Brought up deep in the countryside in the small picturesque village of Great Massingham, which is near King's Lynn Norfolk, he began observing wild animals at a young age, learning to use his sense of smell and sound to find his way at night when studying foxes and badgers.

Ellis first trained to be a gamekeeper, but left the job when the Head gamekeeper found out that Ellis was feeding rather than culling foxes. He then joined and served with the Royal Marines.

After he left the Marines he met a Native American biologist at a wolf seminar, and from that meeting he was able to spend seven years living with the Nez Perce Native Americans on their reservation in northern Idaho, United States as a volunteer in a project studying wolves at the foot of the Rocky Mountains. They taught him how to observe wolves, and he was able to get in to a pack of wolves and live among them. He recorded wild wolf howls and gradually learned to identify individual pack members and began to believe that wolves are highly intelligent and instinctive animals that exude trust and balance within the pack's social structure.

He is the founder and head of Wolf Pack Management at Combe Martin Wildlife Park in North Devon where he works with seventeen captive wolves, which include four pups born on 19 May 2008. There were originally six wolves at the park which he rescued from private ownership. He also regularly gives educational talks about wolves.

In 2005 Ellis spent eighteen months living in captivity at Combe Martin Wildlife Park with three abandoned wolf pups - Yana, Tamaska and Matsi, educating them to be wild wolves and becoming the pack's alpha male.

Ellis has spent much of his adult life studying and living with wolves and has learned to communicate with them through scent and sound. He currently lives directly outside the wolf enclosure at Combe Martin Wildlife Park, so that he is in close proximity to the wolves at all times.

The research projects Ellis is involved with in Poland and Yellowstone National Park in the United States have the goal of developing humane methods to discourage wolves from entering areas of potential conflict with humans.

Ellis has stated that he would like to see wild wolves eventually reintroduced into England, where they last lived in the 17th century when the last wolves were killed (see Wolves in the British Isles). Ellis has said about wolves, "Although many people refer to wolves as savage killers, I’ve come to know and love them as family."

He has written three books about wolves: The Wolf Talk (2003), Spirit of the Wolf (2006) and The Man Who Lives with Wolves (with Penny Junor, 2009). In 2004 BBC South West nominated Ellis as a "Local Champion" in South West England, a campaign that aims to highlight the work of people who are not always publicly recognised. He was featured on BBC Radio 4 on 2 May 2005 in a programme A Life with Wolves.

The Wolfman

Ellis was the subject of a documentary, The Wolfman which first aired on Five in the UK as The Wolfman on 18 May 2007, and has also been shown on the National Geographic Channel in the United States, where it was titled A Man Among Wolves. The documentary shows how, by carefully mimicking wolf behaviour, Ellis was able to raise the three wolf cubs to maturity. It also shows how his expertise brought him to the attention of a Polish farmer, whose livestock had suffered wolf attacks. Since wolves are a protected species in Poland the farmer hoped that Ellis might be able to find some non-violent way to deter the marauding pack. Ellis travelled to Poland to study the local pack, bringing with him audio recordings of wolf howls.

Ellis believed that if the local wolves heard howls coming from the farm they would believe another pack had already claimed it as their territory, and keep clear to avoid a conflict. In order for this to work Ellis had to determine the size of the pack and play back recordings of a similar-sized pack. Initial results were encouraging and in the first few weeks after the farmer began playing the recordings the farm suffered no further attacks. The documentary then shows Ellis returning to Devon, where he attempted to reintegrate himself with the three wolves. In his absence the wolves had established a new hierarchy, and though they recognised Ellis and welcomed him back he was now the pack's omega, relegated to a peace-keeping role between the new alpha and beta males.

Martin Clunes: A Man and His Dogs

Ellis featured in the first episode of Martin Clunes: A Man and His Dogs, a two-part documentary that aired on ITV on 24 August 2008 in which Clunes explores the canine world, and visited Ellis at in Devon as part of an attempt to discover what binds wolves with pet dogs, with Ellis revealing that a lot of dog behaviour which is interpreted as human, is inherited from the wolf's hierarchical pack instincts. Filmed in January 2008, Clunes joined Ellis with the pack at Combe Martin.

Living With the Wolfman

Living with the Wolfman is an eight part documentary about Ellis which aired in the United States on Animal Planet in October and November 2008. It is also due to be shown in the UK on Five. The documentary follows Ellis as he lives with the wolf pack at Combe Martin and his relationship with his partner, Helen and their life in Devon. It also shows how Ellis integrated his girlfriend into the pack.

Mr and Mrs Wolf

In February 2009, Five screened a follow-up two part documentary, Mr and Mrs Wolf which focused on his attempts to get partner Helen Jeffs adopted as a member by the wolf pack at Combe Martin, as a new "wolf nanny" for the pregnant alpha female, Cheyenne. The programme aired on 17 and 24 February.

Ellis has five children from two previous relationships. He met his current partner, Helen Jeffs in 2005. They live by the wolf enclosure at Combe Martin Wildlife Park.