Do you feel like your dog is always sad when you leave the house? There's a reason for that. Alexandra Bassett, a dog trainer and animal behavior expert, told BestLife that "all dogs are born with a set of survival instincts," including one to be in a pack.

So, because "survival in the wild requires them to stick together at all costs, pack instincts compel your dog to watch you and follow you wherever you go—which is why our dogs follow us from room to room," she added.

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Eventually, these behaviors can lead to dogs developing separation anxiety when they're away from their owners. "Just like a human having a major panic attack, a dog with separation anxiety has a hard time calming down once the stress response has kicked in." There are signs that can help you identify the condition. Check out the list.

Signs of separation anxiety in dogs:

• They become destructive. Typically, "dogs tend to chew, lick excessively, or soil the house when they are anxious," explained Josh Snead, the CEO of pet insurance company Rainwalk Pet Insurance;
• They bark or howl excessively. "Excessive barking, whining, or howling when their owner leaves the home" are some of the more obvious signs of separation anxiety, said veterinarian Melissa M. Brock;
• They get restless before you leave. Look for body language cues, like a furrowed brow, pinned-back ears, or a tucked tail, advised Alexandra Bassett;
• They drool (or pant) more than usual. "Excessive drooling, panting, or salivation [or] increased heart and respiratory rate" are some of the more common physical signs of separation anxiety, according to veterinarian Lindsay Butzer;
• They go to the bathroom in the house, even if they're potty trained, warned Melissa M. Brock;
• They start self-mutilating. In severe cases, for example, dogs may begin "excessively licking or chewing themselves, causing skin lesions."

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