Homing behaviors are seen across the animal kingdom, with the magnitude and scale of these movements varying to a great degree. Invertebrates, such as crayfish, prove to be excellent models for comparative research, with relatively simple nervous systems that have been extensively studied combined with a rich behavioral repertoire that has been well documented. Here we explore whether two crayfish species (a primary burrower and a tertiary burrower) can home to artificial burrows and if so, whether their homing abilities differ. The two species of crayfish, Orconectes rusticus and Fallicambarus fodiens, were examined for their ability to home to artificial burrows in a laboratory setting. Animals were placed in a homing arena, motivated to search by the presence of food, and subsequently return to the burrows. The movements of each individual crayfish were digitized and analyzed for changes in walking speed, velocity and heading angle relative to burrows, total distance travelled and path turning angles. Crayfish of both species successfully returned home, although F. fodiens had a higher homing success rate than O. rusticus. Detailed kinematic analysis showed that walking speeds almost doubled during homing to burrows and heading angles were significantly closer to zero than on the outward journeys for both species. Path turning angles were significantly lower for O. rusticus than for F. fodiens. These findings indicate that these species of crayfish can successfully home without the visual landmark of burrow chimneys and that the primary burrower (F. fodiens) appears to be more successful with straighter return paths. The differences in these two species to home and the underlying mechanisms of homing may be due to the differences in burrow use with primary burrowers showing more efficient homing than tertiary burrowers.

Salmon straying is often defined as the failure of adults to return to their natal river system. However, straying within a river basin can be problematic if hatchery salmon do not return to their hatchery of origin and subsequently spawn in the wild with natural-origin salmon. We examined within-river straying patterns from 34 years of coded-wire tag data, representing 29 941 hatchery fall Chinook salmon (Oncorhynchus tshawytscha) in the Elk River, Oregon, USA. Using classification tree analysis, we found that females and larger salmon were more likely to be recovered on the spawning grounds than males and smaller fish. Females larger than 980 mm had a 51.6% likelihood of recovery on the spawning grounds rather than at the Elk River Hatchery. Our findings raise questions about the behavior of straying adults and implications for management of these stocks, with a focus on methods to reduce within-river straying. We recommend further studies to determine whether carcass recoveries are fully representative of hatchery salmon that stray within the Elk River basin.

Crayfishes are an excellent model for examining complex behaviors such as homing. We examined homing behaviors in two species of crayfish. Individuals of Creaserinus fodiens (Cottle, 1863), a primary burrower, and Faxonius rusticus (Girard, 1852), a tertiary burrower, were placed in an arena with artificial burrows embedded within a rotating disk. The disks allowed for the displacement of burrows by 90° relative to the original location. Individuals were motivated to perform search behavior with the presence of food. The burrows were displaced once individuals had left the burrows and their return pathways were examined. The paths were digitized and analyzed for kinematic parameters. Crayfishes in the control group located the burrows successfully but individuals in the experimental group (displaced burrow) were unable to locate the burrows successfully. There were significant differences (P = 0.001) between the control and treatment groups in heading angles relative to burrow on the return trip, with the heading angles of the control group being significantly lower (P = 0.0003). There were species-specific differences in velocity toward the burrow, with the primary burrower being more negatively impacted by the displacement. The results confirm that the effect of burrow displacements severely impacts homing success in both species and a local cue associated with the burrow is not utilized in homing. We demonstrate that there are no significant species-specific differences in homing behavior.

Many adult hatchery‐origin Pacific salmon Oncorhynchus spp. return to their natal river but do not enter the hatchery, instead spawning in the river, where they can have detrimental genetic and ecological effects on naturally reproducing wild populations. This phenomenon is especially well documented in Elk River (Oregon) Chinook Salmon O. tshawytscha based on previous analyses of coded wire tag recoveries. Here, we used radio tags to compare the movements of natural‐ and hatchery‐origin Chinook Salmon (n = 11 and 15, respectively) to determine whether their behavior could explain the in‐river straying patterns of hatchery salmon. Most of the tagged hatchery‐origin (87%) and natural‐origin (73%) adults initially moved upriver to the vicinity of the Elk River Hatchery. Most natural‐origin adults then moved downstream of the hatchery entrance to spawn, but the movements of hatchery‐origin adults were different. Hatchery‐origin males and females had the highest and lowest variation in total distance moved, respectively. Our results are consistent with the hypothesis that while most hatchery‐origin salmon return to the vicinity of the hatchery, some fail to enter, perhaps because the hatchery’s odors were not perceived as distinct from those of the river or (in the case of hatchery‐origin males) because they stopped short of the hatchery after encountering spawning conspecifics. Thus, spawning distributions may not always reflect in‐river movements of Chinook Salmon, and we encourage fisheries managers to continue investigating methods that reduce potentially harmful interactions between hatchery‐ and natural‐origin fish.