Studying Wild Animals Without Harming Them

The ongoing COVID-19 pandemic has once again underlined that animals, humans, and the environment are connected. To protect against future health threats, the wellbeing of all beings has to be considered in one single framework, a One Health framework. In other words, if we care about human health, we must also care about the health of animals.

Wild animal diseases and the health status of animal populations have sparked the interest of researchers over the last few decades. As this trend seems to continue, the question arises of how we can gather information from wild animals without having to restrict, captivate, or even kill them. To provide some answers to this question, this report reviews the latest sampling methods that aim to keep disturbance of animals as little as possible. 

The report includes 272 articles spanning from 1998 to 2021. Non-invasive methods (for example, collecting animal droppings or urine) can be used to investigate numerous issues ranging from diseases to stress and hormone levels, but they’re also used to conduct pollution and dietary studies. Just like the animals they’re applied to, non-invasive sampling methods can differ. To keep their review clear and usable, the authors classify all methods into different categories. For example, they distinguish methods according to the material that was collected, how researchers collected it, and from which class of animals they took it. 

Animal welfare in research itself is not a new concept. It’s been growing since the 1960s, when researchers first prompted the 3Rs principle. This principle aims to replace animal use in research whenever possible, reduce the numbers of animals employed, and refine the methods to limit their pain and distress. However, applying this principle to laboratory animals is less challenging than applying it to free-living animals. For example, many wild species live in remote places, which makes it considerably harder to store and transport their samples. Perhaps for this reason, welfare in wild animal research has gotten less attention, and the development of ethical standards has been comparatively slower. 

Fortunately, the results of this report suggest that the interest in minimally invasive methods has rapidly increased since 2010. This may be a sign that moral awareness is growing, but there are practical reasons for choosing non-invasive methods. If animals feel stressed while you take samples from them, the results of your investigation can be distorted. And as most conventional methods trigger stress in animals, this is surely another reason to cause as little intrusion as possible. This would also explain why the topic of “stress” had the highest number of papers published (67).

Of all reviewed papers, 39% were related to diseases, while 58% focused on other topics like diets or stress. The remaining 3% concentrated on both. Terrestrial mammals were by far the most investigated animals, accounting for 75% of all papers. For comparison, only 1% of all articles examined fishes. While this means we already have numerous animal-friendly methods for mammals, it also means there’s room for improvement regarding classes like amphibians, reptiles, or fishes. Collecting materials from an animal’s habitat was the most frequently used method to obtain samples (39%), immediately followed by trapping and handling animals (36%). Likewise, immunoassays (which are tests used to detect the quantity of substances like hormones) were the most common technique applied to samples. 

Half of all articles relied on feces as sampling material, simply because they offer numerous advantages: They’re easy to collect, they can be investigated on a wide range of topics, and it’s possible to collect them from several species. Thanks to their flexibility, the authors believe feces are currently the most promising substitutes for conventional samples like blood. 

Urine, body fluids like saliva, as well as hair, feathers, and skin have also been proven to be effective samples for the detection of pathogens. But many of them are used sparingly in research, probably because their collection can be more challenging for researchers compared to conventional invasive mediums. More resources and education dedicated to evolving these sampling methods may reduce some of the barriers preventing researchers from employing them. 

It’s motivating to see the rapid growth of interest in non-invasive methods, especially as society becomes more interested in protecting wild animal welfare. However, if we want to maintain this growth, animal advocates must keep pushing for change — with governments, funders, and the researchers themselves. Even if it comes in stages, every small step will make a big difference for wild animals.