News / Science & Technology

Crocodiles, Alligators May Lure Prey with Sticks

A well-camouflaged mugger crocodile (Crocodylus palustris) in stick-displaying behavior. Madras Crocodile Bank, Tamil Nadu, India. (V. Dinets)
A well-camouflaged mugger crocodile (Crocodylus palustris) in stick-displaying behavior. Madras Crocodile Bank, Tamil Nadu, India. (V. Dinets)

Related Articles

Cyanide Kills Elephants, Ecosystem

Poachers kill hundreds of elephants in Zimbabwe

Lion Population Devastated by Illegal Snares

Snares set to catch antelope and other bush meat often catch lions, often crippling or killing them

Oil Rush in Africa's Parks Drives Hunt for Eco-friendly Methods

Oil companies explore new oil sources without damaging the environment
TEXT SIZE - +
Egrets and other birds building nests near ponds that harbor crocodiles or alligators should be suspicious of sticks they see floating in the water. That twig or branch may be bait for a trap set by the reptiles, as new research suggests they may have joined the few species that use tools to lure prey.

According to Valdimir Dinets, a zoologist known for his studies of crocodilian (crocodiles and alligators) behavior, two species of the large reptiles have been observed using twigs and sticks as bird lures.

“At least one of them uses this method predominantly during the nest-building season of its prey,” he writes in a paper published in the journal Ethology Ecology & Evolution. “This is the first known case of a predator not just using objects as lures, but also taking into account the seasonality of prey behavior. It provides a surprising insight into previously unrecognized complexity of archosaurian behavior.”

According to the study, the use of objects as hunting lures is very rare among animals, only seen in captive capuchin monkeys, a few bird species and one insect.

Writing in the study, Dinets states that “it is common for some bird species to preferentially nest in trees growing in ponds with large numbers of crocodiles or alligators, apparently using the crocodilians as protection against tree-climbing nest predators such as snakes, monkeys and raccoons.”

But, he says, the birds have to “pay” for the protection because their chicks can sometimes fall into the water where they are usually devoured by crocodilians.

“But the protection seems to be worth the cost,” Dinets writes. “Almost any crocodile farm or alligator park with appropriate trees will sooner or later become the location of an egret rookery.”

An American alligator chomps a snowy egret at the St Augustine Alligator Farm Zoological Park, Florida. (Don Specht)An American alligator chomps a snowy egret at the St Augustine Alligator Farm Zoological Park, Florida. (Don Specht)
x
An American alligator chomps a snowy egret at the St Augustine Alligator Farm Zoological Park, Florida. (Don Specht)
An American alligator chomps a snowy egret at the St Augustine Alligator Farm Zoological Park, Florida. (Don Specht)
Dinets says he repeatedly saw crocodilians laying in shallow water with small sticks or twigs across their snouts around rookeries.

“The crocodiles remained perfectly still for hours, and if they did move to change position, they did it in such a way that the sticks remained balanced on their snouts,” he writes.

Dinets says the predators get the sticks onto their snouts by submerging under them.

“Then it takes some balancing act to keep the sticks in place,” he said in an email.

Observing alligators at two egret nesting sites for a year, Dinets saw stick displaying mostly during the bird’s breeding season, between March and June and more frequently during nest building, from late March and April.

Dinets noted that the increase in the behavior could be explained by higher amounts of sticks in the water, either because of nest building or trees shedding. He thinks, however that that explanation “seems unlikely.”

“Virtually no freely floating sticks or twigs were seen by the observer at that time, and none are visible in photographs of rookery ponds made at that time,” writes Dinets. “Any available sticks were probably quickly picked up by birds looking for nest material.”

Also, he notes that the most common trees around the waters don’t often shed branches.

Dinets says it’s “unknown” what factors lead to the stick-displaying behavior at particular locations and at certain times of the year.

“The predators might be reacting to the presence of large numbers of wading birds flying low over water, to the sounds made by courting birds, or to some other environmental clue,” he writes.

He also doesn’t know if the behavior is a learned behavior or an evolved instinct.

While Dinets says crocodilians have historically been viewed as “lethargic, stupid and boring,” the new research adds to the complex behavior already known such as signaling, advanced parental care and “highly coordinated group hunting tactics.”

“These discoveries are interesting not just because they show how easy it is to underestimate the intelligence of even relatively familiar animals, but also because crocodilians are a sister taxon of dinosaurs and flying reptiles,” he concludes.

You May Like

Multimedia Anti-Keystone XL Protests Continue

Demonstrators are worried about pipeline's effect on climate change, their traditional way of life, health and safety More

Thailand's Political Power Struggle Continues

Court gave Prime Minister Yingluck Shinawatra until May 2 to prepare her defense over abuse of power charges but uncertainty remains over election timing More

Malaysia Plane Search Tests Limits of Ocean Mapping Technology

Expert tells VOA existing equipment’s maximum operating depth is around 6 kilometers as operation continues on ocean bed for any trace of MH370 More

This forum has been closed.
Comments
     
There are no comments in this forum. Be first and add one

Featured Videos

Your JavaScript is turned off or you have an old version of Adobe's Flash Player. Get the latest Flash player.
Pet Kangaroo Helps Spread Environmental Messagei
X
Penelope Poulou
April 22, 2014 5:53 PM
Children’s author Julia Heckathorn travels the world to learn about different ecosystems and endangered animals. She pours her knowledge into children’s books, hoping the next generation will right the environmental wrongs of our times. As in many children's books, the main character in Heckathorn's stories is an animal. Unlike those other characters, though, this one is real - a kangaroo, that lives in the author’s backyard. VOA’s Penelope Poulou has more.
Video

Video Pet Kangaroo Helps Spread Environmental Message

Children’s author Julia Heckathorn travels the world to learn about different ecosystems and endangered animals. She pours her knowledge into children’s books, hoping the next generation will right the environmental wrongs of our times. As in many children's books, the main character in Heckathorn's stories is an animal. Unlike those other characters, though, this one is real - a kangaroo, that lives in the author’s backyard. VOA’s Penelope Poulou has more.
Video

Video Pro-Russian Separatists Plan 'Federalization Referendum' in Eastern Ukraine

Pro-Russian separatists in eastern Ukraine say they plan to move forward next month with a referendum vote for greater autonomy, despite the Geneva agreement reached with Russia, the U.S. and Ukraine to end the political conflict. VOA's Brian Padden reports from the city of Donetsk in Eastern Ukraine.
Video

Video Pope Francis Hopes Dual Canonizations Will Reconcile Church

On April 27, two popes - John the XXIII and John Paul II - will be made saints in a ceremony at St. Peter’s Square. VOA religion correspondent Jerome Socolovsky says the dual canonization is part of the current pope’s program to reconcile liberals and conservatives in the Roman Catholic Church.
Video

Video In Capturing Nature's Majesty, Film Makes Case for Its Survival

French filmmaker Luc Jacquet won worldwide acclaim for his 2005 Academy Award-winning documentary "March of the Penguins". Now Jacquet is back with a new film that takes movie-goers deep into the heart of a tropical rainforest - not only to celebrate its grandeur, but to make the case for its survival. VOA's Rosanne Skirble reports.
Video

Video Boston Marathon Bittersweet for Many Runners

Monday's running of the Boston Marathon was bittersweet for many of the 36,000 participants as they finished the run that was interrupted by a double bombing last year. Many gathered along the route paid respect to the four people killed as a result of two bombings near the finish line. VOA's Carolyn Presutti returned to Boston this year to follow two runners, forever changed because of the crimes.
Video

Video International Students Learn Film Production in World's Movie Capital

Hollywood - which is part of Los Angeles - is the movie capital of the world, and many aspiring filmmakers go there in hopes of breaking into the movie business. Mike O'Sullivan reports that regional universities are also a magnet for students who hope to become producers or directors.
Video

Video Pacific Rim Trade Deal Proves Elusive

With the U.S.-led war in Iraq ended and American military involvement in Afghanistan winding down, President Barack Obama has sought to pivot the country's foreign policy focus towards Asia. One aspect of that pivot is the negotiation of a free-trade agreement among 12 Pacific Rim nations. But as Obama leaves this week on a trip to four Asian countries he has found it very difficult to complete the trade pact. VOA's Ken Bredemeier has more from Washington.
Video

Video Autistic Adults Face Housing, Job Challenges

Many parents of children with disabilities fear for the future of their adult child. It can be difficult to find services to help adults with disabilities - physical, mental or emotional - find work or live on their own. The mother of an autistic boy set up a foundation to advocate for the estimated 1.2 million American adults with autism, a developmental disorder that causes communication difficulties and often social difficulties. VOA's Faiza Elmasry reports.
AppleAndroid