16 Oct 2020

On our quest to prevent the extinction of the Asian elephant, we take a closer look at what our Hi-Way herd get up to at night.

For a world-leading modern day zoo, improvement of standards for animal management, husbandry and welfare, is an essential and ongoing scientific process. Particularly for long-lived, highly social and intelligent animals, we must rise to the challenge of solving puzzles quickly and collaboratively, to succeed in preventing their extinction. 

The Asian elephant (Elephas maximus) is no exception. Over recent years, Chester Zoo’s multigenerational ‘Hi-Way’ herd has provided a great deal of vital insight for this endangered species, and study group, for some of Europe’s leading elephant behavioural experts. 


Historically, abnormal behaviours have been the dominant factor in assessing elephant health. In our latest study, our researchers and elephant keepers have shed light on the subtleties of their night-time behaviour, to answer questions of elephant welfare.

Just as it is for humans, sleep is an ever present part of elephant life. Without adequate rest for the brain, we both face serious health consequences in the short and long term. 

Elephants need sufficient sleep for rest and development, so the right conditions to get a good night’s sleep, is just as important. Whilst late night roadworks, a lumpy mattress or a noisy neighbour are enough to ruin anyone’s sleep, elephants too need a place with acceptable noise levels, lighting and sleeping surfaces for a quality rest.

We’ve been keeping a close eye on the sleeping behaviour of our ‘Hi-Way’ herd for a decade, grasping the opportunity to connect the dots between herd sleeping behaviours and important animal management decisions.

What did we find?

We noticed the effects of age first. Mirroring the night-time experience of a new human family, Hi-Way elephant herd infants sleep much more than adults, but in significantly shorter bouts, waking up regularly for bursts of activity between naps. Meanwhile, the adults preferred longer sleeping periods, but needed on average an hour less at night than infants overall.

In their Asian homeland, elephant sleep behaviour would be affected by an environment changing with the seasons. Any well managed ex-situ population is of course provided with a stable indoor environment all year-round, so our keepers must innovate to encourage natural variation in seasonal behaviour.

In this instance, Chester Zoo keepers decided that rather than keeping the herd in their house during the moonlit hours, females and infants would have 24/7 access to outdoor roaming spaces over the warmer months of May-November. The ability to roam through the night had no effect on the amount of sleep the elephants were getting – a great sign. Periods of sleep however, either increased or decreased depending on the individual.

In order to fully understand this, it becomes essential to examine the herds’s interactions more closely. Do the nightly movements of their herd mates more easily disturb certain elephants than others? Are we accounting for natural male nocturnal behaviour? Broad studies such as this, work hand-in-hand with expert keeper knowledge of the individual elephant behaviour.


The most critical change in the herd’s twilight lifestyle came as a result of change in the herd itself. Our scientists and elephant experts have long championed the crucial significance of social compatibility for Asian elephant welfare. As part of the European breeding programme, we’ve worked for years to build a multi-generational family unit – the Hi-Way herd – in line with how elephants structure themselves in the wild. A proven structure to maximise welfare and breeding. 

Maintaining genetic diversity within a breeding population is paramount, however, unrelated individuals within the herd, and the movement of individuals between populations, will always be a necessity. 

Our most fascinating findings from the nocturnal dataset occurred during a year of change for the elephants here at Chester. A female – Jangoli – had been present in the Hi-Way herd for a number of years, though shared no relation with the herd core. It was clear to the elephant team and mammal curators that there was a high likelihood of social incompatibility. She would have frequent negative interactions with other elephants, while positive interactions were a rarity.

Dr Lisa Holmes, Lead Scientist for Behaviour & Welfare 

Lisa continued: “The call was made that she would be moved to a European zoo for both welfare and husbandry reasons. Immediately afterwards, keepers observed the herd engaging with each other much more positively during the day. We of course had our eyes on the darkest hours however – where the changes were most stark.

Following the move, the average sleep duration across the herd increased by an astounding 25 minutes per night. The most critical aspect of elephant welfare – social compatibility – is deeply linked with sleeping patterns.”

Over the past decade, we’ve developed and refined techniques to pinpoint the most relevant behaviours to monitor elephant wellbeing. It takes less time now than ever to collect meaningful data for management decisions.”

We’ve been going even further to develop a welfare monitoring tool, adding social network analysis to quantify social bond strength between individual elephants, and calculating daily movement habits using a novel method. All of this will soon be published for other zoos to utilise. By pushing our understanding even further, we can be increasingly confident in our acts to keep this endangered species safe.”

Year after year of hard work and research makes us better and better equipped to protect this endangered species through ex-situ population management. If we can expand this sleep study and knowledge across the global zoo community, together we can make huge strides in welfare monitoring and translocation decisions, at a time when it means more than ever for the Asian elephant itself.

Andrew Mckenzie, Assistant Curator of Mammals


While the moon shines in the sky above the zoo, the sun is rising over the forests of Assam, India. Here, we are engaged with the Wildlife Trust of India and the human communities sharing their homeland with what remains of India’s elephant population.

While work goes on in Europe to maximise the success of ex-situ conservation, we’re also supporting work in-situ, to tackle the drivers of human-elephant conflict. We wish to foster coexistence and prosperity between people and wildlife in the years ahead.

Stay tuned for more news as these projects unfold…

NOW is the time to ACT FOR WILDLIFE. Conservation is CRITICAL; species are under threat. TOGETHER we can make a BIG difference. Take action TODAY and join us in PREVENTING EXTINCTION.