Turkeys and Parthenogenesis

Regular readers know how much I esteem turkeys.  Unfortunately I worry that my writings are not winning additional admirers for these astonishing birds.  It is time to play a trump card and reveal one of the great bizarre strengths of turkeys.  They are capable of virgin birth.

A New Mexico Whiptail (Aspidoscelis neomexicana). All New Mexico Whiptails are female. The entire species reproduces by parthenogenesis.

Before you spring up in alarm and start shouting, allow me to present a miniature biology lesson. Parthenogenesis is a form of asexual reproduction. Some female organisms are capable of producing an ovum which develops into a new individual without being fertilized by a male gamete.  In these cases, the mother contributes her genetic material to the offspring.  Although natural parthenogenesis is frequently observed in rotifers, insects, mollusks, crustaceans, and flatworms, this method of reproduction is much less common among vertebrates. However a few species of fish, amphibians, and reptiles are known to reproduce via parthenogenesis (movie-goers may recall that this happened to the dinosaurs in Jurassic Park.)  The turkey is very unusual in being a bird which can reproduce through this means (or at least we think it is unusual—perhaps parthenogenesis is more common among birds then we realize but we just don’t know about it except in settings like farms where it becomes obvious). Chickens can also produce self-fertilized eggs but they almost never develop beyond embryonic stages, whereas female turkeys can and frequently do produce living offspring which lack fathers.

This diagram from the BBC actually explains shark parthenogenesis but you get the idea.

Parthenogenesis occurs in turkeys through the doubling of haploid cells.  Biologists have discovered that the rate at which this occurs can be increased by selective breeding. Poults produced by parthenogenesis are capable of growing into healthy viable toms indistinguishable from toms with more traditional parentage.  You will note that I wrote “toms”—all turkeys conceived via parthenogenesis were created from doubled haploids and are are homogametic. Consequently they are all all male. (This will leave mammal enthusiasts scratching their heads–since female mammals are homogametic and have two x chromosomes. However for birds and for some reptiles, males have two Z chromosomes and thus are the homogametic sex. In such species, females have one Z and one W chromosome and are the heterogametic sex.)

Mammals do not naturally utilize parthenogenesis as a method of reproduction. Certain portions of mammalian genes consist of imprinted regions where portions of genetic data from one parent or the other are inactivated. Mammals born of parthenogenesis must therefore overcome the developmental abnormalities caused by having two sets of maternally imprinted genes.  In normal circumstances this is impossible and embryos created by parthenogenesis are spontaneously rejected from the womb. Biology researchers have now found ways to surmount such obstacles and a fatherless female mouse was successfully created in Tokyo in 2004. With genetic tinkering, human parthenogenesis is also biologically feasible. Before his research was discredited and he was dismissed from his position, the South Korean (mad?) scientist Hwang Woo-Suk unknowingly created human embryos via parthenogenesis. To quote a news article by Chris Williams, “In the course of research, which culminated with false claims that stem cells had been extracted from a cloned human embryo, Hwang’s team succeeded in extracting cells from eggs that had undergone parthenogenesis… The ability to extract embryonic stem cells produced by parthenogenesis means they will be genetically identical to the egg donor. The upshot is a supply of therapeutic cells for women which won’t be rejected by their immune system, without the need for cloning.”

All of which is fascinating to biology researchers (and those who would seek greatly prolonged life via biogenetic technologies), however it seems that in nature, the turkey is the most complicated creature capable of virgin birth.

Spring Gobbling

Domestic Tom Turkey Gobbling (Photo by WildImages--Charlie Summers)

It has been a long time since I put up a turkey post.  In a way this is appropriate, since people other than hunters and farmers usually only think about the majestic fowl around holiday time when the sharp axe comes out (or–more likely—when one wanders over to Krogers to check out the price of Butterballs).  Meanwhile live turkeys have been slogging away through the long winter.  For farm turkeys this has meant dull days perched in dark coops huddled together for warmth while living on daily water and grain hand-outs from the farmer.  For wild turkeys the winter is more like a Russian war novel.  The wind, ice, and snow are enlivened by desperate hunger and by fear of omnipresent predators stalking through the bare trees of the frozen forests.  The cold nights are filled with the howl of the wind and the coyotes while the days are filled with desperately scraping the dead ground for remnants of food.

But that was winter–spring is here, and with it, mating season.  This time of year highlights one of the signature features of turkeys wild and domestic—gobbling.  In fact today’s post is really an auditory one.  Here is a movie of a Tom turkey gobbling!

The gobble is rightfully the most famous turkey vocalization.  It is similar in nature to the humpback’s song or the deafening yodel of the siamang: a magnificent declaration of self which proclaims dominance and health to females. This ululating yodel alerts all nearby hens to the fact that an alpha male tom turkey is in the area and is at the top of his game (it also lets rival males know where to go for a fight and hunters where to go for a meal, so it is a true and heartfelt declaration of bravery and lust on the part of the issuer).

Gobbles are hardly the only turkey vocalizations.  Turkeys both wild and domestic are extremely garrulous characters and produce many different calls for a variety of reasons.  Here is a list of the more common turkey vocabulary from the national Wild Turkey Federation.  By using a variety of tools and the full range of the human voice a tiny number of truly expert hunters can produce most of these noises, however turkeys are clever enough that they don’t usually fall for such guile.