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Answers From the Caribou Expert
Included in this Message:
Answers from the Caribou Expert
Special thanks to Don Russell, for providing his time and expertise in responding to your questions below.
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Nanaimo
Q: In what negative ways has global warming / pollution/ and habitat restriction affected this species? Thank you for your time.. :-)
A: Well you ask a good question. Across the north these three issues are important to caribou - climate change, pollution, and development.First global warming: In general global warming results in snow melting faster in the spring which is not good during spring migration because as the caribou are moving north from their winter ranges they have to move and feed through deep snow. If during that time the snow is constantly thawing and freezing because the warmer weather, then they have a harder time feeding under the snow because of all the ice layers that are formed by freezing and thawing. If things get bad in the valleys they will move on to ridges where there is little snow. If they do, wolves have an easier time killing them because even though caribou are better than wolves in deep snow, wolves have the advantage when there is very little snow and hard ground. Later in the spring when they get to their calving grounds, the warmer weather is good for caribou because the fresh green plants grow earlier. Green plants are important to nursing mother caribou to produce high protein milk for the calves. We have seen that if plants grow earlier because of warmer weather, we see better survival of the calves in their first month of life.
If the summer is warmer, then we see more insect harassment on the caribou. Mosquitoes and warble flies harass the caribou keeping them from feeding normally and forcing them into windier areas where feeding may not be as good (such as windy ridges where there are fewer plants around). However even though insects are more active in warmer weather, we have seen that warm weather in summer also means drier summers. In dry summers there are fewer mosquitoes around because there are fewer pools of standing water for them to breed. Warmer summers may mean more active mosquitoes but there will be fewer of them to harass the caribou.
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In fall the only problem with warmer weather may be a more frequent occurrence of freezing rain, rain that comes down and freezes on the ground. If there is enough freezing rain the food will be harder to eat because of the ice layer. If this happens the caribou usually just move to new areas.
In winter warmer weather usually means more snowfall (unlike summers where warmer means drier). Deeper snow is not good for caribou. Unlike moose, caribou get all their food under the snow, they don't eat shrubs that poke out of the snow in winter but must crater down to the ground to eat lichens. If snow is too deep, it takes more energy to dig down then the caribou would get from the food. They will lose a lot of weight in winter's with deep snow because they have to burn off their fat and muscles to get enough energy to maintain their body temperature.
Pollution in North America has not been a major problem for the caribou themselves, even though it is important for those that eat a lot of caribou. The two main concerns are radioactive elements like Cesium which comes from nuclear testing or accidents like Chernobyl in the Ukraine (a nuclear power plant that blew up sending radioactivity into the atmosphere). Close to the Chernobyl accident, in Sweden, lichens picked up a lot of the radioactivity and were eaten by reindeer. Many reindeer in Sweden had to be slaughtered and discarded because the levels of radioactivity in their muscles were too high for human consumption. We did see some of the radioactivity from Chernobyl in North America but only small amounts which didn't present a health problem for the animals or the people that ate them. Most pollution in North America comes from the atmosphere so the areas with higher rainfall usually receive the most pollution. Across the north, we see that there are higher levels of pollution in eastern North America than the west because there is a pattern of increasing rain going from west to east in the north. The other pollution concern is from heavy medals such as Cadmium. Usually cadmium comes from heavy industry and refining which occurs most in the United States and northern Europe. Caribou concentrate these medals in their kidneys and liver (because these organ's function is to filter out impurities in the diet). Although the caribou are healthy, there has been some health advisories in some area's to reduce the number of kidney' or livers in the diet - good new for kids. I should point out though, that you would get a lot more Cadmium from smoking cigarettes than from eating caribou liver and kidneys.
Development - the impacts of development is a VERY big question and there is no easy answer. Let me say that it depends on the type of development, the time of year, the extent of the development and how well a particular herd of caribou can cope with development. Some herds are very productive and can withstand more development within their ranges than other herds. In North America, we have relatively little development compared to areas of Russia where large herds of wild reindeer have been dramatically affected by oil and gas activity, hydro dams etc. In North America, the herd that has had the most development in its range is the Central Arctic Herd in Alaska. The Prudhoe Bay oil development is the largest oilfield in North America and the trans Alaska pipeline pumps about 1 million barrels a day to southern United States. This oilfield is located in the summer range of the Central Arctic Herd. Studies have shown that the development has resulted in the herd moving its calving ground, in large groups of caribou having a hard time crossing roads and pipelines and in having them shift away from roads, especially if they have small calves. However the herd has continued to grow as the development has spread. We think the main reason is that the areas the herd shifted to was still good habitat and the herd was naturally very productive and could withstand the negative impacts of development.
So I hope that is more information than you ever wanted. Caribou herds across North America have natural cycles where they increase and decrease. This cycle occurs every 40-50 years. In the early 1970's most herds across the north were at very low numbers and then all increased until the 1990's, most have stopped growing and some have started to decline. Our challenge as researchers of caribou is to ensure that these cycles remain natural and the 3 factors you list - pollution, climate change and development - don't cause catastrophic declines or prevent herds from recovering from low numbers.
From: New York
Highview Elementary School
Q: How do caribou's bodies adapt to warmer weather when they
have reached
their migration location?
A: As soon as cows give birth they start to shed their heavy winter coat. If you capture a cow in the summer you can literally pull handfuls of winter fur off her body. A sleeker new coat develops below which will become a full winter coat later in the fall when temperatures increase. Bulls will lose their winter fur much earlier than the cows. Migrating north does help as well. When the cows reach the calving grounds in early June, there is still lots of snow around and the temperatures are cool. Even throughout the hot summer sheltered valleys or the north sides of hills will have late snow patches. In the summer if you want to find caribou seek out these snow patches and you will probably find caribou lying down in the snow. As well as cooling off the animals, the cooler temperatures reduce mosquito harassment. Even so the temperatures will get hot during the day and often on those days you will see a lot of feeding and movement at "night" when temperatures drop. I say "night" but for much of the summer the sun doesn't go down so even though it is cooler because the sun is low in the sky, there is still plenty of light.
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Q: How do caribous decide what group they will migrate with?
A: That is a good question and there is a lot that we don't know. There is a bit of information to suggest that sometimes family groups of females will stay together - grandmothers, mothers, yearlings and calves, although it is hard to prove this with wild caribou. We do know that animals use different migration routes in different years so the same animals aren't always travelling in the same places. During spring migration the pregnant cows will be the first groups to start their journey north, often with their female calves. The male calves will stay behind with the other bulls and the cows that didn't get pregnant the previous fall. Some of these female calves will return to the calving grounds with their mothers but most will fall behind the migration along the way, especially if there is still deep snow to move through. In late June when the temperature increases and the mosquitoes start to harass them, the caribou will form larger and larger groups, sometimes 20,000 to 30,000 animals all in one group. Some researchers suggest that one reason for the large groups is to socialize again and rejoin family groups, separated after spring migration. In the fall, migration usually starts when the first snow fall drive the animals into the trees again. All animals, cows and bulls, travel together and they are all together in October, which is the breeding season. I think in fall they just start following groups that are feeding in the same area and the weather has a big part in where and how fast they move south to their wintering area.
Q: Why doesn't a pregnant caribou shed its velvet?
A: Normally pregnant cows do lose their velvet in the fall after the antlers are fully grown. However, sometimes we find caribou that haven't lost their velvet - we found one this year that was fitted with a satellite collar. Shedding velvet is controlled by hormones (we have a lot of different types of hormones that control a lot of body functions). We think that those caribou that don't shed their velvet may have a hormone imbalance - meaning the right levels of hormones are not present in the body to control velvet shedding. This could be caused by genetics (the caribou inherited the problem) or the caribou may have eaten plants that contained toxic chemicals which would prevent normal hormone production. We will see next year if our collared cow still doesn't lose its velvet which will mean that it is likely a genetic problem.
From: Massachusetts
Woburn
Q: How do you know so much about caribou?
A: Well, I started studying caribou in 1973 - 30 years ago! At that time I was doing a Master's project studying how caribou used the area in Alaska where they wanted to develop oil fields. After writing my Master's I worked in British Columbia studying how logging impacted caribou. In 1976 I moved to the Yukon to work with Yukon Government and studied the Porcupine Caribou Herd - the herd that you are following on the Journey North website. I have been studying this herd and others ever since. So the short answer is that I have been studying these animals for 30 years and I am always finding out new things and have always worked with new biologists and students that ask questions that I can't answer, so I study more.
From: Minnesota
Deephaven Elementary
Q: What would the impact of drilling for oil in Anwr have on the caribou?
A: Of course the correct answer is that nobody knows for sure. But it is important to ask this question now and come up with the best answer so that we can help those that have to make the decision, in this case the U. S. Congress. The best way of answering this is to see what happened to caribou where oil development has occurred - with the Central Arctic Caribou Herd just to the west of ANWR.
 Tundra lakes from the air credit US Fish and Wildlife Service |
 Oil installation, North Slope Credit Pam Miller |
Biologists have been studying this herd for years because there is a lot of oil development in their summer range and have learned that cows that are about to give birth don't like human activity too close so they will calve somewhere else. For the Central Arctic herd this meant their calving ground, the area where most of the cows give birth, moved south to another part of the wet coastal plain. If oil development were to happen in ANWR the much larger Porcupine Caribou Herd (123,000 Porcupine caribou compared to 28,000 Central Arctic caribou) would have to shift into the foothills and mountains because the wet coastal plain (where they like to calve) is very narrow. By moving into the foothills many more calves will die because of predators. Their main predators are golden eagles, grizzly bears and wolves and these species are in greater numbers in the foothills. Besides the cows need good quality food then they have their calves so that they can produce good quality milk. The best food is where their calving ground is now, so they need to be able o stay there without being disturbed. Another impact may be that once the oil wells and roads and pipelines are in place it may block access to the coast where the caribou like to go when the weather is hot and the mosquitoes bother them. It is cool on the coast because the winds come off the ice out in the Arctic Ocean. Studies of the Central Arctic herd showed that the larger the groups of caribou, the more trouble they had trying to cross roads and pipelines. For the Central Arctic herd a large group is 1000 animals. For the Porcupine Caribou Herd a large group can be 40,000 animals. We think these large groups may not be able to cross the roads and pipelines and will be bothered by mosquitoes a lot more.
I hope this gives you a little idea what some of the impacts may be.
It is
an important question to ask.
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