Platypus Physiology

• The Platypus´s bill is sensitive to small electrical fields. The animal uses the electrosensitivity to locate the source of foodstuffs on the bottom of lakes and rivers. Being mostly nocturnal, the animal closes its eyes, ears and nostrils while foraging under water. It sweeps its bill from side to side 2 to 3 times a second, possibly sensing the weak electric fields generated when water flows over stationary objects, and thus obtaining an electric image of the river bed.
  
  
• The Platypus has an euthermic body temperature of 31-32 degrees C that can be maintained over an ambient air temperature range of 0.5 - 25 degrees C. A zone of thermal neutrality was found to exist between 15 and 25 degrees C (Smyth, 1972).
  
  
• It has a BMR about 70% of that predicted for a eutherian of the same size (Dawson et al, 1979). The minimum resting metabolism in air is 2.0 W/kg at an ambient temperature of 25 degrees C (Grant & Dawson, 1977).
  
  
• Platypus spend long periods (up to 7 hours) continuously foraging in water at nearly 0 degrees C (Grant 1984). Compared to other aquatic endotherms of similar size, the platypus is extremely well adapted to minimise energy loss under these conditions. Grant and coworkers have shown that Tb does not fall significantly during immersion in water at 5 degrees C (Grant & Dawson 1978, Grant 1983, Grigg et al 1992), while metabolic rate is raised to only 3.2 times the resting level (Grant & Dawson 1978).
  
  
• The Platypus is generally regarded as nocturnal and shows a distinct daily cycle. No evidence of hibernation or even brief periods of tropor have been found (Grigg et al., 1992).
  
  
• Reports of the diving ability of the Platypus differ. Most dives in the laboratory were between 30 s and 4 min duration, and heart rate fell in all dives, from per-dive rates of 140-230 to 10-120 beats/min (Evans et al., 1994). However, foraging trips in the wild consist of repeated dives of between 20 and 90 seconds duration, separated by 10 to 20 seconds on the surface (Grant, 1981, Kruuk, 1993, Gust & Handasyde, 1995).