Gaits at high speed in free ranging cursorial mammals

Terrestrial mammals with vertically oriented limbs moving in a parasagittal plane, and generally larger than 1 kg of body mass, are defined “cursorial”. Most of them belong to the orders Carnivora, Artiodactyla and Perissodactyla, which comprehend the fastest terrestrial mammals: the cheetah, the fastest land animal on sprint, and the pronghorn, the fastest land animal on long distance. Cursorial mammals can be preys or predators, living in open or mixed habitats and different terrains. We investigated the two high-speed gait used by cursorial species, transverse and rotary gallop, from both biomechanical and functional point of view. In transverse gallop the placement of the second hind foot is followed by that of the controlateral forefoot, while in rotary gallop it is followed by the ipsilateral forefoot, and the sequence of footfalls appears to rotate around the body. 351 sequences, filmed in the wild, have been analysed to assess the gallop type of 89 investigated mammal species belonging to the three mentioned orders. Biometrical, ecological and physiological parameters have been collected for each species both from literature data and from experimental measures. Non-parametrical statistical analyses, using 10000 sampled tables with Monte Carlo simulation, indicated that transverse “horse-like” gallop was significantly more frequent in diurnal, gregarious species that live in open habitats, such as grasslands and plains. Rotary “cheetah-like” gallopers resulted significantly more frequent among crepuscular, solitary predator species that live in more mixed habitats. Around 20% of the investigated species, mainly canids, pronghorns and some antelopes, performed transverse gallop at slow speed and rotary gallop at higher speed. Our results indicated a strictly relationship among body shape, gait, speed and manoeuvrability. Rotary gallop, gait adopted by the majority of fast-running mammals, gives also the advantage of higher manoeuvrability at any speed, especially useful when running on rugged terrains in mixed habitats. Larger bodies advantage species that live in open habitat, like grasslands and deserts, with the consequences of less agility and less spine flexibility. Among these species transverse gallop is prevailing. Some gregarious preys and cooperative predators, which live in grasslands and savannahs, have to balance the needs for high endurance, strength and longer limbs to run faster. More likely they show a speed dependent gallop pattern.