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Long-distance transequatorial navigation using sequential measurements of magnetic inclination angle.

ABSTRACT: Diverse taxa use Earth's magnetic field in combination with other sensory modalities to accomplish navigation tasks ranging from local homing to long-distance migration across continents and ocean basins. Several animals have the ability to use the inclination or tilt of magnetic field lines as a component of a magnetic compass sense that can be used to maintain migratory headings. In addition, a few animals are able to distinguish among different inclination angles and, in effect, exploit inclination as a surrogate for latitude. Little is known, however, about the role that magnetic inclination plays in guiding long-distance migrations. In this paper, we use an agent-based modelling approach to investigate whether an artificial agent can successfully execute a series of transequatorial migrations by using sequential measurements of magnetic inclination. The agent was tested with multiple navigation strategies in both present-day and reversed magnetic fields. The findings (i) demonstrate that sequential inclination measurements can enable migrations between the northern and southern hemispheres, and (ii) demonstrate that an inclination-based strategy can tolerate a reversed magnetic field, which could be useful in the development of autonomous engineered systems that must be robust to magnetic field changes. The findings also appear to be consistent with the results of some animal navigation experiments, although whether any animal exploits a strategy of using sequential measurements of inclination remains unknown.

SUBMITTER: Taylor BK

PROVIDER: S-EPMC7879752 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:BackgroundDifferent theories suggest birds may use compass or map navigational systems associated with Earth's magnetic intensity or inclination, especially during migratory flights. These theories have only been tested by considering properties of the Earth's magnetic field at coarse temporal scales, typically ignoring the temporal dynamics of geomagnetic values that may affect migratory navigational capacity.MethodsWe designed a simulation experiment to study if and how birds use the geomagnetic field during migration by using both high resolution GPS tracking data and geomagnetic data at relatively fine spatial and temporal resolutions in comparison to previous studies. Our simulations use correlated random walks (CRW) and correlated random bridge (CRB) models to model different navigational strategies based on underlying dynamic geomagnetic data. We translated navigational strategies associated with geomagnetic cues into probability surfaces that are included in the random walk models. Simulated trajectories from these models were compared to the actual GPS trajectories of migratory birds using 3 different similarity measurements to evaluate which of the strategies was most likely to have occurred.Results and conclusionWe designed a simulation experiment which can be applied to different wildlife species under varying conditions worldwide. In the case of our example species, we found that a compass-type strategy based on taxis, defined as movement towards an extreme value, produced the closest and most similar trajectories when compared to original GPS tracking data in CRW models. Our results indicate less evidence for map navigation (constant heading and bi-gradient taxis navigation). Additionally, our results indicate a multifactorial navigational mechanism necessitating more than one cue for successful navigation to the target. This is apparent from our simulations because the modelled endpoints of the trajectories of the CRW models do not reach close proximity to the target location of the GPS trajectory when simulated with geomagnetic navigational strategies alone. Additionally, the magnitude of the effect of the geomagnetic cues during navigation in our models was low in our CRB models. More research on the scale effects of the geomagnetic field on navigation, along with temporally varying geomagnetic data could be useful for further improving future models.

Project description:Pelvic sagittal inclination (PSI) is often evaluated in patients with hip pathology using lateral radiographs. However, it would be useful if PSI could be predicted from an anteroposterior radiograph since this film is ubiquitous in the evaluation of hip pathology. Herein, computer-modeling was applied to predict PSI from radiographic measurements assessed in the anteroposterior plane. Three-dimensional surface models of the pelvis, femur, and sacrum were reconstructed from computed tomography images of 50 women with hip dysplasia. This study cohort was selected as changes in PSI alter femoral head coverage, which is relevant to the diagnosis and treatment of hip dysplasia, a known cause of hip osteoarthritis. Five radiographic parameters commonly used to independently estimate PSI were evaluated after bone surfaces were projected to an anteroposterior plane, including the symphysis to sacrococcygeal joint distance (S-S distance), the pelvic foramen aspect ratio (PF ratio), the distance between the symphysis and a line connecting the femoral head centers (S-H distance), the sacro-femoral-pubic angle (SFP angle), and the pelvic vertical ratio (PVR). Regression models determined the ability of these parameters to predict PSI from -20° to 20° at 1° increment. All five parameters showed a strong correlation with the PSI (all r > 0.9). From the regression models, PSI was estimated with a median (maximum) absolute error of 3.6° (18.4°), 3.8° (17.7°), 5.2° (17.9°), 5.8° (28.8°), and 3.2° (23.5°) for the S-S distance, PF ratio, S-H distance, SFP angle, and PVR, respectively. The regression model for S-S distance had a mean slope of 2.18 that ranged from 1.98 to 2.41 when the sacrococcygeal joint was located superior to the symphysis. Results indicated that substantial errors occur when estimating the actual value of PSI from an anteroposterior radiograph. However, the change in PSI could be estimated from the S-S distance, which may aid surgeons to successfully increase head coverage through periacetabular osteotomy and to locate the acetabular cup in a functional position for total hip arthroplasty.

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Long-distance transequatorial navigation using sequential measurements of magnetic inclination angle.

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