News of the Wild
From the April/May 2010 issue of National Wildlife magazine
Female Gators Show Surprising Fidelity
A long-running study at the Louisiana Department of Wildlife and Fisheries’ Rockefeller Wildlife Refuge has concluded that nearly three-quarters of the refuge’s female alligators remain faithful to a single mate, often for several years—the first such evidence of mate fidelity among crocodilians. “I don’t think any of us expected that the same pair of alligators that bred together in 1997 would still be breeding together in 2005, and may still be producing nests together to this day,” says study coauthor Stacey Lance of the University of Georgia’s Savannah River Ecology Laboratory. The family dynamics of alligators and other crocodilians were already considered unusual among reptiles because they nurture their young and defend their nests from predators—behavior that is much more common in birds than reptiles.
Coots Use Birth Order to Discern Their Young
Like some other bird species, American coot parents will often slip a chick or two into another coot’s nest. Often, however, the parents of the second nest spot the parasitic chicks and reject them in favor of their own—something that many other species are unable to do. A new study from University of California–Santa Cruz scientists shows that coots use their own first-hatched chick as a kind of template. To test this, the researchers removed eggs from their nests and hatched them in incubators. Then they performed two sets of experiments. In one, they gave the parents one of their own chicks first, then followed it up with a mix of siblings and unrelated chicks. In the other, the first chick placed in the nest was a parasite. In both cases, study coauthor Dai Shizuka found that the first chick and its siblings were more likely to survive than the others. “In coots, half the brood dies anyway—they lay more eggs than they can care for,” says Shizuka. “Given that some chicks have to die, they choose the ones that they think are their chicks.”
For the Blues, A Happy Note
For years, marine scientists have noticed that the pitch of blue whale songs is becoming lower across the globe. Researchers proposed a number of possible reasons, including increased ambient noise from shipping traffic and global warming. Now a recent study offers a new explanation for the change, and it’s a happy one: the whales’ growing population. In 1986, the International Whaling Commission placed a moratorium on harvesting to allow blue whale populations to recover. A coauthor of the new study, John Hildebrand of University of California–San Diego’s Scripps Institution of Oceanography, says that as population densities rise, the distance between potential mates shrinks, lessening the need for higher-frequency songs, which travel farther through the ocean. Instead, males’ songs can be deeper and longer—and more impressive to nearby females.