Survival Analysis and Computer Simulations of Lethal and Contraceptive Management Strategies for Urban Deer

I monitored survival of 34 female white-tailed deer (Odocoileus virginianus) in Bloomington, Minnesota, from October 1996 to December 1999. Twenty deer died: nineteen were killed by vehicles, and one was killed in a deer-removal program conducted by an adjacent suburb. Summer survival was high and varied little over the 3 years of study (range = 0.93 to 0.95). Fall survival ranged from 0.84 to 1.00, and winter survival was generally high during the 3 years of study, except during a severe winter (range = 0.72 to 0.95). I calculated population growth rates (λ) from Leslie matrix projections, using these survival estimates and productivity data collected from road-killed female deer in the Twin Cities (Minneapolis-St. Paul, Minnesota, USA) metropolitan area. When winter survival was high (0.94), my model simulations indicated the Bloomington deer population increased by 21% when no deer management program was in place. When a low winter survival rate (0.72) was modeled, the population decreased by 7%, even when no deer management program was implemented. I modeled what impact contraception may have on population growth and concluded that treating \u3e50% of adult female deer was necessary to stabilize population growth, and treating all females was necessary to decrease population growth under high winter survival conditions. I concluded that removal programs are more effective than immunocontraception programs because survival contributes more to population growth rates in deer populations than fecundity. I recommend removing 20% and 40% of adult female deer in the population to cause the population to stabilize or to reduce deer numbers, respectively. I recommend managers collect deer–vehicle collision data because these data potentially represent the most accurate and easily-obtainable life history component of an urban deer herd

Evaluating Competing Preferences of Hunters and Landowners for Management of Deer Populations

Most state wildlife agencies consider public input in the management of whitetailed deer (Odocoileus virginianus) populations. In 2013, we surveyed deer hunters (n = 3,600) and landowners (n = 4,604) in southwest Minnesota to gauge their preferences for managing deer. We hypothesized a priori that, irrespective of their perceived impacts of deer, hunters would prefer deer populations to be increased and landowners would prefer deer populations to be decreased. Our findings suggest that defining stakeholder groups according to primary associations with deer (i.e., farming and hunting) accurately categorized differences in tolerance levels for deer populations in our study area. Deer damage was considered relatively minor by landowners, yet, 51% of landowners wanted deer densities reduced. Although 59% of hunters were satisfied with the number of deer, 62% of hunters still wanted deer densities increased in the future. Almost two-thirds of hunters were not satisfied with the number or quality of bucks where they hunted, and an antler-point restriction was the only potential regulation supported by hunters to reduce harvest mortality rates of bucks. To enable managers to monitor trends in public satisfaction relative to the fundamental objectives of deer management in an area, we recommend conducting frequent surveys of primary stakeholders

Bullet Fragmentation and Lead Deposition in White-Tailed Deer and Domestic Sheep

In February 2008, a private physician in North Dakota radiographed hunterharvested venison and found that 60 of 100 packages contained metal fragments. This discovery had implications for public-funded venison donation programs, and it prompted several Midwest states to examine their programs. Approximately 500,000 deer hunters harvest \u3e200,000 deer annually in Minnesota, and the state has a donation program similar to North Dakota’s program. Therefore, we analyzed fragmentation patterns and lead deposition in carcasses of 8 white-tailed deer (Odocoileus virginianus) and 72 domestic sheep (Ovis aries). We fired 5 different bullet types from centerfire rifles, and we also fired projectiles from both a shotgun and a black-powder muzzleloader. Centerfire bullets, which are designed to expand quickly upon impacting the animal, left bullet fragments and lead deposits throughout the entire abdominal cavity of carcasses. We also used 2 types of centerfire bullets that were purportedly designed to resist fragmentation. One of these bullet types had fragmentation patterns and lead deposition rates similar to the rapid-expanding bullets; the other bullet type resisted fragmentation, and no lead was detected in muscle tissue that we sampled. Centerfire bullets made from copper resisted fragmentation, and of course did not deposit any lead in muscle tissues. Projectiles fired from the shotgun and black-powder muzzleloader did deposit lead into carcasses but did not fragment as much as bullets fired from centerfire rifles. Our study suggests that rinsing the abdominal cavity may spread the lead contaminant to other areas of the carcass, thereby worsening the contamination situation. We suggest that hunters who use centerfire rifles and are concerned about lead exposure should purchase a bullet type that resists fragmentation

Using Distance Sampling to Estimate Densities of White-Tailed Deer in South-Central Minnesota

Distance sampling is a method of estimating population abundance and density used by wildlife biologists for several species because of its advantages relative to other techniques. However, few wildlife biologists have used distance sampling to estimate abundance of white-tailed deer (Odocoileus virginianus). We describe a distance sampling technique used to estimate prehunt and post-hunt population densities of deer in Watonwan County, Minnesota. Estimates of white-tailed deer density were compared between distance sampling versus population modeling, and costs for distance sampling versus aerial surveys were determined. We drove 2,704 km during 24 spotlight surveys conducted from 21 October to 28 December 2004. We observed 537 white-tailed deer during the pre-hunt period and 620 deer during the post-hunt period. Estimates of white-tailed deer density obtained via distance sampling were more than three times larger than estimates derived by population modeling. Costs for aerial surveys would have been four times greater than costs for distance sampling surveys. We concluded that wildlife biologists should consider implementing distance sampling for estimating deer density because of the advantages and lower costs of distance sampling relative to other techniques

Quantitative Assessment of Bullet Fragments in Viscera of Sheep Carcasses as surrogates for White-Tailed Deer

Avian scavengers, such as bald eagles (Haliaeetus leucocephalus), can be exposed to lead through the consumption of spent lead from ammunition in carcasses of animals shot with lead-based projectiles. Few studies have examined the degree of bullet fragmentation in viscera (offal) of game mammals. Our objective was to quantify the number of bullet fragments deposited in sheep carcasses shot with different types of lead and lead-free, high-velocity centerfire rifle bullets and with lead projectiles fired from shotguns and muzzleloader rifles marketed for hunting white-tailed deer (Odocoileus virginianus). We hypothesized that after controlling for velocity, angle of entry, distance from target, and shot placement (thoracic region), most of the bullet fragments would be deposited in the impact zone (heart and lungs). After radiographic examination of all viscera from each carcass, we detected metal fragments in 96% of the viscera and found that metal fragments were deposited in greater quantities in the abdominal viscera (organs caudal to the diaphragm) compared to the thoracic viscera (heart and lungs). Additionally, bullets fired from the centerfire rifle fragmented more than the projectiles fired from the shotgun and muzzleloader rifle. Rapid-expansion lead bullets fragmented more than controlled-expansion lead bullets and lead-free bullets. However, 1 type of controlled-expansion bullet that is comprised almost entirely of lead and advertised to retain \u3e90% of its weight, fragmented similarly to the rapid expansion lead bullets. We observed lead fragments produced by centerfire rifle bullets and shotgun and muzzleloader projectiles present in sheep carcasses and conclude that lead is made available to scavengers from the distribution of lead fragments lodged in the carcasses of game through viscera left in the field by hunters.To eliminate this type of lead exposure, shooters must employ the use of lead-free projectiles or completely remove the remains of shot animals from the field