The Eastern Flock "Family Tree"

What if Whooping Crane Siblings Get Together as Mates?

Tom Stehn, Whooping Crane Recovery Team

All the eggs for the new Eastern flock have come from Whooping Cranes in captivity. Did you know that the Eastern flock cranes include many siblings? Cranes that are produced by the same Sire and Dam (parents) for each project year are siblings. You can check out their "Family Tree."

You might wonder: Will any of the siblings (chicks who come from the same parents) get together as mates? What are the genetic risks, if any? We asked this question of Tom Stehn, Whooping Crane Coordinator for the USFWS. Here's Tom's reply:

We don't know if Whooping Crane siblings would have any mechanism to avoid breeding with each other. Certainly siblings produced in the same year from the same nest (Whooping Cranes occasionally are able to have both of the chicks they hatch every year survive), those siblings probably would never attempt to breed with each other. In captivity, Whooping Crane juveniles raised together in a cohort tend to not to want to pair with each other. I think the problem of sibling pairings is a long-range concern involving the overall genetic makeup of the population, and not a problem in a single isolated case. In reintroductions of small populations of endangered species, one often has little choice, with genetics so limited to start with.

We currently (2003) have a brother-sister pair of Whooping Cranes in Florida that has successfully raised 2 young. If they lay more eggs next year (2004), we would like to substitute an egg from another pair so that that they raise a youngster with less in-bred genetics. Siblings from the same nest in different years may just treat a sibling as they would any other Whooping Crane. Sibling pairs would not be good from a genetics standpoint and would presumably lead to less fitness and lower survival of offspring. So these types of sibling pairings — if they occurred — would probably be self-limiting, since those pairs would not be as successful at breeding and thus their genetic material would eventually be reduced in the population.

Tom Stehn, Whooping Crane Coordinator
U.S. Fish and Wildlife Service
Aransas NWR
P.O. Box 100
Austwell, TX 77950

Journey North is pleased to feature this educational adventure made possible by the Whooping Crane Eastern Partnership (WCEP).