Registration and Identification
It is the responsibility of the owners of animals between the age of 3 to 6 months to have them identified with a microchip and registered (Decreto nº 313/2003 of the 17th of December artº 3º).
The electronic identification (microchip) can only be implanted by a veterinarian, by the subcutaneous application of a capsule in the left lateral side of the neck (Decreto nº 313/2003 of the 17th December 2007 artº 3º):
After the implantation of the microchip the owner has 30 days to register and license the animals in its residence area, at the local office of the "Junta de Freguesia". (Portaria nº 421/2004 of the 24th April art nº 2º and 3º):
The registration of the animal must be renewed annually at the office of the "Junta de Freguesia" where the animal was first registered (Portaria nº 421/2004 of the 24th of Aprilart nº 4º).

Walking your dog
Every cat and dog that walking in public places must wear a collar or harness with inscription of the name, address, and or telephone number of the owner, in any possible way.(Decreto nº 314/2003 of the 17th December art 7º)

Should the registered animal dies, is sold to another owner or disappears, It is the owner´s responsability to report it to the "Junta de Freguesia" where the animal is registered in order for the registration to be canceled. Failure to do so and in the event that the animal is subsequently found or captured the registered owner can be accused of abandonment.(Portaria nº 421/2004 of the 24th of April art nº 3º). The deadline for reporting the death or theft or lost of the animal is 5 days, change or losing his sanitary card - 30 days (decreto nº 313/2003 of the 17th December art nº 12º)

Owners of all dogs are obliged by law to ensure that his dog over the age of three months is vaccinated against rabies (Portaria nº 81/2002 of the 24th January art nº 2)

Animals in appartment
Animal owners resident in a building may only have 3 dogs or 4 adult cats per appartment, never exceeding 4 animals in total. (Decreto nº 314/2003 of the 17th December art nº 3º). Please bare in mind other restrictions on building regulations.

Responsibility for dog Actions
The owner or other person in control of a pet shall be held responsible for any injuries or damages caused to a third person or his property, and will also be held liable for any expenses incurred as a result of medical treatment and subsequent damage caused, along with any other crime or civel responsabilities.(Portaria nº 81/2002 of the 24th January art nº 29º)

Animal abandonment
It is considered as animal abandonment the following:
a)Taking no effort to provide the necessary care and accommodation.
b) Freeing the animal from his usual accomodations without helding anyone responsible for its care and accomodation, such as other person, the local authority, or animal shelter.

These acts are considered a small offence punishable from 25€ to 3740€ (Decreto nº 315/2003 of the 17th of December art nº 6ºA and 68º)

Dangerous and Potentially dangerous animals
Dangerous, by definition, are the animals that in any way have revealed aggressive behaviours; potentially dangerous animals are the ones that according to species or its behaviour may cause injury or death to people or other animals, as well as certain breeds and crossing of that breeds referred in a public list of the Agriculture Ministery (Decreto Lei nº 312/2003, de 17 de Dezembro), as indicated below.

List Type of breeds and crossing of breeds
The list of breeds and crossing of breeds considered potentially dangerous is ruled by Portaria, wich can modifiable at any time. For now, it consists of the following breeds:
I. Fila brasileiro
II. Dogo argentino
III. Pit Bull Terrier
IV. Rottweiler
V. American Staffordshire Terrier
VI. Staffordshire Bull Terrier
VII. Tosa Inu

It is mandatory for all dangerous and potentially dangerous dogs referred above to have electronic identification (microchip), a special licence issued by the "Junta de Freguesia as well as a liability insurance made by the owner.
It is also required that the owner, over 18, undergoes a psychological aptitude evaluation, sign a responsibility term, and shows no criminal record.

The microchip is also obligatory for all hunting dogs, for show dogs, for dogs with commercial or lucrative purposes, in shops, fairs and competitions, breeding kennels, publicity and similar purposes:

Regardless of breed or purposes, all dogs born after the 1st of July 2008 must have a chip.
In the case of cats this obligation will take place once a date, yet to be defined, is declared by the Ministery of Agricultura
All animals must be identified between the age of 3 to 6 months.

Note: This is information should not substitute the reading of the law itself.