What effect does stress have on animals? More than you can imagine. Recently, scientists have started to identify the major cause of stress in animals and what they’ve discovered might surprise you. The biggest impact isn’t from predatory attack or disturbance, it is land degradation. These findings are starting to alter the way we think about conservationWhy is animal conservation important? Animal conservation is important, because animals are the only mechanism to create biodiversity, which is the mechanism that creates a habitable planet for humans. Without animals, the energy from today’s plants (algae, trees, flowers etc) will eventually reach the atmosphere and ocean, much of it as carbon. The quantity of this plant-based waste is so More and should give us pause to think about the less obvious benefits to our own health, of restoring wildlife populations and ecosystemsHow ecosystems function An ecosystem is a community of lifeforms that interact in such an optimal way that how ecosystems function best, is when all components (including humans and other animals) can persist and live alongside each other for the longest time possible. Ecosystems are fuelled by the energy created by plants (primary producers) that convert the Sun's heat energy More.
What is chronic stress?
If you’ve ever suffered stress, you’d know it isn’t something sudden. It creeps up to create a general sense of anxiety. You might feel occasional heart palpitations, some sense of despair and lethargy. The sources of chronic stress are defined as things that will “change people’s identities or social roles, are more beyond their control and seem endless”. The word ‘chronic’ doesn’t mean intense, it means persistent or recurring.
Increases in depression, anxiety and stress affected people during the early stages of COVID lockdown – you may have felt it too. This is your body reacting to uncertainty. The white matter in your brain has physically built itself over many years, into neural patterns that reflect your lifestyle and connect you to a world you understand. If your outside environment changes or it becomes more chaotic, it corrupts the connections you have and this leads to stress.
What causes stress in animals?
Stress is caused by an imbalance of hormones, chemicals that are triggered by our brain. These translate into physiological actions and are how your body and mind are connected. We can measure the after-effects of these outpourings of chemical emotions to get an estimate of stress levels in individual animals. That’s exactly what scientists in South America did with small mammals in the Atlantic Forest in Paraguay [1].
They found that animals living in large forest fragments experienced only a fraction of the stress of animals in smaller fragments. The scientists have suggested this might have to do with predator interaction but this is the least likely major cause of stress in animals, as discovered by Edward Narayan working on koalas in Australia [2]. Narayan collected faecal samples from koalas and found that the impact of land degradation was by far the most significant.
The level of stress hormone in animals living in areas of land clearance was 15 times higher than the average stress hormone levels in healthy koalas. Notably, the impacts we usually think are ‘extreme’, such as injury, dog attack, disease or vehicle collision, are relatively benign. Animals are adapted to these types of incidents and occasional increases in stress hormone levels are even good for our health. Understandably, burns and organ failure are highly stressful but two factors came out on top: being on the ground and land clearance. Both are changes in the external environment and impose no direct impact on the animal.
What is the conservation significance of major stress in animals?
Our preconceptions about stress in wild animals can bias the way we think about them, how we behave and the actions we take to limit our impact on them. Direct intense effects such as collisions with vehicles or dog attacks are important as they kill animals. The indirect effects of land clearance, however, are often thought to be benign. An animal sitting in a tree that’s suffering from chronic stress will look just like someone sitting in a café – quite normal.
That’s not the important bit though. Ecological Impact Assessment separates an ‘effect’ from an ‘impact’ An effect is something that happens. Stress is an effect and its impact, as we have discovered, can be both good and bad. So, it’s not even the impact that we should be concerned about, but its consequence and that is where ecology risks getting weighed down in long-term research and debate. Because when we’re talking about land clearing, the context in which we evaluate consequence has changed so much, we can hardly tell the difference between what is normal or not.
Stress, it turns out, is a major cause of ill-health in all animals including humans. So what is the consequence likely to be?
What is the consequence of major stress in animals?
There is the consequence on the animal and that’s obviously important but there’s also the effect that widespread stress has on the ecosystems we need for a habitable Earth. All throughout this article, I’ve been talking about the impact of land clearance on stress levels in animals but that’s not how ecosystems work. That’s only how our impact on animals works.
The fact is, ecosystems and their animals are inextricably bound together. Ecosystems can only function(Of an ecosystem). A subset of ecosystem processes and structures, where the ecosystem does something that provides an ecosystem service of value to people. More properly when there is sufficient abundance and diversity of animals to absorb free energyThe energy of a system that is emitted as waste and is not part of ecosystem processes. There is always some free surplus energy as this creates the basis for evolution where new species exploit gaps in the ecosystem where free energy becomes available. Surplus energy can occur as a result of disruption or disturbance. When free surplus energy reaches More from plants. It’s a process of planetary stabilisation that has taken many millions of years. The food we eat and indeed our own existence, is because we are part and parcel of that process. Food security is the result of animal impactWhat is Animal Impact? Without wildlife, Earth would not be habitable for humans, because it's animals that stabilise ecosystems. It’s a fundamental law of nature that animals (and humans) exist because we are the most likely lifeforms to minimise environmental chaos. Animal impact, therefore, is a measure of how much all wildlife is collectively responsible for creating a habitable Earth. The More on ecosystems, it’s not a result of ecosystems.
If you understand that, you can better imagine why land degradation causes stress. It’s the constant inability to find a regular source of food that causes chronic stress. We often refer to animals as ‘making a living’ which is what they do when they forage. Substitute that for ‘having a job’ and imagine what it feels like to find yourself perpetually unemployed … perhaps on a zero hours contract, or having lost your prospects due to a pandemic. Or maybe you’re a renter who doesn’t know when you’ll be turfed out of your home. What does that do to your stress levels? We’re not so different, because we are animals.
Healthy wildlife and healthy people
The health of wild animals is by extension, our own health. We behave similar to other animals and rely on their diversity and abundance to maintain our life support. We cannot do this alone.
It’s exciting to see veterinary science converging with wildlife conservation as ecologists have tended to ignore our animality – it’s not a universal ideology, scientists are warned constantly, not to bestow human emotions and feelings on animals. But today, there is too much evidence to ignore the fundamental origins and mutual dependence we have with wildlife. Veterinarians, who literally handle animals ever day, tend to be more aware of that kinship.
That land clearance is the major cause of stress in animals should come as no surprise and if we can accept this, it will be easier to start rebuilding a habitable Earth and securing our own future.
References
- Boyle, Sarah & De La Sancha, Noé & Pérez-Estigarribia, Pastor Enmanuel & Kabelik, David. (2021). Small mammal glucocorticoid concentrations vary with forest fragment size, trap type, and mammal taxa in the Interior Atlantic Forest. Scientific Reports. 11. 2111.
- Narayan, Edward. (2019). Physiological stress levels in wild koala sub-populations facing anthropogenic induced environmental trauma and disease. Scientific Reports. 9. 10.1038/s41598-019-42448-8.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3341916/
