Underwater and surface behavior of homing juvenile northern elephant seals

Abstract

SUMMARYNorthern elephant seals, Mirounga angustirostris, travel between colonies along the west coast of North America and foraging areas in the North Pacific. They also have the ability to return to their home colony after being experimentally translocated. However, the mechanisms of this navigation are not known. Visual information could serve an important role in navigation, either primary or supplementary. We examined the role of visual cues in elephant seal navigation by translocating three seals and recording their heading direction continuously using GPS, and acceleration and geomagnetic data loggers while they returned to the colony. The seals first reached the coast and then proceeded to the colony by swimming along the coast. While underwater the animals exhibited a horizontally straight course (mean net-to-gross displacement ratio0.94±0.02). In contrast, while at the surface they changed their headings up to 360deg. These results are consistent with the use of visual cues for navigation to the colony. The seals may visually orient by using landmarks as they swim along the coast. We further assessed whether the seals could maintain a consistent heading while underwater during drift dives where one might expect that passive spiraling during drift dives could cause disorientation. However, seals were able to maintain the initial course heading even while underwater during drift dives where there was spiral motion (to within 20deg). This behavior may imply the use of non-visual cues such as acoustic signals or magnetic fields for underwater orientation.

Identification of animal movement patterns using tri-axial magnetometry

“…Although, to date, magnetometers have been little used in studies of behaviour in this regard (but see [18]) excepting the notable, and increasingly rich, literature of them being used in tandem with gyros and/or accelerometers to dead-reckon (e.g. [29, 32–34]).…”

Can gray seals maintain heading within areas of high tidal current? Preliminary results from numerical modeling andGPSobservations

“…However, little work has been carried out on seals (but see Matsumura et al . ). A number of experiments have been conducted on captive seals in order to test their sensory systems and orientation capacities ( e.g ., Kowalewsky et al .…”

“…Several ideas have been put forwards about marine animals' ability to orientate and navigate at sea (Mills Flemming et al 2006, Lohmann et al 2008, Chapman et al 2011. However, little work has been carried out on seals (but see Matsumura et al 2011). A number of experiments have been conducted on captive seals in order to test their sensory systems and orientation capacities (e.g., Kowalewsky et al 2006, Mauck et al 2008, but such experiments are difficult to conduct on free-ranging seals.…”

Long-Distance Animal Migrations in the Oceanic Environment: Orientation and Navigation Correlates

“…More recently, studies employing special data loggers recording animal headings have provided convincing evidence of a compass orientation in the open sea. Both loggerhead turtles and northern elephant seals have been clearly shown to be able to keep and maintain a given direction while swimming at depth in the open ocean, and to continue to do so even at night, suggesting reliance on a magnetic compass [184][185][186]. us, the evidence derived from these �eld studies, together with the various laboratory �ndings described above, makes it reasonable to assume that one or more biological compasses should be within the orientation tools available for the oceanic travels of marine animals.…”

“…More recently, the homing behaviour aer displacement has been studied in marine turtles and seabirds breeding in oceanic islands, reconstructing the homing paths through satellite telemetry [55,104,[163][164][165][166][167][168]214] or speci�c direction recorders [215]. Isolated offshore displacements have been done with Jackass penguins (Spheniscus demersus; [216]) and northern elephant seals [184,186,217]. e results have shown that displaced animals are mostly able to come back home, even when released from very distant locations [55,163,164,167,168], although they oen follow rather circuitous or nondirect routes [55,[163][164][165][166].…”