Resource guarding is when a dog controls access to food, objects, people or places that are valuable to them through defensive body language or aggression. This is a relatively common behaviour that is influenced by various environmental and situational factors, including a natural survival instinct, but can also develop into a problematic habit.
If your dog does take to 'stealing' and guarding a particular thing...
Do not chase them. Not even if it's your best slippers and your feet are cold! They may interpret this as a fun game, and in fact do it more often to instigate play time and get your attention. They may learn to run, hide, and keep up the chase.
Do not steal it back. Stealing the item back from them may also teach them that your approach means they are about to lose their 'thing', and exacerbate the the protective or aggressive behaviour in anticipation of you taking it back. Some dogs may even nip or bite any stray hands sneaking in to pinch 'their' stuff.
Instead of chasing your dog and stealing their new found favourite things back from them, you will need to introduce behaviours and routines such as Drop, Leave It, Impulse Control, and implement preventative measures to begin to avoid the behaviour altogether. It is important to take an issue such as resource guarding seriously and consult a professional with how to tackle the behaviour together effectively for your individual circumstance.
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