Lava lizards, native to the Galápagos Islands, exhibit sexual dimorphism, where distinct differences exist between males and females of the same species. These variations play roles in their daily survival and reproductive strategies. The physical and behavioral distinctions between male and female lava lizards are key to understanding their lives in this archipelago.
Physical Distinctions
Male lava lizards are generally larger and more robust than females, often reaching lengths of 15 to 25 centimeters, while females typically measure 12 to 20 centimeters. Males can also be two to three times heavier. Males possess a distinct spinal crest along their backs, composed of keeled scales, and often have considerably larger heads. Their skin may also appear rougher with more patterning.
Coloration provides another clear distinction between the sexes. Males display brighter, more vivid hues, including yellow specks, gold stripes, and black and yellow throats. Females have more subdued body colors but are recognized by a distinct red or orange flush on their throats or heads. This red coloration often becomes more pronounced during the breeding season.
Behavioral Differences
Male lava lizards exhibit pronounced territorial behaviors, often defending areas as large as 400 square meters. These territories frequently encompass the home ranges of several females. To assert dominance and ward off rival males, they perform displays such as head bobs and “push-ups.” If these warnings are insufficient, interactions can escalate to tail slapping and biting.
Females, while generally less territorial than males, also engage in push-up displays to protect their immediate areas. During the breeding season (November to March), male territorial displays intensify. Males actively seek to mate with and guard females entering their territory. After mating, female lava lizards lay clutches of three to six pea-sized eggs in deep burrows, with no further parental care. Females reach sexual maturity at nine months, while males mature later, at three years of age.
The Purpose of These Differences
The physical and behavioral differences in lava lizards are linked to evolutionary pressures, particularly sexual selection. Larger size and vibrant coloration in males are favored traits, signaling fitness and strength to potential mates. Females may prefer larger or more colorful males, indicating a higher quality mate. Color differences, especially in the ventral regions, are crucial for sexual displays and communication.
Male size and aggression are related to their ability to defend prime territories. A larger male can secure areas rich in resources like sunning spots and food, providing greater access to females. Push-up displays exaggerate a male’s size, deterring rivals without direct conflict. For females, subdued coloration offers better camouflage, protecting them from predators, especially during nesting. These distinct traits contribute to the successful reproduction and survival of lava lizards in their unique island habitats.