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A Total Forest Management Plan
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This section is Under development. The major concepts being developed are now within The Deer Group, (alternatively) a proposed enterprise within Rural System. Sections are being added from Antler Points and elsewhere.
Deer Damage
Car Collisions - There are about 12 deer claims per 1000 insured vehicles in 2002, a 12% increase over 1998. The average cost of a claim is $1,960. These costs represent 38% of all comprehensive losses. Fencing, using under- and overpasses works but can be very expensive and intrusive. Reducing the deer abundance is effective. Creating broad areas of cleared vegetation allow drivers to see deer. For wester deer where migrations are evident, temporary signs placed during deer movement peaks (spring and fall) seem be effective. These are moved, have reflective flags and lights. Small signs are placed every mile and signs specify distance before leaving the zone. (Cost $1,740 for a 4 mile section.) This seems feasible when combined with highway crew and police recovery of dead deer and clarified routes in Eastern states (e.g., using radio collars). Deer-movement activated signs are being studied. Detection instruments include infrared light, radar, laser, radio frequency beams parallel to the road, and heat detection. Ten studies of reflectors along road sides casting reflected light into the road edges yield mixed results. Repellents seen ineffective. Feeding away from roads has evident disadvantages. Passive signs (of deer crossings) are ignored. Whistles mounted on cars (that emit sounds at 30 mph) have no effect Speed zones related to deer observations and strikes seem to be one useful alternative. A deer insurance was suggested but discounted since "every dink in a car would be blamed on a deer hit." (from Insurance Institute for Highway Safety, Status Report 39(1) January 3, 2004
Deer Damage to Gardens and Plants Resistant to Deer
See Virginia Cooperative Extension and
http://deerxlandscape.com and
Deer resistant plants at
http://lonestar.texas.net/~jleblanc/deerplants.html and
Breck's
Males and Females
To get the structure of your deer herd or the part of it on your property, it is necessary to get a good estimate of the proportion of adult females in the population. The number is important because it indicates the productive potential of the population. "Indicates " is a key word because there are many aspects to productivity. The proportion of females is also important because it indicates the proportion of huntable males and even the amount of food the herd will eat (smaller animals eat more, on average).
On hunted areas, the proportion of females is high (because some bucks have been removed). On other areas, the proportion will be approximately 0.50. A Chi-square statistical test should be performed by the staff to determine whether the difference (from equal numbers of males and females or 0.50) is significantly different from what is expected.
The proportion of females is expressed, for example, as 0.64. This example means that if there are about 200 deer on an area, then about 128 will be adult females. There are about 72 adult males ( (1.0 - 0.64)(200) = 72 ).
Getting a good estimate of the proportion is difficult because deer are hard to see.; getting close enough to see antlers is difficult; they change their behavior by seasons (Michael 1970, Poux 1972); does are underestimated from June through September because of fawn-related behaviors (Poux 1972, Hawkins and Klimstra 1970); antlerless bucks can confuse a count; female counts of large groups of deer are difficult...and many a hunter has confused branches for antlers. In small populations, the proportion can change rapidly due to migrations and accidents. Many techniques need to be used to get a "good" but practical estimate. At least you or your staff and volunteers need to use:
Track counts (by size) do not work. Fawns and adults can, however, be separated.
If only a few deer are counted, it is easy to be very wrong about the proportion of females.
If there are less than 100 deer involved, then we recommend stating a proportion but saying "plus or minus 15 percent." Using the previous example of 0.64 females as "does", then the proportion should be thought of as between 0.54 and 0.74, a fairly broad range.
Many papers in ecology and wildlife management list population sex ratios as males per 100 females. For example, 50:100 means that the estimate is 50 males per 100 females or to get the proportion of females, the arithmetic is (females/total) or (100 / (50 + 100)) or 0.67). The ratio can be confusing to first-time users of the numbers (that is, 50:100 does not mean 50% males but 33% males (i.e., 50 / (50 + 100)).
The equation for the proportion of total females in a population is
F = (adult females + 0.50 fawns) / ( males + females + fawns)
The proportion of adult females in a total population is:
FF = adult females / (adults + fawns)
A peculiar thing happens as the female proportion increases in an area (for example, due to buck-only hunting) and the food supply per adult doe (after a hunt) goes down (just due to the way that food is divided up among the remaining deer). The usual 50:50 males-to-females in the new-born fawns shifts to more males (say a proportion of 0.52) so in the above equation the proportion of female fawns drops to 0.48. When this happens (as expected), the proportion of females in the total population changes as shown in the next figure.
At this point we re-emphasize the relationship of this part of population structure to the habitat or "faunal space", the way the land is treated, and food supplies. When abundant, nutritious food is made available, then fawns per doe are slightly increased. Temperature may affect sex ratios in turtles (Vogt anMacArthur4) but the effect is unknown in deer. Natural selection seems to favor the 100:100 ratio in young (MaacArthur and Connell 1966). If the proportion of females is very great (as is found in a herd in which only bucks are taken) then many does producing at a high rate can produce an enormous population in a few years. The population, lightly hunted, can destroy its food base -- kill the quality forage plants or remove all of them within reach with a long period before harvests or natural tree gaps occur.
The proportion of females in a population is of the most important variables used in uunderstanding any deer population, but yet it is one of the most difficult to estimate precisely. If 80% of adult does produce 25 fawns per 20 adult does (an average of 1.25 each) and there are 1000 animals in the population, then the next graph
shows the consequences. The future population (and any estimate of it) is very sensitive to knowledge about the proportion of females.
The proportion of does should never go above 0.95 or 1 buck per 20 does. Even at this extremely uunnaturalcondition it is likely that fertile does will be bred.
When sex ratios are determined from highway carcass counts, males are over-counted (even if corrected for vehicle use). Does are hit less from June through September; more bucks are hit during their period of the rut (late October through January).
Similarly, hunter-kill data from an either-sex season that shows a preponderance of males may produce an erroneous estimate of proportion of females. Best counts are likely ffromlate January to mid-May due not only to group behavior but also ssparsevegetation. August observations are well correlated with those in September, October, and December and Poux (1972) recommended that counts be made in August or from October 10 to November 30. At this time, about 10 % more does are seen than in other periods of the year due to their activity. (Fawns are easily mistaken for does and yearlings in December.)
Emphasis is again made that the precise proportion of females is difficult to estimate. When sample size or number of observations is small, there is real danger of being wrong about the estimate.
When you or other landowners ask "proportion of what?" then the the proportion of females in a population can take on the meaning it deserves. The proportion,P, once clarified, is important when used as a multiplier to study:
The Desired Future Population = (Present Population x P x Young per female + Males ) - Losses
Techniques For marking the hair of deer (or antelope or prairie dogs) for various purposes, try using Nyanzol-D, a commercial hair dye. It comes in powder form and you mix it with hydrogen peroxide. It lasts quite a long time (markings visible for 7 months until the molt. It is manufactured by J. Belmar Inc. in North Andover MA. (purchased it from Albinal Dyestuff Intl. in NJ. phone: 800-526-3192).
References
Michael, E.D. 1970. Sex ratio and group composition in white-tailed deer. Proc. Annual Conf. S.E. Assoc. Game and Fish Comm. 24: 51-56
Vogt, R.C. and J.J. Bull. 1984. Ecology of hatchling sex ratio in map turtles. Ecology 65(2):582-587.
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Last revision January 17, 2000.