Hunt Nevada
Hunt Season & Regulations
Mule Deer Population Model
Operational Instructions for Mule Deer Model
An important decision to make before you first enter any information into the model is to determine what year to begin the model. The general rule of thumb is to start as far back as there is reliable survey and harvest data regardless of what environmental or demographic events have occurred. In the reality of modelling wildlife populations, the outcome or population estimate is typically the important value out the back end for the various hunting and management activities. But truthfully, the most important facet of modeling is exposing, evaluating, testing, and understanding the hows and whys of population fluctuations. Unfortunately, the world around us has no sense of humor or intellect to appreciate this fact.
Each sheet has already been formatted to print landscape but you need to label each sheet with the header title – "Mule Deer Model Unit or Unit Group xxx". To label all 7 sheets at the same time:
- Place cursor over survey sheet tab and right click mouse
- Choose "Select All Sheets"
- Go to top pull down menu and select "File-Page Setup-Custom Header"
- Type your header and click "OK" twice
- Place cursor over survey sheet tab, right click mouse, and choose "Ungroup Sheets"
SURVEY SHEET
• The first thing to do is to determine the first year of the model. You will be asked in the "Aprilpop" sheet to guesstimate the starting sex and age structure of the population for this first year. Once you feel comfortable in doing this for a particular year, then click on the hot button labeled "First Year" in the first row of the "Survey" sheet. This will prompt you to enter the first year (four digits). A macro will automatically label the year in the left-most field in all of the sheets.
• The blue-lettered fields are where you enter data; the black lettered fields are formulas. The formula cells are not locked because macros must be able to copy and paste cells in adding rows that are unprotected. (DO NOT ENTER DATA INTO ANY BLACK-LETTERED FIELDS!)
• Enter survey data as number of bucks, does, and fawns classified.
• Model generates observed totals and ratios; biologist is allowed to make minor adjustments to fawn ratio if he has justification either through a biased survey or if future years within the model indicate that past fawn ratios were insufficient or in excess to allow model to accurately represent the population. You must enter a value in the "Adjust" field – either same as observed or adjusted in order for the model to run.
• Last few columns show the adjustments made to fawn and doe numbers in the model based on the observed fawn ratio and estimated doe survival data.
• To add years (rows) to the model, click your mouse pointer on the "Add Row" button and a macro will generate a new row in each sheet and increment the year value. Add as many rows or years to the model that you need.
HARVEST SHEET
• Enter the number of does (fawns and yrlg +) as a negative number to represent they are removed from the population. The formulas will proportionally allocate the total doe harvest across all age classes.
• Enter the number of bucks as fawns and by point class as a negative number based on best information available if even some of the point class values are estimates.
• Enter an estimate of the number of 2-point bucks that exist in the population that year that are yearlings. Based on past harvest check stations and literature, it seems to be anywhere from 60 – 90% (suggest starting at 70%) depending on the some local genetics and forage quality that may restrict some yearlings from attaining 2 points on at least 1 side.
• The next input is very important in order to transform point-class data to age-class. For most mule deer harvest strategies, the 2-year old age class takes it in the shorts. So you need to estimate the percent of 2-year old bucks that existed in the model pre-hunt (Septpop) that were harvested during the hunting season. In herds managed for higher buck ratios and quality hunting experiences, this percent will be very important. By having a fairly accurate assessment of buck harvest by age where you know that mature bucks are readily available and being harvested; you will be able to use the post-hunt buck age structure as a barometer to the magnitude of the total population estimate and its accuracy; by stocking pile bucks it is clear you are overestimating the population size and by having negative numbers in the buck age classes post-hunt, it tells you the population size is underestimated. It will be a iterative process for a few years until you refine or calibrate the percent of 2-years old harvested in relation to population size and bucks remaining post-hunt. Obviously known- or estimated-aged bucks in the harvest would great data to collect every 5 years or so to calibrate this percentage.
• Lastly, scroll to the right and enter a decimal value for the percent of wounding loss (including unreported harvest or poaching) that you estimate occurs in addition to the known buck and doe harvest.
• (DO NOT ENTER DATA INTO ANY BLACK-LETTERED FIELDS!)
TRAP SHEET
• For animals removed from a population through capture, enter negative numbers. For animals transplanted into a population, enter them as positive numbers. For unknown aged animals, assume a broad age distribution unless you have evidence to the contrary, and allocate the total number of unknown animals across age classes in reasonable fashion.
• (DO NOT ENTER DATA INTO ANY BLACK-LETTERED FIELDS!)
RATES SHEET
• Contains all the survival and reproductive rates for all age classes. Biologist has ability to modify survival rates by age group each year if he has justification for variation. Should not be bashful to make changes in survival rates from year to year. In fact, you will find how sensitive survival rates in affecting population changes. This is the weakest part of our modeling exercises and likely fluctuates annually and seasonally, but since we don't collect survival data, we really don't know. Survival is broken into two time periods across the biological year – April through August and September through March. These two periods were chosen not necessarily because of the similarities in factors affecting survival (but is considered to separate mortality into spring/summer and fall/winter) but due to the timing of when we collect data and generate prehunt population estimates.
APRILPOP SHEET
• Enter the starting population by either 1) typing in a single value for female fawns and allowing the formulas in the other cells to generate an even age distribution and relatively good buck ratio or 2) you can type over the formulas and generate your own age and sex distribution.
• The adjusted fawn ratio value (Survey datasheet) is used as the basis for the APRILPOP fawn numbers along with survival rates from September through March.
• One of the checks and balances to the model is using buck harvest to track whether your buck ratio and total population estimate are in the ballpark. If you have negative numbers in any cell in APRILPOP (conditional format turns cell red if value is < 0) you will need to make adjustments to eliminate these negative numbers – buck survival rates, buck harvest selectivity, past fawn ratio is bogus that generated the bucks in the cell that is negative, or your starting population too low.
• The diagonal lines in each cell beyond the 1st year and fawn fields are intentionally displayed to allow you to track a specific cohort through time. There are many benefits to tracking a cohort through time. You can see the impacts of a very week or very strong fawn crop over time.
SEPTPOP SHEET
• DO NOT ATTEMPT TO ENTER ANY VALUES AT ALL INTO THIS SHEET!
• Same as the APRILPOP but different point in time. Between the APRILPOP and SEPTPOP, animals become one year older.
• The number of fawns is calculated from number of pregnant does, fawn ratio at birth and survival rate from May through August. If you don't properly adjust these values to match reality, your survey data in the winter and/or spring are used by the model to appropriately drop the fawn numbers; the results show up in either the DECPOP or APRILPOP.
• The annual population value doesn't include the newborn fawns and therefore represents the prehunt estimate of yearling and older animals.
• To the far right are fields that display the same population by age groups instead of specific ages. The fact of the matter is that we cannot accurately estimate the number of animals in each age class and base management (harvest or capture) decisions on specific age classes. The display of age groups is appropriate in relation to the precision and accuracy of the model, just as displaying only a certain number of significant digits for a fraction. If you are asked to print out or display the population, you should only use this format of age groups to depict the population.
RESULTS SHEET
• DO NOT ATTEMPT TO ENTER ANY VALUES AT ALL INTO THIS SHEET!
• This sheet displays totals, ratios, % change in population for each year of the model, and buck harvest information.
MULE DEER POPULATION MODEL SHEETS
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