Weakly electric fish live in a variety of freshwater habitats in Central and South America as well as in Africa. These two geographic variations have evolved separately, dividing the weakly electric fish to two orders: gymnotiformes (Central and South America) and mormyridae (Africa). In both orders the fish are nocturnal, causing their electric organ to be most active at night. The fish tend to live in shallow streams of dark, murky waters. The EOD, therefore, is extremely advantageous because it essentially replaces sight in these low visibility environments. The fish also often hide in the aquatic plant life. For example, in autumn, when the leaves fall, the fish often clump together in groups amongst the debris. They will rarely swim in open water, especially during the day. In general, females tend to be more site-retentive, while males are more mobile. In a study with the Panamanian gymnotid Hypopomus Occidentalis, conducted by Mary Hagedorn, 90% of the marked females were recaught at the same sites, while only 50% of marked males were recaptured. In most species, courtship occurs in the transition between the wet and dry seasons, and breeding continues throughout the dry season. Juveniles and adults are classified by their length, yet this type of classification varies between species.