How proceeds the decomposition of dead animals (i.e. “carcasses”) in nature? Which nutrients are stored in carcasses? How important is the role of scavengers in the cycle of these nutrients? And how fundamental is the process of carcass decomposition, and how important is it in an entire ecosystem? These are key questions in the PhD research of Elke Wenting.
Imagine an animal dies in the woods. What will happen? It may be eaten by other animals, or it decomposes. Surprisingly, we know very little about what exactly happens when carcasses decompose in nature. It is actually well-known that many animals benefit from the presence of carcasses as food source or breeding site (so-called “scavengers”), and thus that carcasses have a positive effect on biodiversity (the diversity of species present in an ecosystem). Examples of scavengers are birds like vultures and raven, mammals like foxes, but also plenty of insects (e.g. beetles and flies). But how important are scavengers in determining the fate of a carcass, and what happens when crucial scavengers are absent?
The race for the carcass
All living organisms consist of nutrients. Nutrients are needed to build up a body and to maintain its life functions. Animals gather their required nutrients over large areas and long timespans, and accumulate these nutrients in their bodies. Consequently, when an animal dies, the nutrients stored in its body suddenly become available for scavengers. But at the moment an animal dies, a real race starts between scavengers and microbes (e.g. bacteria).
Like scavengers, microbes also want to feed on the carcass, but they eat much slower than scavengers. Therefore, microbes need other “tools” to make sure that scavengers won’t take the part of the carcass that they want: the idea is that they try to render the carcass as disgusting and toxic, and so unusable, to the scavengers as fast as possible. When the scavengers are fast enough in detecting the carcass, they can eat the carcass before the microbes get the chance to render it. In that scenario, the scavengers “win”. But, when the scavengers are too late, the carcass is already spoiled and unusable to the scavengers at the moment they can detect it, and then, the microbes “win”.
When there carcasses and scavengers are common in nature, we think that the natural cycle of the nutrients stored in carcasses proceeds faster than when carcasses and scavengers are scarce. We propose that, ultimately, there will be more animals and plants - more biodiversity - in nature areas with ordinary carcass supply, compared to nature areas where carcasses are rare. Elke Wenting investigates whether this idea indeed applies.
Scavenger presence or absence
During this PhD research, Elke Wenting tests how the scavengers that are present in an ecosystem determine how carcasses decompose. She tests this in several experiments. For example, she will systematically exclude subsets of scavengers from carcasses: e.g. excluding all mammals, all birds, all insects, etc. She will monitor which scavengers use the carcasses using camera traps, and she will monitor what happens with nutrients stored in the carcasses by periodically measuring the soil nutrients.
The outcomes of this PhD research will provide new insights into the impact of population management on scavenger populations and the natural cycle of nutrients in ecosystems. Furthermore, it will provide new insights into how - and why - the presence of carcasses can contribute to biodiversity.
Article in the Dutch newspaper Nederlands Dagblad
Radio-interview in Buitengewoon, Omroep Gelderland
This project is funded by: Graduate School for Production Ecology & Resource Conservation