Edinburgh Zoo: Pandas may have missed home too much to produce cub

And it’s all to do with the weather.

Scientists at the University of Stirling have spent more than a year watching pandas at other zoos and have come to the conclusion that the animals just don’t get in the mood for love because they are not among home comforts.

Pandas, like other animals, have body clocks which respond to the changing of seasons and evolved in their natural habitat in the far-off bamboo forests of China.

Taken out of this environment, the animals become less active and are less likely to breed. Like humans, the furry beasts experience seasonal affective disorder (SAD) in the winter, though unlike us they have a breeding season in the spring when they also feel the need to migrate.

At different latitudes this basic instinct is interrupted, and they stop displaying “sexual-related behaviours.”

Kristine Gandia of the University of Stirling’s Faculty of Natural Sciences, lead author of 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.

“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.”

Tian Tian and Yang Guang - also known as Sweetie and Sunshine - were treated like rock stars when they arrived in Edinburgh on 4 December 2011, and there were high hopes the pair would produce a pup.

READ MORE: Panda pair's departure date from Edinburgh Zoo announced

Both were mature young adults at eight years old and both had had cubs before, although not with each other.

Female giant pandas have a breeding window of just 36 hours once a year, and zookeepers carefully stage managed the pair’s first attempt, bringing them together at exactly the right moment and even keeping Tian Tian’s tail out of the way during the delicate mating process with a long stick.

But the effort was not a success, and over the years eight attempts were made to use artificial insemination to produce a baby bear.

However, each panda pregnancy ended in failure.

Ms Gandia and led a team of 13 observers from the University of Stirling who used webcams to monitor 11 giant pandas at six zoos both inside and outside pandas’ natural latitudinal range, noting general activity and sexual behaviour.

The team observed the animals between midnight and 6am at regular intervals throughout the year, from December 2020 until November 2021, which is a more immersive approach than most animal welfare assessments which often take place at specific time points.

She said: “Conducting these observations overnight at the height of the Covid pandemic took its toll on me, which is somewhat ironic because the research is about the importance of maintaining healthy circadian rhythms, but I wanted to demonstrate how crucial it is to assess animal welfare throughout the day and night, and across the seasons.

“This approach can be applied by zoos to determine how environmental factors may be affecting their animals to address questions at the forefront of captive animal welfare on whether species should be housed outside of their natural climatic and latitudinal conditions.

“Zoos exist to conserve animals and conduct breeding programmes for endangered species, so our approach may also help them to understand behaviour and the best timing for breeding.”

READ MORE: The true price of Scotland's failed panda experiment

She added: “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. This could help us further understand how to promote successful reproduction for a vulnerable species which is notoriously difficult to breed.”

It was announced earlier this month that Edinburgh’s pandas will return to China in December, now their loan is over.

Tian Tian and Yang Guang have to go back under the terms of a 10-year loan, which was extended by two years due to the Covid pandemic.