There has been a threefold increase in the number of families contesting wills over money left to pets and animal charities.
Nicola Marchant, contentious wills and probate expert at law firm Pannone Solicitors, said she believes this increase is down to the economic climate.
"Interestingly, most of those challenges concern legacies and gifts to charities for animals," she said.
"It doesn't seem to matter whether the gift is only a few thousand pounds or the entirety of a £1 million-plus estate. It seems that in tough times, we are not quite the nation of animal lovers we once were!"
Marchant has seen cases where estates worth £1 million have been left to charities such as the RSPCA. She noted that donkey sanctuaries are particular favourites "for some reason".
"There is a stereotypical image of single, elderly people without children of their own leaving everything to the local cats' home, but in reality there are a number of cases where even children have been left out of their parents' wills completely in favour of charities, in particular animal charities.
"In one case, the children were seeking to contest the will of their late mother who left several hundred thousand pounds to two animal charities.
"Only last week we were contacted by the nephews of a lady who has bequeathed her £700,000 estate to the local donkey sanctuary."
Charities like the RSPCA are heavily reliant on donations. The animal charity says over half its work is paid for with money left by people in their wills.
Marchant said people who want to contest a will against an animal charity should be prepared for a lengthy battle.
In RSPCA v Gill, the claimant challenged the will of her parents after they left the family farm to the charity. Dr Gill said her mother had been bullied into signing the will.
She eventually won her challenge, but Marchant said that this was an exceptional case and that overturning the contents of a will can be extremely difficult.
"The problem is that a charitable trust is required by its constitution to act in the best interest of the charitable institution - therefore many will take the view that defending potential legacies and gifts in wills is in fact, in the best interest of the charity."
THE PET RICH LIST
Ella Wendel's Poodle Toby
When American heiress Ella Wendel died in 1931, she left an estimated $15 million (then £3.3 million) of her family's estate to her Poodle Toby, although some believe the bequest was worth up to $30 million. The rest of her wealth was left to churches and charities. Before she died, Toby slept in a brass bed beside his mistress.
Maria Assunta' cat Tommaso
In 2011, Maria Assunta left $13 million (£8.2 million) to her rescue cat Tommaso, which she took in after finding it on the streets of Rome. Assunta did not have any children so she left the money to her cat via her nurse Stefania, who said: "I promised her that I would look after the cat when she was no longer around. She wanted to be sure that Tommaso would be loved and cuddled."
Leona Helmsley's Maltese Trouble
New York property tycoon and hotelier Leona Helmsley left $12 million (£7.5 million) to her pet dog Trouble when she died in 2007 at the age of 87. Helmsley also stipulated that her entire trust, valued at up to $8 billion (£5 billion), should be used for the care and welfare of dogs - according to New York Times sources.
Alexander McQueen's dogs Minter, Juice and Callum
The flamboyant fashion designer Alexander McQueen was found dead in his London apartment in February, 2010. In his will, he bequeathed £50,000 to his dogs, which was put in a trust to pay for their upkeep for the rest of their lives. He also gave £100,000 each to animal charities Battersea Dogs & Cats Home and the Blue Cross.
Awaiting inheritance: Oprah Winfrey's dogs
Oprah Winfrey has said she has put aside $30 million (£18.9 million) in a trust fund for her pet dogs when she dies. A source told Australia's Woman's Day magazine: "Oprah has a menagerie of animals and she wants them to be pampered for the rest of their lives if she were to die first. She has four dogs, plus various other pets, so she rewrote her will to include millions for their care."