural range in China.
Just like their wild counterparts, captive pandas showed three peaks in activity over 24 hours, including a peak at night. Moreover, adult pandas only engaged in sexual behavior during the daytime, which makes it easier to find mates in the wild.
Pandas outside their natural latitudes were less active, most likely because daylight and temperature cues were different – a finding also supported by the fact that the behaviors of pandas in mismatched latitudes differed from those in matched latitudes the most when the pandas in mismatched latitudes were exposed to more divergent daylight and temperature cues.
“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 atypical behavior,” Gandia explained.
The experts also discovered that captive pandas reacted to zoo-specific cues, becoming extremely active in the morning and displaying abnormal behaviors in anticipation with keepers providing them food in the first part of the day.
Finally, the animals’ abnormal and sexual behaviors were found to fluctuate at similar points, suggesting that they might be frustrated because they cannot migrate or mate as they would normally do.
Thus, pandas living at mismatched latitudes performed fewer abnormal behaviors, most likely because they were not getting the same cues for sexual behaviors.
“To expand on this research, we would want to incorporate cycles of physiological indicators. Importantly, we would want to assess sexual hormones to understand the effects the environment may have on the timing of release,” said Gandia.
“This could help us further understand how to promote successful reproduction for a vulnerable species which is notoriously difficult to breed.”
The study is published in the journal Frontiers in Psychology.
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