Whitetails mix with humans in exurbia
May 01, 2008
Humans are moving into the countryside, among working farms and undeveloped forest land, and into wildlife habitat, producing a landscape referred to as exurbia. This new landscape — a mixture of farms, forests, estates, and large-acreage suburbs dominated by the well-to-do — is creating new headaches for deer managers.
According to Daniel Storm, and his research colleagues from Southern Illinois University, an estimated 10 million people were added to exurbia in the United States during the 1990s. This is considerably more than were added to urban, suburban,
or rural areas.
In contrast to suburban landscapes, where wildlife habitat occurs in patches, human dwellings in exurbia tend to be more interspersed throughout wildlife habitat. In other words, the larger lots and areas of native vegetation between human dwellings makes ideal deer habitat, helps contribute to deer overpopulation, leads to increased human-deer conflicts, and makes deer herd management difficult.
Although the ecology and management of deer living in urban and suburban environments have been extensively studied, until recently, little was known about deer behavior and population dynamics in exurbia. Research conducted by Storm and his group in southeastern Illinois, as well as that by Auburn University scientists Sarah Saalfeld and Stephen Ditchkoff, in Alabama, have shed new light on how whitetails cope with humans in this highly diversified environment.
The basic goal of these investigations was to provide wildlife managers with critical information necessary to manage whitetail populations in exurban settings — where humans are encroaching upon deer in their natural habitat.
Home Range Size
In southeastern Illinois, the group led by Storm radio-tracked
43 adult does near Carbondale, in order to determine how deer used the exurban landscape during the fawning season and during winter. They chose these two time periods because they represent extremes in habitat conditions and deer behavior.
The researchers found that deer living in exurbia typically had larger home ranges than deer in the suburbs, but smaller home ranges than those in more rural settings.
During the fawning season, deer in exurbia maintained home ranges averaging about 131 acres in size, compared to ranges as small as 42 acres for suburban deer and as large as 546 acres for rural deer.
Likewise, during winter exurban deer traveled ranges 225 acres in size, whereas suburban deer had ranges as small as 54 acres and some rural deer had ranges larger than 1,000 acres in size.
In the suburbs, highways, railroads, commercial developments,
and residential housing create impediments to deer movements that result in small deer home range size. However, such barriers to deer movement are less prevalent in exurbia, likely accounting for somewhat larger deer home range size.
Even so, exurban development causes forest fragmentation and increases human produced food sources for deer. This also contributes to smaller deer home ranges in exurbia, as compared to that for deer in rural environments, because exurban deer can probably meet their metabolic needs on less acreage.
Since deer had a lower density of human dwellings in their core fawning areas, as compared to their overall home range, the authors concluded that exurban deer generally avoided humans as much as possible when they had newborn fawns.
This behaviorism differed from that of deer in suburban areas. Apparently, deer in the suburbs can not reduce their home range or core area size, even during the fawning season, because of the high density of human dwellings.
Exurban deer also avoided using residential lawns as birthing areas. Instead, does favored use of grassland away from human dwellings during the fawning season. Such habitat apparently provides ideal hiding cover for young fawns, as well as relatively quite areas away from noise and disturbance associated with homes. However, the Illinois researchers had no measure of newborn fawn mortality rates and studies conducted in Alabama produced different results.
Unlike deer in suburban settings, deer in exurbia did not shift their core areas of activity closer to human dwellings during winter. Compared to suburban deer, this might suggest that exurban deer rely less on human food sources during the winter season.
Newborn Fawn Mortality
Although numerous studies have examined causes and rates of newborn fawn mortality, Saalfeld and Ditchkoff were the first to conduct such study in an exurban environment. Their study took place near Auburn, Alabama, in a setting of large lots (1 to 5 acres in size) with much native vegetation and wooded
|Exurbia will continue to expand in the future. As a result, deer hunting and deer population management opportunities will decrease, creating new deer management challenges. Kenny Darwin photo|
areas between houses.
The Auburn University researchers used a relatively new technique, employing vaginal implant transmitters, specifically designed to be expelled during the birth process and then emit a signal. They captured and fitted 46 adult does with these devices.
Once a transmitter was expelled, the researchers waited for at least 4 hours before searching the birth site, to ensure adequate time for mother-fawn bonding. Fawns they found were then fitted with radio-transmitters that also emitted a special mortality signal.
During the two year study (2004 and 2005) a total of 36 fawns were captured, transmitter-equipped, and monitored daily. Overall, only 12 of the 36 fawns (33.3 percent) survived longer than 8 weeks — a poor survival rate as compared to other studies.
Predation by coyotes accounted for 10 of the 24 mortalities and predation may have caused another 5 fawn deaths. Hence, more than one-half of the marked fawns may have been killed by predators.
Emaciation, probably due to abandonment, resulted in 6 fawn deaths (46.2 percent) the first year of study. However, no such mortality occurred during the second year.
Surprisingly, none of the fawn mortality was due to vehicle accidents. Apparently, the sedentary nature of fawns during the first two months of life minimized such risk, despite their close proximity to humans and roadways.
The overall fawn mortality rate of 66.7 percent for exurban deer was considerably higher than the average rate of 54.8 percent calculated from the literature for foot searches made in rural areas.
This difference may have been due to different capture techniques: use of vaginal implants versus foot searches. That is, fawns captured employing vaginal implants were less than one day old, whereas foot searching generally results in marking older fawns. Since, 50 percent of the mortality often occurs during the first week of life, as in the Alabama study, traditional foot searching studies tend to underestimate overall newborn fawn mortality.
Likewise, in Alabama, the fawning season is much later than on northern range, occurring from late July to early September. This means that dispersing coyote pups, as well as adults, are hunting independently when young fawns are especially vulnerable to predation.
Also, the open landscape characteristic of the exurban study area undoubtedly made visual detection of fawns easier for marauding coyotes. According to the investigators, fawns were often found bedded in sparse cover, such as areas of open understory, hedge rows, and landscaping areas.
Many of the fawns that died from emaciation were close to heavily used paved biking and walking trails. As a result, the researchers speculated that high human activity near birth sites interfered with does being able to return to their bedded young and led to abandonment.
At any rate, this particular study suggested that newborn fawn mortality in exurban areas is probably as high or higher than in most rural forested areas where deer coexist with effective predators such as coyotes, wolves, or black bear.
Adult Doe Mortality
On the flip side, Storm and his group found that adult does in their exurban Illinois study area experienced a higher annual survival rate (87 percent) than reported in both rural areas (57 to 76 percent) and suburban areas (62 to 82 percent).
Only 7 deer died during the study: 3 were harvested by shotgun
hunters, 2 were killed by archers, 1 was poached, and 1 was struck by a vehicle.
Relatively few deer were harvested by hunters, because only 19 percent of the landowners allowed deer hunting on their property.
The lack of hunting opportunity led the Illinois researchers to conclude the following: "Exurban development has been demonstrated to reduce efficiency of county-level deer harvest in Illinois and this is clearly true in our study area. The extremely low harvest rate of deer in our study area indicates that recreational hunting alone is not likely effective for managing deer in exurbia.''
Exurbia will continue to expand in the future. As a result, deer hunting and deer population management opportunities will decrease, creating new deer management challenges.
This is not to say that exurban expansion will decrease deer numbers. To the contrary, while such development will markedly decrease deer hunting opportunities — simply because landowners will not permit hunter access — it probably will not reduce the amount of deer habitat nor the number of deer.
According to Storm and his associates, "The likely end result of exurban development is highly abundant deer populations, moderate human populations, and high potential for deer-human conflict."
Unfortunately, given their study evidence, these researchers are not optimistic that hunters will play an important role in controlling increasing exurban deer numbers. Instead, they contend that "agencies must identify alternative policies and regulations to manage deer."
They admit that they are uncertain what these alternatives may be, but warn, "any solutions that may exist will have to be implemented in the context of increasing human and deer populations and decreasing hunter numbers" — not a particularly encouraging scenario.
The study conducted in Alabama by Saalfeld and Ditchkoff showed that coyote predation of newborn fawns may be an important mortality factor in such an environment.
Although coyotes are normally considered a hindrance to deer management, these researchers recommend the following: "Coyotes and their predation on neonatal deer should be considered an integral part of any population control strategy in the exurban landscape" — which may not set too well with exurban community members.
The results from these two studies may or may not be indicative of circumstances throughout the whitetail's range. Remember, the whitetail is a highly adaptive critter. Exurban deer could behave differently in other sections of the country and exhibit population dynamics different than found in these two studies. Clearly, there is need to study whitetails living in this unique landscape in other areas.
Unfortunately, well-to-do exurban humans — often being nonhunters or even anti-hunters — probably aren't too different from north to south, or east to west. Consequently, gaining access and controlling highly productive exurban deer populations via hunting is gonna be a tough ticket.