NO ROOM TO DIE: Captivity can drive fish to cannibalism, uncommon in nature
The results of the experiments pointed to population density and resource availability as the key drivers of cannibalism.
SCITECH DAILY: Even though mosquitofish and guppies are known to be cannibalistic in captivity, it is very improbable that they would engage in cannibalism in the wild. Instead, the few instances of cannibalism in these fish are probably the result of an intense struggle for food. The results of a recent study led by researchers from the United States and the United Kingdom…
Cannibalism, or preying on and devouring members of your own species, is an odd practice that often appears in human mythology and literature. But how often is it in nature, and why would animals take such drastic measures to get a meal?
In order to find out, Rüdiger Riesch, senior lecturer in evolutionary biology at the Royal Holloway University of London, and Brian Langerhans, associate professor of biology at North Carolina State University, decided to analyze data collected over a 10-year period from nearly 12,000 fish belonging to 17 different species that were caught in the wild. The research team examined the diets of 11,946 fish in the wild… They found only 35 cases of cannibalism, in just three species of mosquitofish – less than 0.30% occurrence…
“These are data accumulated from several different projects over the years,” says Langerhans, the study’s senior author. “To identify the mechanisms responsible for this sort of phenomenon in the wild, we needed really large sample sizes. So, we accumulated the data for this work while also doing other projects”…
Cannibalism was most frequent in populations with very high levels of competition for food; that is, populations lacking major predators where population densities of the fish surveyed were especially high… The results of these experiments also pointed to population density and resource availability as the key drivers of cannibalism…
“Resource competition seems to be the main predictor of cannibalism,” Langerhans says. “We also saw that a lack of predation has an indirect effect on cannibalism: Release from predation allows population density to skyrocket, which decreases resources. This same driving factor may be responsible for many cases of cannibalism across the animal kingdom in natural settings”…
“Cannibalism in these fish is an issue that biologists have to regularly contend with in lab and hatchery settings, so it was widely thought to be at least somewhat common in nature,” Langerhans says. “But we’ve shown here that it really isn’t. SOURCE…
RELATED VIDEO: