Experts say their body clocks can end up out of sync - leaving them less active and affecting their sexual behaviour.

Academics at the University of Stirling in Scotland studied 11 giant pandas at six zoos for a year.

The impact they experience has been compared to how seasonal affective disorder affects humans.

Kristine Gandia, who led the study, said: "We found that housing giant pandas in zoos outside of their natural latitudinal range, where environmental cues like light have different cycles to those which they have evolved for, has an effect on rhythms of behaviour throughout the day and across the year.

"Animals synchronise their internal clocks to external cues like light and temperature so that they can display adaptive rhythms of behaviour like sleeping or eating at the right times of day or mating at the best time of year.

"When internal clocks are not synchronised 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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Ms Gandia added: "We found that giant pandas housed in zoos at higher latitudes than their natural range will show lower levels of activity.

"We also found sexual-related behaviours and abnormal and repetitive behaviours have similar rhythms throughout the year, implying that giant pandas may display abnormal and repetitive behaviours when they are unable to express sexual-related behaviours, replacing one behaviour for the other."

The researchers used webcams to monitor the giant pandas at six zoos both inside and outside pandas' natural habitat, noting general activity, sexual behaviour, and abnormal behaviour.

The animals were observed between midnight and 6am at regular intervals throughout the year, from December 2020 until November 2021.