Bacteria in the human gut may help fight off disease, but the bacteria living in hyenas may serve a different purpose entirely.
Microbes living in a hyena's scent pouch may actually be responsible for how it smells, as well as signaling its identity to other animals, according to microbiologists at Michigan State University. The research was published Monday in the journal Proceedings of the National Academy of Sciences.
Kevin Theis, lead author of the research paper, said that hyenas use smell to communicate with one another through an action known as pasting. "Their scent pouch is between their butt and their tail," he told ABC News. A pasting hyena extrudes its scent pouch outwards and drags it across a stalk of grass, leaving behind a thin layer of secretion in its wake. "Some people say it smells like cheap soap, but it smells more like mulch to me."
The distinct odor of hyena paste (Theis and his colleagues say they can detect it in the air and follow their noses to find where it's coming from) is likely a collaborative effort between the hyena's bodily chemistry and the bacteria living within its scent pouch. To support this theory, Theis collected 40 different samples of hyena paste in the Kenyan wilderness and sent it back to Michigan State University for further analysis.
Though there was a significant difference between the pastes of spotted and striped hyenas, Theis observed that there was more information hidden both in the bacterial and chemical makeup of those pastes. For example, hexanoic acid and a strain of bacteria known as OTU-1 are found in different concentrations between males, lactating females and pregnant females. In a similar vein, if two paste samples had the same bacterial profile, they would also have the same odor profile.
"Some people say it smells like cheap soap, but it smells more like mulch to me."
But is it the bacteria that causes the odor, or do specific odors naturally attract specific types of bacteria? Theis believes that the former is more likely. "The types of chemicals that we studied are known to be results of bacterial fermentation," he said. However, he added that he still plans to verify this hypothesis by manipulating bacteria in a lab setting.
These types of elaborate scent profiles may offer an explanation as to how hyenas reinforce their elaborate and somewhat unusual social structure.
"All adult female hyenas as well as their kids are dominant to all of the adult males," said Theis. "They exhibit low rates of aggression among themselves, so it's interesting to see if scent mediates this relationship."