What winter actually does to an alpaca
An alpaca in full fleece is built for cold, dry mountain air, and a crisp frosty night is far less trouble to it than a mild day of driving rain. The winter enemies are wind that parts the fleece and strips its insulation, wet that soaks through and destroys it, and the combination of the two on an animal that is old, young, thin, or recently shorn late in the season. Shelter design should be aimed squarely at wind and wet, not at warmth — a sealed, heated building creates the stuffy, humid air that this species' respiratory system dislikes.
That is why experienced keepers build for choice: a shelter the herd can walk into and out of freely, positioned so that using it is easy, and then let the alpacas decide, which they do precisely.
The three-sided shelter, sited properly
The standard alpaca winter shelter is open-fronted with three solid sides and a sound roof, deep enough that rain cannot blow to the back wall where the herd lies. Site the opening away from the prevailing winter wind and weather, on ground that drains — a shelter whose floor becomes a pond in every thaw is worse than a windbreak, because alpacas commit to lying in their chosen spot for hours. Raise or gravel the floor if your only available site holds water.
Leave the front fully open rather than gating it. Alpacas are prey animals with a strong herd instinct and a real reluctance to be shut into a space they cannot see out of or leave; a herd that distrusts its shelter will stand in the sleet beside it. Width matters too: the whole herd should be able to lie down inside together without the lowest-ranking animals being pushed out to the edges, since the animal excluded from shelter is reliably the one that most needed it.
Bedding, bodies, and the animals to watch
Deep straw or similar dry bedding inside the shelter is not a luxury. Alpacas rest in a sternal position with legs folded under, bellies close to the ground, and thin fleece underneath; a frozen or muddy floor draws heat out of them all night. Keep bedding genuinely dry, topping up rather than letting layers pack down wet, and clear the communal dung area alpacas naturally keep, which they will usually place at a distance from where they sleep if the layout allows it.
Within the herd, watch the individuals winter picks on: crias born late in the year, elderly animals, any alpaca that came into winter thin, and one that has been ill. A waterproof coat on a vulnerable animal during a wet cold snap is a reasonable keeper's tool, checked daily so it never traps damp.
Feeding and watering around the shelter
Winter is when forage quality drops and the herd's energy needs rise, so hay should be available under cover or right at the shelter where eating does not mean standing in the wind — alpacas will skip meals in bad weather in a way that costs them condition quietly. Water is the other chore that decides winter welfare: check that it is liquid, not merely present, morning and evening on hard days, and site the trough where a dominant animal cannot guard it away from the shy ones while the rest shelter.
An alpaca that is shivering persistently, lying apart from the herd, or off its feed in cold weather should be seen by a veterinarian promptly; this species hides decline until it is advanced.
The winter routine — bedding checks, water breaking, the list of animals on watch — reads best as one shared page, and KinsLe Family Sharing keeps that page in front of every family member helping with the herd.