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Semelhante a Doug Cottam - Big Game in Early Seral Forests
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Doug Cottam - Big Game in Early Seral Forests
- 1. Big Game and Early Seral Habitat Doug Cottam Herman Biederbeck Oregon Department of Fish and Wildlife
- 17. Questions?
Notas do Editor
- Herman and I both spend a considerable amount of time on big game issues especially damage to private lands and managing hunting seasons. It is easy to recognize habitat issues are of primary importance to managing these wildlife. We are appreciative of being given the chance to speak about current habitat issues. In this presentation I will focus on early seral forest habitat from the Cascades west.
- Most people do not realize how many and which species are considered big game. Of these big game species, cougar, black bear, deer and elk would be the primary users of early seral forest habitat. Because cougars are carnivores they use any habitat that is frequented by there prey: deer and elk. So I will assume what is good for deer and elk is also good for cougars although because cougar are ambush predators hiding cover within early seral habitat is crucial. I will talk a little bit about bears, but focus on deer and elk.
- What is early seral forest habitat for wildlife? I suppose wildlife biologists could define early seral forest habitat differently than foresters and differently for different wildlife species. For deer and elk, early seral forest habitat is primarily a source food, some cover, a place to have their young or grow their antlers and so on. Within this habitat there will also be important micro-habitats and climates. There are also differences in quality and quantity of food and cover within early seral forest habitat, which I will discuss later. In this talk for simplicity sake we will define early seral habitat as post disturbance to closed canopy forest with little or no understory.
- Black bears easily occupy many habitat types including early seral forests. Their attraction to most areas is food. They are omnivorous, but are primarily vegetarians and show a real capacity to learn and remember. During drought years or years when weather conditions result in a poor berry crop, we anticipate considerable bear problems because of their propensity to eat berries. The native and non-native, berry producing vegetation in early seral forests is obviously important to bears, but early seral forest habitat can also provide valuable food sources throughout the growing season. Bears will consume skunk cabbage and grasses especially before they dry out. After awaking bears are commonly observed in early seral forests, meadows and riparian areas seeking foods from early herbaceous plants to insects and animals. Bears are shy and secretive, but may be active up to 20 hours a day. Vegetative diversity in early seral forests that provide not only food resources but concealment would likely be utilized more than a more homogenous or open area.
- The predominant deer species of the Cascades west is black-tailed deer which range from California to Alaska. These secretive deer rarely form large groups and can survive in a variety of habitat types. However, highest densities of black-tails have been documented in areas with a large proportion of early seral forest type.
- The ratio of the volume of the deer’s rumen to their body mass is relatively small. As a result, microbial digestion of the vegetation in their rumen has less time to occur than other ruminants with a larger ratio. The end result is that deer need a high quality diet: nutritious and easily digestible. The greater the cellulose of cell walls and crude fiber the less breakdown will occur. Deer forage quickly then ruminate in cover to digest their food. In winter, their metabolic rate decreases as an adaptation to scarce food supply. They are less active and burn fewer calories in winter. To survive a winter they must put on considerable fat supply during the growing season
- Because of their need for a high quality diet, vegetative diversity is very important. Browse is their primary food. It may seem that browse would not be of high quality; however leaders and leaves of woody plants, especially those that are not dormant can be highly digestible. Some browse species such as native blackberries like trailing blackberry do not dramatically change in crude fiber content between summer and winter and are highly nutritious even in winter. As you would expect the deer seek plants that are actively growing and seasonal differences can be profound.
- This is a list of some of the plants documented to be preferred by deer in various seasons. Studies on their use and preferences indicate that deer prefer green leafage in all seasons. Evergreen and semi-evergreen shrubs that retain leaves in winter would be consumed. In winter, grasses can become a large part of the diet if they are not dormant. Forbs are predominantly used during the growing season unless they maintain leaves during winter.
- One of the new challenges big game species are faced with now are non-native invasive plants and low value native increasers. The top photo is of a one year old clearcut in Lincoln County completely dominated by Conyza canadensis (horseweed) which likely provides little if any value to deer or elk due to its rapid growth and maturity and monoculture. The common Himalaya blackberry may provide green leafy vegetation, but due to its growth form and tendency to form monocultures it is likely it provides considerably less value than native species. Some increasers such as several species of the Senecio family such as wood and common groundsel or tansy, can be toxic to mammals. Another challenge to deer is the lack of fire in creating early seral forest habitat. Not only does fire aid in germination of many native early seral plant species, but the alternative modern re-forestation methods, such as the use of chemicals to reduce competition to conifers, reduces or eliminates the plant species most important to deer.
- Roosevelt elk is the subspecies of elk found from the Cascades to coast, northern California to British Columbia. Elk, like deer, can occupy a wide variety of habitat types, but also reach their highest population densities in areas with considerable amounts of early seral forest habitat. There are significant differences between elk and deer in their use of early seral habitats due to their physiology, social structure and behavior.
- An elk has a much larger rumen volume to body mass ratio than other North American cervids. Elk are more similar to cattle. Because of this large ratio, an elk is more capable of digesting plants with higher cellulose content . In other words an elk can survive on a lower quality diet than deer as long as there is enough quantity. I’ve heard it commented before that an elk can eat anything a deer can eat, plus 50% more. Their eating pattern is similar to deer: they eat quickly and spend a large part of their time ruminating. Because their social structure tends to form groups, their predator defense mechanisms are different than black-tails and they can select areas to ruminate that is considerably different than deer. Elk also lose weight during winter months, but as their metabolic rate slows they burn less calories in winter. As with deer, elk must gain weight and body fat during the growing season to survive winter.
- As I mentioned before, but want to emphasize, elk are more capable of surviving on a low quality diet than deer as long as they have suitable quantity. One interesting note about the effect of nutrition and plant communities: Roosevelt elk fetal rates are significantly lower than Rocky Mtn elk and it is highly correlated with a kidney fat index. As a result a typical Roosevelt cow will have a calf every other year, a Rocky Mt elk cow tends to have a calf annually. Even though they can survive on a lower quality diet than deer, Roosevelt elk can be affected by poor nutrition. High quality forage found in early seral forests with a full compliment of native plant species diversity also benefit elk.
- Elk tend to graze more than deer but as I mentioned they can eat anything a deer can. Grazing can occur even on grasses that reach maturity, but grass consumption occurs predominantly in winter and spring. In northern California, grasses make up more than 50% of their diet in all seasons. It is clear that elk prefer a grass legume mixture when available. In Oregon, browse predominates their diet in spring and summer. Like deer, elk diets vary among seasons.
- Cover is another important factor influencing elk use of various habitat types. Thermal cover is important in both summer and winter especially in locations with more harsh conditions. The mild annual climate of the coast range may allow greater use of early seral forest areas annually than the Cascades where elk may have to migrate in some circumstances. The age of an early seral forest and plant species diversity combined with the juxtaposition of this habitat type with other aged forest stands will influence the use of early forest habitat by elk. Both elk and deer spatially segregate between sexes for most of the year and their use of all habitats will differ between sexes. Antler development is important for males in establishing their dominance heirarchy. Nutrition plays an important role in antler development, but also density of vegetation may influence use of certain areas if physical damage could occur to antlers
- Deer and elk are considered as generalists: they can occupy a wide range of habitat types. However, to re-emphasize, deer and elk populations reach highest densities when their range includes a substantial proportion of early seral forests. Deer are somewhat more specialized in their food habits than elk, but neither deer or elk are dependant upon early seral forests. Our brief discussion here is a simplification of the true interaction among deer and elk with the plant and animal communities that predominate in an early seral forest.
- Although deer and elk are abundant in many areas and occupy a variety of habitats, that does not mean their populations are stable. Although we have no valid means of estimating their population we have circumstantial evidence that there has been and continues to be a decline in black-tailed deer populations since the late 1980’s. Most of us believe this is a result of loss of premium black-tail habitat. Although elk populations are expanding in many areas, they were re-introduced to former range beginning in the 1970’s, The increase in their populations may only be a result of occupying new areas, not an increase in habitat. Currently, it appears that federal lands provide quality early seral forest habitats that is in low quantity. Conversely, early seral habitats on industrial forest lands are abundant, but are of low quality. If black-tailed deer are in decline due to loss of abundant quality early seral forests, what is the status of other wildlife species that are more dependent or specialize in such habitats? We can only speculate because of the paucity of scientific information. We strongly encourage more comprehensive scientific research in the PNW to study the status the effects of modern forestry techniques on plant and animals communities.