Size-recessive reversal Amphibians often prey on
beetle larvae. However, the ground beetle
Epomis' larvae reverse this and prey exclusively on the amphibians that are trying to consume them. Two species of
Epomis (
E. circumscriptus and
E. dejeani) use the amphibian's
predation behavior to their advantage by luring the amphibian to them. "The
Epomis larva combines a sit-and-wait strategy with unique movements of its antennae and mandibles to draw the attention of the amphibian to the presence of a potential prey." Out of 400 tests, the larvae avoided the amphibian's tongue, and counterattacked by attaching to the body of the amphibian with an approximate 98% success rate. Once attached, the
Epomis larvae begin to feed. A species of South American ant has adapted the ability to hunt creatures that are up to 13,350 times their mean weight. The
Azteca andreae ants have developed a physical hook that enables their ambushes: the ants are
arboreal and ambush flying insects that land on their trees. Whenever a bug lands on the leaf, the ants spring into action: a small number bite down on the legs of the winged creature. While the bug is stuck and attached to the leaf, more ants come to dismember the prey. The average ant can hold up to 5,700 times its own body weight. The reason for this is suggested by a possible co-evolution between the
Azteca andreae ants and the
Cecropia obtusa leaves. The leaves have pronounced velcro-like loops that the ants are able to hook on to. The ants prevent other bugs from eating the leaves, while the leaves gives the often preyed-upon ants a predatory edge.
Juvenile predators and size-dominant reversal The giant water bug
Kirkaldyia deyrolli, in the subfamily
Lethocerinae within the
Belostomatidae, is an
endangered species native to
Japan that primarily feeds on small frogs and fish. Dr. Shin-ya Ohba has captured photos of
K. deyrolli eating outside of its known primary diet. A 58mm male water bug was found consuming a juvenile
Reeves turtle during a nighttime sampling. Dr. Ohba has found
K. deyrolli eating snakes, another rare behavior for the water bug. The hunting of juveniles has developed as an effective anti-predator strategy and role reversal. Young predators are at risk from members of their own species and competitors, and they may also be vulnerable to adults of prey species, as young predators pose nearly no predation risk to adult prey. An experiment where juvenile prey were exposed to adult predators while they developed were more likely to kill juvenile predators as adults than prey that was not exposed as juveniles. Increased levels of attack against juvenile predators can deter the adult predators, as the adult predators will avoid locations where their young may be attacked. This in turn reduces the risk of predation on the prey species.
Predator competition A more common reversal is interspecific killing among predators. Some species may experience 68% of their known mortalities from being killed by other predators. It is possible that one predator species may kill another and not the other way around, or both species may kill each other. Killing among predators can reduce populations, even to the point of
extinction, and may reduce or enhance prey populations.
Changing population densities Two islands off the west coast of
South Africa have very different
seafloor ecosystems. On
Malgas Island, the population is mostly seaweed and
rock lobsters. Rock lobsters act as predators, preying on
mussels that try to settle. The lobsters also prey on
whelks, except for one species,
Burnupena papyracea, the shell of which is usually encrusted with a
commensal bryozoan. In contrast,
Marcus Island has a large mussel population, and almost no seaweed or rock lobsters. Whelks,
Burnupena spp also have a large population density at Marcus Island. Rock lobsters brought to Marcus Island were quickly consumed by the whelks, which outnumbered them. This interaction showed a role reversal between a prey species (the whelk), and a predator species (the rock lobster). ==In pop culture==