Scientific experiments have conclusively shown that reasonable sport hunting does not cause game populations to decrease. The pheasant density in the Iowa counties remained higher than that in the adjoining Minnesota counties, and the trend in the pheasant population in the two states remained parallel in spite of the fact that the Iowa pheasant seasons were twice as long as the Minnesota seasons. The mortality rate of pheasants is similar for both hunted and adjacent non-hunted areas. The yearly mortality rates usually exceed 70 percent, and the high rate for unhunted populations negates the effect of hunting on the following year's population. In general, the size of an animal correlates with its metabolic rate and thus with its life expectancy and reproductive rate.
Small animals have high metabolic and reproductive rates, and short life expectancy.
Conversely, larger animals have a longer life expectancy, lower reproductive rate, and hunting mortality has a greater effect on the number alive the following reproductive season. The effect of hunting on small animals with high mortality rates is well demonstrated by songbirds. We do not hunt songbirds, yet the number does not increase yearly. To close or shorten the pheasant season would substantially reduce hunting recreation with no positive effect on subsequent bird populations. Many hunters fear that long seasons will result in an overharvest of roosters and too few roosters to assure egg fertility.