Elephants are widely assumed to be among the most cognitively advanced animals, even though systematic evidence is lacking. This void in knowledge is mainly due to the danger and difficulty of submitting the largest land animal to behavioral experiments. In an attempt to change this situation, a classical 1930s cooperation paradigm commonly tested on monkeys and apes was modified by using a procedure originally designed for chimpanzees ( Pan troglodytes ) to measure the reactions of Asian elephants ( Elephas maximus ). This paradigm explores the cognition underlying coordination toward a shared goal. What do animals know or learn about the benefits of cooperation? Can they learn critical elements of a partner's role in cooperation? Whereas observations in nature suggest such understanding in nonhuman primates, experimental results have been mixed, and little evidence exists with regards to nonprimates. Here, we show that elephants can learn to coordinate with a partner in a task requiring two individuals to simultaneously pull two ends of the same rope to obtain a reward. Not only did the elephants act together, they inhibited the pulling response for up to 45 s if the arrival of a partner was delayed. They also grasped that there was no point to pulling if the partner lacked access to the rope. Such results have been interpreted as demonstrating an understanding of cooperation. Through convergent evolution, elephants may have reached a cooperative skill level on a par with that of chimpanzees.

Objective: To describe the clinical characteristics and outcomes in a population of dogs with negative-pressure pulmonary edema (NPPE) and to identify the main causes of the disease. To evaluate any associations with morbidity and mortality.Design: Retrospective study.Setting: Three university teaching hospitals and two private referral centers.Animals: Thirty-five client-owned dogs presented with NPPE. Interventions: NoneMeasurements and Main Results: Data collected included patient characteristics, clinical history, clinicopathological abnormalities, radiographic features, treatments and outcome. Median age was 4 months (range 2-90) and median weight was 7.1 kg (range 1.7-37.2). There were many causes of NPPE including leash tugs, near hanging, accidental choking, anatomical obstruction to airflow and purposeful airway obstruction by people. The most common cause of NPPE was accidental choking (40% of cases). Dogs with an anatomical obstruction were older than 24 months. Hypoxemia with an increased alveolar-arterial gradient was common on presentation. The majority of thoracic radiographs (65.7%) showed an alveolar or interstitial pattern in the caudodorsal area as previously described in the literature. Oxygen therapy was administered to 33 (94.3%) dogs. Furosemide was administered to 18 (51.4%) dogs. Median length of hospitalization was 2 days (range 0-14). Twenty-eight (80%) dogs survived to discharge. Seven dogs were mechanically ventilated and only 2 of them (28.6%) 2 survived to discharge. Requirement for mechanical ventilation (p<0.001) was the only parameter associated with mortality.Conclusions: Most cases of NPPE occur in juvenile dogs. Different incidents associated with upper airway obstruction can produce an episode of NPPE.Choking on food or toys and near hanging have not been previously described in the veterinary literature as inciting causes of NPPE. The overall prognosis is good.

The structure and motion of elephant limbs are unusual compared with those of other animals. Elephants stand and move with straighter limbs (at least when walking), and have limited speed and gait. We devised novel experiments to examine how the limbs of elephants support and propel their mass and to explore the factors that may constrain locomotor performance in these largest of living land animals. We demonstrate that elephant limbs are remarkably compliant even in walking, which maintains low peak forces. Dogma defines elephant limbs as extremely "columnar" for effective weight support, but we demonstrate that limb effective mechanical advantage (EMA) is roughly one-third of that predicted for their size. EMA in elephants is actually smaller than that in horses, which are only one-tenth their mass; it is comparable to human limb values. EMA drops sharply with speed in elephants, as it does in humans. Muscle forces therefore must increase as the limbs become more flexed, and we show how this flexion translates to greater volumes of muscle recruited for locomotion and hence metabolic cost. Surprisingly, elephants use their forelimbs and hindlimbs in similar braking and propulsive roles, not dividing these functions among limbs as was previously assumed or as in other quadrupeds. Thus, their limb function is analogous to fourwheel-drive vehicles. To achieve the observed limb compliance and low peak forces, elephants synchronize their limb dynamics in the vertical direction, but incur considerable mechanical costs from limbs working against each other horizontally.lephants have unusual limb structure and function. They use walking footfall patterns, have seemingly straightened limbs, and lack an aerial phase in their stride throughout their speed range (1-7). However, at faster speeds, they switch to biomechanical running (i.e., bouncing; refs. 8, 9), without a discrete gait transition (4-7, 10). Elephants also seem unable to exceed speeds of ∼7 ms −1 (15 mph) (1-5). These odd features relate to elephants' massive size and thus have broader comparative relevance, but they remain unexplored in a deeper biomechanical context. These features suggest that elephants do not use their limbs in the same mechanical ways as typical quadrupeds do, perhaps involving considerable limb compliance (11-13). In the present study, we examined how elephant forelimbs and hindlimbs function across a wide range of speeds, and compared these mechanical functions with those of other animals.Furthermore, elephants are particularly relevant to a major biomechanical concept regarding the relationship of body size and the limbs' effective mechanical advantage [EMA; the amount of ground reaction force (GRF) generated at the foot per unit muscle force, or simply "overall leverage"] (Fig. 1A). EMA is proportional to the moment arm of each joint's muscle force divided by the moment arm of the GRF about that joint (14-16). Larger animals tend to increase their EMA mainly by straightening their limbs, thereby reducing GRF moment arms. This helps ...

SUMMARYElephants are the biggest living terrestrial animal, weighing up to five tons and measuring up to three metres at the withers. These exceptional dimensions provide certain advantages (e.g. the mass-specific energetic cost of locomotion is decreased) but also disadvantages (e.g. forces are proportional to body volume while supportive tissue strength depends on their cross-sectional area, which makes elephants relatively more fragile than smaller animals). In order to understand better how body size affects gait mechanics the movement of the centre of mass (COM) of 34 Asian elephants (Elephas maximus) was studied over their entire speed range of 0.4-5.0ms -1 with force platforms. The mass-specific mechanical work required to maintain the movements of the COM per unit distance is ~0.2Jkg . At high speeds, elephants use a bouncing mechanism with little exchange between kinetic and potential energies of the COM, although without an aerial phase. Elephants increase speed while reducing the vertical oscillation of the COM from about 3cm to 1cm.

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