Ashes to Ashes, Dust to Dust

In keeping with our June 2018 theme of dirt and how animals interact with it, the topic of animal death arises. World Pet Memorial Day occurs every year on June 10, further adding to the relevance of the topic. This post will not discuss the loss of pets but rather animal death from an environmental standpoint in both a forest and desert environment.

Animals, like humans, can die in countless ways. Some die before they are born, such as sea turtle eggs being eaten by a fox while still in the nest. If they make it to hatching, then the sea turtles must survive a gauntlet of birds, dogs, crabs, and other predators before making to the ocean to deal with another set of predators. Despite millions of years of evolution and the seemingly perfect niche in which many animals reside, death is never far and very few animals die simply of “old age.” Animals are always battling predators, disease, habitat destruction, hunting/farming, or climate change and typically, many of these at the same time!

So what happens when an animal, lets say a squirrel, dies in the forest? If not the victim of predation, a squirrel facing death through disease or starvation will often hide in a nest or other solitary place until the end. If a squirrel dies on the forest floor, there is no shortage of fungi and bacteria that will begin to break the body down. Within the first few hours after death, the body’s temperature will either rise or fall towards the temperature of the surrounding environment (algor mortis). Shortly thereafter, the muscles are no longer able to relax and stiffen (rigor mortis). The body will then begin to bloat, indicating that decay is well underway. Decomposition often begins working on the inside of the animal as well, with enzymes and chemicals from the animals’ gut working from the inside-out. This process is known as autolysis whereas putrefaction occurs when bacteria and fungus from outside the body aid in decomposition. At this point, flies are often the first insects on the scene and they will begin to eat the flesh of the dead animal while laying eggs, which can only grow in decomposing flesh, and will shortly become maggots.  

Over the course of several weeks, the animal will go from being alive to being a small collection of bones and occasionally fur. The rate of decomposition varies greatly between forest ecosystems, as those with lots of dead leaves will have higher decomposition rates than those with fewer leaves. The rapid decomposition of animals along with the organic matter from rotting leaves becomes part of a cycle leading to rich, fertile soils packed with bacteria, fungus, and vital nutrients being recycled as part of the decomposition process. Each of these processes result in chemicals that, um, don’t smell so great.

The bacteria, fungi, and animals that help break down animal remains are known as ‘decomposers.’ Many decomposers prefer moist, humid environments and are therefore more rarely found in the desert. Bacteria are the most common types of decomposers found in the desert and play a vital role in breaking down remains. Millipedes, termites, earthworms, and dung beetles can also aid in desert decomposition. The dung beetle held vital importance in ancient Egyptian societies, perhaps due to its vital role in desert life and death. The lack of decomposers due to the heat and aridity of the desert cause decomposition to take much longer in the desert and often results in mummification. Through the mummification process in the wild, animal skin and organs are dried out and “preserved” over time.

Although decomposition may seem like an end, it provides the ongoing beginnings that have made generations of life possible on this planet. Carbon recycling is the most important effect of rot and decay. The ‘carbon cycle’ encompasses the breaking down of dead plant and animal material, the resulting release of carbon dioxide into the atmosphere, and then carbon’s role in photosynthesis, the rebirth of life!

Interesting facts about animal death:

• The bowhead whale, which lives in the Arctic, is the mammal with the longest lifespan, sometimes up to 200 years!
• The giant tortoise is the terrestrial animal with the longest lifespan, up to 175+ years!
• The world’s population of wildlife decreased by 52% from 1970-2010.
• A body decomposes twice as slowly in water than it does when air is present and eight times as slowly when buried in earth than when air is present.
• Presence of insects is the most important factor regarding the rate of decomposition of animals in the wild.
• Flies often lay 50-200 eggs in a decomposing animal, which become maggots roughly 8 hours later and then adult flies after about 2 weeks.

Sources: The Citadel, Science News for Students, and Weather.com