"These kinds of cases come up quite a bit," Ms Marshall said.
"People get quite emotional about it."
Another recent case involved exotic birds - one partner wanted the birds but the other wanted the aviary.
The value of pets is also a factor - particularly with horses and race horses.
"Quite often we have arguments about the valuation of animals and what they are worth.
"You get one partner saying 'you are taking the dog, it's worth $2000, so I want half that amount in my pot'.
"It's happening all the time, even with standard pets - you can have cats worth $1000."
In other cases, the pet is given away as one partner doesn't want it and the other can't have it in their new rental accommodation.
Lawyer Rachael Adams, of Tauranga firm Adams & Horsley, has also drawn up a shared custody arrangement for a dog.
"It was dealt with exactly the same as a child care dispute. It took as much time, was as expensive and as full of anguish for the parties."
Ms Adams said the couple were young and affluent, and regarded the dog as their "child substitute".
"It became as emotional as a custody dispute. They looked at the dog as their baby, they both wanted to be primary carer.
"They both thought they knew what was best for the dog. It was terribly distressing."
The dog in question began to behave "as traumatised as a child"; it was self-harming and lost fur.
Ms Adams said in most cases pets went with the children.
Pets are legally treated as property in relationship break-ups, and "are dealt with the same way as the linen and the cutlery".
"You sort it out between yourself, or it gets sold and split the proceeds.
"You can't divide the animal in half, you can't take half the dog each, which is probably why people do resolve it themselves - there is no solution."
Tauranga couples counsellor Mary Hodson said she had worked with many people who had been "really quite distressed" when their pet had gone with their ex-partner in a relationship break-up.
"It's another loss, so they have got the grief of the broken relationship but they have also got to face the loss of a pet.
"Depending on the circumstances it can be like a death. If a relationship has been difficult for a long time, the pet might be the one place that the person has found solace."
Tauranga Vets managing director David McDonnell said some clients had been separated as long as three years, but shared ownership and responsibility of their pet.
"You see it particularly with animals with chronic diseases, and on-going financial commitments for their welfare. They seem to put aside their differences and ensure the welfare of their pet."
In relationship break-ups, pets either became top priority, or else were re-homed as neither party wanted them, Dr McDonnell said.
In the case of some couples, particularly young newlyweds, pets were often substitute children, he said.
The animals don't come out unscathed - Dr McDonnell said cats in particular were sensitive to their surroundings.
A relationship break-up and change of environment could trigger stress-induced bladder problems.
