A Spatially Explicit Model of The White-Tailed Deer Population in Delaware

Jennings, Brian
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University of Delaware
White-tailed deer (Odocoileus virginianus) population models are used by many states to predict population levels and aid in making management decisions. Delaware did not have a deer population model, so I developed a model and used it to investigate the implications of changes to the harvest. I used survival rates, reproductive rates, harvest data, a population estimate, and spotlight counts to construct the model. The changes to the harvest regime that I considered were permitting Sunday hunting during the opening weekend of the November firearm season, adding 1 week to the November shotgun season, termination of the severe deer damage permits, closing the October antlerless shotgun season, closing the shotgun season in January, closing the muzzleloader season in January, and closing both shotgun and muzzleloader seasons in January. The model began in February 2006 after the conclusion of the 2005-2006 hunting season and I ran the scenarios until August 2014. Without changing the harvest regime, my model predicted the state population to decrease 28% by the fall of 2014. Allowing Sunday hunting during the opening weekend of the main firearm season and adding an additional week onto the main firearm season caused the population to decline at a greater rate by 2014. Terminating the severe deer damage program did not impact the 2014 predicted deer population compared to the scenario without changing the harvest regimes. Closing the October antlerless season and the January shotgun season caused a 23% increase to the 2014 predicted population, in both scenarios. Compared to scenario without changing the harvest regimes, the deer population was 11% greater in 2014 with the January muzzleloader season closed and 37% greater in 2014 with both January shotgun and muzzleloader seasons closed. The model predicted that the differentdeer management zones have very different population levels and harvest rates. To date, the harvest regimes in Delaware have only been changed at the state level but future changes to the harvest regimes should occur at the zone level. Several options are available for managers to increase or decrease the deer population by 2014. Managers can further reduce the deer population by allowing Sunday hunting during the opening weekend of the main firearm season and/or adding an additional week onto the main shotgun season. If managers decide to slow or stop the population decline, then closing the October antlerless season and/or the late January seasons are the best methods. Terminating the severe deer damage assistance program is not an effective method to slow or stop the declining trend, because removing the deer harvested under the program only caused a 4% increase to the 2014 population. Depending on the desired 2014 population level, managers can adjust the harvest regimes accordingly to meet their population goal.