White-tailed deer. White-tailed deer. White-tailed deer. White-tailed deer. White-tailed deer. White-tailed deer

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1 The most popular big game animal in North America Abundance Distribution = widespread = accessible Early successional species, highly adaptable Elusive and challenging Most abundant and wide-spread large mammal in NA (excluding humans) In 1990s 5.3 million WTD harvested Over 10 million hunters Baker (1984) Mule and WT-D Tail Antlers Metatarsal glands Skull characters Fig 10-1 Geist 1998 Deer of the World 38 subspecies Canada kg Kansas kg Texas kg Venezuela 45 kg Key deer 35 kg Adult (same-aged) whitetailed deer males Venezuela Michigan Baker (1984) 2 T&E populations of WT-D Key deer in Florida (listed in 1967) Columbia WT-D (listed in 1968) 2 T&E populations of WT-D Key deer in Florida (listed in 1967) Populations are doing well Habitat is severely restricted Human development Hurricanes could be problem. 1

2 2 T&E populations of WT-D Columbia WT-D (listed in 1968) Populations in NW Oregon along Columbia river doing poorly Populations in W and SW Oregon doing well Even causing problems in suburban areas Recently delisted, limited hunting allowed. R or K selected compared to all mammals in NA? R-selected: extreme example = mice K-selected: extreme example = whales Compared to other large mammals we discuss in this class? More R-selected than most Population trends during past 500 yrs Early 1900s 500,000 Currently 20 million Range expansion Eastern CO, Northern UT High densities cause problems Affect forest, habitat composition Human-wildlife conflicts Ag damage Road kills Competition with mule deer? from The Science of over abundance by McShea, Underwood, and Rappole Figs 3-4; Journal Wildlife Manage 58:715 2

3 High densities of WT-D causing ecological problems In PA, WT-D browsing affected songbirds intermediate canopy nesting species Recommended deer densities: < 8/km2 (1 deer/30 ac) High densities of WT-D causing ecological problems In MA, deer browsing reduced forbs, increased grass fewer voles and shrews, and more mice Loss of rare or sensitive plant species Damage by WT-D is a concern Ag Damage 51% Ag producers reported deer damage; Wildlife damage to crops $4.5 billion/yr Deer damage to timber industry $1.6 billion Damage by WT-D is a concern Suburban-Urban damage Vehicle collisions 1.5 million annually, 1.6 billion annually, 29,000 people injured and 200 killed annually 2.4 million households reported deer damage, primarily landscape plants Controlling urban deer (WSB 29: ) 4 control methods in MN urban parks Controlled hunts (archery) Shooting by conservation officers in parks (deer drives) Sharp shooting over bait by park rangers Sharp shooting over bait by police officers Table 2, Doerr et al WSB 29: Net cost of each approach $117/deer; $108/deer; $121/deer; $194/deer 3

4 Northern White-tailed Deer ecology, populations, and management change outside of Texas Table 1, Doerr et al WSB 29: More public land, smaller land holdings, and few high fences Few old bucks, low buck:doe ratios Highly seasonal, relatively predictable environment Effects of Snow In the north, conditions are good in the summer and bad in the winter. Because this is predictable, deer have adapted to surviving winter conditions. Reduce food availability Deer must search for high quality food under snow Increase energy expenditure during travel Effects of Snow Adaptations to Survive Winter Accumulate body fat summer & fall Lower metabolic rate and obligate loss of body mass overwinter Habitat use Deer yards High density (1/4 ac) 4

5 Adaptations to Survive Winter Large body size Lower surface area:volume ratio Volume = ability to produce heat Area = potential to lose heat Enables deer to carry more fat relative to metabolic rate Longer legs Less impact from deep snow Severe Winter Impacts Fawns most susceptible Reduced growth and lower survival Does body condition will decline Affects fawn development and lactation Up to 70% of fawns may die soon after birth after severe winter Bad winters = high adult mortality 76% mortality has been documented Timing of Fawning Strong selective pressure Born early = susceptible to late freezes Born too late = can t get large enough and store enough fat to survive the winter What is a possible effect of highly skewed sex ratios on timing of fawning? 3 Populations: Case Studies Illinois Nixon et al Wildl. Monogr. 118 Minnesota Fuller 1990 Wildl. Monogr. 110 Montana Dusek et al Wildl. Monogr. 104 Illinois Farm Land 600 ha park, unhunted and forested in a sea of agriculture with small woodlots Illinois Farm Land Upland woodland plots used as summer range by deer that disperse or migrate from larger forests or refuges in spring. Woodlots were usually vacated each fall. 5

6 Population Highly Productive < 5% yearling had spikes 10 pts common Fawns weighed lbs during winter 76% of female fawns conceived 1.13 fawns/female fawn in October Adults recruited 2.1 fawns/doe in October 14% of does had triplets Fawn survival to Oct. was 90% λ = 1.09 to 1.37 (Population double in 9 years) Deer Movements 50% of fawns dispersed each spring Moved km from the refuge 21% yearling females dispersed from refuge 20% adult does migrated average 13 km off the refuge in spring returned in fall Nixon et al Wildl. Monogr. 118 Tables 5 and 6 Dispersal and highly productive herds necessary to maintain deer in this fragmented landscape Need to protect corridors Central Minnesota Deer herd in boreal forest Habitat conditions relatively constant λ = 0.79 to deer/km 2 (1 deer/25 ac to 1/62 ac) Concern because deer are prey for wolves Is the decline due to excessive mortality or low recruitment Study to determine which 6

7 Fuller 1990 Wildl. Monogr. 110 Tables 4, 5, and 7 Central Minnesota Fawn annual survival was % mortality during the summer of birth Fawn survival overwinter 0.89 when snow depth cm 0.60 when snow depth cm Author modeled population No single factor could result in increasing pop. No doe harvest or 3 day hunting season λ = 0.95 Several mild winter and no doe harvest λ > 1.0 Lower Yellowstone River associated with riparian forests along river Most agriculture in riparian areas Hay meadows (alfalfa) Grain fields (small grains) Sugar beets Left: Lower Yellowstone River valley. Right: feeding in stubble field adjacent to a mature cottonwood stand. Riparian forest and shrub communities interspersed by agricultural croplands provide high-quality habitat for white-tails throughout the northern plains. 7

8 Population trends Lower Yellowstone River Pregnancy rates Recruitment Some evidence of density-dependence. 8

9 Mortality Harvest Lower Yellowstone River info Population increased for 3 years, then declined Dispersal was not a big factor Nearly all dispersing deer stayed in the riparian area Overwinter mortality was low Ag crops > 40% of diet Lower Yellowstone River Harvest was greater than recruitment Main reason for the population decline Harvest rates vs. sustainability Doe harvest > 30% - declining population 25% - stable population < 20% - increasing population Harvest of up to 60% of bucks had no effect on population trend 9