QDMA Articles :
Button Buck Biology
By: Brian Murphy
You could feel the tension in
the air as the truck neared the property's deer check-in station.
Word had spread that Billy had mistakenly harvested a second buck
fawn for the season and disappointed club members were gathered
in anticipation of his arrival back at camp.
Just one month earlier at the pre-season hunt club meeting, members
were strongly encouraged to harvest does, but cautioned against
harvesting buck fawns or "button bucks." In fact, this
year the club even instituted a $100 fine for the first button
buck and a $250 fine for the second to drive this point home.
This sounded reasonable because the club was in its third year
of their Quality Deer Management (QDM) program and wanted to limit
the harvest of their "bucks of tomorrow."
This strategy is fine in principle, but is it based in biology?
Over the past two decades, whitetail researchers have conducted
numerous studies on the movements of male white-tailed deer with
some interesting findings. Collectively, the results of these
studies have significant implications for QDM programs attempting
to maximize the number of adult bucks on their properties. The
primary justification for not harvesting button bucks is that
they will remain on your property until they reach maturity and
become eligible for harvest. Let¹s examine this premise in
closer detail.
A study conducted by Dr. Chris Rosenberry and others in Maryland
provided some interesting findings. During this study, they captured
and radio-collared 75 male whitetails ranging from six to 18 months
of age. Of these, 51 were followed until death or the end of the
study. Of these, 70 percent dispersed from the 3,300-acre study
area with half dispersing more than 3.7 miles. Dispersal distance
varied greatly from 1.2 to 36 miles. A couple of these young bucks
even swam a mile-wide river during dispersal. A similar study
conducted by Dr. Harry Jacobson and others in Mississippi reported
that 42 percent of the 52 male whitetails captured as fawns died
in excess of three miles from their original capture site. A Florida
study by John Kilgo and others reported that all seven male fawns
captured and followed in their study dispersed from their original
capture area by 18 months of age.
Interestingly, the Jacobson study found that once the young bucks
had dispersed, they generally remained within their new home range
until death. In their study, 60 percent of bucks captured at two
years of age or older died within one mile of their capture site
and none died more than three miles from their original capture
site. Collectively, these studies show that a majority of bucks
between 6-18 months of age will disperse some distance from their
birth area before establishing a new home range. But, once their
new home range is established, they will generally remain in this
area until death. These results have significant implications
for QDM, especially on small properties. Given that the average
dispersal distance of young bucks in these studies was 1-4 miles,
this means that even properties 3,000 acres and
larger are potentially losing the majority of the button bucks
produced on their properties. To a large degree, protecting button
bucks on your property increases the number of bucks for the "neighborhood,"
but may do little to increase the number that will mature on your
property.
This emphasizes the need for a cooperative approach to QDM. Since
the button bucks being produced by your neighbors may be "your"
adult bucks of tomorrow, the extent to which your neighbors protect
their young bucks is at least as important as how well the hunters
on your property protect theirs.
This also provides a possible explanation for why some properties
that consistently pass all button bucks and yearling bucks never
observe an increase in the number that reach 2.5 years of age
or older. It could simply be that the young bucks passed on your
property disperse to your neighbors and are harvested there. In
other words, your neighbors are not only harvesting their button
bucks and yearling bucks, they are harvesting yours as well.
Many hunters practicing QDM fail to observe significant increases
in body weight or antler development of yearling bucks despite
monumental increases in high-quality forage through food plots
and intensive habitat management. It is possible that the yearling
bucks observed on your property actually spent their lives on
your neighbor¹s property, where the habitat quality was lower,
and only recently dispersed to your property. While dispersal
is a common occurrence in white-tailed deer populations, the causes
for it are not fully understood. A study conducted by Stefan Holzenbein
and Dr. R. Larry Marchinton in Georgia revealed that dispersal
of young bucks was greatly reduced if the buck¹s mother was
harvested prior to dispersal. Prior to this study, it was believed
that adult bucks in the area were responsible for forcing young
bucks to leave their birth area.
The Holzenbein study monitored 34 buck fawns divided into two
groups - 19 that were left with their mothers (non-orphans) and
15 whose mothers were harvested or removed (orphans). The results
were surprising. By 30 months of age, 87 percent of the non-orphans
had dispersed from their birth areas, but only nine percent of
the orphans had left theirs. In addition, the non-orphans died
at more than twice the rate of the orphans.
They reasoned that dispersing bucks were less aware of their new
surroundings and more likely to succumb to harvest by hunters
as well as death from predation, accidents and other mortality
factors. This was supported by the Rosenberry study, which revealed
that only 36 percent of yearling bucks that dispersed survived
their first hunting season, whereas 66 percent of those that did
not disperse survived. The primary reason for death of the dispersers
in this study was harvest by hunters on surrounding properties
that were not practicing QDM.
The Rosenberry study also revealed another possible dispersal
mechanism. They found that dispersers were more likely to associate
with other yearling bucks and participate in breeding season behaviors
more often than non-dispersers. In addition, dispersers tended
to be more subordinate in these interactions. They concluded that
sexual competition among yearling bucks was a potential explanation
for dispersal. Given that the social structure of a deer population
may be affected by age structure (buck and doe), sex ratio, density,
habitat quality, and more, it¹s not surprising that these
studies reported different dispersal mechanisms.
Most deer researchers agree that dispersal in white-tailed deer
coincides with changes in a young buck¹s social position
within the herd. In simple terms, yearling bucks are social outcasts
recently expelled from their own family group and excluded from
joining other family groups or associating with older males. Often,
the only members of the herd that will "befriend" them
are other yearling bucks, buck fawns, and occasionally yearling
does. The actual dispersal "trigger" is likely a complex
interaction of social pressures within a deer herd.
Given these findings, is there anything that can be done to reduce
dispersal of button bucks on your property? The Holzenbein study
suggests that harvesting adult does with button bucks at their
side may increase the number that remain on your hunting area
and potentially reach maturity there. It is believed that dispersal
in young male whitetails (and many other mammals) may be a mechanism
to prevent inbreeding. In other words, it prevents sons from breeding
with their mothers, sisters, and other related females. Given
this, will preventing natural dispersal produce negative genetic
impacts within your deer herd? While no one can say for sure,
it is not believed to be a problem, especially in areas with relatively
high deer populations and high degrees of "genetic mixing"
from deer on surroun
ding properties.
Now, back to Billy. Should club members fine Billy for harvesting
the button buck and maybe even expel him from the club? Not necessarily.
Billy has demonstrated a willingness to harvest "antlerless"
deer and this should be commended. Often, reducing the total deer
density on a property is the most important goal, even if a few
button bucks are taken in the process. The worst approach a QDM
club can take is to make penalties for harvesting button bucks
so severe that too few antlerless deer are harvested. Should the
club continue to aggressively protect button bucks? Of course,
not all button bucks disperse and even those that do will help
improve surrounding deer herds. Additionally, buck fawns (doe
fawns as well), provide useful data on habitat quality and herd
condition. Because
fawns grow rapidly their first year, their body weight is one
of the best indicators of changes in habitat quality. If penalties
are too severe, the chances that these deer will not be reported
or included in the harvest data are increased. As such, penalties,
if imposed, should be sufficient to encourage hunters to look
carefully before making harvest decisions, but not so severe that
they refrain from harvest altogether or do not report their "mistakes."
The best approach is to provide the proper training and educational
resources to your hunters to enable selective antlerless harvest
decisions.
As a QDMA member, you are likely aware of our new educational
poster on selective antlerless harvest that provides this instruction.
We strongly encourage you to obtain a copy of this for your hunting
club and all hunting clubs in your neighborhood. Most importantly,
target your efforts to protect button bucks and yearling bucks
not just on your property, but on all properties within possible
dispersal distance at least four miles. Otherwise, the success
of your QDM program may be negatively impacted.
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