Whether looking out of a window, reclining beneath a Christmas tree or sitting in a suitcase, Nicole Kidman’s pet cats are frequently the star of her Instagram page. The actor’s affection for Ginger and Snow has extended to taking them along to last year’s Telluride film festival for the premiere of crime drama Destroyer.

But Kidman’s revelation in an interview with You magazine that she regularly takes hikes with the pets in a backpack has met with a more muted reception, with animal rights groups questioning the comfort of the cats while being so transported.

“I’ve just got one of those carriers,” said Kidman. “Have you seen those? Those backpacks that you can put them in? A cat carrier that’s a backpack and it has a window that they can peek out of and it’s got air and everything and they love it.”

Nicole Kidman. Photograph: imageSPACE/Rex/Shutterstock

Kidman added that the luggage is “really cute” and that her cats “can’t wait to get in” them.

However, Daniel Cummings, behaviour manager at Cats Protection, cautioned against such transportation for regular recreational use.

“We don’t advise people taking their cats out unless absolutely necessary as they are very territorial and crave freedom of movement,” he said.“Placing them in small and confined spaces and taking them to unfamiliar environments will cause a lot of cats stress. When transporting a cat it should be for a minimal amount of time; the cat should comfortably be able to have all four paws firmly on the base of the cat carrier and have space to turn and to lie down.

“Putting them in a backpack with a window means they have little opportunity to hide, which is what they would want to do in situations where they are scared. It’s unlikely that an experience like this will be beneficial for most cats.”

It's a very human perspective to think then would enjoy seeing the world like this

Cummings conceded that Kidman might well genuinely believe Ginger and Snow were happy with the experience, saying: “It’s a very human perspective to think they would enjoy seeing the world like this, rather than considering the situation from a feline perspective.” However, he added: “Cats would much prefer to explore outside, in their own territory, with control over their own movements.”

Meanwhile Elisa Allen, director at the UK wing of People for the Ethical Treatment of Animals, commented that “although most cats would prefer to lounge indoors than to go hiking, all cats are different, and it’s possible some may enjoy the outdoor experience.”

She added: “PETA encourages anyone who uses specially designed cat-carrying backpacks or any other animal-carrying accessory to be responsible and ensure that animals are carried gently and with care, aren’t confined for long periods of time, and are never left unattended.”

Elsewhere in the interview, Kidman said she also owned alpacas, chickens and 10 fish, and that she has in the past eaten ants, describing the taste as “sort of off. Just acidic-y. Kind of weird. And I’ll eat anything. I’ve eaten almost anything. Witchetty grubs, worms and insects…”