Cannibalism may be an understudied factor in the spread of disease among insects, according to new research.
Associate Professor of biological sciences Bret Eldred and his lab are researching how changes in temperature and resource quality influence disease transmission, particularly in fall armyworms, when they noticed something odd.
“We go out into the field and create mini-disease outbreaks and we noticed that while trying to recover individuals from the field, they were cannibalizing each other,” Eldred said. “We started looking into how cannibalism might impact disease transmission because it seems to be part of the armyworm’s natural history.”
Cannibalism is actually quite prevalent among different species in the wild. However, other scientists have not directly tested the disease aspect of it, Eldred said.
For example, a study of desert scorpions in 1980 showed that other scorpions are their fourth-most common meal. Another study showed that of 190 female rattlesnakes observed, 68 percent consumed at least some of their offspring according to discover magazine.
“A lot of scientists were looking at cannibalism from the individual’s perspective, so it would be risky to be a cannibal, but if it’s so risky then why were we actually seeing this in the field?” Eldred said.
Eldred and his team invented mathematical models to determine whether cannibalism is as risky as many believe.
“An individual of your own species represents the perfect meal, it has all the right nutrients and micronutrients you need to survive because it’s basically the makeup of you,” Eldred said. “The risk factor is that individual has the same pathogens and diseases that you would carry so if you consume that individual you have a risk of becoming infected.”
For a long time, cannibalism was thought to be extremely risky in terms of disease. However, Eldred’s research shows diseases need to infect multiple individuals in order to be successful.
“A disease needs to infect more than one individual or it will die out. If a cannibal eats an infected individual, the disease hasn’t spread at all.” Eldred said.
When an individual caterpillar becomes sick with a virus, its growth is stunted. Sick individuals end up being smaller and easier for healthy individuals to consume, or cannibalize.
“Cannibalism not only takes away competitors for your own food resources but it also takes away individuals who can contract that disease and spread it,” Eldred said. “If you eat healthy individuals you decrease the population and the disease has a lower chance of spreading.”
