Sexual selection in amphibians

Sexual selection in amphibians involves sexual selection processes in amphibians, including frogs, salamanders and newts. Many frog species have regular breeding seasons. During these times, males gather by the water and make many different kinds of calls to attract females. The strongest males usually have the deepest calls and the best spots, and females often choose their mates based on these calls.

In salamanders and newts, males compete directly for the attention of females. They perform special courtship behaviors to keep a female’s interest long enough to mate. In some species, males can store sperm for a long time during the breeding season, which might help them succeed in mating by interacting with other sperm from rival males. This competition and choice lead to differences between males and females in size and behavior, known as sexual dimorphism.

Selection in salamanders

In salamanders, males show special behaviors to attract females. These include standing alert, chasing after females, leaving scent trails, and moving their tails in certain ways. Males may release special chemicals called pheromones to catch a female’s attention and increase their chance of reproductive success. For example, in the red-legged salamander, males put these chemicals directly on the female’s nose, while in the smooth newt, males wave their tails to send the chemicals to the female.

Females choose mates based on traits like body size, which shows health and good genes. Larger males tend to have more success in fathering offspring. Sometimes, males may try to mate forcefully, but this is not the main way salamanders choose partners. Females also have ways to control which sperm fertilizes their eggs, storing sperm in special glands until they are ready.

Vocal signaling in frogs

Male frogs use special calls to attract females and show they are ready to mate. These calls help females recognize the right species and choose a mate. For example, some females like long calls, while others prefer short, quick calls.

When a female shows interest, male frogs change their calls to become more attractive. They might call more often or use different sounds. Some frogs even change their body movements to catch a female’s attention. Making these calls uses a lot of energy, so the strongest males can call the longest and loudest. They have special vocal sacs and strong muscles to help them make these calls.

Polygynandry in frogs

Females and males of many frog species breed with multiple partners. This means a female frog might mate with several males at different times, which helps ensure her eggs are fertilized even if some males are not the best parents. This behavior also helps protect her offspring from risks like bad weather or predators.

In some frogs, males help take care of the young, carrying tadpoles to safe water. By mating with more than one male, females increase the chances that at least some of her offspring will survive. Some males try to mate by pushing other males away or leaving early, which can also lead to females mating with multiple partners. This strategy helps females protect their eggs from failing to develop.

Dimorphism and morphology

Sexual dimorphism refers to size differences between male and female amphibians. In many salamanders and frogs, females are larger because they need to carry more eggs. This helps them produce more offspring.

Size also matters in male competitions. Bigger males often win because they can defend their spots better. Some frogs, like the tusked frog and fanged frog, even have special weapons to fight off rivals. However, not all frogs follow this pattern, as some smaller males use clever tricks to find mates instead.

Sexual role reversal in Dendrobates auratus

In the green poison-dart frog Dendrobates auratus, scientists noticed something interesting about how males and females behave during mating. Usually, in many animals, males compete for females, but in this frog, it seemed like the roles might be reversed. Researchers tested two ideas: one that the roles were truly reversed, and another that females were looking for the best fathers.

They found that while females did sometimes compete, males also competed for mates. However, females were more careful in choosing their partners, likely because they wanted males who would take good care of their young. Females even tried to keep their chosen males from mating with others and sometimes destroyed other eggs to make sure their own young were cared for. This behavior supports the idea that females were seeking the best parental care rather than a true role reversal.