Category Archives: Crocodile
ScienceDaily (Oct. 8, 2009) — Alligators display the same loyalty to their mating partners as birds reveals a study published today in Molecular Ecology. The ten-year-study by scientists from the Savannah River Ecology Laboratory reveals that up to 70% of females chose to remain with their partner, often for many years.
The team, led by Drs. Travis Glenn, Ruth Elsey, Tracey Tuberville and Stacey Lance, spent a decade examining the mating system of alligators living in the Louisiana Department of Wildlife and Fisheries’ Rockefeller Wildlife Refuge (RWR) in Louisiana. Once they had successfully re-trapped a female they recognized the potential to examine individual behaviour over multiple mating seasons and determine if mate fidelity or pair bonding occurs.
“Given how incredibly open and dense the alligator population is at RWR we didn’t expect to find fidelity,” said Lance. “To actually find that 70% of our re-trapped females showed mate fidelity was really incredible. 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.”
This new discovery gives a new insight into the complex mating system of the alligator. Parental care is typically lacking in most reptiles, but not crocodilians who display parental care though nurturing young and defending the nest. In 2001 multiple paternity was discovered as the alligator mating system, yet it remains unknown as to how this benefits the species
However, while the females at RWR move freely through male territories, leading to high mate encounter rates, this study reveals that many alligators choose to mate with the same partner over many mating seasons. This amounts to the first evidence for partial mate fidelity in any crocodilian species and reveals a similarity in mating patterns between alligators and bird species.
Crocodilians are the sole surviving reptilian archosaurs, a group of ancient reptiles that includes dinosaurs and gave rise to birds. It is this evolutionary relationship to birds which means crocodilians are in a unique phylogenetic position to provide information about the ancestral mating systems of both birds and many dinosaurs.
“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,” concludes Lance. “Hopefully future studies will also lead to some unexpected and equally fascinating results.”
- S.L. Lance, T.D. Tuberville, L. Dueck, C. Holz-schietinger, P.L. Trosclair III, R.M. Elsey, T.C. Glenn. Multi-year multiple paternity and mate fidelity in the American alligator, Alligator mississippiensis. Molecular Ecology, 2009
ScienceDaily (July 14, 2009) — The Wildlife Conservation Society announced today that critically endangered alligators in China have a new chance for survival. The WCS’s Bronx Zoo, in partnership with two other North American parks and the Department of Wildlife Conservation and Management of the State Forestry Administration of China, has successfully reintroduced alligators into the wild that are now multiplying on their own.
The alligator hatchlings—15 in number—are the offspring of a group of alligators that includes animals from the Wildlife Conservation Society’s Bronx Zoo. The baby alligators represent a milestone for the 10-year effort to reintroduce the Chinese alligator on Chongming Island, located at the mouth of China’s Yangtze River.
The announcement was made at the International Congress for Conservation Biology, convened by the Society for Conservation Biology in Beijing, China (July 11-16).
“We are grateful to our Chinese partners for their commitment to reintroduce Chinese alligators back into the wild,” said Dr. Steven E. Sanderson, President and CEO of the Wildlife Conservation Society. “WCS has championed careful wildlife reintroductions for more than a century. The reintroduction of Chinese alligators is a great example of how WCS partners with governments and local communities around the world to save wildlife and wild places.”
“This is fantastic news,” said WCS researcher Dr. John Thorbjarnarson, one of the world’s foremost experts on crocodilians and a participant in the project. “The success of this small population suggests that there’s hope for bringing the Chinese alligator back to some parts of its former distribution.”
Plans to reintroduce Chinese alligators started in 1999 with a survey conducted by WCS, the Anhui Forestry Bureau, and the East China Normal University in Anhui Province, the only remaining location where the reptiles are still found in the wild in what is a small fraction of the alligator’s former range. The results of the survey were dire, with an estimate of fewer than 130 animals in a declining population.
An international workshop on the species was held in 2001, followed by recommendations for the reintroduction of captive bred alligators. The first three animals released in Hongxing Reserve of Xuancheng County in Anhui in 2003 were from the Anhui Research Center of Chinese Alligator Reproduction (ARCCAR).
To ensure the maximum genetic diversity for the effort, project participants imported 12 more animals to Changxing Yinjiabian Chinese Alligator Nature Reserve from North America, including four from the Bronx Zoo. From this group, three animals from the U.S. were released in 2007 along with three more alligators from Changxing. The alligators were given health examinations by veterinary professionals from WCS’s Global Health Program and the Shanghai Wildlife Zoo and fitted with radio transmitters for remote monitoring before being released.
Experts reported that the reintroduced alligators successfully hibernated, and then in 2008, bred in the wild.
With a former range that covered a wide watershed area of East China, the Chinese alligator—or “tu long,” which means “muddy dragon”—is now listed as “Critically Endangered” on IUCN’s Red List of Threatened Species and is the most threatened of the 23 species of crocodilians in the world today. It is one of only two alligator species in existence (the other is the better known, and much better off, American alligator).
The Yangtze River, where the reintroduction of these alligators took place, is the third longest river in the world (after the Amazon and the Nile) and is China’s most economically important waterway. The world’s largest hydro-electric dam—the Three Gorges Dam—is also located on the river. The high levels of development along the river have become a challenge for native wildlife; in 2006, a comprehensive search for the Yangtze River dolphin, or baiji, didn’t find any, although one isolated sighting of a dolphin was made in 2007.
Other participants in the project include the East China Normal University, Shanghai Forestry Bureau, Changxing Yinjiabian Chinese Alligator Nature Reserve, and Wetland Park of Shanghai Industrial Investment (Holdings) Co. Ltd.
The project is being supported by the Ocean Park Conservation Foundation, Hong Kong.