The rusty crayfish (Faxonius rusticus) is a large, aggressive species of freshwater crayfish which is native to the United States, in the Ohio River Basin in parts of Ohio, Kentucky, and Indiana. Its range is rapidly expanding across much of eastern North America, displacing native crayfishes in the process. The rusty crayfish was first captured in Illinois in 1973, and has been collected at over 20 locations in the northern portion of the state. In 2005, F. rusticus was found for the first time west of the Continental Divide, in the John Day River, Oregon, which runs into the Columbia River.
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ScavengerScavengers are animals that consume dead organisms that have died from causes other than predation or have been killed by other predators. While sc...
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OviparousOviparous animals are female animals that lay their eggs, with little or no other embryonic development within the mother. This is the reproductive...
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starts withAdult rusty crayfish can reach 10 centimeters (4 inches) in length, although they reach maturity at about 4.4 cm (1.7 in), and can range in color from greenish grey, to reddish brown, They can be easily recognized by two "rusty", reddish colored spots on the sides of their back and their large front claws with black bands around the tips. Male rusty crayfish have small hook-like features on their first pair of hind legs that they use to hold onto a female while mating.
Many species of vertebrates that live in communities together utilize a dominance hierarchy to establish order, and studies have shown that some species of invertebrates do as well. The dominance hierarchy is an important aspect of a crayfish's biology and behavior. Crayfish tend to form dominance hierarchies with the other members of their population in a particular environment. The largest male will generally demonstrate the most dominance over the others by being the most aggressive, and picking fights with the other, smaller crayfish. The crayfish that wins the most fights is placed at the top of the hierarchy with the other members generally ranking in descending order based on size and sex. Studies have suggested that the largest determining factor in the formation of dominance hierarchies is size rather than sex. That means that female rusty crayfish can rank higher in the dominance hierarchy than male rusty crayfish if they are larger than them.
