The Birth

This birth, however, does not involve mangers or stars. The birth we speak of is deer.

And when we say deer, we are being literal. Etymology is the study of the origins of words and the way in which their meanings have changed throughout history.

The origin of a word may have danced across your mind on occasion but ,really, who thinks about this stuff? Well, mostly etymologists.

Because we are all inclusive on this blog we are giving a shout out to all those etymologists out there. Honoring the animal that dominates this blog – DEER!

Deer have been traipsing the earth for millions of years. The earliest true deer (Family Cervidae) appeared in Eurasia in the middle of the Miocene.

But they didn’t get their name until millions of years later. It was common by 1500.

The word deer, from German Tier, meaning a wild beast, was at the time a term used to refer to wild animals in general. It gradually became specialized in this country for an animal being the most easily frightened – so the wildest – and running the fastest.

Seems fitting given the species we currently refer to when using that word.

So now you know. Think of it as our gift to you this holiday season.

-Jeannine Fleegle, biologist
PGC Deer and Elk Section 


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Disappointment and Delight

It has been eye opening to learn HOW deer avoid hunters during the rifle season. About 70% of all deer harvested each year are taken during the 2-week rifle season. But there are still many deer that survive.

There is delight and disappointment at both ends of the gun.

To their credit, deer possess an amazing ability to adapt to human activity. Given disappointment for deer means death, it is a key survival skill they must possess.

You remember the doe that before dawn returned to a steep hillside every day to evade hunters.

So what happened this year? Who remained delighted and who was dead…I mean disappointed?

Late archery and flintlock season have yet to conclude, but since few deer are harvested in these late seasons, the information to date gives us a pretty good idea what happened.

Antlered Deer

The most coveted of all deer really. Their life is definitely cut short because of those bony protuberances that grow from their head.

On the southern study areas, we had 3 radio-collared adult males alive at the beginning of the hunting season and all survived.

On the northern study areas, we had 6 adult males radio-collared of which one was legally harvested but not reported to us. Another buck was illegally killed.

Antlerless Deer on Southern Study Areas

On the Rothrock and Bald Eagle state forests, we had 12 adult females radio-collared and alive going into the October archery season. As of today, 2 were harvested, one was illegally killed, and one was found dead believed to be unretrieved by the hunter.

So if you include the illegal mortality, hunting-related mortality accounted for 33% of our collared adult females.

We had 8 fawns alive at the beginning of the hunting season. One was likely killed legally by a hunter but not reported to us – the collar was discovered next to a gut pile. There was a fawn that died of pneumonia and another that died from predation (the predator not yet determined but DNA evidence was collected).

Antlerless Deer on Northern Study Areas

The Susquehannock State Forest had 13 radio-collared adult does alive at the beginning of the hunting seasons and the only mortality was a road-killed adult doe.

Of 8 fawns we were monitoring at the beginning of October, none have died.

Study Areas No. Antlered

alive Oct 3rd

No. Antlered

killed by hunters

No. Antlerless

alive Oct 3rd

No. Antlerless

killed by hunters

Southern 3 0 (0%) 12 4 (33%)
Northern 9 2 (22%) 14 0 (0%)
All 12 2 (17%) 26 4 (15%)

Overall, the hunting mortality rate – the percentage of deer killed related to hunting – was about 16% for both adult males (2 of 12) and adult females (4 of 26). For fawns it was less, 1 of 16 fawns (6%).

Of course, these sample sizes are limited and results preliminary – there is still the potential for deer to be harvested during the muzzleloader season and final estimates will incorporate data from those deer fitted with reward tags that were harvested.

But what we observed for 2015 is basically what we observed during 2013 (1 of 8 collared bucks harvested) and 2014 (0 of 10 collared bucks harvested). Harvest rates are low for bucks on these state forest lands compared to other research we have conducted in Pennsylvania.

During 2002-2008 (after antler point restrictions were implemented), we documented harvest rates of

  • 36-69% for adult males (2.5 years or older) and
  • 26-42% for yearlings (1.5 years old).

These antlered deer harvest rates were for WMUs 2D, 2G, 4D, and 4B.

When we studied female harvest rates in WMU 2G (2005-2006) we found they were 4.4% on public land and 17% on private land. In WMU 4B, there was no difference between public and private land but harvest rates were higher for adults – 30% for adult females (2.5 years old and older) versus 16% for yearlings (1.5 years old).

So it is obvious that a majority of deer are “delighted” while many a hunter is disappointed. No worries. There is always next season.

-Duane Diefenbach

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Adding Insult to Injury

Before the spy-in-the-woods technology, hunters lived in blissful ignorance. The only deer that existed were the ones they saw with their very own eyes.

Well, not anymore. 

Knowing what’s really out there is nice, but can be frustrating. Case in point, Bill, my neighbor.

We have documented lots of deer all summer on our game cameras. Once the rut started we saw lots of different bucks – a spike, a spike with one antler broken, 4-pts, 6-pts, a nice 10-pt and another 4- or 5-pt with the other antler half broken off at the base.

Seeing them on “film” is one thing but it’s all about being in the right place at the right time. Let’s go to the tape.

Deer-Forest Study

Bill got to his stand early (6am) but he won’t being seeing these deer. They were there and gone by 3:30. The early bird (in this case the deer) got this worm.

Deer-Forest Study

Without much to see, Bill decides to shift strategy at 8 am.

Deer-Forest Study

Looks like Bill was right. The squirrels didn’t even come to visit until the afternoon!

Deer-Forest Study

Looks like the deer are early, EARLY birds around Bill’s stand. The next deer didn’t show up until 2:30 the next morning, and it was a spike buck.

Deer-Forest Study

Bill should have abandoned this stand for his other one.

It’s too bad, really. Look what happened there on the last Saturday.

Deer-Forest Study

Hunting. It’s all about being at the right place at the right time!

Game Cameras: Always there to show you when you screwed up.

-Duane Diefenbach

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Separated at birth

Ok, so they were only long, lost siblings to us.

I’m sure it was no secret to mom or either of her twins that the other existed. But we were kind of shocked.

Way back in June, we set out on fawn catching duty. Animal capture seems fun but I find it to be the most stressful part of my job. It’s hard to explain. Handling an animal that is not meant to be handled, tagging it, collaring it, releasing it. There are so many things that can potentially go wrong. It’s hard to enjoy the experience while it is happening.

But before getting all stressed out about handling, you have to find AND catch the little buggers which is a whole other ballgame.

The evening of June 4 our capture team spotted a fawn nursing with a doe. They seized the opportunity. That full belly must have weighed him down. Fawn 6140 was now on the air.

A few days later, fat-bellied 6140’s collar went into mortality mode. After a bit of searching, he was located weak and thin in thick blackberry brambles but alive. He was left to his fate. The field crew decided to come back the next day to collect the collar from what was sure to be a dead fawn. But 6140 made a miraculous recovery and is still sporting his collar.

At about the same time 6140 was having a bad day, the capture team got lucky again. A doe was moving her fawn and crossed the road in front of them. Fawn 5906 was “on air.”

Why am I telling you all of this? There was nothing special about these 2 captures. The fawns were caught over a quarter of a mile apart. Mom had been in attendance for both. Unremarkable really.

That is until routine radio-location checks of 6140 and 5906 showed that they were hanging together. A genetic sample is taken from all captured deer. We checked the samples.

They are in fact full siblings. Now that’s remarkable!

After capture, these fawns were never seen together. It wasn’t until telemetry showed they were best buds that we had any idea they were related. Now that’s good parenting.

Does will separate her twins within a day of birth. They are on average 100 yards apart. They remain isolated from each other for the first 3 to 4 weeks of life.

These fawns were captured 4 days apart. Mom’s reaction to each capture is also textbook. When 6140 was caught, she disappeared. She was likely still close by but remained invisible. Four days later when 5906 was caught, she pitched a fit making her presence known the entire time. Research has documented that does do not begin defending fawns until they are about 4 days old and that male fawns are more likely to be defended than female fawns (I’m slightly offended by this but who can argue with evolution).

The brothers are reunited having survived their most vulnerable period of life. They can thank their mom for that.

-Jeannine Fleegle, biologist
PGC Deer and Elk Section

 

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The Annual Deer Harvest

“The cold, hard truth is that not all hunters report their harvest.”

That’s what Jeannine wrote in her biologists’ lament about deer aging. Is that a bad thing? Does it matter?

Ever since I have lived in Pennsylvania, I have read and heard many disparaging comments about the quality of deer harvest estimates published by the PGC.

You would think this is a no-brainer problem. Make every hunter report whether they harvest a deer or not. We basically do that every 10 years in this country when we conduct the national census.

But hold on – only 74% of households responded to the questionnaire mailed by the Bureau of Census.

It’s the same old problem, just a different situation: not everyone follows the rules. So how do we figure out how many deer were harvested every year in the most cost-effective, accurate manner possible when 50% or fewer hunters cooperate?

The solution is to use multiple sources of information:

• The self-reported harvest information provided by successful hunters
• The 25,000 or so harvested deer field-checked by PGC personnel
• The annual Game Take Survey of 2% of hunters who purchased a hunting license

It all works by first counting up the number of deer self-reported as harvested by hunters. Then you cross-check those self-reported harvests with the field-checked deer to correct for under-reporting by hunters.

For example, let’s say Jeannine checks 100 antlered deer from WMU 2B (basically Allegheny County). When she goes to the computer files she finds out that 50 of those bucks she checked (50%) were self-reported by the hunter.

In other words, for every deer that was reported 2 deer were shot.

That means if you multiply the number of report cards by 2 you would have an estimate of the actual harvest (for that WMU).

Is such a harvest estimate accurate? Most certainly, you can read about it here. And if you want more explanation on the calculations you can go here.

Still don’t believe me? Then check this out. Every year the PGC mails the Game Take Survey to 2% of all licensed hunters and asks them what they harvested (that’s over 10,000 hunters – and we can predict the Presidential election by only asking 500 voters!). It turns out the deer harvest estimates from the Game Take Survey were always within 1-9% of the “official” deer harvest.

Deer-Forest Study

And I know what you’re thinking. Why go to all this trouble when you just need to require every hunter, every year, to tell us whether he or she harvested a deer and the sex and age. There are 3 reasons why that’s not the best option.

  1. It costs 60 cents or more for every harvested deer that is self-reported by hunters as harvested (reported online or by phone, or even more expensive by mail). Multiply that by nearly 1 million general hunting license buyers and you would have an annual expense of about $700,000, of which about $120,000 would be spent for license buyers who don’t even hunt deer. All that money to find out they didn’t kill a deer? Field checking 25,000 deer is a lot cheaper and more accurate.
  2. You will never get 100% of hunters to report their hunting success. Just ask the Bureau of Census.
  3. It turns out that 1 out of 5 button bucks is reported by the hunter as being a doe fawn (Why? I don’t know – perhaps there is a stigma associated with shooting a button-buck?). That means the PGC has to field-check deer anyway to get an accurate estimate of the harvest by sex and age!

But you know what I find most perplexing? The Bureau of Census could use a similar approach to accurately estimate the number of people in our country – and save a lot of taxpayer money. But Congress won’t let it.

At least you know the PGC has accurate deer harvest estimates.

-Duane Diefenbach

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NOT the most wonderful time of the year

It’s the rifle deer season.

For many hunters, it’s the 2 weeks of the year they’ve been looking forward to since last Christmas. For me, it’s the 3 weeks of the year I’ve been dreading since last Christmas.

Our tagged and radio-collared deer provide information on harvest rates (proportion of deer harvested) but it’s the annual visits to deer processors that provide necessary data to calculate harvest estimates (number of deer harvested).

The first Wednesday of the gun season 32 deer aging teams hit the road. For 2 days they visit deer processors and look at barrels upon barrels of deer heads. My team aged 290 deer the first week.

Those deer were scattered among 10 different processors requiring over 400 miles of travel. Oh, did I mention my aging area is predominantly Allegheny County? Pittsburgh traffic and various tunnel monsters are a perk that really can’t be measured.

Deer-Forest StudyQuote of the week: “I’m stepping in brains. I can’t go home to the dog with brains on my shoe.”

Week 2 of deer season brings a new round of fun. More barrels, more heads and, as an added bonus, statewide chronic wasting disease (CWD) sampling. Heads are collected for CWD surveillance testing which means teams need to collect, bag, and transport heads to extraction stations.

Do you know how heavy a deer head is? Well, a bag of them weighs significantly more. At the end of Week 2, my teams sits at just over 600 deer aged.

Deer-Forest Study

By the time Week 3 (the Monday and Tuesday after the last Saturday) rolls around, it feels like I’m in the movie Groundhog Day. Same aging partner, same route, same traffic, same processors, same barrels, same glassy-eyed stare from all those deer heads!

A 50-gallon drum seems bottomless when it’s full of deer heads…especially when your arms aren’t long enough to reach the bottom of said barrel.

This is not my favorite time of year but I’m not alone. Misery loves company and there are 31 other teams sharing the joy.

While it is squarely in the top 10 (maybe top 5) things I don’t like to do (right up there with changing the litter box), it is probably the most important and critical.

Every year, PGC aging teams handle close to 25,000 deer heads. Without this piece of the puzzle, we would be unable to estimate deer harvests.

The cold, hard truth is that not all hunters report their harvest.

So back to the bloody barrels I go.

-Jeannine Fleegle, biologist
PGC Deer and Elk Section

 Deer-Forest Study

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One Time Too Many

You know when you’re doing something and things are going well but you know that it is just a matter of time before they don’t.

Like carrying 3 bags of groceries in each hand so you don’t have to make 2 trips. Ninety-nine percent of the time you’re fine but there’s the lousy 1% when you buy one too many jars of spaghetti sauce and you drop the whole lot just as you hit the back step.

Don’t pretend you haven’t done it. Or like walking the dog after dark with no leash in October when the skunks are out. Let’s say I learned that lesson the hard way…more than once. But I digress.

As usual I am talking about a deer. A doe this time. We’ll call her 8367. Ms. 8367 was captured on March 31 and was super lucky to receive one of the special GPS collars along with a VIT (vaginal implant transmitter). Maybe this wasn’t so lucky after all.

Ms. 8367 made her home in picturesque Cherry Springs State Park. I believe she knew the park staff by name as she greeted them daily as they made their way to work. Life was good for 8367.

She delivered a healthy fawn on May 30 (which was successfully captured and collared as well) right across from the park entrance! Mom and baby spent their summer hanging at the park and the surrounding state forest enjoying all the area has to offer – picnicking, hiking, star gazing – fun for the whole family.

Ms. 8367 was an expert at navigating the roads in her home range, all 5 of them. Over a 7.5 month period, she crossed a road 1,111 times including guiding her days-old fawn across PA44! In fact, 750 of 1,111 crossings were PA44, the busiest road in the area.

Average annual daily traffic (AADT) for PA44 is 3,247 vehicles. This is for a portion of PA44 just north of Coudersport but it’s close to Cherry Springs and the same road. This may seem like a lot but it is actually 4th lowest when compared to other roads in the same class. Of the 12 other roads monitored, only 3 received less traffic than PA44. The remainder were higher. For example, the AADT for PA49 in Tioga County was 4,335 and PA255 in Clearfield County was 5,438.

Unfortunately, one of those 3,247 vehicles met 8367 on November 13th. Her 750th crossing of PA44 was her last.

Deer-Forest Study

Looking at her jaw and tooth wear she was not a young deer. She was probably at least 5 or 6 years old. She probably crossed PA44 thousands of times over her life. I guess her luck finally ran out.

Ms. 8367’s fawn is still alive and likely has no idea what happened to mom or why she isn’t around anymore. Let’s hope he paid attention when mom was teaching him how to cross the road.

Always be sure to look BOTH ways!

-Jeannine Fleegle, biologist
PGC Deer and Elk Section

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WANTED

Recall Buck 8917. He is, by far, the blog’s most famous deer.

Over 55,000 people have read his tragic story.

One cold January, he returned to a summertime retreat to spend the last of his days.

We have no explanation of what caused his death or why he returned to a place he had only visited one time before.

That is, until now.

Buck 8917 appears to have been involved in some sort of altercation with Buck 8937 just before he left the area. After reviewing the movements of Buck 8937, he has been placed at the scene and is probably the last deer to see Buck 8917 alive.

Specifically, note the locations of both deer at 10am on January 23, 2015.

Buck 8937 is wanted for questioning and an APB (All Points Buck) has been issued.

An area-wide search for 8937 will begin Monday, November 30. His antlers are wanted in connection with this potential crime.

If you see or have any information regarding Buck 8937, please contact the DFB hotline.

-Jeannine Fleegle, biologist
PGC Deer and Elk Section

Postscript: How lucky are we to have 2 deer collared in the same area and the ability to identify both deer in the exact same spot just before Buck 8917 left his home range to die? Extremely lucky.

Unfortunately, this really opens up more questions than answers. Buck 8917 was antlerless when he died – but did Buck 8937 still have antlers and did he possibly fatally injure Buck 8917? We’ll never know. Or was Buck 8917 simply ill and these two deer happened to cross paths just before his death? Fascinating.

By the way, why a $0 reward in the wanted poster? It’s because our collared deer do not get reward tags. Deer that are captured but not fitted with a radio-collar receive an ear tag that has a $100 reward for the person who reports the recovery of the deer.

-Duane Diefenbach

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Hillside Doe’s Hiding Spot

Last year I began this blog by sharing with our readers how deer evade hunters during the rifle season. The smart deer (those who have survived at least 1 hunting season) had somehow discovered spots where they won’t be discovered.

I shared with you Hillside Doe’s hiding place and how before dawn she ran to a spot on the side of a ridge and stayed there nearly all day. You can watch her movements in this movie – December 2nd was opening day and you can see by shooting hours most days she had already reached her hiding spot.

Looking at a topo map I could see this hiding spot had some of the steepest topography in all of her home range. And from aerial imagery it appeared to be near some boulder fields.

But what did it look like from the ground?

Well, it only took 2 years for me to find a free weekend (when the leaves were off the trees), so read on for some on-the ground images. I asked my wife, Lisa, about going along for a walk with our 2 dogs – and all agreed it would be a great way to spend a Sunday afternoon.

Getting to this hiding spot was not that difficult. Head south on Rte 322 from State College and then take Stone Creek Rd west. Here’s a topographic image of the area with this doe’s hiding spot marked.

Deer-Forest Study

After we parked the car, we had to cross a small stream and make our way up the hillside. There was some mountain laurel to push our way through, but nothing too difficult.

Then there was the boulder field that appeared just as the ground got steep.

Deer-Forest Study

I thought deer rarely walked through these boulder fields. Myself, I worry I’ll twist an ankle even wearing hiking boots! Apparently, I was wrong about what deer will do.

Following our GPS unit we continued uphill in a NNW direction.

It was not a simple hike. We literally had to pull ourselves up the hillside by holding onto shrubs and small trees or grabbing rocks.

Deer-Forest Study

Eventually, the GPS unit indicated “You have arrived at your location.” Our dog’s tongues say it all!

Deer-Forest Study

The site was a patch of cover above a fairly open slope of rocks.

Here’s what the location looked like to the east.

Deer-Forest Study

And to the west.

Deer-Forest Study

When foresters measures slopes they describe them as a percentage. Zero percent is flat and a 45 degree slope is 100% (for every foot you go up in elevation you also cover 1 foot in the horizontal – that is steep!). I did not bring a clinometer with me, but this was pretty darn close to a 100% slope!

Uphill (north) looks deceivingly easy to ascend in a photo!

Deer-Forest Study

And the view to the south was beautiful!

Deer-Forest Study

If there was ever a place to evade hunters and enjoy the scenery of the Rothrock State Forest, it would be this location! And you will never sneak up on a deer in this perfect hiding spot.

But it was a great way to spend a Sunday afternoon! I think I can convince Lisa to go along to visit the hiding spot of Buck 8917. Even though I already know from the map that this hike is going to be a lot harder! Stay tuned.

-Duane Diefenbach

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Frosty Pumpkins

Depending on your perspective, the week of November 1-7, 2015 was either miserable or fantastic. If you’re a grouse hunter, you are squarely in the miserable camp. If you’re a runner, you are in the fantastic camp.

But what if you’re a deer?

We continually receive emails and comments about how the rut is shut down or how deer go nocturnal whenever the mercury rises this time of year.

This is where we are big fans of the Missouri state moto – Show me! Let’s break out the data and see if this frosty pumpkin proverb holds true.

We need a benchmark so let’s check out 2014.

The studio was fired up and movies were produced that plotted the movements of collared bucks beginning October 1st and ending November 30th. We know those dates encompass the rut.

Below is the 2014 movie for Buck 8917 (Remember him? He’s our most famous blog deer).

When his movements are put on the big screen, his rut starts on October 29th and end on November 22nd (he does make a big movement on November 24th, but that was also bear season). We may quibble about a day or two but it’s fairly obvious when these bucks start looking for a hot date. Conversely, it’s fairly obvious when these bucks lose that lovin’ feeling.

For each buck in 2014, the beginning and end of their “rut-like” movements is recorded in the graph below. Each horizontal line is a different buck. Breeding likely occurred outside the beginning and ending dates, but those rapid, crazy movements pretty much bracket the start and end points.

Deer-Forest Study

Now what about 2015 (the red dashed lines in the graph below)? The rut isn’t over yet but we can look at when it started.

Deer-Forest Study

See any difference? Me neither.

Now, what about this “nocturnal” thing? Does starlight enhance the mood? Did the cool evening breeze remind them what time of year it is?

Let’s look at their daytime and nighttime movements during that hot and sticky week of November 1-6 (We are leaving off Saturday because it was relatively cool compared to the rest of the week).

It’s a special time of year so the collars obtain a location every 3 hours on these bucks.

Here’s how much they moved

  • During the daytime – an average of 455 yards every 3 hours.
  • During the nighttime – an average of 426 yards every 3 hours.

See any difference? Me neither.

So be it hot and sticky or frosty pumpkin weather, bucks don’t seem to care.
But you may notice how variable the beginning and ending date is for the bucks we are following each year. That’s because what turns on each buck depends on their local environment.

What’s a sure fire way to turn on a buck? A doe in estrous.

Does cycle regardless of temperature. So hot, cold, balmy, or brisk – if a doe is in estrous, a buck will be in “rut.”

On average, the rut is the same time every year. And certainly by the first week in November, all bucks are on the move.

Don’t let the weather fool you! Deer don’t wait for frost to be on the pumpkin.

-Duane Diefenbach and Jeannine Fleegle

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MSY – And it’s not the Big Easy

Type “MSY” into google and the first thing that pops up is the Louis Armstrong New Orleans International Airport. Unfortunately, that’s not the MSY I’m talking about.

Scroll down to the third search result: MSY or maximum sustained yield. It isn’t nearly as fun or “easy.”

MSY is an idea that has been around for a long time – over 50 years. And if you can believe the assumptions, it has some profound implications on how we can manage wildlife populations to our benefit.

If you’re willing to put on your thinking cap you can impress your friends and coworkers at the next holiday gathering. We’ll tackle the basics this time. Next week I’ll “apply” it to deer management.

Under MSY we have to make some assumptions about how populations grow and respond to their environment. If we plotted a population that started with 2 animals (a male and a female – that sounds vaguely familiar), this is what its growth might look like.

Deer-Forest Study

Notice how the population increases slowly the first 15 years, then increases rapidly during years 15-25, and then levels off. This is called a logistic growth curve. But all it means is that population growth has an upper limit.

The population grows slowly at first because there are not a lot of animals, but when their numbers do start to increase the population takes off like a rocket. Eventually, however, the population levels off because of some environmental limits to the population. Those limits might be space, food, etc.

That limit is called the Carrying Capacity of the habitat.

Carrying Capacity is the maximum number of animals the environment can support.

[A side note: You might ask how population growth slows. It can occur in two ways: fewer young are born or the mortality rate increases. For our purposes it doesn’t matter which occurs (or how) because all we care about is how many animals are alive at the end of each year]

Are you still with me? Great!

Now you have to really pay attention because this next part is the key to the whole idea of MSY.

Let’s take a close look at the curve at Years 12 and 13

Deer-Forest Study

Notice how it increased by 150 animals. What if we harvested 150 animals? Every year. What would happen to the population?

That’s right, we would be stuck at a population size of about 275 animals, forever. And that would mean that we could have a sustained yield of 150 animals per year and have no effect on population size.

Now let’s look at a different part of the curve – Years 26 and 27

Deer-Forest Study

Here we see population growth is slowing and the population increases by 150 animals. So if we wanted to sustain the population at about 9,700 animals we can harvest 150 animals a year, forever. And the population will remain at 9,700 animals, forever.

Some of you astute readers out there are already inspecting other parts of the curve. What about the annual increases in years 14, 15, and 16? Or during years 25 and 26 in the second close-up graph?

Where is annual growth greatest? Ok, now stay with me. Let’s plot the annual change in population size as a function of year. Think of it like a speedometer and acceleration.

Deer-Forest Study

The greatest annual change in population size occurs in Year 22 when population size is half way to carrying capacity. We can theoretically remove 1,255 animals each year – year in and year out – and the population will not change!

Maintaining a population at a level where the growth rate is maximized is (you guessed it) Maximum Sustained Yield!

MSY is a really cool concept (in my opinion) and what’s not to like? You get the maximum return on your investment. All you have to know is

  • How many animals are out there,
  • What the carrying capacity is, and
  • How many animals die (including those you harvest).

With those 3 pieces of information you can make some pretty solid decisions for managing your population!

But my wife always reminds me I think it’s cool only because I’m different. She’s right (I’m pretty sure all wives are) – I like numbers and math! (I have spared you the pain of all the calculus (and 2nd derivatives at that!) that can go along with what I have written! You can thank me later.)

Before we leave the Big Easy, there are a few things about MSY you should think about:

  1. When the population is at carrying capacity (where the curve flattens out) you cannot remove very many animals if you want to keep the population at that level. If you want to maximize the number of deer in the population, you cannot shoot any! If you do harvest deer when the population is at carrying capacity, it will reduce population size.
  2. Remember the “all you have to know” list? Well, how do you define and measure carrying capacity?
  3. MSY occurs when the population is half-way between zero and carrying capacity. So if you want to maximize the number of deer you can remove, you have to get the population to half of carrying capacity.
  4. We can have a sustained yield at any population level we want, but only when the population is half of carrying capacity do we have a maximum sustained yield.

Ok, that’s it for now. Think about it. Next time we can talk about what happens if we try to apply MSY in the real world of deer management.

-Duane Diefenbach

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Data Double-checks

In 2013, we showed how deer home ranges change from September-December.

Let’s check again for 2014.

One of the reasons science is so cool is that it continually tests ideas and findings. The backbone of the process is to repeat an experiment or observation to see if you get the same result.

For example, when a researcher claims to discover the secret to nuclear fusion at room temperature, other scientists aren’t just going to stand around without doing it themselves. If they can’t duplicate it, well, there’s a problem.

That’s what we’re going to do today. We told you the story using 2013 data of how home ranges of male and female deer changed during September-December, including the rifle season.

A new year and new data, do we see the same pattern and similar home range sizes?

As a refresher, here’s the graph from 2013.
Deer-Forest Study

(Drum roll please) And the results for 2014 are…

Deer-Forest Study

So what are the differences?

  • Female home ranges dipped to about 200 acres during Oct-Nov in 2013 but were about 300 acres in 2014
  • Male home ranges during the rut peaked at about 3 square miles in 2013 but were only about 2 square miles in 2014
  • The males we followed in 2014 also had much larger home ranges in October – essentially the same size as November.

What stayed the same?

  • Home ranges were smallest during the rifle season (~100 acres in 2013 and 130-170 acres in 2014).
  • Female home ranges declined during the rut while male home ranges were the largest. We recently wrote about this behavior.
  • Males and females had similar home ranges in September.

Overall, however, the differences aren’t that great. The overall pattern remained pretty much the same.

Sample size is always a consideration when differences are observed. So could sample size differences explain the variation between 2013 and 2014? Probably not. Seven males and 22 females collared in 2013. In 2014, there were 9 males and 22 females. Some of those animals were even monitored both years, but not all.

So does this support an early start to the rut in 2014 (October as opposed to November)? Doubtful. Of the hundreds of thousands of males and females out there, I wouldn’t hang my hat on the movements of 7-9 males per year.

Remember, there is an individuality factor for all studies. It’s called variability. With more data, you can better understand the effect of this individuality.

But individuality is what is fascinating (and the biggest challenge for hunters).

-Duane Diefenbach and Jeannine Fleegle

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