Abstract

We observed the behavior of overwintering Smooth Softshell Turtles, Apalone mutica, in an outdoor simulated pond with remote cameras. Submerged overwintering turtles partially buried themselves in a sand/mud substrate where they periodically raised and lowered the posterior portion of their body into the water column in a “push-up” fashion. Push-ups occurred with variable frequency and were similar in appearance and amplitude within and among individual turtles. Push-up frequency was positively correlated with water temperature and was paused more often at lower water temperatures. We also observed push-up behavior of A. mutica under simulated winter conditions in laboratory aquaria. Turtles maintained in water with 95–100% dissolved oxygen content executed push-ups less frequently than turtles in water with lower oxygen content. Our observations of push-up behavior in A. mutica in an outdoor enclosure and laboratory are consistent with a respiratory ventilation function. Softshell turtles, known to be highly intolerant of anoxia, ostensibly sustain aerobic metabolism by creating currents that replenish the oxygen-depleted boundary layer between the turtle's thin vascularized skin and oxygenated water.