Exploring the limits to turning performance with size and shape variation in dogs.

Manoeuvrability, the ability to make rapid changes in direction, is central to animal locomotion. Turning performance may depend on the ability to successfully complete key challenges including: withstanding additional lateral forces, maintaining sufficient friction, lateral leaning during a turn and rotating the body to align with the new heading. We filmed high-speed turning in domestic dogs (Canis lupus familiaris) to quantify turning performance and explore how performance varies with body size and shape. Maximal speed decreased with higher angular velocity, greater centripetal acceleration and smaller turning radii, supporting a force limit for wider turns and a friction limit for sharp turns. Variation in turning ability with size was complex: medium sized dogs produced greater centripetal forces, had relatively higher friction coefficients, and generally aligned the body better with the heading compared with smaller and larger bodied dogs. Body shape also had a complex pattern, with longer forelimbs but shorter hindlimbs being associated with better turning ability. Further, although more crouched forelimbs were associated with an increased ability to realign the body in the direction of movement, more upright hindlimbs were related to greater centripetal and tangential accelerations. Thus, we demonstrate that these biomechanical challenges to turning can vary not only with changes in speed or turning radius, but also with changes in morphology. These results will have significant implications for understanding the link between form and function in locomotory studies, but also in predicting the outcome of predator-prey encounters.

Quantifying koala locomotion strategies: implications for the evolution of arborealism in marsupials.

The morphology and locomotor performance of a species can determine their inherent fitness within a habitat type. Koalas have an unusual morphology for marsupials, with several key adaptations suggested to increase stability in arboreal environments. We quantified the kinematics of their movement over ground and along narrow arboreal trackways to determine the extent to which their locomotion resembled that of primates, occupying similar niches, or basal marsupials from which they evolved. On the ground, the locomotion of koalas resembled a combination of marsupial behaviours and primate-like mechanics. For example, their fastest strides were bounding type gaits with a top speed of 2.78 m s-1 (mean 1.20 m s-1), resembling marsupials, while the relatively longer stride length was reflective of primate locomotion. Speed was increased using equal modification of stride length and frequency. On narrow substrates, koalas took longer but slower strides (mean 0.42 m s-1), adopting diagonally coupled gaits including both lateral and diagonal sequence gaits, the latter being a strategy distinctive among arboreal primates. The use of diagonally coupled gaits in the arboreal environment is likely only possible because of the unique gripping hand morphology of both the fore and hind feet of koalas. These results suggest that during ground locomotion, they use marsupial-like strategies but alternate to primate-like strategies when moving amongst branches, maximising stability in these environments. The locomotion strategies of koalas provide key insights into an independent evolutionary branch for an arboreal specialist, highlighting how locomotor strategies can convergently evolve between distant lineages.

Resting disparity in quoll semelparity: examining the sex-linked behaviours of wild roaming northern quolls (Dasyurus hallucatus) during breeding season.

Semelparity is a breeding strategy whereby an individual invests large amounts of resources into a single breeding season, leading to the death of the individual. Male northern quolls (Dasyurus hallucatus) are the largest known mammal to experience a post-breeding die-off; however, the cause of their death is unknown, dissimilar from causes in other semelparous dasyurids. To identify potential differences between male northern quolls that breed once, and females that can breed for up to four seasons, the behaviours, activity budgets, speeds and distances travelled were examined. Northern quolls were captured on Groote Eylandt off the coast of the Northern Territory, Australia, and were fitted with accelerometers. A machine learning algorithm (Self-organizing Map) was trained on more than 76 h of recorded footage of quoll behaviours and used to predict behaviours in 42 days of data from wild roaming quolls (7M : 6F). Male northern quolls were more active (male 1.27 g, s.d. = 0.41; female 1.18 g, s.d. = 0.36), spent more time walking (13.09% male: 8.93% female) and engaged in less lying/resting behaviour than female northern quolls (7.67% male: 23.65% female). Reduced resting behaviour among males could explain the post-breeding death as the deterioration in appearance reflects that reported for sleep-deprived rodents.

Quantifying finer-scale behaviours using self-organising maps (SOMs) to link accelerometery signatures with behavioural patterns in free-roaming terrestrial animals.

Collecting quantitative information on animal behaviours is difficult, especially from cryptic species or species that alter natural behaviours under observation. Using harness-mounted tri-axial accelerometers free-roaming domestic cats (Felis Catus) we developed a methodology that can precisely classify finer-scale behaviours. We further tested the effect of a prey-protector device designed to reduce prey capture. We aligned accelerometer traces collected at 50 Hz with video files (60 fps) and labelled 12 individual behaviours, then trained a supervised machine-learning algorithm using Kohonen super self-organising maps (SOM). The SOM was able to predict individual behaviours with a ~ 99.6% overall accuracy, which was slightly better than for random forest estimates using the same dataset (98.9%). There was a significant effect of sample size, with precision and sensitivity decreasing rapidly below 2000 1-s observations. We were also able to detect a behaviour specific reduction in the predictability when cats were fitted with the prey-protector device indicating it altered biomechanical gait. Our results can be applied in movement ecology, zoology and conservation, where habitat specific movement performance between predators or prey may be critical to managing species of conservation significance, or in veterinary and agricultural fields, where early detection of movement pathologies can improve animal welfare.