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Archive for February, 2011

The amazing strategies behind Caribou antlers. Nature has its reasons.

Caribou with large set of antlers

Caribou antlers all have a story to tell...

by Ian Thorleifson

Caribou antlers are spectacular to look at, but the strategies behind their growth and importance to an individual caribou are even more amazing. Everyone knows that males like to show off for females – that goes without saying. Caribou bulls are no different than males from other species, and the females do respond appropriately, but the showing off and responding is much more complex than just a look.

A caribou bull weighs about 325 pounds or 160 kg. They start with a bare forehead every spring, and in less than 120 days they grow a complete set of antlers that may weigh as much as 35 pounds – 10 percent of their body weight! That kind of growth is almost magical – in fact, no other living tissue grows that quickly except mushrooms!

While the antlers are growing, they are soft, covered with skin and hair and made up of spongy cartilage. They feel like your nose and similarly also have a bone at the base. Unlike your nose however, in the last month of antler growth the cartilage calcifies and becomes hard bone.

To keep the antlers tough and resilient enough to withstand the incredible pressures of battling with other bulls, the blood flow in the antlers – super quick and of large volume while the antlers are growing – slows to just the bare minimum. This prevents the bone from becoming too hard, as to be brittle and easy to break.

Growing new appendages that weigh 10 percent of body weight in such a short period of time takes more energy and nutrients than a bull caribou can generate by eating, so he robs his own skeleton for building materials like calcium and phosphorus, to the point where his ribs would break easily if they were struck in the summer. This is why the bulls complete their antler growth at least a month before the rut. They need to gobble as much nutrition as possible to replace those borrowed building materials and get strong and fat before the rut.

Antlers are expensive, but they add up to a graphic demonstration of the bull’s health, ability to mobilize nutrients and avoid predation – a measure of his vibrancy and value as a sire of many caribou calves.

Caribou cows grow antlers as well, but their strategies are quite different. Their antlers are much smaller than the ones the bulls grow, and they don’t need them to “show off” with – they need them to fight with at feeding sites and to fend off predators.

Bulls grow their antlers earlier in the year, use them in the rut, and drop them as soon as the rut is over. Cows grow their antlers later, and carry them all winter.  Amazingly, cows that are not pregnant going into the winter drop their antlers earlier as well, so by late spring and calving time, all the antler advantage in competition for nutrients or fighting wolves goes to the pregnant cows. Shortly after the calves are born in early June, newly growing plants offer a flood of nutrients. The cows drop their remaining antlers and…

nature’s elegant cycle begins anew.

1983 – The Worst Year Ever for Western Hudson Bay Polar Bears

by Ian Thorleifson

Ian carrying tranquilized polar-bear

Ian carrying tranquilized polar bear near Hudson Bay

We’ve all heard many sad stories and dire predictions about the future of the polar bears of Western Hudson Bay. And they have had some tough years – particularly in the early 2000s. The worst year they ever had was not recent however, it was almost 30 years ago. In 1983

My knowledge of 1983 is first hand. I was in charge of the Polar Bear Alert Program that year, and I was working as a biologist for Manitoba Wildlife Branch, and with the very capable crew from Ian Stirling’s group of the Canadian Wildlife Service.

But I must qualify that my observations are not backed by rigorous science – we simply did not have that defensible level of knowledge then. We did have a substantial amount of observations, notes and perceptions built up from many people’s observations over many years.

By 1983 the Canadian Wildlife Service had been intently working with the polar bears in Hudson Bay for about 15 years. A large percentage of the bears in the population were tagged – at least half of them, maybe three quarters. We estimated that there were about 1800 bears in the South Western Hudson Bay (SWHB) polar bear population at the time.

Productivity was very good – most mother bears had two cubs with them and many of those cubs were “independent yearlings” – able to hunt and care for themselves, and to allow their mothers to re-breed every two years – the most productive polar bear population known at the time.

Tourism, especially that related to polar bear watching, was starting to roll in Churchill – Dan Guravich and Len Smith and their Cape Churchill crew had been to the Cape for up to three weeks at a time for four years now – and their observations and photos had identified a “rogue’s gallery” of big old male bears who were at the Cape every year.

The winter of 1982-83 saw very heavy snowfall accumulating in SWHB, so heavy one could imagine the bears having a challenge getting through to the seals. When the bears were forced ashore, they were in “ok” condition, but not really fat. But they were early – by the first two weeks of July the ice had broken up and quickly melted completely out of the Bay. Then the summer was HOT. And DRY. We worked on the tundra with no shirts on – and no mosquitoes! The heat stressed the bears even more than the mosquitoes would have.

By November, there were a lot of bears around – and far too many were getting very skinny. In the middle of November, very cold weather brought a quick freeze – and bears started moving out onto the ice. Then came the big south wind with melting temperatures and weeks of fog and mist. The ice was completely melted, and the number of bears along the Coast was amazing – I counted 50 different bears in a 14-mile drive! Eight bears were shot by local people in self-defense. On November 29, a man was killed on the main street of Churchill by a young male bear. The Polar Bear Alert crew was handling as many as 15 bears a day. Walking skeletons were seen too often. And still no freeze-up until almost mid-December.

We did not realize the impact this all had on the population until a couple of years had gone by. At Cape Churchill, Dan could recognize only a couple of the “rogues” they had previously seen. And 1984 saw the lowest number of bear incidents in the history of the Alert Program.

Based on these observations and the “Mark/Recapture” rate of the next few years, we estimated that HALF of the SWHB population perished out on the ice that winter. We find very few dead bears, because they do not die where we can find them. Travel out on the Bay is very difficult and dangerous.

The population built up again in the late ‘80s and ‘90s – to at least 1200 to 1400 bears, then declined to the 950 or so estimated today. But no one year was ever as bad as 1983…the Worst Year Ever for polar bears.

Churchill Wild welcomes wildlife storyteller Ian Thorleifson

Ian Thorleifson with polar bear cubs

Ian Thorleifson with polar bear cubs

Churchill Wild is happy to introduce Ian Thorleifson to the Arctic Adventure/Churchill Wild blog readers.

Ian will be contributing a semi-regular column to the blog. He has been on many of Churchill Wild’s polar bear Arctic Safaris – in fact, many of you may have met Ian at the Lodge so you will know what a wealth of amazing stories he is!

Ian is the lead for GEOS Consulting services (www.ianthor.com) and has been a friend of Churchill Wild since early on. Born and raised in rural Manitoba, Ian completed a degree in Zoology and Biogeography at the University of Winnipeg.

He worked at biophysical resource inventory and land use planning in northern Manitoba and Ontario, then moved to Churchill for polar bear, moose and caribou management with Manitoba Wildlife Branch.

Ian began raising and marketing cattle, elk, bison, deer and horses in 1986, both on his own ranch and as the manager of large corporate farms in New Brunswick and Alberta. He is the co-author of The Elk Farming Handbook and many articles covering elk, deer and cattle farming.

Since 1987, Ian has been leading ecotours to study and photograph polar bears, birds, and nature in general. Destinations have included Riding Mountain, Churchill, Seal River Heritage Lodge, Dymond Lake Lodge, Nanuk Polar Bear Lodge, Wager Bay, Ungava, the Mississippi Delta and the Gulf of Mexico.

With this background, Ian has become an accomplished and appreciated storyteller and public speaker. He has extensive accomplishments in the Communications field, as a freelance or assignment writer, creating informative magazine and newspaper articles, as a project facilitator and as a communications planner.

We all look forward to Ian’s first column which will posted next week.