From geese that guard Chinese police stations to goats trimming the grass of San Francisco's airport, animal employees have some unusual jobs -- many that are too dirty, dangerous, difficult or expensive for humans.

A new proposal out of Indonesia, for example, posits placing a prison on an island whose coasts are guarded by crocodiles. It's part of the nation's anti-drug effort and the prison would house convicted drug criminals who are on death row.

"We will place as many crocodiles as we can there. I will search for the most ferocious type of crocodile," said Indonesia's anti-drugs chief Budi Waseso, according to AFP.

A big plus for the proposal is that crocodiles can't be bribed, unlike their human counterparts.

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Cosmo the goat and friends entertain visitors at the St. Louis Zoo. Katie Wall

Goats' mouth-mowing abilities put machines and herbicides to shame. In the southern United States, invasive kudzu vines choke out native plants and envelop whole buildings. However, an expensive ecological nightmare for humans looks like an all-you-can-eat buffet to goats. Kudzu contains excellent nutrition for goats and the horned herbivores will nibble it to the root. Goats cost less than pollution-producing lawnmowers and pesticides; plus, the goats themselves make for delicious Greek gyros or Mexican birria soup.

Cosmo, the black goat in this photo, doesn't have to worry about the dinner plate, though. His only job is to delight visitors and serve as an ambassador of the animal kingdom at the St. Louis Zoo.

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Virgin Media joked that ferrets were working for them.Virgin Media

Ferrets naturally squeeze into the tightest spots. In nature, this ability allows them to pursue prey into burrows. In the working world, it means ferrets make great electricians.

In the 1940s, Freddie the ferret worked as an electrician's assistant in Auckland, New Zealand, reported Time magazine. The lithe predator would wriggle through tight spaces, dragging a wire behind him. Freddie's owner would hold a dead rabbit at the other end of the pipe to encourage the ferret to stay on the job. In one morning, the ferret could complete a job that would take a month for a human.

Virgin Media once jokingly released a report that ferrets had been at work for years laying broadband cable for the company. The date of the report was April 1.

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Runcho sniffs the mouth of a police animal trainer at a police school in Sibate, Colombia May 3, 2006.DANIEL MUNOZ/Corbis

Rats have a serious image problem. Perhaps humans would think better of rats if people knew how many lives the animals saved.

In Colombia, decades of civil war peppered the countryside with landmines. The Colombian police trained common white lab rats to sniff our the deadly explosives with their sensitive noses. Rats weigh little, so they don't trigger the landmines to explode. The mammalian minesweepers are also cheaper and faster to train than dogs.

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An African Giant Pouch rat is seen before a training session where the rats will learn to detect tuberculosis (TB) at a laboratory in Sokoine University for Agriculture in Morogoro, Tanzania.Corbis

Other species of rats have life-saving jobs. No animal is more associated with medical research than the lab rat, but usually the rodent doesn't conduct the experiment itself. The young Gambian pouch rat (Cricetomys gambianus) in this photo, however, is learning to be a lab technician at Sokoine University for Agriculture in Morogoro, Tanzania. Human trainers teach the rats to identify samples of human spit infected with tuberculosis.

APOPO company's operation in Morogoro, Tanzania has trained 54 rats that can each screen thousands of patients per month. The training process starts with four-week-old rats and takes between six to twelve months to complete.

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Greenbottle flies (Lucilia sericata) lay eggs on raw BSE free sheeps liver at Zoobiotic Ltd, Bridgend, South Wales, UK, Europe's largest sterile maggot production facility.Louise Murray/Corbis

Rats aren't the only animals working in the medical profession, nor are they the only critters with a serious PR problem. Maggots also don't have a reputation as cleanly creatures, but some doctors use maggots as medicinal tools.

Maggots were just what the doctor ordered for some diabetes patients. When wounds on the patients limbs became infected with antibiotic-resistant bacteria, doctors used maggots to gnaw away the dead, infected flesh, reported Reuters.

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Medical maggots have a long history, especially on the battlefield. Physicians from the Napoleonic wars recorded the ability of maggots to clean out wounds and increase survival rates. During World War II, Americans in Japanese prisoner of war camps used maggots because their captors denied the soldiers conventional medical treatment.

A pigeon is seen in a cage. JASON LEE/Corbis

Not every animal concerns itself with human health like rats and maggots do. Cops once busted a carrier pigeon with cocaine and marijuana strapped to its back. The feathered drug mule flopped to the ground a block away from the prison in Bucaramanga, Colombia, reported the BBC.

Criminals had overloaded the unfortunate pigeon and it couldn't complete its smuggling run. Although the bird was taken in by wildlife rehabilitation officials, it didn't squeal on whoever had strapped it with dope. The bird wasn't a stool pigeon.

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Red worms work the sewage line. Holger Casselmann, Wikimedia Commons

Lowly worms get stuck with one of humanity’s filthiest jobs, raw sewage treatment. Red worms (Eisenia fetida) devour human and animal feces, as well as winery, dairy and slaughterhouse wastes, in systems designed by New Zealand-based Biofiltro and other companies. The worms do the work 33 percent cheaper and with 80 percent less energy than conventional waste treatment systems, according to Biofiltro’s webpage. Then, once the sewage has in turn become worm waste, the worm’s excrement serves as rich, organic fertilizer.

Chileans originally developed the waste-to-worms system and the nation has used worms to handle the waste of 250 people at Chile’s Antarctic air force base, reported the Otago Daily Times.

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A manatee swims with a school of fish.Ramos Keith, U.S. Fish and Wildlife Service

For over a century in Guyana, South America, the West Indian manatee (Trichechus manatus) has helped keep canals clear of aquatic weeds, according to a paper in the journal Irrigation and Drainage Systems. The animals grow to more than 12 feet long and can weigh over 1,000 pounds. The creatures have an appetite to match their size and can consume up to 10 percent of their body weight per day.

Even with their massive hunger for watery weeds, manatees might not be up to the job of keeping Florida's waterways free of vegetation. A study in the Journal of Aquatic Plant Management suggested that the growth rate of the problematic plant hydrilla outpaces even hungry manatees' appetites.

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Asuka, three-year-old female chimpanzee, draws her "abstract" oil painting on a canvas at a studio at Izu Shaboten Park in Ito, southwest of Tokyo September 19, 2004.KIMIMASA MAYAMA/Corbis

Pierre Brassau broke new ground in the art world of the 1960s. Critics hailed his work as a mixture of “powerful strokes” and “clear determination.” Brassau was an artist who painted with the “delicacy of a ballet dancer.” But Brassau held a terrible secret the critics didn't know.

Braussau was a chimpanzee named Peter. A Swedish journalist organized an art opening of the chimp's masterpieces as a hoax to see if critics could tell the difference between avante-garde and ape art. The chimpanzee succeeded at a task many human artists find nearly impossible. He gained fame for his work while he was still alive.

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Chimp art flourished after Brassau opened the museum doors to apes. In 2004, Asuka, the chimp shown here, dazzled the art scene of Japan with her abstract pieces. She even had an art opening in Tokyo.

Micheal Jackson's pet chimp, Bubbles, sold a series of paintings for £2,000 ($3,074), reported the Mirror. The funds helped cover the ape's care bill, since Jackson's family abandoned the animal.

Metro Meteor at work.Painted By Metro/Facebook

Art seems to be a popular way for retired animals to support themselves. Metro Meteor, a prize-winning race horse, took up painting after his knees gave out.

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The horse covered his feed bill with the sale of his wildly colorful abstract paintings that he produced with the help of his owners Ron and Wendy Krajewski.

Sheep in a Spanish vineyard.Angelina Llop, Wikimedia

What goes better with a viewing of horse and chimp art than some fine wine that sheep helped produce? The sheep even provide cheese to pair with the wine.

In misty Napa Valley, pruning off excess grape leaves prevents mildew from forming on the fruit. Human workers are expensive, and machines lack the finesse to prune without damaging the vines. Sheep can do the job quickly, plus they leave behind fertilizer.

Five-hundred sheep can prune 20 acres per day and remove weeds as they go, according to Don Watson of Rocky Mountain Wooly Weeders in a YouTube video. Watson employs East Friesian milk sheep, which also provide sheep's milk for artisanal cheeses.