Museum of Vertebrate Zoology Graduate Student Reveals the Secret Life of Turkeys...

In wild turkeys, one sometimes sees teams of males that work together to display to females and defend those females against other males. It was thought that only one of those males actually got to mate, which leads to the question: what are these helper males getting out of it? Alan Krakauer, a graduate student in the Museum of Vertebrate Zoology, showed in the journal Nature (pdf article) that a process called kin selection can explain this apparent self-sacrifice. Using genetic markers called microsatellites, Krakauer found that these teams of males are close relatives (likely made up of brothers and some half-brothers). Since these males have one or both parents in common, they share much of the same genetic material. Therefore, if a helper can increase the number of offspring that his dominant display partner produces, he is actually indirectly passing on some of his own genes, even if he doesn’t mate himself. Genetic paternity analyses confirmed this; subordinate partners do not reproduce, but their dominant partners father so many offspring that the helpers actually pass on more genes by helping than they would by trying to go it alone and breed by themselves. The idea that subordinate male turkeys were benefiting in this way has been around for almost 35 years and became a literal textbook example of kin selection; Krakauer’s study is the first to actually test this hypothesis using genetic measures of paternity and relatedness. He also found no evidence that subordinate males were gaining direct reproductive benefits such as fathering their own offspring or becoming the dominant male once the current dominant dies. This means that while kin selection is well known from a variety of animals, it seems to be unusually important in turkeys compared with most other vertebrate societies for explaining the evolution of cooperative behavior.

Alan Krakauer conducted this research at the MVZ’s Hastings Natural History Reservation, a member of the University of California’s Natural Reserve System, and located in Carmel Valley, California. His field work involved capturing adult turkeys in large walk-in traps, marking them with wing tags and radio-transmitters, and taking small samples of blood for DNA analyses. He then, along with his field assistants, would track the birds, attempting to record their display behavior, note which other turkeys they associated with, and find the female’s nest sites. Once he had genetic samples of the offspring, he returned to the MVZ’s Evolutionary Genetics lab to determine the genetic similarity of the male partnerships as well as figure out which males were fathering offspring.

Other Links:

SF Chronicle news link
Hastings Newsletter (pdf)