In Brazil, dogs do more harm than good

RIO DE JANEIRO - High above this Brazilian city, in a jungle blanketing a mountain, the turtles were out and the scene was hopeful.

Scientists were reintroducing 15 mud-caked tortoises to this urban forest where they had once been plentiful. Children were running around. People were oohing and aahing. A stern-looking security guard briefly appeared to smile.

But not government biologist Katyucha Silva. She was thinking about dogs.

What would they do to these turtles? What were they doing to Brazil?

It’s a question more researchers are beginning to ask in a country where there are more dogs than children - and where dogs are quickly becoming the most destructive predator. They’re invading nature preserves and national parks. They’re forming packs, some 15 dogs strong, and are hunting wild prey. They’ve muscled out native predators such as foxes and big cats in nature preserves, outnumbering pumas 25 to 1 and ocelots 85 to 1.

Every year, they become still more plentiful, spreading diseases, disrupting natural environments, goosing scientists who set up elaborate camera systems to photograph wild animals, only to come away with pictures of curious canines.

“It’s a difficult thing for people to hear,” said Isadora Lessa, a Rio de Janeiro biologist who wrote her doctoral dissertation on domestic dogs causing environmental mayhem. “They love dogs too much.”

How the dog became one of the world’s most harmful invasive mammalian predators is as much a global story as a Brazilian one. Over the last century, as the human population exploded, so did the dog population, growing to an estimated one billion.

That has been great for people - and even better for dogs - but less so for nature, according to a growing body of academic research implicating canines, particularly the free-roaming ones, in environmental destruction.

“The global impacts of domestic dogs on wildlife are grossly underestimated,” researchers concluded in a 2017 study published in the journal Biological Conservation. The researchers, based in Australia, convicted dogs in the extinction of 11 species and declared them the third-most-damaging mammal, behind only cats and rodents.

The International Union for Conservation of Nature maintains a list of animals whose numbers dogs are culling. There are 191, and more than half are classified as either endangered or vulnerable. They range from lowly iguanas to the famed Tasmanian devil, from doves to monkeys, a diversity of animals with nothing in common beyond the fact that dogs enjoy killing them. In New Zealand, the organization reported, a single German shepherd once did in as many as 500 kiwis - and that was the conservative estimate.

“Unfortunately, we have a big problem,” said Piero Genovesi, chair of the agency’s invasive species unit. “There is a growing number of dogs.”

People all over the world are - begrudgingly - beginning to take note.

In Chile, stray dogs were the top concern among city dwellers surveyed this year, topping deteriorating sidewalks and theft. In New Zealand, some communities moved last year to restrict the movement of dogs in a gambit to save little blue penguins. In India, farmers are complaining about stray dogs killing their livestock, just as other predators once had.

Brazil is home to an estimated 52 million dogs, according to the most recent government statistics - more than anywhere in Latin America - but their lives vary widely. In a nation defined by inequality, where the rich fly in helicopters overthe poor in the favelas below, the dog has become one more way of understanding the divide. – WP-Bloomberg