Dolphins maintain cognitive performance during 72 to 120 hours of continuous auditory vigilance

Abstract

The present study reports the first use of a choice visual-vocal response time cognitive task, during 72 or 120 h of continuous auditory vigilance. Two adult bottlenose dolphins (Tursiops truncatus), NAY (male) and SAY (female), maintained a very high detection rate (91.1-98.7%) of random 1.5 s goal tones infrequently substituted in a background of frequent 0.5 s equal-amplitude tones over continuous 72 or 120 h sessions. In addition, a choice visual-vocal response time task (CVVRT) tested cognitive performance during night time sessions, when the dolphins would have ordinarily been resting or asleep as we had observed in previous studies. NAY and SAY detected a single-bar, posterior, vertical, green (S1g) or 3-bar, anterior, horizontal, red (S2r) LED light stimulus presented randomly to each eye. They responded with a different vocalization (whistle or pulse burst) to each stimulus (S1g or S2r) presented randomly to left and right eyes. The animals maintained high levels of goal tone detection without signs of sleep deprivation as indicated by behavior, blood indices or marked sleep rebound during 24 h of continuous post-experiment observation. Acoustic goal tone response time (AGTRT) overall did not change during the 72 h (F=0.528, P=0.655) or 120 h (F=0.384, P=0.816) sessions. Nor did CVVRT slow or degrade over the 72 h (F=4.188, P=0.104) or 120 h (F=2.298, P=0.119) AGTRT sessions.