Why we do what we do

It is the end of the semester, and life gets a bit crazy for students and their professors these days.  During grading of final exams, one can start to ponder why one didn't go into a life of research (no teaching) or running a car wash or some other job that does not require the grading of 5 pages of essays for 45 students.  Not saying it's happened to me, but it might have. 

The alternative job that I would most enjoy would be to be the 'car guard' in the parking lot of a grocery store in a country like Namibia.  Well, specifically Namibia.  I watch your car while you shop and you give me 50 cents. 

The allure of such a prestigious car guarding position can be so great that it is nice to be reminded 'why we do what we do' at the University.  A couple of things recently bounced me back from my foggy dreams of standing on tarmac, watching the shoppers with their treasures.

Josiah Dallmann, sophomore Fisheries and Wildlife major at UNL, explains
his undergraduate research results to fellow delegates at the Midwest Fish
and Wildlife Conference in Des Moines, Iowa.

Last week, four of my students and I participated in the Midwest Fish and Wildlife Conference in Des Moines, Iowa last week.  Students had the opportunity to share their research results and mingle with biologists and managers from across the Midwest.  I went to my first MFWC in 1990 as a graduate student at Iowa State, so am starting to be 'one of the old guys'--although not as old as I made my former advisor feel when I introduced my students to him as his 'academic grandchildren...'  It is always good to meet with colleagues and share this experience with students. 

I make no apologies for trolling social media, because it is an enjoyable passtime for an introvert who has made certain life choices and wants to watch others exploring the choices that I discarded.  Biologists who work for NGOs or agencies.  Friends who decided to stay in my hometown.  Colleagues who selected different regions of the country for their careers.  All worthy choices, and the what-if game is fun as you page through postings of first babies, hunting trips, and new puppies.


Stephanie Walden, UNL Fisheries and Wildlife alum, suits up for a low-level,
aerial waterfowl survey.  Photo stolen from Facebook.

But, I do take my share of ribbing about spending time on social media.  And, then a photo like this pops up, and you realize--this is the other reason you troll if you are a teacher: to see if anything, anything, anything at all rubbed off on your students. 

Nice job, Stephanie!  I enjoyed seeing your excitement as you suited up to do your first aerial waterfowl survey.  Made my day.

Compensatory harvest mortality in deer?

Two fawns find food and water during November in southeast Nebraska.
Photo by Larkin Powell.

The December 2 issue of the Lincoln Journal Star carried an insightful Letter to the Editor, regarding deer harvest.  I'm currently covering 'harvest management' in my Wildlife Management Techniques course.  The concept of Compensatory Harvest Mortality is often over-simplified or applied in a misleading manner.  Because it is hard to explain the concept to wildlife students, it was nice to see a glimmer of appreciation for the concept from a member of the public.

Compensatory Harvest Mortality, in short, is the concept that hunting (harvest of wild animals) does not always result in a net reduction of the population (we call situations in which harvest does result in a net reduction, Additive Harvest Mortality: harvest 'adds' to other forms of mortality).  Think of a situation in which you can make an annual count of a wildlife population immediately before harvest occurs (this rarely actually happens in the US, but happens in many other countries through 'game counts' on private land).  OK, so you have 100 deer or 100 quail on a piece of property.  Now, harvest happens (in the fall, normally), and 20 animal are removed, leaving 80.  Those eighty animals have to survive through the winter, spring, and summer until the next count, and they also will be mating and having offspring.

If a species has completely Additive Harvest Mortality, those 80 animals survive and reproduce at the same rates that the 100 original animals would have.  Survival and reproduction do not adjust to the new population density.  The 80 animals will have fewer offspring than 100 animals would have had, and the 20 animals removed will add to the number of animals that die from other causes.  If the probability of surviving a year for that species is 75%, then 75 would have survived without harvest.  But, only 60 survive from the 80 that were left after harvest.

But, in a Compensatory situation, the 80 animals that are alive after the harvest will now have higher productivity (more offspring/female) or higher survival, because of the lower density.  More food per animal equals better nutrition equals higher survival or bigger clutches/litters.  It is possible that the net result, measured in the following fall, could (and stress: could) be that the effect of the harvest has been erased by the ability of the remaining individuals to reproduce or survive at higher rates when they face less competition.

Obviously, Compensatory harvest mortality is the optimum situation for harvest biologists (people who set regulations for hunting) who want to provide opportunities for many people to hunt and take game animals.  The problem is that we rarely understand wildlife populations in enough depth to document the effects of density on reproduction and survival.  We have such data for quail (although there is still disagreement) and deer; recently my research lab provided indirect evidence for prairie-chickens in southeast Nebraska and there is some suggestion from the Nebraska's annual wing counts that prairie-chickens produce more young/adult when the breeding population is smaller.

With that, here is the excerpt of the letter from a Lincoln resident in the Lincoln Journal Star:

"This letter is in response to "Lengthen deer season" (letter, Nov. 23).  The writer stated that the "deer population has gotten way out of hand" and that "Nebraska Game and Parks should have a lengthier season."

"I disagree with this for the following reasons.  Studies show that the more deer are hunted, the more they compensate by having more offspring.  After a deer season, when a high number of animals are killed, two things occur.  First, there is more food for the remaining deer, which helps trigger increased reproductive rates.  Second, nature's reaction to the loss of large numbers of deer during a short period of time is for a greater number of does to ovulate and mate at an earlier age.  This increased reproductivity in heavily hunted areas can result in abnormally high deer populations year after year.

"Studies also show that in nonhunted, unmanipulated wild areas that have an optimum number of predators, deer populations tend to stay at or just below the maximum number the habitat can safely support.  Since all game animals in Nebraska are managed to promote hunting, to lengthen the deer season will only result in more deer, not fewer."

A proud youngster with his first buck. 
If bucks are removed without harvesting
does, the result can be higher populations
as the does are left with many resources
and fewer competitors for food.  The necessity
to harvest does has been reinforced by
recent regulations for 'earn a buck' (harvest
a doe before you can harvest a buck) in
many hunting districts in Nebraska. 
Photo by Larkin Powell.

So, a couple comments:

First, the writer nailed the concept of compensatory harvest mortality in the first 'reason' stated: increased reproductive rates are triggered by lower densities.  Nicely worded.

And, second, the writer did a nice job of summarizing how this can happen--higher pregnancy rates (percent of does that are pregnant) and more young does that are pregnant (thereby increasing their lifetime contribution of fawns to the population).

However, the writer overstates the impact of the 'hunting effect'.  Hunting does not result in "abnormally high deer populations year after year".  And, a longer deer season would not result in"more deer" than a shorter season.  If deer had the capacity to have 8 or 10 or 15 fawns at a time, then this type of response might be possible.  But, deer can have 1 (common), 2 (sometimes) or 3 (rarely) fawns.   While they can respond with higher reproduction, they are limited by their species' reproductive potential--it only compensates for increased harvest to a point. 

It is very possible to harvest more deer than the population can compensate for.  In fact, wildlife biologists count on this fact.  This is exactly why Nebraska Game and Parks Commission has increased the number of permits, especially for does, in the past few years.  And, it is why they have lengthened the season--an October 'antlerless' (does and fawns only) season was added to the normal November season to help reduce deer numbers.  To take the example to the extreme, if a longer season and cheaper licenses resulted in reducing a population of 100 does to 10 does, there is no way that the 10 does could reproduce at rates high enough to make the population higher than 100, as the letter-write infers.

Managing wildlife populations always involves stakeholders.  This is an example of how important it is to keep educating the public about the reasons for management decisions.  Kudos to the author of the letter,  however, for explaining the concept of Compensatory Harvest Management.  I may use the letter in my class next year, rather than my long-winded explanation...!

Killer cows

There were stories told on my school bus

by junior high boys

about farmers who were pinned in a stall

by startled steers

or news of a friend's father

crushed by an angry bull

in a corner by the barn.

These men had a unique

perspective on cattle which

was not easy to sing to the

tune of Old McDonald's Farm.

But to share that perspective,

all you need is to come round

the endrows of a field of corn

to face a heifer who has taken

advantage of an open gate

and has a glimmer of an idea

that freedom in corn

is a better option

than the pasture behind the fence.

The way her dark eyes

look past you,

or through you,

toward the open field

with breath billowing in the

early fall morning,

and the way the steam rises off

her broad black back,

and the way she points a front hoof

as a warning that she is moving forward

and is not concerned that you are standing

before her

is enough to remind you that she

could be

a killer cow.

Ee-I-Ee-I-Oh. 

L. Powell, 22 October 2011

Creston, Iowa

Data set envy: long term trends in an agricultural landscape

Grey partridge

I'm spending the week at the Congress of the International Union of Game Biologists, meeting in Barclona, Spain.  I won't complain about the setting of this meeting--it is a great town--but, there are problems that arise when you attend meetings like this.  You get too many ideas to ever actually work on them.  And, you tend to get 'data set envy' when you see presentations from countries around the world.

I encountered such envy when I saw Nicholas Aebischer present a plenary talk about the Game and Wildlife Conservation Trust's long-term data sets of several species of pheasant-like game birds in the UK.  I will start by noting that my colleagues and I are excited if we can access data that goes back to 1966 (Breeding Bird Survey) or 1955 (Nebraska Rural Mail Carrier Survey).  In one case, I've worked with data from the Agriculture Statistics Service that went back to 1866...a record of crops planted in Nebraska. 

But, the GWCT in the UK has a 'bag record' (an index of the population from hunter harvests--the 'bag' counts from hunts like the one in the print at right) of grey partridge that reaches back to 1826.  Wow.  1826!  That's a long-term wildlife data set...!   

Because it is a hunter-bag count, the numbers reflect two things--the number of hunters (and their success) and the number of birds.  The Trust explains the trends on their website as follows (all images are also from their web site):

"Gray partridge bags form the longest series in the NGC. We were able to produce trends in annual bag density that started in 1826, when Darwin was only 17 years old. There are large annual fluctuations, most probably linked to weather. Indeed, the collapse of bags in 1869 corresponds to the coldest year on record since 1740. Despite large swings from year to year, the underlying pattern (green line) charts the rise in popularity of this gamebird during the first half of the 19th century and its heyday during the second half of that century up to the First World War. The high average bags reflect the high densities arising from the extensive mixed agriculture that developed especially after the repeal of the Corn Laws in 1846, the ruthless elimination of predators by private gamekeepers and improvements in shotgun design. Partridge bags remained high until the Second World War, but declined thereafter, especially after the introduction of herbicides and the increase in agricultural mechanisation in the 1950s and 1960s. The BTO index (inset) starts in 1966, and catches the tail end of the decline."

The bag index of grey partridges, as collected by the Game and Wildlife Conservation Trust in the UK.

When we look at our declines of wildlife populations in the US--from records that start in the 50's or 60's (like the period of time in the inset on the figure above)--we always wonder "what did populations look like prior to the 50's and 60's?  How much change had they seen prior to when we started keeping records?"  I would guess that some species in Nebraska would mirror the partridge trends from the UK--because our Nebraska agriculture was following a similar pattern at the same time.  But, it's just a guess---because the data doesn't exist.

Our view is blocked: an evolutionary response?

I’m sitting in my hotel in Barcelona and, of course, I did not receive a room overlooking the Mediterranean.   Instead my room looks up at the hills surrounding the city.   I’m not sure I’ve ever been given the prime room in a hotel, but in this case I would probably rather gaze at the greenery.  The hills are beautiful and rolling, and they remind me a bit of the small mountains that surrounded our family when we lived in Windhoek, Namibia.

On the top of each of Barcelona's hills is a bizarre collection of towers which appear to host receivers and transmitters for radar, cell phones, as well as radio and television communication.  Of course, my first response was: “They’ve ruined a perfectly good hill.”

Why is that?  Why do we have a knee-jerk reaction to landscape alteration when it blocks our view?

The more I thought about this, the more it intrigued me.  We, as humans, don’t react much when a prairie is plowed and fragmented by farming—that is progress and it feeds the world.  We don’t react strongly when we know that our neighbor is dumping oil or chemicals in his backyard—even though it might reach the groundwater.   It’s his backyard, and he can do what he wants.

I grew up on a farm in southern Iowa.  If you want to send your neighbors talking, put a new shed on a hilltop.  Or, better yet, tear down a barn that has always been there.  Or, plant your crops in strips (as my father did) rather than in big blankets of boredom.  Do something to change the way the neighborhood ‘looks’ and you might get a comment the next time you’re in the farm-and-home store.  At the least, people will drive by your place slowly.

This interests me, because I’ve been thinking for the past couple of years about wind energy.  Our lab may become involved in research on how wind energy affects prairie-chicken populations—there is concern that placement of towers in Nebraska’s  contiguous grasslands could disrupt movements, affect choice of nesting locations, or affect survival of adults.  Again, interesting—we should probably be more concerned about timing of haying that affects chicks and their bullsnake predators.  Or, we might choose to be wary of the ever-slow encroachment of cedar trees that provide cover for predators.  But, those things are not visual, or they happen so slowly that we don’t realize it is happening.  But, a wind turbine is something to get excited about.

Why do we shy away from wind turbines?   I’m starting to think that it is mostly all about our view.  They are going to change the way that our grass-scapes look, and we don’t like that.  Something bugs us.

Think about it—you are driving down the interstate (pick Iowa as a place for this thought-story: they just installed a lot of turbines along I-80 in western Iowa).  You come over the hill, and suddenly the landscape is populated with turbines as far as you can see.   Many people’s reaction to this is to make some comment to the effect of: “That has just cluttered up things, hasn't it?” 

We have this aversion to our view being blocked.  Never mind the fact that you are driving in the middle of a pack of 6 semi-trucks and 18 cars who can’t decide who is going to go first and who can’t get their cruise control set at a constant speed.  No, it’s the wind turbines that disgruntle us.  The real risk of danger to our lives is the cars around us, but our gut responds to the change in the viewscape.

I’ll hazard a guess that humans are hard-wired, through evolutionary time, to respond to changes in our viewscape.  We know that our eyes are one of our most important senses, and we pick up on visual cues pretty quickly, compared to other mammals (even I can hide from a deer in an open field if I stand still).  For our cave-man Homo ancestors, and Australopithecus before them, a change in the viewscape probably was the best cue to be on your guard for predators or competitors.   

So, it probably stands to reason that we are uncomfortable at the notion of our landscape being altered by big towers with blades on them.  The question is—is the cue a false cue?  Or, should we listen to our gut?  I’m still wondering, as I look at the hills of Barcelona.

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Note: I created the conglomeration imagery above.  My apologies to their original owners.