Fawn
Recruitment Rates
March
2009
Kip Adams, QDMA Director
of Education and Outreach, Northern Region
because they’re not sure how to use
it for management purposes. With a little help in analysis
and interpretation, managers can
use the data they collect to assess the status of their
management program within their respective state, as well
as compare how well
they stack up to other states and/or regions. To provide a
comparison among states, QDMA surveyed state agencies and
collected
information from 1998 and 2008 on four important management
program indices. This article focuses solely on one of
those indices,
fawn recruitment rates, and future articles will cover the
others. With respect to our survey, all states didn’t
provide the requested
information, but most did and the data provided for
meaningful comparisons among states and between years.
Fawn recruitment rate is a measure of the number of fawns
per adult doe (1.5 years and older) alive in the fall
pre-hunt population.
Basically, this index records the number of fawns that
survive to approximately six months of age and expresses
that number in relation
to the number of adult does in the population. The fawn
recruitment rate is lower than the number of fetuses per
doe and the number
of fawns born in the spring, since not all fetuses survive
to become fawns and not all fawns survive until fall. This
rate is a good
measure of a deer herd’s productivity, and it is an
important factor when determining the biologically
appropriate number of does to
harvest. Monitoring the fawn recruitment rate also provides
insight into herd health, and it alerts managers to
potential problems such
as high fawn predation rates.
Our survey revealed several states do not calculate this
valuable index. For those that do calculate it, most
states’ recruitment rates
remained similar or declined slightly from an average of
0.88 fawns per adult doe in 1998 to 0.83 in 2008. This
means less than one
fawn was recruited for every adult doe in both years, and
it explains why the old adage, “When you shoot a doe
you’re really killing three
deer” is a myth. The fact that actual recruitment
rates are lower than many hunters envision can be a
difficult concept to grasp because
we know healthy, mature does tend to have twins, and they
can even have triplets in high-quality habitats. However,
some fawns will
die before they’re recruited into the fall
population. They may succumb to disease, be abandoned by
their mother, get hit by a car, or be
killed by a predator.
Also, the definition of fawn recruitment rate is the number
of fawns per adult doe (1.5 years and older). Yearling does
are included in
this figure, but many yearlings do not have any fawns.
Obviously, yearlings with fawns were bred as fawns. In
areas such as Iowa, the
majority of doe fawns breed and can have fawns as
yearlings. Some fawns in Iowa even give birth to twins!
However, in other areas
such as Delaware or South Carolina, less than 10% of the
doe fawns breed. That means over 90% of the yearling does
in Delaware and
South Carolina have zero fawns, and that dramatically
reduces the fawn recruitment rate. Let’s use the
following hypothetical data as an
example:
In this
realistic example, Deer Herd B has a higher recruitment
rate simply because a higher percentage of its yearlings
had
fawns. Notice the 2.5 years and older does recruited the
same number of fawns in both herds. If you expand this
recruitment
rate to larger herds, the difference between 0.87 and 1.0
fawns per adult doe will have significant implications in
the rate at
which a deer herd will grow and/or for the number of deer
that you can harvest annually.
Getting back to the survey; many states have worked to
balance deer herds with their habitat and to improve
habitat quality
during the past decade, so you would expect the 2008
average recruitment rate to be higher than it was in 1998.
Since it was
lower, it begs the question, “What impact are
predators having on fawn recruitment rates?” In some
areas predators may have
little impact, but recent research in Alabama, Georgia and
South Carolina confirms that bobcats and coyotes can
significantly
reduce fawn recruitment rates.
We asked for statewide averages in our survey, but it is
important to remember the average recruitment rate can vary
widely
within a state. This is especially true for large states
with diverse habitats, deer management programs, and snow
or rainfall
rates. Our survey revealed there is much variation in
recruitment rates across the whitetail’s range. In
2008, fawn recruitment
rates varied from less than 0.5 in Arizona and Oklahoma to
1.2 fawns per adult doe in Illinois and Iowa. That means
the
average doe in Illinois and Iowa recruits nearly 2.5 times
as many fawns per year as the average doe in Arizona and
Oklahoma!
Given this information, it is not surprising the productive
Midwest grows so many bucks and requires such high
antlerless
harvest rates to keep deer herds in balance with their
habitat.
Sportsmen and women can estimate the fawn recruitment rate
on the property they hunt/manage with observation data,
spotlight counts, and/or scouting camera surveys. Each
technique has biases associated with it, but it’s
more important to
estimate this index in the same manner each year so you can
monitor trends in the data over time. Compare your estimate
to the range reported above, and then closely examine the
direction your trend is moving. Increasing fawn recruitment
rates
suggest herd health is improving and may permit higher
harvest rates. Decreasing recruitment rates suggest herd
health is
declining and/or fawn mortality is increasing. These
figures can help fine tune your annual target doe harvest
and help you
achieve success in your management program.
Kip’s Korner is written
by Kip Adams, a Certified Wildlife Biologist and Northern
Director of Education and Outreach for the Quality Deer
Management Association (QDMA). The QDMA is an
international nonprofit wildlife conservation organization
dedicated to ethical hunting, sound deer management and
preservation of the deer-hunting heritage. The QDMA
can be reached at 1-800-209-DEER or www.QDMA.com.