An unlikely friendship between Heidi the deer and her best pal Tonka the dog began when Heidi was just two days old.

Heidi, now 10 months, is a much-loved member of the Fulton family, who live on 0.8 hectares in north-west Sydney.

Joel Fulton, an electrician by trade, has a business making light fittings out of deer antlers, so when the family was deciding on which animal would be best to keep the grass down on their block, a deer seemed the obvious choice.

When Heidi arrived in early December, she and Tonka, a Staffordshire bull terrier, bonded immediately.

Heidi and Tonka get to know each other after Heidi's arrival. ( Supplied: Joel Fulton )

"She was really inquisitive from day one, and he [Tonka] quickly learnt he had to be gentle," Mr Fulton said.

"He saw the attention she was getting and realised she was part of the family, rather than something he would chase."

Heidi weighed just 1.1kg when she came home and stood about 30cm tall.

Now she is about 80cm tall, but Tonka is coping well with the ever-increasing size of his friend.

"He's adapting really well. There was a time he could stand over her," Mr Fulton said.

Heidi spends part of her day in a paddock, but her favourite time is early morning and late afternoon when she is let out for a wander around the rest of the property.

She will walk up to Tonka, put her head down and give him a bit of a nudge, jump back and then it is 'game on' and the chase begins.

"She can run along, jump in the air and turn 180 degrees and gallop the other way," Mr Fulton said.

"Tonka, being stocky and with short legs, has a big arc of a turn to take off after her."

Mr Fulton said Tonka was never more than 20 metres away from Heidi, and when she lay down for a rest, he would too.

While Tonka loves Heidi, he is not always keen on sharing his things. ( Supplied: Joel Fulton )

"She sleeps under the trampoline or outside the kitchen window. She likes to explore what we're doing," he said.

"She comes into my workshop and showroom, gets in the way.

"Tonka has taken to eating a lot of grass, but he appears to be chewing it quite well, so hasn't had any issues so far.

"If Tonka is chewing on a stick, Heidi will try and scratch her head on it, and nibble the ends.

"She's very inquisitive, always gets her nose into everything."

Heidi is a much-loved member of the family. ( Supplied: Joel Fulton )

With building work going on around the house, there are even more spots for Heidi to explore.

She has been known to walk through trenches before concrete is poured, and try out the taste of ceiling insulation.

The family has recently introduced two more deer the same age as Heidi to the property, but they have not been hand-reared.

"She thought they were a bit crazy. One dived through an internal fence, which I didn't think was possible," Mr Fulton said.

"Heidi panicked because they were charging around, but the next day they were all lying down sleeping.

"She's okay with them now. They do take flight with anything different in the environment, like a plastic bag on the fence, whereas Heidi will go up to say hello."

Heidi likes to help out in the Rapid Effects workshop, where Mr Fulton makes products from deer antlers. ( Supplied: Joel Fulton )

Racking up style

While Heidi, being female, will not grow antlers, Mr Fulton is a bit of an expert when it comes to using them.

He sources antlers from venison farmers for his business, and makes items such as light fittings, table lamps, candle holders, coat hooks and door handles.

Mr Fulton makes light fittings and other products out of deer antlers. ( Supplied: Rapid Effects )

Antlers grow on male deer over about 120 days, reaching full size in time for mating season.

"Growth starts in October-November and the antlers are covered in velvet, with a blood supply going through them," Mr Fulton said.

"Eventually the testosterone level changes and the blood supply stops, and the antler changes from being like cartilage to being solid bone.

"The head gear is then ready for battle during mating season, when a deer's best mate becomes his mortal enemy."

After mating season, the antlers drop off, around August or September.

"The antlers I use are ethically sourced. They haven't been cut off, and the animal hasn't been shot," Mr Fulton said.

"Antlers are completely different to horns."