Behavioral aggression interactions and aggression levels between juvenile Orconectes rusticus and juvenile Orconectes virilis.

Abstract

Orconectes rusticus, a crayfish species native to the Ohio River Valley, is expanding its home range and has recently been found as far south and east as the Monocacy River, Frederick County, Maryland. In the Monocacy, the most abundant crayfish, 0. virilis, is being displaced as 0. rusticus invades the river. A possible reason for this trend is that 0. rusticus obtain superior resources due to higher aggression levels and behavioral dominance. Aggression levels and behavioral dominance of juvenile 0. rusticus and juvenile 0. virilis were examined through interspecies and intraspecies, head to head, size matched agonistic bouts. Juvenile 0. virilis exhibited higher aggression levels and to also won behavioral dominance over juvenile 0. rusticus in this study. My results suggest that juvenile aggression and behavioral dominance is not the mechanism 0. rusticus uses to outcompete 0. virilis, therefore, other life history and ecological mechanisms should be explored.