Any dog is capable of attacking, the district's dog enforcement agency warns.
Environmental Northland manager Keith Thompson says dog attacks can happen anywhere, any time.
But he says there were just 10 serious dog attacks in Whangarei in 2013 and complaints about dogs were well down on 2012.
Of the 10 serious attacks, seven or eight were against other dogs.
Mr Thompson says in two cases people's pet dogs were killed. In other cases victims needed stitches or vet treatment for puncture wounds.
The serious attacks also included attacks on other animals, including sheep and alpacas.
But Mr Thompson says last year he saw one horrific attack, when a mental health worker was mauled visiting a client in July.
He says it was the worst attack he's seen in 17 years.
The victim received severe bites to her body, legs and head, particularly her ear.
Paul Logan pleaded guilty in the Whangarei District Court to three charges relating to the incident and Mr Thompson says it is the only prosecution relating to dogs to go to court last year.
In 2012 there were slightly more serious attacks by dogs, about 13.
However Mr Thompson says 122 infringement notices for attacks were issued to dog owners in 2013, slightly more than the 116 issued in 2012.
But the number of complaints about dogs last year was well down, at 1480 compared with 1938 complaints in 2012.
Environmental Northland has impounded 514 dogs last year, fewer than the 643 in 2012.
Mr Thompson says the reason for impoundment is not classified but could be because the dog is a stray, unregistered, wandering or may have been involved in an incident such as an attack.
The SPCA re-homes suitable abandoned or unclaimed dogs but they are sometimes put down if they are diseased or involved in an attack.
NO-GO ZONE FROM 9 TO 5
Summer beach restrictions are now place on Whangarei's beaches.
Dogs are not allowed on beaches from 9am to 5pm from December 20 to February 28.
This applies to all beaches, apart from the dog exercise area at Ruakaka, between the old power station site and Mair Rd.
The dog park at William Fraser Memorial Park on Pohe Island is also open all year round, providing a safe off-leash area for dogs to play.
Environmental Northland enforces Whangarei District Council bylaws on dogs, animals, noise and parking.
- Whangarei Leader
Are our classrooms becoming overcrowded?