A new device for monitoring gastric pH in free-ranging animals

An autonomous stomach probe for the measurement of gastric pH and temperature in free-ranging animals is presented. The probe was successfully deployed in four species of penguins and measured pH for periods of up to 10 days under fluctuating pressure conditions. The resolution of pH was better than 0.1 pH units, and the absolute accuracy was on average better than 0.25 pH units for deployment in Pygoscelis penguins and better than 0.1 pH units in Spheniscus penguins. Stomach pH in chickrearing penguins was highly flexible, with values ranging from below pH 2 to virtually neutral, allowing the birds to adjust the rate of digestion to the prevailing demands.