We humans usually think of ourselves as pretty smart. One of the intelligent ideas ourancestors happened upon long ago, was the concept of cooking our food before we eat it. Many modern cultures place a good deal emphasis on cooking as a means to enrich the taste of the food. However, the overriding reason that cooking food has spread throughout human societies is that it is still the most effective way of killing microbes (bacteria, viruses, fungi, and protists) that would otherwise make us ill.
For those of us that love a good steak, we often prepare the steak rare or medium rare, meaning the steak is not cooked all the way through. This is a risk we are willing to take, since not cooking the meat completely leaves the door open for microbes that are able to tolerate high temperatures. Spicing up your favorite dish adds flavor that not only enhances dining experience, but is some cases may also provide antimicrobial activity. Wild animals do not have the option of cooking or adding antimicrobial spices to their meal. As a result, animals have evolved other means of dealing with potential pathogenic (disease causing) organisms.
Spotted hyenas seem to be particularly adept at dealing with microbes that would make you or I extremely sick. This is one of the main reasons I am interested in studying hyenas. Hyenas will eat just about anything, plants being a major exception. Members of the hyena research team have witnessed hyenas eat rotting carcasses that other animals refuse to eat. Many animals will routinely pass up a meal that is decaying, most likely because the risk of infection from the consumption of the decaying meat is high. This widespread behavioral adaptation is an effective method of avoiding dangerous infections. This behavior is so pervasive that some animals have actually developed an anti-predator strategy that includes playing dead, also know as "playing possum." The logic behind this is that if an animal keels over and dies right in front of you, it must be very sick, and thus would probably make you sick if you ate it.
If the behavior of avoiding rotting meat is an effective way of avoiding infection, why are hyenas so willing to eat it? The simplest answer, is that it provides them with an advantage over other animals when prey animals are in short supply. The wildebeest migration is currently in the Mara and food is plentiful. However, the wildebeests will soon migrate back to Tanzania and prey will become more scarce. As the food becomes more difficult to obtain, being able to eat leftovers can be very important for survival. Of course hyenas are not the only animals to take advantage of carcasses, vultures have nearly perfected the art of locating and consuming rotting meat. Hyenas have an additional trick up their sleeve to get nutrients out of a carcass that vultures do not. I will write about this in a future post. If anyone knows what this behavior may be, please feel free to post a comment or email me what you think it is.
Hyenas are one of the most effecient hunters on the African savanna, but they also take advantage of kills made by other animals and animals that have died of disease and/or starvation. This food source can mean the difference between life and death for an animal that cannot go to the grocery store or McDonald's when it is hungry. The drawback of taking advantage of this food source is that hyenas must be able to fend off harmful microbes in the food they eat. This can be done in many ways. I am particularly interested in finding out how the hyena immune system is able to withstand the inexhaustible onslaught of microbes that seeks to exploit them. Over the next 6 months I will continue to write about this topic. I hope some of the readers of this blog will contribute their own ideas as to why hyenas are so resilient to disease.