season, according to a recent four-year study conducted by the Pennsylvania
"Our research has confirmed that Pennsylvania's bucks still are actively
pursuing does, particularly younger ones, at the outset of our firearms
season," noted Dr. Gary Alt, Game Commission Deer Management Section
supervisor. "The peak in breeding for adult females is mid-November, but
for female fawns it occurs in early December.
"This peak in fawn breeding, however, doesn't represent a high point in
overall breeding activity because there are fewer fawns in the population
and a lower percentage of them breed. About 90 percent of the adult does
checked in the study had conception dates ranging from Oct. 27 to Dec. 10;
fawns, from Nov. 5 to Jan. 16.
"For years, we thought and reported Pennsylvania's rut peaked the week
before Thanksgiving, when deer are provided closed season protection. That
information was accurate, but it didn't tell the whole story. Now, thanks
to this groundbreaking research, we have a clearer picture: Pennsylvania
bucks aren't really cooling their jets in the pursuit of the opposite sex
until well into December during our traditional firearms seasons."
Launched in 2000, the four-year deer conception study aimed to answer
questions about pregnancy rates, the peak and range of the rut; when fawns
are born, and the number of young carried per doe. Across the state,
Wildlife Conservation Officers, biologists and other agency personnel
collected data from road-killed deer. In all, 3,180 deer were examined.
The work involved determining the date road-killed deer died and measuring
embryos found within the deer. While it wasn't a pleasant job for those
gathering the data, the results have helped to clarify answers to important
questions about Pennsylvania deer. For instance, the study showed 91
percent of the adult deer and 26 percent of the fawns examined statewide
"It would appear that our bucks are servicing an overwhelming majority of
the available does in Pennsylvania," noted Bret Wallingford, the Game
Commission deer biologist who coordinated the study. "But that interaction
isn't guaranteeing the same reproductive success statewide. For instance,
fieldwork showed the best deer reproduction was occurring in the state's
southeastern and western counties, as well as in counties along the lower
Susquehanna River. The worst rates were in the state's northcentral
counties corresponding with some of the most overbrowsed habitat in
Pennsylvania. The most reasonable conclusion to draw from this documented
lack of reproductive parity is habitat. This isn't about over-harvesting
deer, but rather soil fertility, agricultural crop availability, climate,
overbrowsing and deer health.
Joe Kosack/PGC Photo
The study indicated habitat played a significant role in deer reproduction.
"Differences in reproduction were very noticeable in the number of fawns
that were impregnated in their first year. For example, in northcentral
Pennsylvania, less than 10 percent of the fawns checked were pregnant. In
western and southeastern wildlife management units, however, the number of
impregnated fawns approached 50 percent. That's quite a difference. But
when you consider the vastly different environments these deer inhabit, it
quickly becomes apparent just how important habitat is in defining a
whitetail's life. Our highest reproduction came from agricultural settings,
the worst, from our overbrowsed big woods counties."
The reproduction findings are significant because they suggest that in some
places, at least, habitat conditions are adequate, and that agricultural
areas and suburban sprawl can support plenty of deer. Of course, the
downside of increased deer productivity and accelerated maturity is
property owners are fueling it unwillingly, in many cases. Although these
deer may not exceed the land's carrying capacity, they are impacting
farmers' profit margin, landowner's landscaping efforts and motorist
Timing of the rut may be affected by many factors including the length of
daylight in a given day and age structure of the buck population.
"Some studies, especially those from southern states, suggest age structure
of bucks in the population influences timing of the rut," noted Dr.
Christopher Rosenberry, Game Commission wildlife biometrician. "Other
studies in northern populations suggest length of daylight may have a
greater effect than buck age structure. Given the young age structure of
bucks in Pennsylvania at the time of this study and adult female breeding
dates similar to studies in northern populations with older buck age
structures, length of daylight appears more important than a young buck age
Data collected in 2004 and subsequent years will begin to reveal the
effects of current hunting regulations on reproduction, as well as habitat.
According to Dr. Alt, "As we increase the amount of research on deer in
Pennsylvania, we build a stronger base of information upon which management
recommendations can be made. This helps keep the deer program defendable,
which ultimately benefits our invaluable deer resource and Pennsylvania
deer hunters. This research has provided some excellent information so far,
and additional years of data will help answer even more questions regarding
deer management regulations and reproductive success."