Cardinals
Bilateral gynandromorphism occasionally shows up in northern cardinals, too. The one in this photo sports brown-gray “female” feathers on one half and bright red “male” feathers on the other.
According to a study by Brian Peer of Western Illinois University and his colleague Robert Motz, gyandromorph cardinals not only look different, they also act different, at least the one they observed from 2008 to 2010. During that time, their “half-sider” was never seen vocalizing or mating. On the plus side, other cardinals seemed to accept it: The researchers never witnessed it being bullied or mistreated.
Frogs
Researchers have observed frogs spontaneously changing genders in the lab. Now they’re observing it in the wild too, and it’s not a natural process. More and more male frogs are becoming females, complete with fully functioning reproductive organs. The frog-feminizing culprit? A common weed killer called atrazine.
Banned in Europe, atrazine ends up running into rivers and lakes where it wreaks havoc on frog sexual development, suppressing production of testosterone (the male sex hormone) and boosting the female sex hormone estrogen. Not good news for amphibian populations that are already declining from climate change, loss of habitat and invasive species.
Snakes
Some female snakes, such as copperheads and cottonmouths, are capable of virgin birth, or parthenogenesis, meaning they fertilize their own eggs without a male sexual partner. While not technically a gender reversal, it is an ability to carry out the reproductive functions of both genders at once — and not as a hermaphrodite. Rather, with parthenogenesis a special cell called a polar body that’s produced with an egg sometimes acts like a sperm to “fertilize” it.
Scientists once believed that parthenogenesis occurred only among animals in captivity when males were in short supply. Captive female sharks, turkeys and lizards have all reproduced sans sex. But researchers have since observed virgin births among wild snakes even when males are plentiful. Why? You’ll have to stay tuned for further research.
Bearded dragons
These delightful Australian gender-benders actually do a sex reversal in the egg. Studies show that when warm temperatures occur during egg incubation, male bearded dragons often reverse course to become female. But it’s not a clean switch. They actually remain male genetically, but act and reproduce like females. Even more extraordinary, these he-she lizards are supermoms, laying twice as many eggs as a normal female. Male bearded dragons are currently undergoing sex reversal at a rising rate, likely due to the spike in global temperatures.
Green sea turtles
Like bearded dragons, green sea turtle embryos are also temperature sensitive. The warmer the sand where eggs are laid, the more females are born. In fact, according to a new study, sea turtle hatchlings from beaches near Australia’s Great Barrier Reef, where global warming is particularly intense, are now 99.8 percent female. On cooler beaches to the south, the gender ratio is 65 percent female to 35 percent male.
What impact might this dramatic gender imbalance have? The researchers conclude that females may seek mates in cooler climates so reproduction continues. However, if too many females hatch and can’t find a mate, sea turtle populations could collapse.
Comments