Sure, sure, sure…you immediately think I’m talking about the Lion King. While that number is a good one- in both the film and stage version of the show- it’s not what I’m talking about. The circle that I’m talking about today is one that you can still see in Little Sugar Creek at Freedom Park. Well, you can see these circles on days when it hasn’t rained. These circles are produced by sunfish- and by males, in particular.
The male sunfish finds a good spot in the stream and clears it out, moving small rocks and algae, and builds a slight depression in the sand. Females can then come by and deposit eggs into the nest that the male fertilizes. So these circles are, in fact, little nurseries where the babies develop. The females? They take off after dumping their eggs. In sunfish, it’s the male who sticks around to guard and fan the eggs in the nest. He even puts himself at risk of predation because a male in the center of one of these circles is really quite visible to predatory birds.
If you take a minute to watch these fish, it’s easy to spot the male in the center of the circle, but it takes a minute for your eyes to adjust to see the other fish swimming around the edge. Some of these fish are probably females, but some are most certainly other, smaller males who can’t defend their own circle and who play a different strategy in the wild. These males are known as cuckolders. They hang out near a parental male and when females come in to dump their eggs, they rush in to deposit sperm before being chased off by the big male.
Gross, M.R. 1991. Evolution of alternative reproductive strategies: Frequency-dependent sexual selection in male Bluegill Sunfish. Philosophical Transactions of the Royal Society of London B. 332: 59-66.