Estrelita and Nui in particular were friendly, confident turtles when we first met them. They would rest closely alongside other turtles. Once the tails lengthened, they began to rest off on their own, in sight of other turtles but never as close as they did during their pre-sexual maturity years. We know that these three turtles also prefer resting by themselves away from others. Females, for whatever reason, enjoy clustering.
Males seem less inclined to do so.
When we see a group of 3-6 turtles all touching or piled one atop another, they are typically all females and juveniles. Last year, we noticed a shift in the behaviour of Goofyfoot , a turtle we have known since 1992 and one we have been calling a female. Goofyfoot began behaving more aggressively, particularly to us. Even when we weren't in one of her resting spots, she would sometimes hover over us, prompting us to move. Several times, when we were absorbed with photography, Goofyfoot sneaked up behind us and nipped our flippers.