Woodland Caribou (Rangifer tarandus caribou)
A male woodland caribou near Summit Lake in Northern Mountain Provincial Park (northern British Columbia).
Officially there is just one species of caribou: Rangifer tarandus. However, caribou range over a large part of the northern half of the northern hemisphere and throughout that range there are several groups of caribou with clearly different behaviour and range-use. This particular animal is called a woodland caribou, which is currenly recognised as a subspecies (Rangifer tarandus caribou). There are three other subspecies that live in North America. Caribou are the only deer species in North America with antlers on both males and females, which is generally held as a feature of primitive cervids (deer).
Woodland caribou live in the harsh environment of boreal forest and alpine tundra where they survive mainly on lichen. Lichen is not a very nutrient-rich food and caribou are the only cervids that utilise this foodsource on a big scale. It may seem bad strategy to concentrate on nutrient-poor food, but if you are the only species using it at least means that you will not have a lot of competition. So far, this has served the caribou well. Historically they ranged all over the northern half of the northern hemisphere, which is a clear sign of success.
Lichen is not a plant, but a symbiotic association of a fungus and either green alga or cyanobacterium. The alga or cyanobacterium is able to photosynthesize, which means that it can produce nutrients from sunlight, carbon dioxide and water and this is used to feed the whole organism. Though this symbiosis is very successful, lichens grow very slowly. Those that are most important for woodland caribou are mostly Cladina subspecies and these typically grow between 3 and 6 millimeters a year, which is about 4.5 times slower than a fingernail! This means that, to be able to find enough food, caribous prefer to live in undisturbed places like oldgrowth forests where lichens have been growing for decades or even centuries without much disturbance. Feeding strategies of caribou have evolved in such a way that their browsing will not negatively impact the lichen: they have an enormous individual homerange (581 km2 in Manitoba), are widespread (one animal per 16km2) and never stay in one place for long. Because of this, the impact on the lichen population is low and after being grazed, it has enough time to recover again. This is a beautiful example of a well-balanced system where players somehow survive very well in circumstances that look far from favourable.
Unfortunately, well-balanced is not necessarilly synonymous with stable. In this case they are almost opposites, because it does not take much at all to destroy the ballance beyond repair. The balance started to wobble when the lumber-hungry European settlers saw the rich oldgrowth forests and started logging. With every bit of forest logged, valuable lichen was removed which, even if the forest would grow back, would take many years to recover. In essence, a logged area is lost to caribou. Another problem of logging even small portions of oldgrowth forest is that it opens the area for animals like white-tailed deer (Odocoileus virginianus). Because these animals do not eat lichen, they are not direct competitors for food. The real problem is that they carry a parasitic worm which causes "moose sickness" which is lethal for caribou.
The beginning of the 20th century in particular has seen a great decline in caribou numbers and sadly, the trend still continues in most areas. Until this day, wood is one of the main components of many buildings in North America, so the demand for wood remains high. There is not that much oldgrowth forest left and even what remains is under constant attack from logging companies trying to keep up with the demand. The reduction of suitable habitat ironically means that the caribou's impact on the remaining lichen increases, which further undermines the balance. Apart from this problem, there is the fact that caribou have been overhunted and that livestock has been introduced into their original habitat, which pushed them even further back.
Clearly the overall balance has been disturbed and in many places it has simply been utterly destroyed. Caribou now remain in only a small part of their historic range. An overview of the historic and current range is given in the map besides this text. Alternatively, it can be found here. Problem with this map is that, despite being correct, it paints a picture that is definitely too positive. While caribou do still occur in the southern part of the range, in many places they by now have so little suitable habitat that it is merely a matter of time before some pretty drastic changes to the map of the current range will have to be made. What remains of the population in southeastern British Columbia and southwestern Alberta is not likely to last much longer if there will not be some very big changes and serious restrictions in land use and planned development in the area. Just little islands of suitable habitat remain and these are often either wanted by logging companies, or are used for relatively new and highly disturbing tourism activities like heli-skiing. But even in the remote extreme north of the range the survival of the species is far from certain.
The Bush registration, dubbed the most environmentally unfriendly registration ever, has been trying for years now to open part of the Arctic National Wildlife Refuge in Alaska for oil drillings. There is just enough oil there to serve the United States for about 1.4 years, but to extract it they would need to destroy part of what has served as the calfing grounds for the Porcupine caribou herd for many thousands of years and it is unlikely that the herd would be able to take that blow and survive. So far, the drillings have not happened because the public is against it, but the Bush registration keeps trying to pass the bill that will allow it. Karsten Heuer and his wife Leanne Allison have produced a must-see documentary and a must-read book about the plight of the Porcupine herd.
The caribou is the most endangered large mammal of North America and as long as humanity insists on developing ever more of its habitat for the sake of tourism, housing and oil, their position is bound to worsen. However, even apart from Karsten Heuer and Leanne Allison, who have done a lot to make the world aware of the plight of the Porcupine Herd, there are many other people fighting for the survival of caribou. One recent and very significant success was achieved by a coalition of ten leading environmental groups (including Forest Ethics, Wildsight and Fraser Headwaters Alliance) who managed to convince the gouvernment of British Columbia to legislate protection of 2.2 million hectares of inland temperate rainforest in the south west of the province for the very rare mountain caribou (more information here).
Like a lot of animals these days, caribou will only survive the coming decades if we really want them to. It is in our hands!
Image number: 2007_ASP5277AWMC