Max and Mr O'Brien keep each other company and stay healthy with twice daily walks along the Taieri River.
''He keeps me this fit,'' Mr O'Brien says, gesturing to his sprightly physique.
And when he calls Max to his side, he is likely not the only person across the city doing the same thing.
Dunedin City Council records show many dogs in Dunedin city come to the names Max or Molly.
Max was already named when Mr O'Brien picked him out at the SPCA five years ago, but said if he could have chosen the name himself, he would have called him Jack - the second most common name for a male dog registered in Dunedin. Council statistics show the most popular dog name in 2012 was Max - 1798 of the city's 16,000 dogs were registered with that name.
Max is followed by Molly (1374 registrations), Bella (1298), Jack (1164) and Jess (1198).
The information released through the Local Government Official Information Act and reported on the council's website, also lists the top five dog breeds responsible for attacks reported to the council for the year to July 31, 2012.
The top five breeds responsible for attacks reported to the council were Staffordshire bull terrier crosses and collie crosses (six attacks reported each), followed by American pit bull terriers, German shepherds and Labrador cross breeds (three attacks reported each).
Staffordshire bull terrier crosses (15) and Labrador cross breeds (10) were the worst offenders the previous year.
The total number of dog attacks reported to the council reduced from 191 in 2010-11, to 162 in 2011-12.
Council senior animal control officer Jim Pryde said reporting fluctuated year on year, and many attacks were not reported.
Larger dogs often appeared in the attack statistics as they were stronger and likely to cause more damage. Certain breeds had propensities to attack - for example, they were bred for fighting, hunting, guarding, etc, and behaved in an instinctive manner.
Other dogs had aggressive personalities, and some attacks were brought on by the dog's placement in certain environments.
A few simple things could be done to reduce dog attacks, including de-sexing dogs, as well as being mindful of how to treat them, remembering, for example, that dogs were pack animals and people, as their owners, should behave as the pack leader.
People should understand what upset or made their dogs aggressive and manage situations that led to that behaviour, while maintaining their status as the dominant member of the pack, he said.
A lot of a dog's behaviour came down to how its owner dealt with the animal.
The bottom line was that a bad owner equalled a bad dog, he said.
Top dog names
Most popular dog names in Dunedin -
• Female: Molly, Bella, Jess, Lucy, Ruby, Poppy, Tess, Meg and Holly
• Male: Max, Jack, Sam, Toby, Jake, Oscar, Buddy, Charlie and Mac.
