The Influence of Snow Properties on Speed and Gait Choice in the Svalbard Rock Ptarmigan (Lagopus muta hyperborea)

Abstract

Substrate supportiveness is linked to the metabolic cost of locomotion, as it influences the depth to which the foot of a moving animal will sink. As track depth increases animals typically reduce their speed to minimise any potential energetic imbalance. Here we examine how self-selected speed in the Svalbard rock ptarmigan is affected by snow supportiveness and subsequent footprint depth measured using thin-blade penetrometry and 3D photogrammetry, respectively. Our findings indicate that snow supportiveness and footprint depth are poor predictors of speed (r2 = 0.149) and stride length (r2 = 0.106). The ptarmigan in our study rarely sunk to depths beyond the intertarsal joint, regardless of the speed, suggesting that at this relatively shallow depth any increased cost is manageable. 3D reconstructions also indicate that the ptarmigan may exploit the compressive nature of snow to generate thrust during stance, as a trend towards greater foot rotations in deeper footprints was found. It remains unclear if the Svalbard ptarmigan are deliberately avoiding unsupportive snowy substrates. However, if they do, these results would be consistent with the idea that animals should choose routes that minimise energy costs of locomotion. Resumen La firmeza del sustrato se asocial al costo metabólico de la locomoción ya que influencia cuán profundo las extremidades de un animal se hunden al moverse. A medida hundimiento aumenta, usualmente los animales reducen su velocidad para minimizar potenciales desbalances energéticos. En este estudio examinamos cómo la velocidad de la perdiz de la roca de Svalbard es afectada por la firmeza del sustrato y la profundidad de hundimiento de sus patas, usando penetrometría y fotogrametría 3D, respectivamente. Nuestros resultados indican que la firmeza de la nieve y la profundidad de hundimiento de las patas no son buenos predictores de la velocidad (r2 = 0.149) y de la longitud de la zancada (r2 = 0.106). La profundidad de las huellas de las perdices de nuestro estudio rara vez sobrepasó la altura de la articulación intertarsal, independientemente de la velocidad de locomoción, sugiriendo que a profundidades relativamente menores los costos energéticos son manejables. Las reconstrucciones 3D también indican que las perdices podrían aprovechar la naturaleza compresiva de la nieve para generar suficiente empuje durante la fase de soporte, ya que se encontró una tendencia hacia mayores rotaciones de la pata en huellas más profundas. Es incierto si las perdices de Svalbard deliberadamente evitan áreas con nieve más blanda. Sin embargo, si lo hacen, estos resultados serían consistentes con la idea de que los animales deberían seleccionar rutas que minimizan los gastos energéticos en locomoción.

A Biomorphic Approach to Designing Special-Purpose Vehicles for Arctic Conditions

“…A similar mechanism of a “snowshoe” foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine ( Figure 3 ), and polar bear [ 34 , 35 , 36 ].…”

“…Additionally, they have stiff hair in the interdigital space between their hooves, which is constantly under tension and bent along the radius, which helps break off ice formations on their hooves. A similar mechanism of a "snowshoe" foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine (Figure 3), and polar bear [34][35][36]. A similar mechanism of a "snowshoe" foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine (Figure 3), and polar bear [34][35][36].…”

“…A similar mechanism of a "snowshoe" foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine (Figure 3), and polar bear [34][35][36]. A similar mechanism of a "snowshoe" foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine (Figure 3), and polar bear [34][35][36]. A similar mechanism of a "snowshoe" foot for moving over unsupportive snow is also present in other Arctic animals, e.g., lynx, ptarmigan, wolverine (Figure 3), and polar bear [34][35][36].…”