SE
Washington Mule Deer Buck Escapement
Pat Fowler, District 3 Wildlife Biologist
History
The Blue
Mountains of southeast Washington have always been known for
abundant mule deer populations and the excellent hunting opportunity
they provide in the lowlands and along 150 miles of the Snake
River breaks. This area is mostly comprised of private land,
utilized for farming and grazing. The land consists of an
open, grassland habitat that makes buck deer highly vulnerable
to harvest during the general hunting seasons.
The level
of vulnerability in this area resulted in high buck mortality
and extremely low post-season buck ratios during the 1970’s
and 1980’s. Aerial surveys conducted between 1978 –
89 showed post-season buck to doe ratios were extremely low
for both mule deer and white-tailed deer; 2-4 bucks per 100
does. During this period, the general, modern firearm hunting
season averaged over 20 days in length. Long hunting seasons
and high vulnerability to harvest resulted in low survival
rates for buck deer in southeast Washington.
In 1987,
the WDFW shortened the general firearms season to 9 days in
an attempt to improve post-season buck ratios. The 9-day season
was continued for three years (87-89) with little improvement
in post-season buck ratios; 3 yr. av. 2 bucks/ 100 does. In
1990, the WDFW developed three options to for improving buck
survival and increasing the number of bucks per 100 does post-season.
These options included, 1. limited entry deer hunting, 2.
spike-two point as a legal buck, with 3 points+ by permit,
and 3. a three-point buck regulation. The department recommended
the three-point option for both mule deer and white-tailed
deer and retained the 9-day general modern firearm season.
Continuing the 9-day season was recommended because other
states had failed to improve post-season bucks ratios after
implementing a three-point regulation. The failure of other
states to improve buck ratios appeared to be related to maintaining
long seasons, or actually increasing season length after the
regulation was implemented. At the time, the Wildlife Commission
approved the three-point option for mule deer, but not for
white-tailed deer.
Three-point
Regulation Implemented
In 1990,
the three-point option was implemented for mule deer and applied
to all user groups; archers, modern firearm, and muzzleloader
hunters. However, excluding white-tailed bucks from the three-point
regulation resulted in excessive mortality, because hunters
were selecting for white-tailed bucks. Prior to 1990, mule
deer bucks comprised approximately 70% of the buck harvest,
but the percentage of white-tailed bucks in the harvest rose
to 60% in 1990. In 1991, the department recommended including
white-tailed bucks under the three-point regulation and the
Wildlife Commission approved the recommendation.
Post-season
mule deer buck to doe ratios showed immediate improvement
after the 1990-hunting season, increasing from an average
of 2 bucks/100 does in the 1980’s to 9 bucks/100 does.
In 1991 and 1992, buck ratios continued to improve reaching
17 bucks/100 does. Over the next 10 years (1993-2002), the
post-season mule deer buck ratio averaged 20 bucks/100 does.
Post-season white-tailed buck to doe ratios showed similar
improvement.
Prior
to the three-point regulation, few bucks remained in the mule
deer population after the general season, and most of these
bucks were yearlings. Mortality was so high, that few bucks
survived to become adults. After the regulation was implemented,
bucks 2.5 years and older increased substantially. Between
1990-2004, adult mule deer bucks averaged 29% of the post-season
buck population.
Theoretically,
the three-point regulation should result in fewer bucks in
the older age classes, because hunting pressure and mortality
is focused on bucks that are two years of age or older. Under
a three-point regulation, most of the post-season buck population
should consist of yearling (sub-legal) bucks. Although yearling
bucks do comprise a high percentage of the post-season mule
deer buck population in southeast Washington, the number and
percentage of adult bucks in the post-season population increased
substantially after the three-point regulation was implemented
(+600%).
In 2003,
the WDFW developed the Game Management Plan which set management
objectives for post-season buck ratios at a minimum of 15
bucks/100 does. In 2002, post-season mule deer buck ratios
started to decline reaching 14 bucks/100 does. Since 2002,
post-season
mule deer buck ratios have fluctuated between 11 and 14 bucks/100
does. The decline in post-season buck ratios has created concern
among biologists and the public.
Factors
Impacting Post-season Buck Ratios
Two factors
are contributing to low post-season buck ratios, 1. lower
fawn survival, and 2. maintaining general hunting season length
for all users.
Deer populations
in southeast Washington are dependent on fall green-up that
improves nutrition. Fall green-up in the lowlands provides
the nutrition necessary for deer to add the fat reserves necessary
for winter survival. If fall green-up is minimal due to drought,
deer generally go into the winter in poor physical condition,
which increases vulnerability to winterkill, especially fawns.
If weather patterns include a summer-fall drought followed
by no green-up and snow conditions during the winter, the
situation for deer in the lowlands and Snake River breaks
becomes critical. This type of weather pattern usually results
in higher fawn mortality, and lower fawn production the following
year. Southeast Washington was plagued by this type of weather
between 2001 and 2003, which is the main factor resulting
in lower fawn survival and fewer yearling bucks in the population
Maintaining
or increasing hunting season length during periods of low
fawn production and survival also contributes to lower post-season
buck ratios. Maintaining hunting season length puts steady
hunting pressure on a shrinking buck population, increasing
additive mortality, which exacerbates the problem. Fewer adult
bucks are in the population, and continued harvest along with
lower numbers of yearling (sub-legal) bucks holds the post-season
buck ratio at lower than desired levels.
The
Future
The three-point
regulation has worked very well to improve post-season buck
ratios and the age structure of both mule deer and white-tailed
buck populations in southeast Washington. Fortunately, fawn
survival improved in 2004, and 2005 appears to be a very good
year for fawn production. If, over-winter fawn mortality is
minimal in 2005-2006, the number of yearling bucks in the
post-season mule deer population should improve. An increase
in the number of yearling bucks in the population should bolster
the number of adult bucks in the population over time. However,
biologists will need to monitor populations closely over the
next few years to be sure buck ratios and the age structure
of mule deer bucks is improving. If post-season buck ratios
fail to improve, adjustments in hunting season structure and
opportunity may be necessary to increase buck survival in
the future.
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