A family dog that mauled a two-week-old baby after his mother fell asleep on the sofa may have thought the newborn was a "squeaky toy", an inquest has heard.
Newborn Reuben McNulty was sitting on a teddy bear ring next to mum Amy Litchfield when the Staffordshire bull terrier-type dog - called Dotty - attacked.
His father, Daniel McNulty, who had been outside smoking, heard crying as he returned to the flat in Yaxley near Peterborough, Cambridgeshire, and discovered what had happened in the early hours of November 18, 2018.
Reuben spent nearly a month in hospital fighting for his life but died on December 13, 2018 from his head injuries.
At an inquest into his death that opened on Tuesday, Cambridgeshire's area coroner Simon Milburn said Mr McNulty told a 999 call handler: "I think the [expletive] dog's attacked him.
"My partner was asleep. I just heard crying."
In a police interview, summarised by the coroner, Mr McNulty said he'd returned to the flat and, "on picking [Reuben] up he saw the injuries and saw the dog Dotty licking its lips."
Simon Newbury, a specialist in veterinary forensics, said there were 23 individual puncture marks to Reuben which would have come from "at least four to five bites or engagements".
"I suspect Reuben was shaken between engagements," he said. "This attack would have lasted a minute or longer.
He said he believed Dotty "saw Reuben as a small prey or squeaky toy".
Dotty and a second Staffordshire bull terrier type dog called Fizz, both female and aged between around seven and nine years of age, were seized by police and later destroyed, the inquest heard.
Mr Milburn said: "It's clear on any reading of the evidence there had been no previous issues or concerns with either of those dogs."
He went on: "There's evidence that both parents were suffering from tiredness understandably as a result of caring for a newborn baby and evidence they had agreements as to who would have a turn at sleep and look after Reuben at various times."
Ms Litchfield told police in interviews she remembered her partner saying he was going out for a cigarette but fell asleep before he had come back.
"I think the best way to characterise that series of events is that it was an unintentional short period of inadvertent inattention which sadly had horrific and tragic consequences," Mr Milburn said.
Recording a narrative conclusion, he said: "Reuben died as a result of head injuries caused when he was attacked by a dog which was a family pet inside his home address."
Detective sergeant Emma Compson said police would take no further action against Mr McNulty or Ms Litchfield, who were arrested at the time of the attack.
She added the pair had "separated as a result of the trauma".
Social worker Sophie Bradley said Ms Litchfield described the dogs as "her babies" and had been "warned dogs can be unpredictable and can get jealous".
She said that on visits "both dogs were very friendly and didn't show signs of aggression".
She said that, as part of a child protection plan by social services, it was agreed that Mr McNulty and Ms Litchfield "would keep the dogs in the kitchen behind the stairgate, which they already had in place".
Ruth Hinchey, Reuben's maternal grandmother, said: "I've never seen or known Dotty to be aggressive towards anyone."
Mr Milburn extended his condolences to the family.