The girl had faced "significant hardships" in her life, the court heard, including the death of her mother.
On the first occasion that he sexually assaulted her, he came into her bedroom and told her to lie on her back.
He then sexually assaulted her and filmed it on his cellphone.
It led to an "ongoing pattern of behaviour", the Crown said, where the man had the young woman perform sexual acts in exchange for basic necessities including clothing and deodorant.
"It was through this abuse of power that the defendant was able to exert control over the victim," the summary of facts says.
On one occasion, he tied the victim's ankles and wrists to a bedframe and sexually abused her.
She received bruising and friction burns as she tried in vain to get away.
Afterwards, the man gave her two $50 notes – and drove her to a shop where she bought clothing and a duvet.
But on the way home, he pulled over and attacked her again.
He pretended to be speaking on his cellphone to avoid suspicion from passing motorists, the court heard.
The next day, the grandfather again attacked.
During his sexual assault, he grabbed the victim's Jack Russell terrier puppy by the collar and forced it to also sexually assault her.
Powerless, the victim attempted to "disassociate herself from what was happening" by putting headphones on.
But while she did so, with her grandfather thinking she was just listening to music, she filmed the offending on her phone.
Later, she forwarded the images and videos to a friend who came forward and reported the incestual abuse to police.
After his arrest, police seized a number of electronic devices belonging to the grandfather, which would later reveal 160 images and 69 video files of the victim naked and engaged in sexual activity.
"When spoken to by police, the defendant readily admitted several of the offences and showed little remorse for his actions," the summary of facts says.
The man, who has previous dishonesty-related convictions, earlier pleaded guilty to five charges of sexual connection with a dependent family member and one count of bestiality.
Today, a harrowing victim impact statement was read out to the court.
She told how she often had to ask for basic necessities, including underwear, personal hygiene products and deodorant, which her grandfather would use to "manipulate" her.
Now, she can't call him granddad anymore, saying, "A grandad is someone to keep you safe and he never did".
The grandfather shook his bowed head in the dock while her statement was read out.
She called him a bully and worried where the images are now – and who he sent them to.
During the attacks, she asked him to stop, and afterwards was left feeling "unclean and disgusting". She feels embarrassed and ashamed, and has undergone counselling.
Since she spoke to police, her family has turned against her, she told the court. They believe that she encouraged him to do those things to her.
"I don't understand this - I never wanted him to do anything to me," she said.
Christchurch Crown Solicitor Mark Zarifeh said the actions were "depraved" and involved an element of grooming with a highly-vulnerable victim.
Defence counsel Donald Matthews accepted that the victim had a high level of vulnerability.
Judge Alistair Garland sentenced him to four years and 10 months' imprisonment.
Thirteen people had been charged with bestiality since 2010/11, according to data released to the Herald by the Ministry of Justice under the Official Information Act (OIA) earlier this year.
People have appeared in the District Court, High Court, and Youth Court across the country.
The most active year, according to the Ministry of Justice figures, was 2018/19 where four separate individuals were charged with bestiality.
The charge carries a maximum penalty of seven years' imprisonment under the Crimes Act 1961.
There have been nine prosecutions over the last seven years, according to New Zealand Police data, including two people last year.
There have been some shocking bestiality cases in New Zealand history.
In 2015, a 26-year-old man appeared in Manukau District Court facing charges of bestiality dating back to 2005, in Rotorua, Taupo and Tauranga.
He was charged with bestiality with a bull, a cat, a calf, a dead calf and two dogs.
The man was also charged with committing an act of indecency with two dogs and a goat and wilfully mistreating a cat causing it to die by drowning it, as well as one charge of indecent assault against a child in 2004.
And in 2008, a North Canterbury man admitted having sex with a goat.
There was an infamous Truth newspaper poster from the 1970s after allegations of cow bestiality – also from North Canterbury, this time Ohoka, where the headline read: "Cow Poker From Ohoka".
In 1924, the grand jury at Auckland recommended that judges have the power to inflict the punishment of flogging for cases of bestiality.
The national newspaper archive, Papers Past, also reveals various instances of Kiwis coming before the courts on allegations of indecency with animals.
Several cases surfaced in the law courts between the 1880s and the turn of the 20th century, spanning the country from Invercargill, Dunedin, Hokitika, Christchurch, Carterton, and New Plymouth.
Sexual harm - Where to get help
If it's an emergency and you feel that you or someone else is at risk, call 111.
If you've ever experienced sexual assault or abuse and need to talk to someone, contact Safe to Talk confidentially, any time 24/7:
• Call 0800 044 334
• Text 4334
• Email support@safetotalk.nz
• For more info or to web chat visit safetotalk.nz
Alternatively contact your local police station - click here for a list.
If you have been sexually assaulted, remember it's not your fault.
