The Scoop on Elephant Poop

By: Meg Doran

Elephants are a widely admired animal that many people learn about as children. Maybe you had a stuffed elephant as a kid, took frequent trips to the zoo, or really liked Horton Hears a Who. You would’ve learned that elephants are intelligent, with intricate social behaviours and impressive memories. Despite the interest we take in them, elephant populations around the world are facing numerous threats. Elephants are an endangered species that struggle to survive in a world where humans continuously expand onto their lands, whether for agricultural, industrial, or urbanization reasons. The resulting habitat loss forces elephants to compete with humans for resources leading to high rates of human-elephant conflict. This conflict is what drove Ruchun Tang and his team in Xishuangbanna, China, to assess how human disturbance affects the stress levels and reproductive success of local Asian Elephants. The researchers’ hope was that conservationists could use this research to better protect elephant populations, as understanding how disturbance is affecting the animals is critical when making these decisions.

As you may have guessed from this article’s title, the way they went about measuring stress levels was kind of a crap job, literally. Researchers followed elephants and collected fresh fecal samples to test for hormones indicating stress levels and reproductive functioning. While this is a less glamorous technique compared to something like a blood test, it was a scientifically sound method. Fecal samples were a non-invasive way to measure the elephant’s stress levels without having to interact with them and possibly bias the results of the study. So next time you’re making fun of the guy shoveling elephant poop at the zoo, remember he is actually taking part in a delicate scientific procedure.

The specific hormones that were extracted and measured from the samples were cortisol and estradiol. When animals face a stressor, cortisol is produced to maintain homeostasis and increase energy production. While this hormone is extremely helpful at increasing immediate survival, chronically high levels can lead to health challenges such as reproductive failure and immunosuppression. Therefore, high levels of this hormone not only indicate increased stress, but also decreased reproductive function, the two variables researchers were interested in. Estradiol was the second hormone measured. Estradiol is a hormone that aids in reproductive functioning, but its expression decreases due to chronically high cortisol levels, providing the researchers with an additional method to test for reproductive success.

The team used a “human-elephant conflict risk model” that used data on factors like human presence and resource availability in each area to quantify levels of human-disturbance. They then measured hormone concentrations of the collected fecal samples and discovered strong evidence that human disturbance increased cortisol levels and decreased estradiol levels in the elephants. These findings support the team’s hypothesis that human disturbance acts as a stressor to local Asian Elephant populations, and as a result reproductive success is declining. To further support their hypothesis, the researchers pointed out that the proportion of unstressed elephants was higher in areas with lower human disturbance.

These findings provide important evidence that increased human-elephant conflict resulting from the destruction of Asian Elephant’s natural habitats is stressing elephant communities to a point where health factors like reproduction are impacted. Tang and his team hope conservation decisions can be made more efficiently if more endangered communities are monitored with these methods. Understanding what acts as a stressor and if these populations are feeling the effects of human activity will help determine what communities are at high-risk of negative impacts. This paper also reminds those expanding onto elephants’ habitats that their economic gain comes at an environmental cost, and habitat protection must be considered when making land-use decisions. So next time you’re thinking about elephants, remember they’re not invincible and get stressed just like us. The difference is you and I can go take a bath or read a book to calm down, but they don’t have that option and need our help to feel safe and relaxed. All one can really say after reading this paper is, the proof is in the poop.[MD1]

Tang, R., Li, W., Zhu, D., Shang, X., Guo, X., & Zhang, L. (2020) Raging elephants: effects of human disturbance on physiological stress and reproductive potential in wild Asian elephants. Conservation Physiology, 8(1), coz106.