cow - The Cairngorm Reindeer Herd

19th June 202612th June 2026

Reindeer Metabolism and How it Changes Throughout the Year

The bodies of reindeer go through many changes allowing them to cope with huge temperature difference throughout the seasons. In summer reindeer can cope with temperatures above 30 degrees and the lowest recorded temperature that reindeer have been know to survive is -72 degrees Celsius. Reindeer have two different coats, a thick white winter coat as well as a fine, dark summer coat. Their antlers grow in an annual cycle and the different times of growing and shedding them allows different animals to be dominant at different times of year. One of the most interesting, and important, changes to a reindeer though, you can’t see – their metabolism.

Colorado, Iskrem, Yangtze looking smart in their summer coats.

Reindeer have adapted to eat vast amounts of food throughout the spring, summer and autumn to gain enough weight to survive the winter, when food is scarce. To cope with these changes in food availability their metabolism changes too. In the summer reindeer will graze around the clock, eating a huge variety (between 200 and 300 different species) of plants which are high in nutrition. This allows each individual to grow a new set of antlers, they start to grow in the spring and are fully grown by the end of august and the heaviest set we have had in our herd, weighed a whopping 8.9 kgs. The summer is also the time that the young reindeer grow in body size. Finally, every reindeer will need to gain body fat which will act as reserves over the winter. All these things require their digestive system to work in overdrive converting the food they are eating into energy that can be used by their body to create protein, bone, fat, and whatever is needed.

Ryvita grazing and growing her beautiful antlers.

Cow and calf grazing on the high plateau plants.

On the contrary, winter is all about survival. During the winter most of the plants will have died under the snow and 70% of a reindeer’s diet is made up of lichen. Lichen is a symbiosis of fungi and algae and is very resistant to extreme changes in temperature. Over the winter lichen won’t grow but it will stay dormant, preserved under the snow. Reindeer will then dig down through the snow to reach the lichen. But lichen is relatively low in nutrients, just enough to sustain the reindeer through the winter and their metabolism shifts in line with this. In fact, even if you gave a reindeer a big pile of food, during the winter, they just aren’t as hungry and wouldn’t eat it all.

During the winter reindeer are no longer growing their antlers, they won’t increase their body size at all, a calf will grow lots in the first 6 months of their life and then stay the same size for the next 5 months, until the following spring. They will survive the winter by using their fat reserves. The one important growth that does happen in winter is that of a growing foetus. This is the reason that the females grow antlers and keep them after the males have shed them, as it gives them a physical advantage during the time that they are pregnant and therefore they get first dibs on the food.

*Vienna and Amazon showing off their beautiful antlers right through the winter.*

A group of our males in the winter having cast their antlers.

But how does a reindeer know that it’s time for spring? Rather than responding to food availability or temperature which may well change year by year, the changes in their metabolism are triggered by the changes in daylight. The increased daylight associated with spring is detected by specialised receptor cells in their eyes which then convert to a hormonal signal using melatonin. Melatonin is synthesised during the dark period each day and then synthesis stops during daylight. This means that the amount of melatonin varies based on the time of year. The concentration of melatonin has many effects. In terms of metabolism, in the spring as melatonin decreases, this increases the appetite of the reindeer. In the autumn, as melatonin increases, this decreases the appetite of the reindeer and increases the breakdown of fat stores. The changing melatonin levels also controls their antler growth and release of sex-hormones but that may be another blog in the future.

For anyone particularly interested in a much more in-depth description of the physiology behind these changes, I would highly recommend reading this article.

https://septentrio.uit.no/index.php/rangifer/article/download/335/327/1280

Glacee, Salsa and the herd enjoying a snowy day!

If you have made it this far, thanks for reading my very nerdy reindeer biology blog! Hopefully you have learnt something and enjoyed the pictures of the reindeer along the way.

Lotti

13th August 202114th August 2024

Spy – the reindeer we’re all a bit scared of

A while back, I wrote a blog about how difficult it can be to locate calving reindeer within our hill enclosure (see previous blog). But with one reindeer, finding her is just the start of our problems.

Spy is notoriously protective of her calves, at least for the first few days, and getting her from the main part of the enclosure where she has calved through the gate into the ‘bottom corridor’ (the area of our hill enclosure that we use as a nursery for the newborn calves) can be ‘entertaining’, to say the least. Most reindeer will lead their calf away from us if they can for the first two or three days, but that is the extent of their protective motherly instincts. After that the lure of food wins out, and they decide that actually, they probably can’t be bothered to march away, and that we’re no threat anyway. Some very tame (or greedy) reindeer just totally skip the avoidance phase and are completely blasé about us being around their calf, even if it’s literally just been born.

The way it *normally* works: Myself gently pushing Cheese and newborn Kiruna in the right direction across the hill enclosure a couple of years back.

Spy? Spy’s instinct to protect goes into overdrive, to the point that we are all VERY wary of her for a couple of days. It would be fine if we could just leave her to get on with everything herself, but in reality we do need to get hold of the calf just once, to spray it’s naval with the antibiotic spray and to put some insect repellent on it’s back, and this has to be done when the calf is less than 24 hours old (otherwise it can run too fast to be caught). The first time that Spy calved in the hill enclosure I was the one who was first on the scene, and discovered that for the first time ever, I wasn’t going to be able to walk straight up to the little furry heap on the ground, despite the fact the calf was obviously not yet strong enough to stand up and run away. Whatever I tried, Spy constantly circled to keep herself directly between the calf and myself, and made it abundantly clear that should I persist, I would be the one coming off worst in the situation.

The only way to get hold of Spy’s calf is to get her through a gateway ahead of us, and then manage to get the gate shut behind her before the calf gets there. Thankfully newborn calves don’t understand fences or gates and will generally just blunder in a straight line towards mum and into the fence, sticking their wee heads and necks between the wires and wondering why their bodies don’t follow. At this point we can swoop in, catch the calf, sort out what we need to do as quickly as possible, and then post it through the gateway back to mum. That first year when Spy had calved, I returned to Reindeer House to announce that yes, she’d calved, yes it seemed fine and strong, but no, I had no idea what sex it was, and no, it was not yet in the nursery area. I think I was then off the following day, and by the time I returned to work Spy and calf were in the right place but Fiona had an epic tale of woe about the trials and tribulations this had involved.

With Nok, the calf who I’d failed entirely to get close to.

This year was the hardest yet, not helped by the fact that in 2020 Spy had grown her nicest set of antlers ever, tall, elegant but very, very pointy, and she still had one of them. A reindeer armed with 2’ tall spiky weapons on her head that she’s not afraid to use is considerably more daunting a prospect than a bald reindeer. We managed to gently push Spy all the way to the gate into the bottom corridor without issue, but getting her through the gateway itself took four of us about 30 minutes, with an awful lot of time spent in a total stand-off. Watching Fiona move gradually towards Spy, arms out trying to push her gently towards the gate whilst the rest of us hung back was like watching a lamb go to the slaughter. I wondered whether Fiona would remain unscathed, and to be honest it was a close run thing! All four of us closed around her in a semi-circle, tighter and tighter, but it was a delicate operation of continuously reading Spy’s body language and reacting to every movement and step. Quietness is needed in this sort of situation, there was no rushing or shouting or flapping of arms, until the sudden speed needed to get the gate shut once she finally went through. Catch the calf quickly, all hearts thumping quicker than usual, and a flood of relief! Calf sexed (male), antibiotic spray on naval, fly-spray on back, post through gate, and high-fives all round.

Not one of Spy’s calves (this is Angua’s calf Chickpea), but a quick cuddle is usually needed once all calf duties are done and everyone’s in the right place!

By two days later Spy had completely chilled out once again, knowing perfectly well that once she’s in the bottom corridor none of us are going to try and touch her calf, and was eating off the feed line with the rest of the mums as happy as larry. And then rest of us were also very happy to have survived another calving season involving Spy unscathed! She’s always a reindeer we treat with respect and never handle anyway, unless we have to, for 363 days of the year, but for those two other days she is a very different kettle of fish.

Spy in the nursery part of the enclosure a day after trying to kill us all this year, antler having fallen off in the meantime. Suddenly she doesn’t look quite so intimidating when not waving a large, spiky antler around!

Hen

19th February 20169th March 2024

Memorable Reindeer of the Past: Flake

I thought maybe I’d start an occasional blog series remembering particular characters in the herd who are no longer with us, because some readers amongst you may have met them once upon a time, and those of you that didn’t can at least have a brief glimpse of some of the most memorable reindeer from our herd.

I scrolled through our photo archive of reindeer no longer with us, and my eye alighted on Flake. Well, there is a fine place to start! Plenty of memorable things about Flake, and what a fabulous reindeer she was over the years. I first met her in summer 2009, having been away for several months, and arrived back and headed up to the hill enclosure for the first time. Most of the reindeer there I recognised, or managed to work out pretty quickly, but who was this bull with a blue ear tag? Quite narrow, upright antlers compared to some, but still a very good size, and ‘clean’ in design rather than the chaotic, many tined antlers of the castrate males. I was flummoxed. Turns out it was Flake, in the enclosure for the summer months rather than out free-ranging like the other females, due to her calf Diddly (who we’ll get to in a tick).

Flake’s fabulous antlers set her apart from many of the other cows, as they were much more elaborate than the average female set and a very decent size most years. In 2009 however, the year I first saw her, they were a particularly fine set and there is a specific reason for that…

Flake was a notoriously bad breeding female. Her calving record, filed away on our computer here, is basically a list of disaster after disaster, from stillborn calves, to ones that got stuck and needed pulling out by the vet, to premature twins, you name it. In 2011 she produced a calf who had a problem with his joints, probably not helped by the fact that Flake had calved right next to a large boulder which he had promptly got stuck beneath! The entry on her records for her final calf Brave, born in 2012, reads ‘Normal!!!!’.

But before that, in 2009, there was Diddly. Born prematurely, she was tiny, so much so that she couldn’t reach Flake’s udder. Even if she had been able to, Flake didn’t produce any milk that year anyway, so right from the start we had to hand-rear her, bottle feeding through the night to start with.

Heather feeding Diddly — Heather working hard to look after Diddly, while Flake stands by

Flake and Diddly started off in the paddocks, then eventually moved up to the hill enclosure for the remainder of the summer and the autumn. And that is the reason for Flake’s great antlers – while we slaved away feeding Diddly for the first 5 months of her life, Flake basically sat back and let us do all the work – a ‘designer mum’. All the energy going into her body from the feed we lug up the hill every day went straight to her antler growth rather than to milk production. The antlers of the other females, out on the high tops foraging for themselves, all showed the detrimental effects of the effort of raising a calf, being smaller and wigglier, but not Flake. She resided in state in the hill enclosure all summer, fat as butter and with fancy headgear, with a queue of reindeer herders tending to her every need and raising her calf for her!

Flake passed away in 2013, an old girl by that point. Very sadly, Diddly followed later that year, but not before producing her son Crowdie, who is now nearly 3 years old and a great fun wee reindeer. Diddly was an interesting character in her own right as she never produced any antlers at all, remaining bald for her whole life, a little quirk that sometimes happens with female reindeer.

Hen