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October 12, 2009

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“Loyal” gators said to display bird-like mating habits

Oct. 12, 2009
Courtesy Wiley-Blackwell Publishers
and World Science staff

Al­li­ga­tors dis­play the same loy­al­ty to their mat­ing part­ners as birds, a study has found: up to 70 per­cent of fe­males at one wild­life ref­uge showed at least some loy­al­ty to their mates, of­ten stay­ing with him for years.

A baby alliga­tor on its mo­ther's back at Rock­e­fel­ler Wild­life Ref­uge in Lou­i­si­ana. (Cour­tesy Wi­ley-Black­well Pub­li­shers)
The ten-year-study by sci­en­tists from the Sa­van­nah Riv­er Ecol­o­gy Lab­o­r­a­to­ry, a re­search un­it of the Un­ivers­ity of Geor­gia, tracked al­li­ga­tors liv­ing in the Rock­e­fel­ler Wild­life Ref­uge in Lou­i­si­ana.

“Given how in­credibly open and dense the al­li­ga­tor popula­t­ion is at [the ref­uge] we did­n’t ex­pect to find fi­del­ity,” said Sta­cey Lance, a re­searcher with the group. “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.”

Crocodil­ians, an ev­o­lu­tion­ary clan that in­cludes crocodiles and al­li­ga­tors, are among the few rep­tiles that nur­ture their young and de­fend nests. Many fe­male al­li­ga­tors mate with mul­ti­ple males, but a high num­ber al­so stick with the same part­ner over many mat­ing sea­sons, the re­search­ers found. 

This is the first ev­i­dence for par­tial mate fi­del­ity in any croc­o­dil­ian and re­veals a si­m­i­lar­ity in mat­ing pat­terns be­tween al­li­ga­tors and bird spe­cies, added Lance and col­leagues.

Crocodil­ians are the sole sur­viv­ing rep­til­i­an ar­cho­saurs, a group of an­cient rep­tiles that in­cludes di­no­saurs and gave rise to birds, Lance said. This ev­o­lu­tion­ary rela­t­ion­ship to birds means croc­o­dil­i­ans are in a un­ique po­si­tion to pro­vide in­forma­t­ion about the an­ces­tral mat­ing sys­tems of both birds and many di­no­saurs, she added.

“In this stu­dy, by com­bin­ing mo­lec­u­lar tech­niques with field stud­ies, we were able to fig­ure some­thing out about a spe­cies that we nev­er would have known oth­er­wise,” con­clud­ed Lance. The stu­dy ap­pears in the Oct. 7 is­sue of the re­search jour­nal Mo­le­cu­lar Eco­logy.

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Alligators display the same loyalty to their mating partners as birds, a study has found: up to 70% of females at one wildlife refuge showed at least some loyalty to their mates, often staying with him for years. The ten-year-study by scientists from the Savannah River Ecology Laboratory, a research unit of the University of Georgia, tracked alligators living in the Rockefeller Wildlife Refuge in Louisiana. “Given how incredibly open and dense the alligator population is at [the refuge] we didn’t expect to find fidelity,” said Stacey Lance, a researcher with the group. “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.” Crocodilians, an evolutionary group that includes crocodiles and alligator, are among the few reptiles that nurture their young and defend nests. Many female alligators mate with multiple males, but a high number also stick with the same partner over many mating seasons, the researchers found. This is the first evidence for partial mate fidelity in any crocodilian species and reveals a similarity in mating patterns between alligators and bird species, added Lance and colleagues. Crocodilians are the sole surviving reptilian archosaurs, a group of ancient reptiles that includes dinosaurs and gave rise to birds, Lance said. This evolutionary relationship to birds means crocodilians are in a unique position to provide information about the ancestral mating systems of both birds and many dinosaurs, she added. “In this study, by combining molecular techniques with field studies, we were able to figure something out about a species that we never would have known otherwise,” concluded Lance.