Virile Crayfish, Faxonius virilis

OTHER COMMON NAMES

None

ETYMOLOGY

Faxonius, named for Walter Faxon (1848-1920), American ornithologist and carcinologist. Former genus, Orconectes, is from Orcus, god of the underworld in Roman mythology + nectes: swimming (Greek); virilis, from Latin for virile.

Ecology, Habitat, & Behavior

While generally regarded as a habitat generalist, you’re more likely to find them hiding under logs and rocks or wherever else they can find cover in rivers with moderate to low flow. They emerge at night to forage on a wide range of foods. Detritus makes up about a quarter of the diet, but they’re also active predators. Their larger body and chelae size allow them to predate on small vertebrates (e.g. small fish, reptiles, salamanders, and tadpoles). Though restricted to the bottom of rivers and lakes, virile crayfish can compete with fish, like the flannelmouth sucker, for food resources (source). They can consume large quantities of fish eggs, and in higher abundances can have dramatically negative impacts on bluegill and pumpkinseed reproduction.

Virile crayfish are generally non-burrowing. Many crayfish species will excavate burrows when water levels drop in the summer or freeze in the winter, but virile crayfish are generally non-burrowing. This excludes them from intermittent streams and shallow waters that freeze completely. In winter, they retreat to deeper water where activity rates decline significantly. But, as with most crayfish, mortality in the winter is severe. they’re common throughout the state and easily recognizable by their rather distinctive large bluish claws.

They are solitary creatures, and can maintain rather high population densities. During the day they’ll hunker down in rock crevices or shallow burrows. They emerge to feed at night (adults are more nocturnal than juveniles), where they’ll move up to 200m in a single evening (males move shorter distances but more frequently than females). In cases where crayfish fought for a burrow, the larger crayfish usually won. There appears to be some habitat partitioning, where juveniles utilized the shallows more than adults.

Virile crayfish are edible, and sold commercially in other parts of its range (here in Vermont it is the primary species sold by the Vermont Crawfish Company).

QUICK FACTS

Avg carapace length: 3-5 inchesLife expectancy: 2-3 yearsAge at maturity: In second summerHabitat: Generalists, but often under rocks & logs in lakes & rivers# of eggs: 100-300Diet: Plant matter, fish eggs, invertebrates, and small fish, amphibians, and reptilesNative or non-native: Non-nativeActivity pattern:

Diurnal or Nocturnal

Uses: Bait, aquarium pet, science resource

Life History Event Date/Season
Males in F1 
Mating Fall, or rarely in early spring, particularly in the warmer part of its range
Fertilization Delayed, in early spring
Laying Eggs Delayed fertilization, eggs laid in spring; Hatch in 1-2 months
Young detach from female After 2 molts
Males in F2

Key features for ID + similar species

  1. Bluish chelae
  2. Abdomen has paired dark markings on each segment
  3. Narrow areola
  4. S-shaped dactyl
ROSTRUM

Margins of rostrum tapering, with prominent side projections, and sharp acumen. Strong ridges on margins of rostrum, Center of rostrum U-shaped, lacking carina.

COLOR/MARKINGS

Abdomen with paired dark dark spots on each segment. Algae growth on the exoskeleton can give them a rather dark appearance (particularly females who only molt once per year).

CHELAE

Large, robust, bluish to greenish, with light tubercules on margins. Dactyls are S-shaped, fingers have orange tips. Setae between fingers, from sparse to abundant.

AREOLA

Narrow, but never overlapping

Range map for Virile Crayfish

Range map based on observations from iNaturalist.org

General Research on Crayfish

  • NOBANIS: Invasive Alien Species Fact Sheet : source
  • Crayfish of the White River Watershed: source
  • Crayfish curriculum for educators: source
  • The Crayfishes of New England: source
  • Species of Ontario Crayfish: source
  • Lecture on Crayfish: video
  • Some aspects of the life histories of three closely related crayfish species, Orconectes obscurusO. sanborni, and O. propinquussource
  • Dictionary of crayfish names: source
  • Biological synopsis of the rusty crayfish: source
  • Observations on the life cycle of Procambarus acutus acutus in South Carolina culture ponds: source
  • Natural History of the two Crayfish of Northwestern Iowa, Orconectes virilis and Orconectes immunis: source

Crayfish of Vermont species profiles