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Measuring stress in working elephants

Studies suggest that both physiological and behavioural approaches can be used to reliably assess the wellbeing of semi-captive Asian elephants

Researchers from the University of Turku, Finland, have investigated how best to measure stress in semi-captive working elephants. Their findings are published in two articles in a special issue “Captive Elephant Welfare and Behaviour” of the journal Animals.

In the first study, the researchers wanted to find out if two biological measures of stress – cortisol levels and heterophil to lymphocyte ratios – were correlated and whether animals with high levels of cortisol also had a high heterophil to lymphocyte ratio. They studied Asian elephants from a semi-captive population of working timber elephants in Myanmar.

“Some previous studies have found a positive relationship between stress hormones and heterophil to lymphocyte ratios, while others have found no relationship at all. It was also unclear from previous studies whether these two measures of stress are comparable across individuals of different sex and age, as well as across the seasons. In this population, we found that elephants with higher levels of the stress hormone cortisol also had higher ratios of heterophils to lymphocytes. This was true regardless of sex and age,” says Postdoctoral Researcher and the lead author on the first study, Martin Seltmann, from the Department of Biology at the University of Turku.

An additional aim of the study was to test if stress hormones and heterophil to lymphocyte ratios are related to body weight in Asian elephants.

“We did not find a link between the white blood cell ratios and body weight, but elephants with higher levels of stress hormone had a lower body weight, indicating that elevated stress is linked to weight loss. It is useful to see that both a biological marker (cortisol) and physical indicator (body weight) of welfare respond in the same way. This means that both markers can be used to assess the wellbeing of elephants,” says researcher Susanna Ukonaho, who participated in the study.

In the second study, the researchers investigated whether welfare can also be reliably assessed by observing an animal’s behaviour. While elephant specialists may be able to quickly identify behavioural changes, expert knowledge is not always available, so the researchers wanted to test the reliability of behavioural assessments by non-experts. First, they filmed over 100 working Asian elephants undertaking tasks that were either familiar or new to them.

“The elephants were asked to pick up different types of objects, including objects they had never seen before. This included items such as a plastic bottle, which some elephants were clearly unsure about,” says the lead author on the study, Jonathan Webb.

The researchers constructed a list of elephant behaviours, which was then used by three volunteers with no prior experience of Asian elephants to collect behavioural data from the films.

To assess the reliability of the behavioural data, the researchers looked at how similar the observers’ scores were for each film. They also assessed observer consistency by getting the volunteers to score films twice. They found that all three volunteers consistently and reliably identified many elephant behaviours, indicating that even with limited experience, people can reliably monitor elephant behaviour in a way which could improve the quality and safety of working elephant-human relationships.

Behavioural markers could therefore be a simple but useful tool for elephant welfare assessment on a larger scale, although the researchers caution that we still need to know how different behaviours are linked to biological measures of stress.


Seltmann, M.W., Ukonaho, S., Reichert, S., Dos Santos, D., Nyein, U.K., Htut, W., Lummaa, V. (2020). Faecal Glucocorticoid Metabolites and H/L Ratio are Related Markers of Stress in Semi-Captive Asian Timber Elephants. Animals 10(1) 94. doi: 10.3390/ani10010094

Webb, J.L., Crawley, J.A.H., Seltmann, M.W., Liehrmann, O., Hemmings, N., Nyein, U.K., Aung, H.H., Htut, W., Lummaa, V., Lahdenperä, M. (2020). Evaluating the Reliability of Non-Specialist Observers in the Behavioural Assessment of Semi-Captive Asian Elephant Welfare. Animals 10(1) 167, doi: 10.3390/ani10010167

Article details

  • Date
  • 03 April 2020
  • Source
  • University of Turku
  • Subject(s)
  • Zoo-, Wild-, Laboratory-, and Other Animals