Researchers found that pandas outside their latitude were less active, perhaps because daylight and temperature cues differed at different latitudes.
All animals have an internal clock called a circadian clock that is regulated by cues from their surroundings yet animals in zoos may be exposed to cues that are significantly different from those found in the wild.
Because all animals' circadian clocks are related to their behaviour and physiology, this could have a big impact on their welfare, which is critical for preserving captive populations of animals at high risk of extinction in the wild, such as giant pandas.
The study was published in Frontiers in Psychology.
Scientists wanted to know how pandas are affected by the 'jet lag' of living at latitudes they did not evolve in and thus receiving cues for their circadian clocks that they are not suited to.
“Animals, including humans, have evolved rhythms to synchronize their internal environment with the external environment,” said Kristine Gandia of the University of Stirling, lead author of the study in Frontiers in Psychology.
“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 live highly seasonal lives, they are an ideal study species for understanding how the circadian clock affects well-being and behaviour.
Pandas prefer to eat certain species of bamboo and love new shoots, which triggers a migration as these shoots emerge in spring.
The migratory season is also the breeding season, likely because finding mates is easier when they are all following the same nutritious shoots. Pandas are also so popular that many zoos that house them maintain public webcams, so behavior can be monitored around the clock.
Zoos also provide an opportunity to understand why the circadian clock matters for animal wellbeing, by moving animals to latitudes outside their normal range where important cues like daylight and temperature ranges will be different.
These changed conditions could potentially leave animals ‘jet lagged’, especially if their circadian rhythms are very dependent on seasonality, like pandas. Animals in captivity could also be affected by anthropogenic cues, like keepers’ regular visits.
Gandia and her fellow observers used webcams to monitor 11 giant pandas at six zoos both inside and outside the pandas’ natural latitudinal range.
Every month for 12 months, they carried out a day’s worth of hourly focal sampling to gauge how pandas’ behaviour changed across a day, and how that changed across a year. 13 observers took part, noting general activity, sexual behaviour, and abnormal behaviour.
The scientists found that daylight and temperature were particularly important cues for pandas, closely associated with general activity in latitudes that matched their natural range in China.
Captive pandas showed three peaks of activity over 24 hours, including a peak at night, just like their wild counterparts. Adult pandas only displayed sexual behaviours in the daytime, which could make it easier to find mates in the wild.
The researchers found that the behaviour of the pandas in mismatched latitudes differed from those in matched latitudes most when the pandas in mismatched latitudes were receiving 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 abnormal behaviour,” said Gandia.
The researchers also found that all study pandas reacted to zoo-specific cues, becoming very active in the early morning and showing abnormal behaviours that could represent anticipation of keepers visiting with fresh food.
Finally, the pandas’ abnormal and sexual behaviours fluctuated at similar points. The researchers suggested this could represent frustration that they can’t migrate or mate as normal.Pa
ndas who lived at mismatched latitudes performed fewer abnormal behaviours, possibly because they weren’t getting the same cues for sexual behaviours.
“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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