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					            Nutrition and Carrying                                                         Nutrition
                    Capacity                                               • One of the basic interactions between an animal
                                                                             and the environment is through nutrition

“I differentiate the two kinds of carrying capacity by calling the range
manager’s version ‘economic carrying capacity,’ and the unharvested        • Ingestion and metabolism of chemicals and
equilibrium ‘ecological carrying capacity.’ Although I know what a range     energy that animals need for maintenance and
manager means when he declares a range overpopulated, I am less
certain what a wildlife manager means. He may be using the term in           production
either sense.”
–Graeme Caughley
                                                                           • Food may dictate where a species can live and
“Management decisions must be made, based on past experience, but
no information about the weather forthcoming. A manager’s success or         population density
failure may depend on weather he or she cannot foresee. It is a serious
guessing game. Millions of dollars and thousands of hunters are
influenced. In the aftermath, the manager may be blamed, for there is
no satisfaction in blaming the weather.”                                   • Operates through impacts on reproduction and
–Paraphrased from Robert H. Giles, Jr.                                       survival




                         Nutrition
                                                                                           Nutrition
                              Habitat
                                                                            • To understand an animal’s interactions
                Cover           Food         Water
                                                                              with its nutritional environment, need to
   Energy (CHO, fat)         Protein      Vitamins       Minerals             understand its digestive system
                   Potentially act to influence
                      Age at puberty
                      Length of breeding season
                      Proportion of adults breeding
                      No. ova shed
                      Prenatal losses
                      Post natal losses
                      Subadult and adult survival




                                                                                                                               1
        Abomasum




Rumen       Omasum

         Reticulum




                     • Figure 2.1 from Hofmann




                                                 2
               Nutrition
                                                               How much is “food”
• Animals differ in part because of their
  digestive systems

• An animal’s adaptations enable it to eat
  and digest some foods well
  – Makes animal inefficient at using other foods

• Understanding these differences can
  be important in managing wildlife




         How much is “food”                                    How much is “food”




 Provide Proper Nutrients at the                          Provide Proper Nutrients at
          Proper Time                                          the Proper Time

Spring/Summer – high productivity                       Spring/Summer - high productivity
 – protein
 – energy                                           Energy
                                                    % Increase over Maintenance
 – minerals
                                                    • 3rd trimester Gestation- 30 4%
                                                                                - 5
                                                    • Peak Lactation - 170%
                                                    • Fawn Growth- 25%
                                                    • Antlers- < 5%




                                                                                            3
              Provide Proper Nutrients at                                                                                                                  Provide Proper Nutrients at
                   the Proper Time                                                                                                                              the Proper Time
        Spring/Summer - high productivity                                                                                                            • Spring/Summer - high productivity
                                                                                                                                                        – protein, energy, minerals
 Protein
                                                                                                                                                     • Fall - increase body fat; does ovulating
                   2
 • Body Growth 10- 1 %
                                                                                                                                                        – energy
 • Gestation                                      12 %                                                                                                  – weaned fawns
 • Lactation                                      18 %                                                                                                    need protein
 • Antlers                                            2
                                                  10- 1 %




              Provide Proper Nutrients at
                   the Proper Time                                                                                                                  Seasonal Variation in Forage Quality
                                                                                                                                                        Dietary DE (kcal/g DM)
                                                                                                                                                                                  3
    • Spring/Summer- high productivity                                                                                                                                           2.5
            – protein, energy, minerals
                                                                                                                                                                                  2    Maintenance
    • Fall- increase body fat ; does ovulating                                                                                                                                   1.5   (2.17 kcal/g DM)
            – energy                                                                                                                                                              1
            – weaned fawns need protein
                                                                                                                                                                                 0.5
    • Winter- Post rut recovery; gestation
                 -                                                                                                                                                                0
            – energy                                                                                                                                                                                  r
                                                                                                                                                                                               b




                                                                                                                                                                                                            n
                                                                                                                                                                                  ct

                                                                                                                                                                                        ec




                                                                                                                                                                                                                   g
                                                                                                                                                                                                    Ap




                                                                                                                                                                                                                Au
                                                                                                                                                                                                          Ju
                                                                                                                                                                                             Fe




            – maintenance protein requirements – 6%
                                                                                                                                                                                 O

                                                                                                                                                                                       D




                                                                                                                                                                                       Carrying Capacity
                              Carrying Capacity
Table 1. Definitions of carrying capacity (adapted from McCullough 1992)                                                                          • Many definitions of C.C., must clarify what you are
        Notation                                          Definition                                                 Synonyms                       talking about
Ecologically-based

  KCC                     k-carrying capacity. Maximum number of animals of a given                Subsistence density (Dasmann 1964, Bailey
                          population supportable by the resources of a specified area (K of the    1984)
                          logistics model)                                                         Ecological carrying capacity (Caughley 1976)
                                                                                                   Potential carrying capacity (Riney 1982)         - arrying capacity: populations are limited by forage
                                                                                                                                                  • K c
  BCC                     Behavioral carrying capacity. Maximum density of a population            Saturation point (Leopold 1933)
                          limited by intraspecific behavior such as territoriality                 Tolerance density (Dasmann 1964)
                                                                                                                                                    resources
  RCC                     Refugium carrying capacity. Maximum population density below             Threshold of security (Errington 1934, 1956)
                          which animals are relatively invulnerable to predation                   Security density (Dasmann 1964)

  ECC                     Equilibrium carrying capacity. Density of a population at a consistent
                                                                                                                                                    – maximum # of animals supported by the habitat
                          equilibrium, but the limiting variables are unknown (May include
                          KCC, BCC, or RCC)                                                                                                         – equivalent to subsistence density, potential C.C, and
Culturally-based

  ICC                     i-carrying capacity. Population density that yields maximum              Optimum density (Dasmann 1964)
                                                                                                                                                      ecological C.C.
                          sustained yield (i.e. inflection point of the logistic growth curve)     Economic carrying capacity (Caughley 1976)
                                                                                                   Maximum harvest density (Bailey 1984)

  OCC                     Optimum carrying capacity. Population density that best satisfies        Relative deer density (deCalesta and Stout
                          human expectations for it (may be equivalent to any of the other
                          definitions of k)
                                                                                                   1997)
                                                                                                                                                  • Other C.C. definitions incorporate behavior, space,
  MCC                     Minimum-impact carrying capacity. Population density that                Wildlife acceptance capacity (Decker
                          minimizes impact on other wildlife, vegetation, or humans without
                          eliminating the population (Bailey 1984)
                                                                                                   And Purdy 1988)                                  cover, etc.




                                                                                                                                                                                                                       4
                     Carrying Capacity                                                         Logistic Growth
  -
• K C.C. is the basis for most models of population                                                        K, behavioral, equilibrium,
  growth and game harvest management                                                                            or refugium C.C.




                                                                         Population Size
• Simply, density will increase to the point where
                                                                                                               Maximum Harvest
  equilibrium will be reached between herbivore
                                                                                           I or MSY
  numbers and food supply


• Population growth rate at K = 0                                                                              Minimum Impact
   – mortality increases via increased adult or juvenile mortality
   – natality decreases due to depressed reproduction and                                               Time
     advanced age of sexual maturity




                     Carrying Capacity                                                        Carrying Capacity

• Competition for forage is the factor in mortality and
                                                                     • Substantial damage to forage base, population
  reduced body condition
                                                                       will “crash” severely

• Animal condition will be poor at K and the habitat
  quality will be reduced                                            • Further oscillations of growth and decline

• Ungulate populations may overshoot K before                        • Species with high reproductive rates are more
  equilibrium is reached = “irruptive behavior”
                                                                       prone to overshoot K (e.g. white-tails)




                  Carrying Capacity                                            Basic Carrying Capacity Model
• Forage quality and quantity determine how many
  animals an area can support

                                                                                                          A
• C. C. models require information on:                                                           k=
   –   animal diet                                                                                    B × Days
   –   forage availability
   –   nutritional quality of forages
   –   animal nutritional requirements
                                                                                  K = carrying capacity
                                                                                  A = usable forage
• Carrying capacity is estimated from the relationship
  between available forage and animal requirements                                B = average daily intake (dry matter)
                                                                                  Days = season length




                                                                                                                                         5
             Example: Basic Model                                               Carrying Capacity
                                                               • The basic model is dependent on forage quantity or
          1,000 kg / ha                                          total biomass only
                             = 111elk / ha
                                .                                 – it assumes that all forage meets minimum nutrient
     5.0 kg / day × 180 days                                        requirements


• Biomass on a study area is estimated at 2,000 kg/ha          • If forage quality is limited, the basic model will
• Assume 50% of biomass is available: >50% use may result in     overestimate carrying capacity
  damage to the forage resource
• Elk eat about 5 kg/day (or 2.5% of their body mass)          • All biomass is NOT of the same quality
• The habitat will be used for about 180 days




             Nutrition-based Models                                         Nutrition-based Model

                                                                                            ∑ (B              )
                                                                                             n

                                                                                                   i   × Fi
• Models that incorporate forage quality are assumed to                                     i =1
                                                                                    k=
  be more accurate
                                                                                          ( R × Days) − E
          - ased models also require more data
• Nutrition b                                                          •   k = number of animals the area can support
   – quantity of forage biomass                                        •   n = number of principal forages (>1% of diet)
   – quality of forage biomass                                         •   Bi = biomass of forage species i
   – nutrient requirements                                             •   Fi = nutrient content of forage species i
                                                                       •   R = animal requirements
                                                                       •   Days = number of days habitat will be used
                                                                       •   E = endogenous energy reserves




               Estimated Daily Energy                                           Elk Carrying Capacity:
            Requirements For a 200-kg Elk                                         Hobbs et al. 1982

                                                  Daily
 Activity           Time         Energy cost      costs        • Estimated daily energy requirements for elk fitted with
                  (hrs/day)      (kcal/kg/hr)     (kcal)         radiotelemetry activity collars
 Feeding            11.38               2.37      5,394
                                                               • Determined quantity of principal forages
 Bedding             9.77               1.03      2,013
 Traveling           2.85               3.12      1,778        • Estimated nutrient quality of forages

 Total                                            9,185        • Forages <5.6 g N/kg were not included
                                                                  – elk lose 5.6 g N/kg forage in their feces daily (MFN)
                                                                  – elk require forages containing 0.56% N or 3.5% protein




                                                                                                                             6
               Elk Carrying Capacity
                                                                                                Elk Carrying Capacity
• The model produced energy-based carrying
  capacity estimates:                                                           • Notice the extreme annual variation in carrying
   – 1,481 elk during year 1 (0.37 animals/ha)                                     capacity estimates
   – 991 elk during year 2 (0.25 animals/ha)
                                                                                • Even though the C.C. estimates changed, the overall
• Nitrogen-based estimates:                                                        density of elk did not
   – 1,674 elk during year 1 (0.42 animals/ha)
   – 994 elk during year 2 (0.25 animals/ha)                                    • How can we explain this discrepancy?




              Example: High-quality forage with                                  Low-quality Forage With Endogenous Reserves
                   no animal weight loss
                                                                                • Previous research revealed that elk have fat reserves
(1,000 kg / ha) × (3,000 kcal / kg) = 3,000,000 kcal / ha = 181animals / ha       averaging 15% of their body weight
   (9,185 kcal / day × 180 days)
                                                             .
                                        1,653,300 kcal
                                                                                • 90 % of this fat is catabolized during winter
                                                                                • Catabolized fat averages 6 kcal ME/g
              Example: Low-quality forage with
                  no animal weight loss                                               - g
                                                                                • A 200 k elk would have 30 kg fat @ 6 kcal/g
                                                                                    – 180,000 kcals

(1,000 kg / ha) × (1,000 kcal / kg) = 1,000,000 kcal / ha = 0.60 animals / ha
                                                                                    – if 90 % is catabolized = 162,000 kcals

   (9,185 kcal / day × 180 days)        1,653,300 kcal
                                                                                     (1,000 kg / ha) × (1,000 kcal / kg)    =
                                                                                                                              1,000,000 kcal / ha
                                                                                                                                                  = 0.67 elk / ha
                                                                                (9,185 kcal / day × 180 days) − 162,000 kcal 1,491,300 kcal




                   Carrying Capacity
                                                                                              Limitations of C.C. Models...
• A limitation to these models is that they treat
  food resources as the sum of all available
                                                                                                                         Less forage, diet quality is high
  forage
                                                                                           1000 kg/ha forage
                                                                                                                                      500 kg/ha
                                                                                               5.5% N
                                                                                                                                        11% N
• These models do not distinguish between                                                                                            =5,500 gN/ha
                                                                                              =5,500 gN/ha
  areas with large quantities of low-quality forage
  and areas with small amounts of high-quality
                                                                                   Much forage, diet quality is low
  forage




                                                                                                                                                                    7
                                                                                                                             Distribution of Nutrients Within Plants
     Distribution of Nutrients in the Habitat                                                                                  Follows the Same Relationship...




                                                                                                           Forage Biomass
                                                                                                                                                                                     Fruits or Mast =
                                                                                                                                                                                     often very high
      Forage Biomass




                                                                                                                             Forage Nutrient Concentration
                                                                                                                                                                                          quality

                                                                                                                                                                                Young leaves =
                                                                                                                                                                                 high quality

                                                                                                                                                                             Mature leaves =
                                                                                                                                                                            medium-low quality
                                                  Forage Nutrient Concentration
                                                                                                                                                                            Nonlignified stems =
                                                                                                                                                                               lower quality
                       •There is a large amount of low-quality forage
                       •There is relatively little high-quality forage                                                                                                               Lignified stems =
                                                                                                                                                                                       lowest quality




                        Carrying Capacity With Explicit                                                                     Explicit Nutritional Constraint Model
                            Nutritional Constraints                                                                                                    Only consider plants that meet
                                                                                                                                                       animal nutritional requirements
     • Based upon these ideas, Hobbs and Swift

                                                                                                                                                              ∑(N B )
                                                                                                                                                               t
       (1985) developed the following model...
                                                                                                                                                                            i    i
                                                                                                                                                              i =1
                                         Forages < animal                       Forages > animal                                                                      t                  ≤ CONC
                                                                                                                                                                   ∑ Bi
                        Forage Biomass




                                         nutrient requirement                   nutrient requirement
                                                                                                                                                                     i =1


                                                                                                        • Bi = Biomass of the ith forage
                                                                             CONC                       • Ni = Nutrient concentration of the ith forage
                                                       Forage Nutrient Concentration
                       X1 = mean nutrient concentration                                XMAX = Highest   • CONC = Specified diet nutrient concentration
                       of all forages to the right = CONC                              quality forage




                                           Using the Model…...                                                                                               Using the Model...
• Arrange forages in descending order of nutrient concentration                                         • We want to estimate C.C. based on a diet that meets
                                                                                                          animal requirements
• Sum the biomass until adding another forage causes the                                                   – Mix good and poor quality forages so that the average
  mixture’s nutrient concentration to be #CONC                                                               attainable diet = animal requirements

                                                                                                           – We need to figure out how much biomass from the last
• Usually, adding one of the last forages (Bt) causes nutrient
                                                                                                             added low-quality forage t that we can ADD to = CONC
  concentration < CONC…….
                                         t −1

                                         ∑(N B )+ Ni     i         t   Bt                                                                                          ⎛ t −1 ⎞ t −1
                                                                                                                                                              CONC ⎜ ∑ Bi ⎟ − ∑ N i Bi
                                         i =1
                                                                            < CONC                                                                                 ⎝ i =1 ⎠ i =1
                                                t −1                                                                                        ADD =
                                                ∑ Bi + Bt                                                                                                                       (N   t   − CONC )
                                                i =1




                                                                                                                                                                                                         8
                                                                                                                  Using the Model….
                        Sample Data
                                                                                                           t = # of forages that can be mixed
                                                                                                           so that the total is no longer > 2.0% N
                                                                    t=1                                                               t=2
    Data                     Biomass         N content               1
    (t)     Forage           (kg DM/ha)      (g N/g DM)            ∑B N                                  150 × 0.025
                                                                                                                                       2

                                                                                                                                     ∑BN                          (150 × 0.025) + (50 × 0.020) = 0.023
                                                                                   i           i
        1   Grass, green          150             0.025             i =1
                                                                                                       =             = 0.025          i =1
                                                                                                                                                  i       i
                                                                                                                                                              =
                                                                           1
                                                                                                                                                                           150 + 50
                                                                      ∑B
                                                                                                                                             2
                                                                                                            150
                                                                                           i
                                                                                                                                        ∑B            i
       2    Eriogonum              50             0.020                  i =1
                                                                                                                                           i =1




       3    Grass, dead            400            0.015             t=3
                                                                         3
       4    Purshia stems          80             0.014              ∑BN
                                                                     i =1
                                                                                       i           i
                                                                                                           (150 × 0.025) + (50 × 0.020) + (400 × 0.015) = 0.018
                                                                                                       =
                                                                               3
                                                                                                                         150 + 50 + 400
                                                                         ∑   i =1
                                                                                       Bi




                Using the Model….
                        ⎛ t −1 ⎞ t −1                                                                             Using the Model…..
                   CONC ⎜ ∑ Bi ⎟ − ∑ N i Bi
                        ⎝ i =1 ⎠ i =1
             ADD =
                       N t − CONC
                                                                  • Total amount of forage that can be mixed such that

    ( 0.02) × (150 + 50) − (150 × 0.025) + 50( 0.020)
                                                                    the attainable diet = 2.0% N
=                                                       = 150kg
                     0.015 − 0.020
                                                                             ⎛ t =1 ⎞
                                                                             ⎜ ∑ Bi ⎟ + ADD = (150 + 50) + 150 = 350kg
                                                                             ⎝ i =1 ⎠
• Amount of forage t = 3 that can be mixed with forages 1 and 2
  so that the total has a N content of 2.0%




                                                                             Example: Burned vs. Unburned Mule Deer
                  Using the Model…..                                                   Habitats in Colorado

                                                                                                                 Traditional CC Estimate
• Assuming dry matter intake rate of 1.5 kg/day, C.C. for                                                                   1 year post-burn                             Unburned
  animals consuming diets with N concentrations of
  2.0%...                                                                                                   Forage          651,000 kcal/ha 904,000 kcal/ha

                                                                                                        Nutrient Req.                        4,613 kcal/day

      350 ÷ 15 = 233 animal days / ha
             .                                                                                         Traditional C.C. 141 deer/day/ha 195 deer/day/ha


                                                                                                           Unburned range appears to be better?!!




                                                                                                                                                                                                         9
                                                Considering Forage Nutrient                                                     Example: Desert Bighorn Sheep in West Texas
                                                    Concentration…..
                                                                                                                                                                    Study Area
                                 ME kcal/g                                                                                                  Sierra Diablo
                                                   Burned Unburned                                                                          Mtns.
                                      3.00           14      0
                                                                                                      Lactation: 2.67                                                                N
                                      2.75           28      0
                                      2.50           84      1                                                                                  Baylor Mtns.
                                      2.25          185      4                                        Gestation: 2.02
                                                                                                                                            Beach Mtns.
                                                                                                                                                     I-
                                      2.00          206     160
                                      1.75          206     330                                       Maintenance: 1.62                               10
                                      1.50          206     359                                                                          Van Horn


                                                                                                                                                      85 km




                                      Sheep Survey Results 1992–1998                                                                  Sheep Nutrient Requirements
                                                                                         Sierra
                                        Year                Baylor        Beach          Diablo                Total
                                      1992                                                                     112                     Diet quality
                                      1993                    6             58                  58              122                    %N (%CP) Requirement
                                      1994                   22             88                  73              170                    0.89 (5.6) Adult maintenance

                                      1995                   32             70                  58              160                     1.20 (7.5)     Above maintenance
                                      1996                   25             59                  76              160                     1.50 (9.4)     Lactation
                                      1997                                                                      132                     1.80 (11.3)    Growth (weaned lambs)
                                      1998                                                                      160


        Population stable to declining… what is happening? Predation?




                                                Carrying Capacity of Desert Sheep
                                                                                                                                                    Other Methods
                                                 Spring                                                Summer
                                50
                                                                                    70
                                                                                                                               • Various methods exist for assessing C.C.
Carrying capacity (sheep/km2)




                                40                                                  60
                                                                                    50
                                30
                                                                                    40
                                20                                                  30
                                10                                                  20
                                                                                    10
                                                                                                                               • Direct measures include measuring forages,
                                 0
                                         0.89       1.20          1.50      1.80
                                                                                     0
                                                                                         0.89        1.20        1.50   1.80
                                                                                                                                 estimating nutrients, diet preferences, etc.
                                 30               Fall                              14
                                                                                    12                      Winter             • Other techniques include:
                                 20                                                 10
                                                                                     8
                                 10                                                  6                                           – using tame animals to index C.C.
                                                                                     4
                                 0                                                   2
                                                                                                                                 – using activity and energy budgets for predators
                                         0.89        1.20          1.50      1.80    0
                                                                                         0.89        1.20        1.50   1.80

                                Baylor                                                                                                          -         - o
                                                                                                                               • This can be time and labor c nsuming
                                                                  Attainable diet quality (%N)
                                Beach

                                Sierra Diablo




                                                                                                                                                                                         10
                    Other Methods                                   Habitat & Animal Condition
• Managers often use indirect measures to index
  C.C., such as                                                 • Assess habitat and animal condition in
  – Forage use/availability (bite/stem counts)                    choosing management actions
  – Fat stores (kidney, abdominal)                                 – Reasons for low population performance
                                                                      • Predation vs. nutrition
  – Blood or urine parameters
                                                                      • Effects of hunting/poaching
  – Structural measurements (size & weight)
  – Reproductive performance (age, number)
  – Trends in relative density                                  • Habitat & animal assessment
                                                                   – What could you measure?

You must know what you are doing to use
 these reliably!




               Habitat Condition                                             Habitat Condition
   • Browse surveys give way of assessing herbivore
     density relative to available forage
      – Classify browse as 1st, 2nd, or 3rd tier in quality

      – Count current year’s growth that has been browsed




                Animal Condition
                                                               Animal Condition
 • Evaluate trends in animal condition among
   areas and across years
    – Antler characteristics
       • Yearling bucks
                                                              • Use corpus luteum to
                                                                determine how many
    – Body mass                                                                                       Fig. 7, Chapter 11
                                                                ova were released                     Wildlife Techniques Manual
       • Yearling bucks, does

    – Reproductive data
       • Age at first reproduction
       • Proportion of females breeding
       • Number of offspring/female




                                                                                                                                   11
Fetal ages, avg. number/doe Avg. corporea lutea/doe
                                                                                     Survey or harvest data:
                                                                         indirect measure of reproduction & survival




                                                                              • Use with caution, age classes not accurate
                                     Length of breeding season                • Can reveal trends
                                                                              • Predict cohort size in future




                  Animal Condition                                                     Animal Condition
   • Body fat content                                                 • Kidney fat index
     – Often indexed by kidney, rump fat                                – Perirenal fat mass/kidney mass * 100
     – Represents energy intake above requirements                                     Weigh this fat

                                                                           Discard                      Discard
   • Bone marrow fat
     – Can be used several days after death
                                                                                          Kidney
         •   White – decent to excellent condition
         •   Pink or reddish – poor condition
         •   Red jelly – starvation condition                           – A measure of abdominal fat stores, easy to obtain
         •   Can also dry the marrow, extracting fat                    – Fat stores that are used early when fat is mobilized




                  Animal Condition
                                                                                       Animal Condition
                                                                      • Subcutaneous fat
                                                                         – Related to total body
                • Fig. 2 from JWM on white-                                fat in deer, moose,
                  tailed deer fawn body                                    and elk above 5 cm
                  condition
                                                                         – Can measure with
                                                                           ultrasound, but
                                                                           requires training
                                   Harder to obtain
  Easy to obtain                   Little change until animal
  Plateaus at good condition       condition very poor = starvation




                                                                                                                                 12
               Animal Condition




           Important Considerations...                          Important Considerations…
• Animals are limited by the amount they can eat:         • C.C. estimates difficult in areas with fluctuating
  – Gut capacity and passage rate                           environmental conditions, low-quality habitats

• As attainable diet quality decreases, there are not     • Environmental variations overshadow density effects
  enough nutrients for specific purposes, such as           – Density does not affect food limitation, but weather, etc.
  lactation, etc.
                                                          • DD, logistic growth may not operate as expected
• Searching for high q
                   - uality forage is energetically         – Harvest/remove deer, all you may have is fewer deer!

  expensive when these forages are patchily distributed




                                                                                                                           13
      Rainfall patterns in Texas (mm/yr):                                                Fawn production as a
      Importance of environmental variability                                             function of rainfall

                                                                                                                    Different areas =
                                                                                                                   different response

                                                                                         DD, Logistic growth may
                                                                                              not operate




          Important Considerations…                                                                                      Important Considerations…
                                                  Adult (same-aged) white-
Ungulate populations differ…                         tailed deer males                   • Broad scale:
• Body size                                                                                                        – Some geographic areas
• Antler size                                                                                                        have inherently low quality
                                                  Venezuela                                                          habitat
• Breeding date
• Coat color, length                                                                                               – Forage quality limitations
                                                                                                                        • Never attain high diet quality
                                                                                                                          regardless of density
• Wide geographic variation
      – Regional variation often not considered
                                                  Michigan                               • Often can see similar
      – Unrealistic expectations
                                                                                           trends at regional scales
                                                                                                                   – Not generally appreciated
                                                                          Baker (1984)




                   Regional Soil Quality:
                      May be highly variable
                                                                                                                   Regional Variation in Body Mass
                                                                                                                                                                                    Soil regions in MS
                                        High                                                       Influence of soil quality on buck body mass
  •    Delta
                                                                                         Dressed body mass (lbs)




                                                        Delta
  •    Loess                                                            UCP
                                                                                                                   95                                                                    Delta
                                                                                                                                                                                                     UCP
                                                                                                                   85
  •    Upper Coastal Plain                                      Loess
                                                                                                                                                                                             Loess
                                                                                                                   75
  •    Lower Coastal Plain                                                                                         65
                                                                                                                   55
  •    Coast                                                                                                                                                                                     LCP

                                                                                                                   45
                                                                        LCP
                                                                                                                   35                                                                                  Coast

                                                                                                                           0.5       1.5      2.5          3.5         4.5        5.5+
                                         Low                                  Coast
                                                                                                                                           Age class             Strickland & Demarais (2000)
                                                                                                                                                                 Journal of Wildlife Management 64:903-911




                                                                                                                                                                                                               14
                                                                                                                  Regional Trends in Deer Physical
                    Regional Variation in Antler Size                                                                      Measurements
                                                                                     Soil regions in MS
                         Influence of soil quality on buck antler size
                                                                                                                 – Same trends for doe body weights
                    75                                                                  Delta
                                                                                                    UCP
Antler size index




                    65                                                                                           – Same trends for growth rates of bucks & does
                                                                                            Loess

                    55
                                                                                                                    • Higher soil quality = faster growth

                    45
                                                                                                LCP
                    35                                                                                           Soil quality (nutrition) plays a major role in
                    25                                                                                Coast       the potential for growth, physical
                            1.5           2.5           3.5        4.5           5.5+
                                                                                                                  development of ungulate populations
                                           Age class           Strickland & Demarais (2000)
                                                               Journal of Wildlife Management 64:903-911




             Antler Size Differences by Region                                                                        Important Considerations
                            Combination of:
                            soil quality, nutrition, management
                                                                                                              • C.C. estimates more precise in areas with stable
                                                                                                                environments
                                                                                                                – Competition for resources drives populations, responses to
                                                                               Total number of
                                                                                                                  environment are small
                                                                               Boone & Crockett,
                                                                               Pope & Young
                                                                                            1-4
                                                                                            5 - 20
                                                                                            21 - 50
                                                                                            > 50
                            Quality Deer Management
                            Association




                                  Important Considerations...
• C.C. estimates more precise in areas with stable
  environments
                    – Competition for resources drives populations, responses to environment
                      are small


• These and all C.C. estimates are averages of separate
  instantaneous points in time
                    – In reality, C.C. fluctuates constantly


• Models are not used to predict absolute numbers
                    – Show relative differences between areas, over time
                                                      C.C.




                                                                              Time




                                                                                                                                                                               15

				
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