Chicago's O'Hare International Airport Tuesday presented its latest ecological initiative: a flock of goats, sheep, llamas and burros that will graze on 5,000 square meters of airport ground, far from the runways, to control the vegetation there in a cheap and sustainable way.

 

Chicago Department of Aviation chief Rosemarie Andolino said Tuesday that the initiative will allow the airport, one of the country's busiest, to contribute ecologically with a sustainable and efficient operation.

 

 The four areas designated for grazing by the animals are separated from the runways by fences and are difficult to keep trimmed with available machinery since the terrain is rocky, uneven and has lots of dense brush where animals live that could be dangerous to airport operations.

 

 Those areas are also difficult to fumigate and thus poison ivy, poison oak and other invasive species thrive there.

 

 In the bidding instructions for the project, it was specified that the airport was seeking a way to replace the use of herbicides and help preserve the local fauna and flora as well as reduce the use of heavy machinery that pollutes the environment and causes erosion.

 

 The goats are the property of the Butcher & The Burger restaurant in the city's Lincoln Park neighbourhood, which originally intended to use the animals raised on a farm in the suburb of Barrington to make hamburgers.

 

 However, when the city announced the bidding for a pilot program for sustainable vegetation control at the airport, "we thought that it was a very good idea to use the goats", said Joseph Arnold, one of the partners at the firm that won the contract.

 

 The restaurant rounded out the flock of 25 animals in association with Settler's Pond, a shelter specializing in rescuing farm and exotic animals.

 

 Calculations are that the goats and other animals in the flock will eat the vegetation on up to 25 square meters of land each day.

 

 Pinky Janota, a specialist at the animal refuge, said that the flock had gotten so used to the noise of the airplanes that Tuesday a lamb was born to one of the sheep and named O'Hare.

 

 "Neither the mother nor he were frightened" by the noise, Janota said.

 

 Other US airports are also using animals to eliminate unwanted vegetation with varying results.

 

 In San Francisco, goats were used for three weeks last June to clean an area west of the airport that is used as a firebreak.

 

 The animals eat the vegetation and respect the protected species that live in the area, species that the use of heavy machinery would endanger.

 

 However, at the Seattle airport goats were only used for a week in 2008 since apparently the animals devoured every bit of vegetation in their assigned plots, including trees and native plants that authorities had wanted to protect.

 

 In Chicago, while the animals and their herders are on the job, they will spend the nights in a specially constructed shelter. It is expected that they will be returned to the Barrington Hills farm in the autumn and remain there until the spring of 2014, when their services will once more be needed at the airport.