Three-bar deer capture

By Amanda Moors

The sweet, wonderful fragrance of catclaw flowers captured my senses as I finally turned onto the Three-Bar road after leaving the AZ Deer Association (ADA) board meeting in Phoenix only hours earlier.  The air was cooler here and the amazing smell of the desert tonight made it easy to forget the traffic jams and bustle of city life I had just been in.  Near midnight and in the dark, I searched for the camping spot where my husband and I had stayed last year while working on an ADA water catchment project nearby.  I found the spot and pulled in.  As I unloaded my Jeep I heard elf owls, common poorwills, and a great-horned owl calling nearby.  I watched in the full moonlight as the great-horned owl landed on a saguaro and called.  Minutes earlier I had imitated his call and in response he came swooping overhead and landed in that saguaro and called every few minutes hoping to intimidate the intruder in his territory (me).   

It was a short, but pleasant night as I needed to meet the deer capture crew at 5:30 the next morning.  About 15 people gathered at the staging area on the road to the Three-Bar enclosure by Roosevelt Lake.  We set up our gear as we waited for the helicopter to start capturing deer.  Today our goal was to capture mule deer does, determine if they were pregnant, and implant a radio transmitter in them to tell us when they gave birth.  Those transmitters called vaginal implant transmitters (VITs) are expelled at birth, making it easier to locate and telemeter the fawns to determine fawn survival and cause-specific mortality rates.   

    
Photo showing the VIT that is inserting into the deer and then expelled when the deer gives birth.

This capture starts the 2^nd year of the study and in the previous year, 24 does were captured and implanted with VITs.  About 50% (13) of the VITs came out prematurely for unknown reasons.  The VITs were modified this year and hopefully will result in better retention.  During the first year, fawn mortality was high with only 2 of the 20 telemetered fawns surviving.  Since this is the first year of the study, the data are too preliminary to identify cause-specific mortality rates.  The results from the current capture will provide a larger sample size and allow us to attribute mortalities to specific causes. 

This study is being conducted in cooperation with the Arizona Game and Fish Department, Texas Tech University, and the ADA.  The ADA believes strongly in the need for good science to give us answers to management questions.   As most hunters and biologists know, mule deer populations have declined range-wide and an important question is what can be done to help mule deer populations rebound?  This kind of project moves us toward answers that can be used to increase mule deer populations.   

For those of you not familiar with the Three-Bar Study Area, it is located west of Roosevelt Lake.  Within this study area, there is a fenced enclosure (about 1 sq. mile) that until recently was maintained to keep predators out and deer in.  With predators excluded from the enclosure, the deer population within the pen grew rapidly to very high densities, while the deer density outside the enclosure remained relatively stable.  As an interesting note, even with the total lack of predators, many fawns died over the course of the year.  In some years, particularly during extreme drought, over 50% of the fawns died before counts were made in early winter.  I imagine most hunters would be surprised to hear that so many fawns are lost to causes other than predation.  The two primary questions that lead to the current study are why so many fawns died in the absence of predators and to understand the reasons for the differential population growth rate inside and outside the enclosure. 

Workers packing the net that would be used to capture deer from the helicopter.

Today our plan was to capture as many does as possible before it got too hot.  The helicopter crew would use radio telemetry to locate does and then fire a net at them to capture them.  Use of the net gun allows us to avoid having to drug the deer which eliminates one potential hazard for the deer during capture.  There is always risk of injury to the animal during capture, but net guns have been found to be one of the safest and most efficient ways to capture big game.  Once captured, the doe was hobbled and transported dangling from a helicopter to our station.  The doe was then placed on a stretcher and carried to the scale and weighed.  Her body temperature was measured to assess if she was overheating.  The does are not drugged and have just been chased by the helicopter during capture, so they are stressed and generally hot and panting by the time we got them.  To help cool them down, a large spray bottle was used to apply cold water to the deer.  One deer required administration of cold intravenous fluids and packing with ice to cool the deer down very quickly.   

    
Helicopter bringing in deer and students weighing the deer.

Dr. Ole Alcumbrac, the project veterinarian, was on hand to administer first aid to the deer.  He used ultrasound equipment to determine how many fawns were present in the doe and also measured the amount of rump fat as an indicator body condition.  A graduate student from Texas Tech, Nicole Tatman, is doing her Master’s thesis on this project and she inserted the VITs into the does that were pregnant.  Once all the poking and prodding was complete, the doe was carried to a nearby spot where she was untied, unmasked, and released.  Deer were often a little uncoordinated from having their legs tied for awhile, but they bounded off looking for safety away from all the people.

 I only helped out on one day, but the capture work continued into the next day.  A total of 26 deer were captured and 25 of them received VITs (one deer was euthanized due to its front legs being broken during capture).  Most of them were previously radio collared, but some were new captures.  For those, a tooth was also pulled to get an accurate age on the deer. 

The does will be monitored during the summer so that when the fawns start dropping, they can be captured and radio collared.  Then the fawns will be monitored to determine survival rates and causes of mortality.  The ADA is proud to support this kind of research to help find ways to improve deer herds throughout the state.  I plan to go back out and help locate fawns in July or August.  If anyone is interested in volunteering on this project, you can contact Nicole Tatman (cell 505-720-0489 or email: ntatman@gmail.com). 

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