Covid lockdowns have left us with a legacy of unwanted and increasingly dangerous dogs.

Auckland's canine population exploded during the pandemic. Now, reports of stray and aggressive dogs are exploding, too.

They're our faithful companions - but leave them on their own too much and they become dangerous doggies.

The number of dogs in New Zealand has risen dramatically, leading to more dogs in the pound and more dog attacks.

In today's episode of The Detail, Tom Kitchin visits Auckland Council's Henderson animal shelter to find out what's caused the problems.

"Covid-19. Over the shutdown periods, a lot of people went in search of dogs as companions to keep themselves company," Auckland Council animal management northern team leader Shaun Murray tells The Detail.

"After the shutdown, everybody went to work, and some even left to go overseas, and unfortunately, the dogs stayed, and we had to come and collect them."

Auckland Council statistics show dog attacks have risen by about 30 percent (2,437 reported over the last financial year), while the number of known dogs in the city has gone up by about five percent.

"Our known dogs from the 2018-19 registration year was 110,000. It's now gone up to 132,000 - it's a considerable jump," Murray says.

"When we impound a dog, we give the owner seven days to claim the dog. In some cases, the owners don't even pitch up."

Just over half of owners claimed their dogs from the shelter in the last financial year.

If the owner does not show, the council does its best to re-home the dog through rescue organisations. But in some cases, if the dog's temperament means it's unsafe to adopt, staff will put it down.

But Murray says euthanising dogs is "very hard" on staff.

"Every dog comes in, do their absolute best to give it a second chance, we really try."

Despite this, thousands of dogs are put down every year: there were over 1,600 dogs euthanised in the Manukau shelter alone.

In Wellington, a Council dog report showed the number of uncontrolled dogs had risen by 26 per cent in the last year. There were 65 attacks on people and 78 attacks on animals, with 697 reported uncontrolled dogs.

New Zealand wide, there's been an increase of about 70,000 dogs - the population sits at around 800,000.

"Dogs in homes are a wonderful thing, particularly when you've got a population under stress and difficulty," dog training expert Mark Vette tells The Detail.

A husky patiently waiting in Auckland Council's Henderson shelter…

Go to this episode on rnz.co.nz for more details