Intraspecific aggression and competition can govern access to food and shelter in many marine organisms, but these interactions can be impacted by life stage and presence of predators. Juvenile lobsters (Homarus americanus) have social hierarchies that govern access to valuable resources like food and shelter, but these hierarchies could be impacted by the presence of invasive green crabs (Carcinus maenas). The goal of this study was to determine whether the presence of green crab effluent affected aggressive behavior in different sizes of juvenile lobsters, with the hypothesis that all juvenile lobsters would be more likely to share shelter under threat of predation. Small juveniles (15 mm carapace length) and larger juveniles (45 mm) had substantially different interactions and responses to predator threat cues, with small individuals more likely to both fight over shelter and share shelter when exposed to green crab effluent. There were also several size-based behavioral differences in control treatments, as small juvenile lobsters challenged each other more frequently for shelter and spent vastly more time in the shelter, less time stationary outside the shelter, and less time fighting. Despite being vulnerable to green crab predation, larger juvenile lobsters were generally unaffected by crab chemical cues. This suggests that life history plays a strong role in predator avoidance behavior and that both lethal and nonlethal effects of invasive species on native prey can vary markedly with life stage. Future research should examine these crab-lobster interactions in lobster nursery habitats in the field, as invasive green crabs in these habitats could change behavior, activity patterns and survival of juvenile lobsters.

种内侵略和竞争可以控制许多海洋生物获得食物和庇护所的途径，但这些相互作用可能受到生命阶段和掠食者的存在的影响。少年龙虾（Homarus americanus）的社会等级制度控制着对诸如食物和庇护所等宝贵资源的获取，但是这些等级制度可能会受到侵入性绿色螃蟹（Carcinus maenas）的影响。）。这项研究的目的是确定青蟹流出物的存在是否会影响不同大小的龙虾的攻击行为，并假设所有的龙虾在捕食威胁下都更有可能共享庇护所。小型幼体（甲壳长15毫米）和大型幼体（45毫米）对捕食者威胁线索的相互作用和反应有很大不同，小型个体在暴露于青蟹流出物时更有可能争夺庇护所并共享庇护所。在控制治疗中，还存在基于大小的行为差异，因为小龙虾更经常相互挑战以寻求庇护所，并且在庇护所中花费的时间更多，在庇护所外面停留的时间更少，战斗时间也更少。尽管容易受到青蟹的捕食，较大的少年龙虾通常不受螃蟹化学提示的影响。这表明生活史在避免捕食者行为中起着重要作用，而且入侵物种对本地猎物的致死和非致死作用都可能随着生命阶段而显着变化。未来的研究应在田间龙虾苗圃栖息地中研究这些蟹-龙的相互作用，因为这些栖息地中的侵入性绿蟹可能会改变幼龙虾的行为，活动模式和生存。