jefflaporte a écrit :
sans repartir de débat...je crois que la génétique joue un role cléf...dans cette histoire....le plus fort s'accouple et possede le plus beau panaches...voila...
J'ai lu ceci d'intéressant sur un autre forum, ça concerne la fameuse génétique.
The Culling Myth Exposed
February 05, 2009
by John J. Ozoga
Conflicting penned deer research findings have fueled the age-old culling controversy. Study results on captive deer have produced recommendations ranging from removing all spike-antlered (presumably genetically inferior) yearlings, to complete protection of all yearling bucks regardless of their antler traits.
Those favoring selective removal of small-antlered young bucks claim such a practice will remove small-antlered genes from the herd and improve antler quality.
For example, recent research published by Mitchell Lockwood and his cohorts from the Texas Parks and Wildlife Department, indicates selective breeding by superior-antlered yearling bucks improves subsequent yearling buck antler scores.
Lockwood and his group concluded, “Our findings clearly indicate that under constant suboptimal environmental conditions, phenotypic change in antler quality can be realized with intensive selective harvest of yearling males.”
However, Harry Jacobson argues that little or no improvement in future antler quality can be expected by culling based on yearling antler traits.
Jacobson and Texas A&M geneticist Steven Lukefahr based their conclusions on the examination of 220 yearling bucks raised at research facilities in Mississippi. They found that the doe’s nurturing ability was far more important than genetics in determining the yearling buck’s antler points, spread, weight and beam length.
Hence, Jacobson and Lukefahr concluded the following: “Our results do not support the use of yearling antler records as criteria for selective breeding management or harvest schemes to alter the genetic quality of a white-tailed deer population.”
The Latest Research
Unfortunately, until recently, the culling debate has been founded almost entirely upon studies using captive deer, held at unnaturally high densities and fed either high-quality or restricted diets.
One of the most recently published studies, concerning the question of culling effects on antler development in a wild deer population, was by Ben Koerth and James Kroll, from Stephen F. Austin State University. The objective of their study was to determine if a white-tailed buck’s first set of antlers was a good predictor of antler growth at maturity in wild populations. The study was conducted on 12 ranches, ranging from nearly 2 square miles to over 23 square miles in size, in south Texas. All but one of the ranches were fenced.
Using helicopters and net guns, Koerth and Kroll captured bucks in late January through February from 1999 to 2007. Initially, they captured as many fawns and yearlings as possible ... to serve as known-age animals. All handled animals were aged and marked for individual identification with ear tags color-coded to year of birth. In subsequent years, the researchers attempted to recapture and examine as many of the marked animals as possible. Some were also taken by hunters.
Yearling bucks were divided into two antler-point categories, those with three or fewer antler points and those with four or more antler points. Then, the researchers compared recaptured bucks in the two antler-point categories to determine differences in antler growth at 2½ years, 3½ years, 4½ years, and 5½ or more years in age. Antler measurements included number of antler points, inside spread, total beam length, total tine length, total antler circumference, and gross B&C score. (See Table 1, above).
Interesting Results
At 2½ years of age, males that started with three or less antler points remained smaller in all measured antler traits, as compared to those starting with four or more points.
Even at 3½ years of age, the small-antlered yearlings still had smaller B&C antler measurements except for circumference.
However, those starting with three or fewer antler points appeared to be accelerating antler growth at a faster rate as compared to those in the larger yearling antler group.
By 4½ years of age there were no differences in any antler measurements regardless of the yearling antler-point category.
By that age, smaller antlered yearlings had attained a mean antler size equal in width, mass, length and number of points to those starting with larger antlers at yearling age. The same was true for bucks handled when 5½ years of age or older.
Assuming a trophy buck has antlers scoring 150 points or more, the data revealed that a yearling buck with small antlers is just as likely to attain trophy status as one with larger antlers at yearling age. About 17 percent of the yearlings in the small antler category and 13 percent of the yearlings in the large antler category achieved such stature when mature.
Therefore, this research showed that a whitetail buck’s first set of antlers was a poor predictor of antler growth at maturity in a wild population. In other words, selective removal of small-antlered yearling bucks will not increase overall mature buck antler size.
Antler Growth Patterns
Although antler measurements increased for all males as they matured, small-antlered yearlings added antler mass at a faster rate in succeeding years, as compared to large-antlered yearlings. This resulted in no difference in antler size, regardless of their yearling antler size, by the time bucks grew their fourth set of antlers when 4½ years old.
Koreth and Kroll theorize there are different antler growth patterns in whitetail bucks. One pattern is a high rate of antler growth for the first few years, followed by a slower rate each year thereafter. Another pattern is steady (incremental) growth throughout the productive life of the animal. A third pattern is slow antler growth at first, followed by an increased growth rate at some point in the animal’s life.
Theoretically, all three patterns end with roughly the same antler score at maturity. If so, then number of antler points at 1½ years old might only reflect different antler growth patterns — not genetic potential for antler growth. Likewise, since yearling antlers do not serve as a reliable predictor of antler growth potential, selectively removing yearling bucks with small antlers is not likely to improve overall mature buck antler quality.
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