How we cite our quotes: (Line)
Quote #4
To a coarse croaking that I had not heard
before. The air was thick with a bass chorus. (25–26)
The frogs' croaking is part of showing off for female companions. Is there anything hotter than a baritone croak? Not for lady frogs, there isn't. The fact that the speaker hadn't heard it before might be Heaney's sly way of saying that he's naïve when it comes to sex (both about the frogs, and potentially about humans, too).
Quote #5
Right down the dam gross-bellied frogs were cocked
On sods; their loose necks pulsed like sails. Some hopped (27–28)
Again, this is the bullfrogs' display. To get in good with the ladies, they slap around and make a lot of noise. The boy, however, is disgusted by the show and makes a break for it. Is this when he makes the connection between the gross display and sex? Who knows. Regardless, this show makes a profound impact on him.