Any serious change in life needs 30 days:even the decision to buy a green sweater in stead of black...sounds trivial & shallow huh?
Well if stores give me 30 days to be sure about a trivial purchase adjustment shouldn't it be way too much to expect a dog used to being the only attention receiving pet to totally buy into someone whom is most likely stealing everything theirs let alone encroaching in GIZMO"S domain?
In a perfect world it would be a gradual adjustment of the new dog into the home: world's not perfect, unless there is a serious aggression issue they need to give it some time for both to adjust IMHO.
Did you remind them of common dog jealousy issues? Favorite spot, toy, person& to think of trying a gradual 'togetherness' divided attention & maybe separate areas, even just for sleep, feedings etc?
Hey worse comes to worse
at least they are loyal to their 10 year old dog right? Way too many "pet owners" ignore or worse dump their older dog over getting a new pup.
Sounds like maybe they are super loyal & concerned people who need patients & a little insight on adding an edition that's all.
Hiding doesn't always mean fear. I'm scared of lil kids sometimes too...especially ones that are loud, hyper, or just researching their new environment
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