You’ve put trail cameras all over your property and one buck in particular has snagged your attention. He’s the wide 8-pointer with the split brow tines on the right and a sticker off the left G3 — the one you have photos of throughout the summer licking your mineral block. The one you’ve been careful not to pressure too much during the first few weeks of deer season. You’ve been closely monitoring his activity since the start of the hunting season, when all of a sudden, he’s just gone!

By Dr. Stephen Ditchkoff  and Todd Jacobsen
Auburn University School of Forestry and Wildlife Sciences

A few days later, you swing by the local deer processor to see what was killed over the weekend. There you see Joe, who owns 40 acres 5 miles down the road from you. Joe just happens to be lean- ing against his tailgate, proudly showing off a particularly wide 8-pointer with split brow tines on the right and a sticker off the left G3. Heated words ensue, and accusations of Joe spotlighting your green field this buck routinely visited leaves you and Joe at odds with each other.

While the dramatic outcome of this theoretical story probably doesn’t really happen all that often, many deer hunters have likely been in a similar situation or heard of an instance where a particular resident buck magically disappears off the face of this Earth, only to return a few days later, or maybe never to return again. In this story, Joe didn’t actually spotlight and poach this buck. Rather, Joe caught this buck moving through his property while the deer was exhibiting a behavior characterized as an irregular, infrequent, long-distance movement outside of its typical home range — commonly referred to as an “excursion” among deer biologists.

Not much was known about patterns of deer movement until the advent of radio telemetry during the mid-1900s. At that time, VHF radio collars enabled scientists to begin to examine spatial behavior of white-tailed deer and other wildlife species. While this technology was an incredible asset to scientists and managers who were interested in the spatial ecology of deer, data collected with the use of VHF radio collars had limitations.

However, studies utilizing VHF collars during the 1960s, ’70s, ’80s and even ’90s provided some evidence that while white-tailed deer usually had fairly predictable patterns of space use, they occasionally exhibited strange, long-distance movements that were both unpredictable and unexplainable.

It wasn’t until GPS-tracking collar technology came on the scene in the early 2000s — with the capability of regularly collecting deer locations on the scale of hours or even minutes — that researchers began to see additional evidence of long- distance excursive behaviors and were able to carefully examine these unique movements.

With the relatively recent history of GPS-tracking capabilities, only a handful of studies have been conducted that examine the occurrence of, and the motivation behind, excursive movements by white-tailed deer. Unfortunately, while these studies have been successful at documenting long-distance excursive movements of deer, excursion research is still in its infancy and not enough data have yet been generated to provide defensible explanations for these movements. This lack of conclusive data, however, has not kept scientists from speculating on possible explanations for some of these observed movements.

Some possible explanations for excursions that have been proposed include: an attempt to locate a mate; avoidance of inbreeding; trips back to natal (birth) home ranges; mineral lick visitations; and other food- or nutrient-motivated movements.

In 2010, research based out of the University of Georgia examined excursions by does during the breeding season. They documented that adult does primarily engaged in excursive behaviors near the peak of the breeding season, and they speculated that these behaviors were associated with mating. The following year, research conducted at North Carolina State University examined excursions by bucks during the breeding season. They suggested that excursions observed during the rut were likely breeding-related, but could not provide an explanation as to why some males also went on excursions earlier in the fall.

Finally, in 2015, researchers at the University of Georgia examined excursions by mature bucks in north-central Pennsylvania during the spring. They found that excursions during this period were common, but could offer no explanation for the variety of excursive behaviors they observed. What can be gleaned from these studies is that excursive behaviors seem to be highly variable, suggesting that there are likely multiple reasons why deer go on these long-distance movements.

Understanding these movement behaviors has the potential to yield extremely important insights for hunting and deer management. What might these excursions mean for a landowner trying to attract and retain deer on a property? How about for the hunting club trying to manage for quality mature bucks? Finally, what might these excursion events mean to the hunter trying to pattern a particular buck’s behavior?

The better we understand deer behavior, the better we can provide for, manage and hunt deer. Knowing which deer are most likely to leave their normal home ranges and when they are going on these excursions can help hunters predict deer movement and understand why a deer might wander off a piece of property (or, conversely, be drawn to a hunter’s property away from its normal home range). Additionally, insights concerning long-distance deer movement behavior can be critical to understanding how wildlife diseases such as CWD might spread across the landscape.

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OUR RESEARCH
In 2014 and 2015, we outfitted 33 white-tailed deer with GPS tracking collars as part of a large-scale study on deer movement and survival at four study sites in Alabama.

This study was funded by the Alabama Department of Conservation and Natural Resources, the Westervelt Company and individual landowners. Using night-vision tranquilizer guns from elevated treestands, we darted and collared bucks and does of all ages.

The GPS collars we used were set to collect deer location data at regular intervals until this past April. Data collected from these deer have advanced our understanding of excursive movements considerably.

WHAT DO EXCURSIONS LOOK LIKE?
As it turns out, deer go on a lot more excursions than previously thought, and it’s not just bucks that do this. In our study, we documented 320 long-distance movements by 32 deer. While 75 percent of these movements extended less than 1 mile outside of the deer’s home-range boundary, 79 excursions extended beyond 1 mile.

Thirty-seven excursions (12 percent) extended past 2 miles, with 13 excursions reaching 4 miles or more outside of the home range. Of these, two were made by the same doe. The maximum excursion distance recorded during this study was nearly 8 miles! Only one deer out of the 33, a doe, did not go on any excursions, but this was likely because she was collared only for about three months during summer 2015.

Besides straying outside of the typical home range area, why are excursions different from any other movement a deer makes throughout its day-to-day life? Deer excursion paths are generally direct. Rather than roaming across a small area or bouncing around from one part of its home range to another, most excursions we observed were linear (Figure 1).

Instead of aimlessly wandering around or performing methodical searching behaviors, deer tend to continue moving in a straight path for the duration of the excursion. Deer on excursions tend to travel at a fairly rapid and constant rate. Additionally, it is not uncommon for a particular deer to utilize the same path for multiple excursions. In several instances, each subsequent excursion along a repeatedly used path extended farther than the previous excursion. It is possible that this behavior is a deer’s way of increasing the efficiency of excursions, or that a deer is applying its memory of a previously “safe” route to expand its search for resources.

What also makes excursive movements extremely interesting is that 82 percent of all excursions we observed lasted less than 24 hours, and 96 percent ended within 48 hours of leaving their home range. This suggests that deer might be assessing some sort of cost-benefit tradeoff while on these excursions, and might start heading back from the excursion when they decide straying farther away is not worth the risk of being in unfamiliar territory.

Furthermore, the vast majority of these excursions were strictly out-and-back type trips with continuous movement. Deer weren’t spending much time, if any, exploiting a particular resource on the excursion. These were most likely exploratory trips. If a resource of interest was found, the deer could then return at a later date to utilize that resource and incorporate it into its home range.

WHEN DO DEER GO ON EXCURSIONS?
As other studies have documented, deer excursions during the breeding season and spring are not uncommon. With the exception of June, we documented excursions occurring in every month of the year. However, starting in October, we noticed a drastic increase in excursive movements. This sudden rise in movement continued through December, but then excursion rates steadily decreased throughout the rest of winter and spring (Figure 2).

In many parts of the country, this increase in movements would seem to align with peak breeding activities; however, this was not really the case at the study sites where our research took place. Due to the extensive deer restocking efforts from populations in southwestern Alabama during the mid-1900s, many areas of Alabama today have a delayed breeding season, with peak rut occurring from mid- to late-January or even into early February.

While we still noticed an elevated level of excursion activity during this period, the breeding-motivation hypothesis does not explain the dramatic increase in excursions occurring from October through December. Alternately, this behavior might be more closely related to the availability of certain resources such as hard mast or corn from deer feeders.

DAILY TIMING
Another important insight we gained from this research concerns the daily timing of excursions. When we looked at the starting time of each excursion, we found a significant amount of them began within one hour of sunrise (Figure 3), while the ending time of each excursion was much more variable.

Deer tend to leave their home ranges first thing in the morning and then maintain fairly constant movement until they return to their home range. Conventional wisdom and past deer research have long suggested that deer are less active during midday. This line of thinking has contributed to the formation of the “strictly mornings and evenings” hunter, the one who climbs down from the stand each day by 9 a.m. and returns to the stand an hour before sunset.

As deer are generally more active during the hours surrounding sunrise and sunset, this mentality is not unfounded. However, it means hunters might be missing out on catching deer engaged in excursive behaviors as they travel across the landscape during daylight hours.

If deer embark on excursions at sunrise and continue to move for another six, 12, or even 24 hours, the amount of time they could potentially be exposed to hunting and harvest risk is much greater than if deer are just moving back and forth between bedding and feeding grounds during dawn and dusk hours.

Furthermore, this finding reinforces the importance of being prepared for an early morning hunt. With deer on the move before sunrise, hunters have a good chance of catching excursive bucks leaving the familiarity of their home ranges by being up in the stand early.

DO JUVENILES EXCURSE, TOO?
It is generally well known that juvenile bucks tend to disperse from their natal home ranges sometime between their first and second birthdays. Often, this occurs during the spring just prior to when their mother gives birth to another generation of fawns, or during the early parts of the breeding season when juvenile bucks seek areas with less aggression from mature bucks. While we have known about this dispersal behavior for quite some time, it was not until recently that we have been able to continuously track juvenile movements leading up to dispersal.

Research conducted by Southern Illinois University in 2015 suggested that these juvenile bucks embark on excursions several times prior to finally dispersing, and that these excursions could be characterized as “failed dispersals.”

We noticed a similar pattern with all four of the 11⁄2-year-old bucks that we collared in our study. Each buck went on multiple excursions to several different areas prior to dispersing. Interestingly, in every single case each buck explored an area via an excursion prior to eventually dispersing to that area (Figure 4).

In other words, none of our collared yearling bucks dispersed blindly, but rather had some prior knowledge of the area they were dispersing to. This suggests that juvenile bucks undertake test-trips prior to dispersal in an effort to identify suitable habitat for a future home range.

IMPLICATIONS
Deer excursions are of equal importance to both the hunter who has been patterning a particular buck all season on 500 managed acres (such as in our opening story) and to the hunter who hunts his or her small, 50-acre lease just outside of town and has never seen a decent resident buck on the property.

If you’ve been watching a particular buck and know his habitats, bedding areas and travel corridors and have been waiting for the perfect temperature and wind to make your move, be aware that this buck might end up in the back of neighbor Joe’s pickup when you least expect it. Now, though, you have a better idea of when to expect it and how to catch this buck as he leaves his home range on an excursion in Joe’s direction.

Conversely, if you’re leasing a small plot and have never seen a good buck on camera, that doesn’t mean one won’t be passing through the property on an excursion some crisp, November morning. While you won’t be able to know exactly when a deer from a neighboring property will wander over in your direction, you now know that excursive behaviors are not uncommon. The more time you spend in the woods, the more likely you are to catch one on such an excursion. And, since many excursions are resource-driven, you might just be able to convince that buck to make your property part of his home range by providing the right incentives.

We realize that this isn’t a shocking revelation, but the more attractive a piece of land is to a deer, the more likely it is that a deer will be drawn to that property while on an excursion. While we have not yet isolated which specific resources deer are in search of while on excursions, we do have evidence of deer shifting their home ranges to incorporate newly discovered areas.

In our study, deer M07 (“M” for male) left his home range (which consisted primarily of planted loblolly pine) on an excursion in mid-November (Figure 5). While on the excursion, M07 stopped at two particular spots along different hardwood fingers. Over the next month, M07 shifted his home range to incorporate these two areas, visiting them more than 20 different times. The most likely explanation for this shift in space use is that while on the excursion, M07 discovered a couple of mast-producing oaks and frequently returned to exploit these resources.

A similar scenario occurred where another one of our collared bucks — M18 — discovered a green field while on an excursion. This buck set up camp in a young planted pine stand adjacent to the green field and made daily trips back and forth to this field for five days before returning back to his pre-excursion home range. While a landowner might not know exactly what resource a particular deer might be drawn to, maintaining productive deer habitat could increase the likelihood of drawing excursive deer onto one’s property.

As GPS-tracking technology continues to advance and as biologists begin to dig deeper into some of the excursion trends documented here by our research, we can continue to unravel these once-mysterious movement behaviors and provide additional insights related to hunting, land management and deer biology.

The next time you see a new buck arrive on your property, try to keep track of his movements. He might be on an excursion in search of resources. Hopefully, your land has what he needs, and he might just decide to incorporate the property into his home range area.

— Dr. Steve Ditchkoff is a professor in the School of Forestry and Wildlife Sciences at Auburn University. He manages the deer research program at Auburn and has been conducting research on white-tailed deer for 25 years.

— Todd Jacobsen is nearing completion of his M.S. degree at Auburn University under the supervision of Dr. Steve Ditchkoff. His thesis research is focused on excursive behaviors of white-tailed deer.

LITERATURE CITED
Olson, A.K., W.D. Gulsby, B.S. Cohen, M.E. Byrne, D. A. Osborn, and K.V. Miller. 2015. “Spring Excursions of Mature Male White-tailed Deer (Odocoileus virginianus) in North-central Pennsylvania.” American Midland Naturalist 174:96-104.

Karns, G.R., R.A. Lancia, C.S. DePerno and M.C. Conner. 2011. “Investigation of Adult Male White-tailed Deer Excursions Outside Their Home Range.” Southeastern Naturalist 10:39-52.

Kolodzinski, J.J., L.V. Tannenbaum, L.I. Muller, D.A. Osborn, K.A. Adams, M.C. Conner, W.M. Ford and K.V. Miller. 2010. “Excursive Behaviors by Female White-tailed Deer During Estrus at Two Mid-Atlantic Sites.” American Midland Naturalist 163:366-373.

Springer, M.T., C.K. Nielson and E.M. Schauber. 2015. “Estimating Dispersal and Excursion Movement Rates of White-tailed Deer Using Demographic and Landscape Variables.” Proceedings of the Annual Southeast Deer Study Group Meetings 38:36.