The doe is one of about 900 deer living on the 8,371-acre refuge, located along the Missouri River east of Blair. Since 1991, Gilsdorf and other University of Nebraska-Lincoln researchers have trapped and monitored more than 400 deer at the refuge, and have fitted more than 170 with radio collars. The focus of the research, one of the longest-running telemetry studies of deer anywhere, has changed over the years. But its scope - learning about a deer's home range, the area where the deer spends most of its life, and what factors affect the range's size and location - has not. Through the research, the deer have taught researchers lessons that can be put to use by farmers, wildlife managers and hunters.
Deer research at DeSoto began in 1991 under the direction of Scott Hygnstrom, a wildlife damage specialist and professor in UNL's School of Natural Resources. He continues to guide it today.
Before launching the DeSoto study, Hygnstrom had studied damage to corn by deer. At DeSoto, he wanted to find out when foraging deer cause the greatest reduction in yield. He also wanted to examine how a deer's home range and crop fields overlap, and if that range changed through the year. "Come hunting season, we wanted to know, 'Were the deer that were feeding in those fields all summer still in the vicinity to be harvested?' " Hygnstrom said.
Answers to those questions could only be assumed because they had never been studied. Home range studies had been done in other states, but none had been conducted in a riparian system cutting through intensively farmed areas in the eastern Great Plains. With its mix of habitats - about half woodlands, one-fourth cropland and the remainder grasslands or
Kurt VerCauteren began the study as a master's thesis project. Between January 1991 and March 1992, 72 deer were captured on the refuge. Most were caught in walk-in traps - a steel frame covered in netting and baited with corn. Wildlife managers fitted half of the deer with ear tags, allowing researchers to gather information through direct observations and to track them through hunter returns. The other deer were fitted with radio transmitters: 31 does with radio collars and five juvenile bucks with smaller radio ear tags. Does were the focus of the research because they are about 75 percent of the deer population in areas where hunting is allowed - a result of hunters harvesting more bucks than does.
During a two-year period ending in February 1993, VerCauteren noted the location of each deer from one to four times each day. "Once you know your deer, especially in the daylight hours, you can just go right to it," he said.
The study found the largest home range for a radio-collared doe on the refuge was about 700 acres, a little more than a square mile, and the smallest range was about 170 acres. The average was about 420 acres, close to the average range documented in previous studies in Illinois, Missouri, Wisconsin and Iowa.
VerCauteren's intense tracking allowed him to detect seasonal shifts in a deer's home range and how human disturbance and crop growth affected those shifts.
In the spring, visitors may gather morel mushrooms in parts of the refuge that are closed the rest of the year. During this period, researchers found little change in the size of the home ranges, although the core areas - where deer bed down during the day - shifted slightly, presumably in response to human disturbance.
Later in the spring, when does gave birth, their home ranges shrank and remained small until their fawns were old enough to move with them.
In the summer, home ranges shifted closer to corn. Researchers found that deer fed on corn during every stage of its growth, but when the crop reached its silking and
During refuge deer hunts, held every December since 1968, VerCauteren found that a few collared deer moved off the refuge, or into areas closed to hunting, only to return to their home ranges a few days after the hunt. Most deer, however, never left.
During one hunt, VerCauteren watched four hunters walk through a narrow strip of woods, attempting to drive deer toward other hunters. VerCauteren knew there was a buck equipped with a radio ear tag in those woods, and he watched from a distance. The buck never left the woods.
VerCauteren saw similar cases during his study. "That tells you they're tucked in next to a downed log or they were just staying in the thick stuff and letting the guys walk by them," he said. The "thick stuff" was often stands of scouring rush (Equisetum), where a bedded deer could easily detect the approach of a hunter.
Hygnstrom said, "We found that deer didn't move long distances. There was a little bit of a shift, but the center of their home range was within 200 yards of where it was during the summer, meaning hunters could take those deer, reduce local deer densities and have an impact on crop damage."
Because only five bucks were equipped with radio transmitters during the initial study, and because the batteries in those transmitters lasted less than a year, VerCauteren learned less about buck movements.
But, as in similar studies, he found bucks had larger home ranges than does. He also documented several excursions bucks made to areas up and down the Missouri River, including several trips made by a pair of bucks. "I could see them leave the center of the refuge, come up along the river under the [U.S. Highway 30] bridge and head north to, say, California Bend, and be back by morning," he said.
VerCauteren said those bucks were looking for a new home and eventually, they found one near Tekamah. Deer have moved farther since. Last summer, a car struck and killed an ear-tagged buck northeast of Sioux City, Iowa, 75 miles from DeSoto. Other deer have traveled as far north as Winnebago and as far south as Council Bluffs and Omaha to set up new home ranges.
VerCauteren found that deer in the study fell into one of three categories: residents, emigrants or migrants. Emigrants sought new home ranges beyond the refuge, and migrants left the refuge in spring to give birth to their fawns and returned in the fall. One doe spent the eight summers researchers were following its movements near Arlington, 20 miles east of DeSoto, and returned to the refuge in the fall most years.
Seasonal deer migrations have been observed in other parts of the country where deer disperse in the spring and then return to areas that provide food during the winter.
VerCauteren said, "We have deer go 50 miles away. But come fall, once all the corn is out of the field and the leaves fall off the trees, what was great deer cover in the middle of summer is no longer good deer cover. So they have to come back to some area of permanent cover."
These movements were not limited by the Missouri River, as many area residents once believed. Just weeks into his research, VerCauteren found that deer would swim the river's swift current.
"Scott was thinking, 'I've got this rookie kid out there who doesn't know how to do telemetry very well and now he's on the wrong side of the river,' " VerCauteren said. "I was thinking it, too. But you follow the signal where it goes." It led him to an adult doe that had swum the river full of ice floes.
When deer left the refuge, VerCauteren found juvenile does traveled an average of 20 miles to find a new permanent or seasonal home range, more than twice as far as
VerCauteren said several factors cause deer to leave the refuge. Does live in matriarchal groups made up of an adult and its progeny. But does prefer to give birth in areas devoid of other deer. Before birthing, they are antagonistic toward their young from the previous year, especially bucks, and cause them to disperse. "The densities [of deer in DeSoto] are so high, they all can't stay," VerCauteren said. "So someone's got to go, probably the one that's the lowest on the totem pole - the young one."
Often, the new habitat a doe selects is not ideal. That was the case when a collared doe established a home range in an 80-acre strip of woods between Interstate 29 and the Missouri River on the southwestern edge of Council Bluffs, Iowa.
"She's going to die," Hygnstrom said when he was told that the deer selected that area.
The deer crossed busy Interstate 29 every night to feed in crop fields. A little more than a month after she settled in the area, she was struck and killed by a car.
"Why did she set up shop there?" VerCauteren said. "Probably because it was open. The last one that lived there was likely smashed on the highway."
That finding led to one aspect of VerCauteren's doctoral dissertation study, source-sink dynamics. That study, which began in 1995, also looked at home range fidelity, what caused deer to move and the vulnerability of both resident and transient deer to hunting and other factors. By the time the study ended in 1998, VerCauteren had captured 98 additional deer, including 45 does he fitted with radio collars. Those does, and others with functional collars from his earlier study, were tracked weekly to determine their annual home ranges.
The study confirmed his earlier findings that most deer are extremely loyal to their home range. Of the 76 does he tracked during both studies, 71 percent were residents, 16 percent were emigrants and 13 percent were seasonal migrants.
The number of deer leaving the refuge showed how important areas with high deer densities, like DeSoto, are as a supply source for the deer population in the surrounding region.
Some of the habitat, however, including that 80-acre woods at Council Bluffs, were found to be population sinks.
The annual survival rate for deer in the study was more than 85 percent, which Hygnstrom said is probably somewhat higher than deer populations in most areas.
Hunting was the cause of death for 77 percent of the radio-marked resident deer that died during the study and for 58 percent of migrants and emigrants. Other human-related causes of death, including vehicle collisions and poaching, were lower for deer that live on the refuge because it is a public-use area with few high-traffic roads. Off the refuge, all deer, including migrants, are exposed to a gauntlet of one or more archery and/or firearm hunting seasons. Migrants are especially vulnerable during these hunts while they return to the refuge in the fall.
To reduce hunting pressure on migrants - the segment of the population most likely to produce offspring that live beyond the refuge - researchers proposed that any additional hunting seasons on the refuge be held in October, before those deer returned, rather than December. Refuge managers followed that recommendation and established an antlerless deer season in 1999.
In 1999, Jason Gilsdorf took over the DeSoto research from VerCauteren. The graduate student continued to trap and collar deer and to monitor home ranges, but his master's study focused on finding a frightening device that could reduce the amount of damage that deer do to corn.
During his first summer, Gilsdorf tested two commercial noise-making devices intended to protect crops and livestock. While corn was in the silking and tasseling stage, he measured field use by counting deer tracks and monitoring radio-collared deer in the area. He found the devices did not reduce crop damage. The deer got used to the noisemakers and continued to eat.
The following year, Gilsdorf monitored the reactions of deer to a variety of recorded sounds - people screaming, banging pots and pans, rock music and deer distress calls. "Everything worked," he said. "The deer would walk by, I'd hit play and they would just run."
Distress calls had proven effective in dispersing birds, but little research had been done with mammals. So Gilsdorf built a frightening device that would play a distress call whenever deer tripped infrared beams on the field edge. When it was tested in 2001, deer were observed running from the sound, but again, Gilsdorf found no noticeable reduction in crop
In 2003, researchers began to look at how home ranges had shifted with habitat changes, including crop rotation and the conversion of cropland to natural habitat, since the first study began.
DeSoto managers are keenly interested in this study because their conservation plan calls for gradually converting all but 500 acres of the refuge's 1,500 acres of cropland to natural habitat, primarily into high-diversity grassland. Since deer research began on the refuge, 1,000 acres have been taken out of production.
That plan has been delayed until the deer population, which has increased rapidly in recent years despite more hunting pressure, can be reduced. Hygnstrom predicts that
Recent work has also looked at habitat selection by migrant and emigrant deer. Most selected permanent or summer home ranges in riverside woodlands surrounded by cropland. The size of the home ranges for these deer was about half as large as those for deer on the refuge.
This year, researchers refocused the study to determine how far and how fast chronic wasting disease (CWD) might spread through a riparian system. To measure this, researchers are now tracking the movements of bucks, which occupy larger home ranges than does and are more likely to leave their birth areas.
Greg Clements, who has worked on the deer study as an undergraduate at the university for more than three years, will conduct the three-year study as part of his master's work. Since last winter, Clements and Gilsdorf have captured 23 bucks at DeSoto and at Boyer Chute National Wildlife Refuge a few miles to the southeast near Fort Calhoun. Their goal was to have 30 bucks - 10 fawns, 10 1½ year olds and 10 2½ years old or older - fitted with collars by fall. Some have been caught in traps, but most were immobilized using tranquilizer guns - a
Existing research shows that older bucks move less. "They're more established," Clements said. "During the fawning season, the mothers will kick the younger bucks out. And also during the breeding season, if they are not gone by then, the mothers will drive them away. So we're expecting the younger bucks to move greater distances.
"The [existing] literature says about 80 percent of buck fawns will disperse from where they were born. I'm interested in seeing if that many will actually disperse or if they will stay in and around the refuge."
Many older bucks disperse when the rut begins. Males fight for breeding rights, and those that lose often move on to look for territory they can claim. Mature bucks are expected to stay in their home range, but those home ranges are expected to expand during the breeding season. "It will be really interesting to see how far the deer have moved once the rut rolls around," Clements said.
Clements and Gilsdorf will continue to track the 37 does that still have working radio collars and use that data when developing the CWD model.
Doe No. 244 has not moved. She still calls the woods south of the visitor center at DeSoto home, bedding there during the day and feeding in the fields across the road at night.
At night, she might take a break from feeding and lie down in the ditch next to the road. On hot summer days, Gilsdorf has seen her bedded beneath vine-covered plum bushes on the side of the road.
"You could go over there and see her every night if you wanted to," he said. "It's like clockwork. You could stop and sit [on the road] and three of them in that area, they'll come across the road in the same general area every night."
It gives a whole new meaning to "Home on the range."Radio Telemetry 101
Biologists use radio telemetry to monitor the movements of many wildlife species. Currently in Nebraska, studies involve elk, bighorn sheep, massasauga rattlesnakes, white-tailed and mule deer, northern pintails, pheasants and American burying beetles.
Each species is fitted with a transmitter of an appropriate size that emits a signal with a specific frequency. With a directional antenna and receiver, biologists pinpoint a subject's location using biangulation. The researcher draws a line on a map from his or her location in the direction of the transmitter signal. Within a short period, the researcher takes a second reading from a different location and draws a second line. The point where the lines intersect is the approximate location of the subject. A reading taken at a 90-degree angle offers the most accurate location.
Until recently, researchers tracking deer at DeSoto National Wildlife Refuge took readings from 60 established points, recorded the compass heading of each deer's signal and analyzed the data later. Researchers at DeSoto and at a related project on the North Platte River now use a system that links an electronic compass, a Global Positioning System receiver and a laptop computer with specialized software that permits readings from anywhere. The system provides more precise results and saves time on data entry.DeSoto's Deer Herd
DeSoto National Wildlife Refuge, created in 1958, took its name from a bend in the Missouri River and a nearby town. The oxbow lake at the heart of the refuge is what remains of the bend after the U.S. Army Corps of Engineers excavated a new channel in 1960 to shorten the river. The refuge straddles the Nebraska-Iowa border, and has land in both states.
White-tailed deer have flourished in the riparian habitat and farm ground that make up the refuge. To keep the population in check, annual firearm hunts have been held each December since 1968. Initially, hunters were allowed to use high-powered rifles to harvest
Despite increased hunting pressure, DeSoto's deer herd has continued to grow. A helicopter survey in February counted 983 deer on the refuge - more than 90 per square mile. It was the first direct count of deer there, and the density was well above previous wintering estimates of 55 per square mile.
The larger deer herd is taking a toll on the environment. A browse line is visible on trees and shrubs, and increased crop losses have brought complaints from adjacent landowners, said refuge manager Larry Klimek.
To reduce the deer herd, hunters will be allowed to harvest an additional antlerless deer during both muzzleloader seasons this fall. Also, two more hunts will be held on consecutive weekends in January, one for Nebraska hunters with Season Choice Area 21 permits, and another for Iowa shotgun hunters. Each will be opened to 135 hunters, who will be required to obtain a special permit from the refuge office beginning in November.
The population issue has caused managers to delay a plan to convert 75 percent of the cropland on the refuge to native grassland and cottonwood forest during the next ten years. Converting the land before deer numbers are reduced could lead to more crop damage both on and off the refuge.
"We want to get back down to natural habitat, but we want to listen to the sensitivity of our neighbors and farmers on the refuge," said Klimek.Advice for Hunters about Bucks
While research at DeSoto has not focused on bucks, researchers have made many observations of interest to deer hunters.
Jason Gilsdorf said one buck they caught and tagged debunked a common belief among hunters that young bucks with spike or forked antlers will not grow a trophy rack. The proof came when a hunter checked in a 4-year-old, 5-by-5 buck that was a forkhorn when it was trapped and tagged as a 11/2-year-old.
"It just goes to show you, if you let those deer go … age is huge as far as getting deer with big antlers," Gilsdorf said.
Gilsdorf's job gave him a luxury that many who hunt DeSoto wish they had - the ability to scout the area year-round. But the only time he hunted the December season, when hunters can harvest bucks, he held out for a trophy buck, and left empty-handed.
Gilsdorf said he is amazed how buck behavior changes in the fall. "The big bucks, when they're in velvet, they're like clockwork. You can pattern them so easy. They come out to the same fields all the time. When September comes around, they just go nocturnal and you never see them."
But not all bucks fit that description. Kurt VerCauteren did not see one yearling buck he trapped and fitted with an ear tag until 31/2 years later, when it was brought to the refuge check station by a hunter during the December hunt. In talking to the hunter, VerCauteren learned the buck, now a 5-by-5 trophy, was harvested 70 yards from where it was trapped. "He was probably there the whole time," he said.
VerCauteren believes many deer taken by hunters on the refuge, especially mature bucks, are probably eluding one hunter when they walk into the lap of another. During an October hunt, he paid close attention as kickoff approached for a University of Nebraska football game. He expected many hunters would leave their stands and listen to the game in their vehicles. "There was a barrage of shots right around that time because people started moving," he said.
His observation backs up a strategy often used by hunters in areas with heavy hunting pressure - stay in your stand all day, or at least be there when others leave their stands at lunch, or when they return in the afternoon.
Scott Hygnstrom said another strategy hunters could use in high-pressure areas is to hunt escape cover rather than traditional feeding and bedding areas. Those areas include bottlenecks in woodlands, or narrow strips of cover connecting larger areas. "You can think you have a deer patterned, but that pattern just blows up when you have a bunch of hunters in the area," he said.
Hunters will be able to glean much more information on buck behavior when the current study is completed. But from watching does at DeSoto for 13 years, Hygnstrom knows one thing for certain: "The bucks are parasites. They hang around the does."Doe No. 15
From the deer population study at DeSoto National Wildlife Refuge, some intriguing stories about individual deer emerge. The story of doe No. 15 is one of the most interesting.
Captured as an adult during Kurt VerCauteren's first season, No. 15 showed him that not all deer head for deep cover within their home range in response to hunting pressure. Before the first shot was fired in the 1991 December muzzleloader hunt, the doe had moved nearly three miles from her home range in the center of the refuge to a patch of woods at its western edge that was closed to hunting. A few days after the hunt, she returned to her home range.
With radio telemetry equipment, VerCauteren documented her behavior for several years. One year, he decided he wanted to see it with his own eyes. Before sunup on the first morning of the annual hunt, he parked his truck near a strip of woods that he suspected No. 15 used as escape cover when leaving the hunting area.
"Some guys parked kind of near us and were walking into the woods, down this overgrown fence line full of trees 15 yards wide or so to get to their stand. All of a sudden, from the other direction, here come 13 deer," he said. Leading the pack was doe No. 15.
"She knew that it was time get to the safe area. All it took was the activity of guys walking through the woods for her to know, 'Whoa, this only happens once a year, having guys in the woods before it's light out.' So she knew. And she did that year after year," he said.
VerCauteren had trapped and collared two of No. 15's progeny - No. 19 and No. 137. Both were in the pack, providing evidence that deer form matriarchal groups and learn behavior from the oldest.
Doe No. 15 was trapped several times. The sixth time, in 1997, VerCauteren was glad to see her because the batteries in her radio collar had died.
When researchers open the front door of a trap, most deer try to escape through the netting in the back. This tendency makes it easy for researchers to grab a deer from behind and wrestle it to the ground. But No. 15 had learned where the door was. "I opened up the door and 'Boom!' She plants the fat of her head in my chest and just runs over me," VerCauteren said.
Two weeks later, he trapped her again. This time he was ready when the deer came at him as he opened the door. He won the battle, but shed some blood and walked away with a black eye. "She really pummeled me," he said.
Jason Gilsdorf tracked No. 15 for three more years. She survived the refuge's first October hunt in 1999, moving to a different closed area. Gilsdorf trapped her once more in early 2000. That October, he and Scott Hygnstrom found her in a cornfield a half-mile west of her home range with 30 other deer on the night before the hunt. The following morning at sunup, a hunter harvested the 131/2-year-old deer as she headed to her home range.
"She made a mistake," Hygnstrom said.
VerCauteren said he reviewed literature and found no records of deer that had been monitored as intensively or as long - for nine years - as No. 15.
Doe No. 137 didn't leave her home range during the December hunt in 2000, but did in 2001. She died the following summer of natural causes, probably from epizootic hemorrhagic disease. Doe No. 198, a collared deer that lived two miles south of No. 15's home range, also moved to the same closed area during the December hunts. Whether she is related to No. 15 or simply followed her to safety one year is not known. Gilsdorf said neither of these deer moved during the October hunts. No. 198 was harvested in the October hunt in 2001.