Post by Woody Williams on Aug 2, 2006 8:33:45 GMT -5
Posted by a friend of mine on another site..
"You have to understand how herd population dynamics work. As herd density increases, herd health decreases. And as herd health decreases, fawn production and survival decrease. A doe population will actually produce the maximum number of surviving fawns at 50-60% of maximum herd capacity. In essence, when there are fewer does, they actually produce more surviving fawns than a higher doe population would.
Of all the plants out there deer will eat, only a small percentage are high-quality food sources. Most plants are only moderately nutritious and there's a bunch of things deer will only eat if nothing else is available. When herd density is low, each deer gets to eat primarily those limited high-quality food sources, hence each deer is extremely healthy and fawn production per doe is maximized. As herd density increases (through fawn production), those top-quality foods get eaten up, leaving only the moderate quality food sources. Now each deer has a diet consisting of less of the high-quality foods and more of moderate-quality foods. Herd health declines and fawn production declines per doe. But since there are more does around, they can still produce more total fawns than the fewer ultra-healthy does could. Once density begins to max out (due to reproduction), the deer only have the low-quality survival foods available. All of the top-quality and moderate-quality foods have been eaten out of existence. Now herd health is very low--just above survival limits--hence fawn production is extremely low (the does are still getting pregnant and having fawns, but the vast majority of fawns die soon after birth due to low birth weights, lack of milk production in the mother, and abandonment by the mother--a common response to nutritional or social stress). This large number of does are now producing very few surviving fawns. In fact this large number of under-fed does are producing fewer total surviving fawns than the moderate density herd did.
That is why biologists/managers watch fawn recruitment rates very closely (along with doe body weights per age-class and lactation rates). Fawn recruitment is often a very good indicator of herd health (as well as predation rates). An adequately fed deer herd, that has access to adequate cover to hide their fawns from predators, will display a fall-season observed fawn recruitment rate of around 80%, which means there are 8 surviving fawns for every 10 adult does. However, an over-populated, under-fed herd--with many more total does than the adequately fed herd--will have a fawn recruitment rate below 50%. I've even seen herds with fawn recruitment rates of only 5-20% (1 to 4 surviving fawns for every 20 adult does).
What I'm getting at is, in much of the Southeast, to maximize fawn production you actually have to kill more does (lower the herd density down towards that 50-60% of maximum capacity). I know this sounds strange, but that's the way deer herds work.
Most hunters assume fawn production is a given. It is not. It is a function of herd health, and poor herd health--most commonly caused by poor nutrition due to over-population--can cause very low fawn survival."
"You have to understand how herd population dynamics work. As herd density increases, herd health decreases. And as herd health decreases, fawn production and survival decrease. A doe population will actually produce the maximum number of surviving fawns at 50-60% of maximum herd capacity. In essence, when there are fewer does, they actually produce more surviving fawns than a higher doe population would.
Of all the plants out there deer will eat, only a small percentage are high-quality food sources. Most plants are only moderately nutritious and there's a bunch of things deer will only eat if nothing else is available. When herd density is low, each deer gets to eat primarily those limited high-quality food sources, hence each deer is extremely healthy and fawn production per doe is maximized. As herd density increases (through fawn production), those top-quality foods get eaten up, leaving only the moderate quality food sources. Now each deer has a diet consisting of less of the high-quality foods and more of moderate-quality foods. Herd health declines and fawn production declines per doe. But since there are more does around, they can still produce more total fawns than the fewer ultra-healthy does could. Once density begins to max out (due to reproduction), the deer only have the low-quality survival foods available. All of the top-quality and moderate-quality foods have been eaten out of existence. Now herd health is very low--just above survival limits--hence fawn production is extremely low (the does are still getting pregnant and having fawns, but the vast majority of fawns die soon after birth due to low birth weights, lack of milk production in the mother, and abandonment by the mother--a common response to nutritional or social stress). This large number of does are now producing very few surviving fawns. In fact this large number of under-fed does are producing fewer total surviving fawns than the moderate density herd did.
That is why biologists/managers watch fawn recruitment rates very closely (along with doe body weights per age-class and lactation rates). Fawn recruitment is often a very good indicator of herd health (as well as predation rates). An adequately fed deer herd, that has access to adequate cover to hide their fawns from predators, will display a fall-season observed fawn recruitment rate of around 80%, which means there are 8 surviving fawns for every 10 adult does. However, an over-populated, under-fed herd--with many more total does than the adequately fed herd--will have a fawn recruitment rate below 50%. I've even seen herds with fawn recruitment rates of only 5-20% (1 to 4 surviving fawns for every 20 adult does).
What I'm getting at is, in much of the Southeast, to maximize fawn production you actually have to kill more does (lower the herd density down towards that 50-60% of maximum capacity). I know this sounds strange, but that's the way deer herds work.
Most hunters assume fawn production is a given. It is not. It is a function of herd health, and poor herd health--most commonly caused by poor nutrition due to over-population--can cause very low fawn survival."
