An “orientation sphere” visualization for examining animal head movements

Abstract

1. Animal behavior is elicited, in part, in response to external conditions, but understanding how animals perceive the environment and make the decisions that bring about these behavioral responses is challenging.2. Animal heads often move during specific behaviors and, additionally, typically have sensory systems (notably vision, smell, and hearing) sampling in defined arcs (normally to the front of their heads). As such, head-mounted electronic sensors consisting of accelerometers and magnetometers, which can be used to determine the movement and directionality of animal heads (where head "movement" is defined here as changes in heading [azimuth] and/or pitch [elevation angle]), can potentially provide information both on behaviors in general and also clarify which parts of the environment the animals might be prioritizing ("environmental framing").3. We propose a new approach to visualize the data of such head-mounted tags that combines the instantaneous outputs of head heading and pitch in a single intuitive spherical plot. This sphere has magnetic heading denoted by "longitude" position and head pitch by "latitude" on this "orientation sphere" (O-sphere). 4. We construct the O-sphere for the head rotations of a number of vertebrates with contrasting body shape and ecology (oryx, sheep, tortoises, and turtles), illustrating various behaviors, including foraging, walking, and environmental scanning. We also propose correcting head orientations for body orientations to highlight specific heading-independent head rotation, and propose the derivation of O-sphere-metrics, such as angular speed across the sphere. This should help identify the functions of various head behaviors. 5. Visualizations of the O-sphere provide an intuitive representation of animal be-

Pose-gait analysis for cetaceans with biologging tags

“…Unlike the beluga, the dolphin data shown in Figure 9 indicate that the animal rolled all the way around during the studied period. In this regard, the presented orientation sphere, to a degree, resembles the m-sphere generated using magnetometer data in [35] as well as the o-sphere for visualizing animal’s head orientation in [31].…”

“…As the animal changes pose, the amount of the gravitational force measured by each of the component axes of the accelerometer changes in the tag coordinate frame ( A ( tag ) ), but the magnitude of the total signal is constant. We use A ( tag ) , together with the rate of the depth change, to reveal the pattern associated with the animal’s gait, and we refer to the plot as the orientation sphere (Figure 2, to be distinguished from the “orientation sphere” presented in [31] for animal head movement visualization). Even though the animal could be in any pose at a particular time, common characteristics are assumed about the general gait patterns.…”

Viewing animal migration through a social lens

“…using head movement and gaze direction from video footage [73], or through specialized sensors like accelerometers and magnetometers [74]. In addition, acoustic communication is an essential form of information exchange in many species.…”

Certainty and integration of options in animal movement

“…Analogous to the well-established playback experiments for the study of auditory signalling, unmanned autonomous vehicles, robots, or virtual reality can be used to create cues for high-quality physical energy patches where there are none (e.g., [67,68]). This can be paired with monitoring techniques that record an animal's perception of their environment (e.g., gaze direction [69,70] or exposure to sound cues [71]) as well as their movement outputs. Should studies find that social sampling allows animals to make more efficient movement decisions than uninformed individuals, we can quantify the adaptive value of social sampling of the physical energy landscape at an individual level.…”