The Rose Petal Hypothesis: Why Deer Hunting Spots Go Dry

The Rose Petal Hypothesis: Why Deer Hunting Spots Go Dry

We’ve all heard it or said it: that deer spot just ain’t like it used to be. You might speculate that too many hunters are going in there, or predators have increased, or the deer have just moved—but the lack of deer definitely didn’t have anything to do with simply an unlucky day out with a rifle. What would need to happen for that statement to be true? How could somebody’s favorite hunting spot just dry up?

I research how mule deer develop and establish their home ranges as a graduate student in Dr. Kevin Monteith’s research group at the University of Wyoming. Somewhat surprisingly, the behaviors that mule deer use to set up their home ranges might play a pretty big role in shaping the deer in your favorite hunting spot.

I work on the Wyoming Range Mule Deer Project, a massive project led by PhD researcher Tayler LaSharr. As part of this work, we put GPS collars on mule deer fawns the day they are born and follow them throughout the remainder of their lives. This project lets us see, among other things, how mule deer establish home ranges. With this information we hope to be able to better understand what leads to robust populations of mule deer and how wildlife managers might bolster populations.

Following deer from the day they are born throughout their lives provides unique opportunities to learn about the nuances of deer behavior. Take Doe 96, for example. Throughout the summer, 96 will meander over a square mile or so of steep foothills covered with mountain mahogany, aspen stands, and mixed pine forests. In June of each year she gives birth midway up a west-facing slope, usually right along the edge of an aspen stand.

From 96 coming back to her summer range year after year, we see just how faithful mule deer are to their seasonal ranges. In addition to this faithfulness, we also think that female offspring tend to set up summer ranges pretty near where they were born, a behavioral propensity known as philopatry. From an evolutionary standpoint, faithfulness and philopatry offer the benefit of familiarity, which can be advantageous in the rugged environments where mule deer live. Either because your mom successfully raised you there or because you lived there before, you know an area works.

We think that these elements of mule deer behavior provide the foundation for how mule deer arrange themselves on a landscape. When a female gives birth, we expect that her daughters will stay pretty close to where they were born. As the matriarch and her daughters give birth and successfully rear offspring over subsequent years, then the home ranges would expand out from the center. Some researchers have likened this pattern to the petals of the rose and have termed this spatial arrangement of closely related females the “rose petal hypothesis.” The original female serves as the center of the rose, her daughters the petals.

The rose petal hypothesis has been tested pretty extensively in whitetail deer since the 1990s. This knowledge has actually been used to help control nuisance populations. In areas where there are too many deer and the number needs to be reduced, one strategic management approach is to remove all of the animals within a rose. Whitetails won’t often seek out new habitat, which means that if there’s no deer left in that family group, that pocket will stay empty longer.

Although the rose petal hypothesis has been studied extensively in whitetail deer, less research has been done on mule deer. We could expect that some of what we learned from whitetails would hold true with muleys, but because the species differ in ecology and habitat it’s worth looking into mule deer in their own right. Also, with mule deer we’re interested in the opposite problem as we are with whitetails: instead of trying to figure out how to control nuisance populations, we usually want to figure out how to grow more mule deer.

Testing whether the rose petal hypothesis holds in mule deer and the potential implications of this behavior is one of the things I’m working on with my graduate work. Right now, our sample size is small because we are studying wild populations, which means we are at the mercy of events such as remarkably harsh winters. And, although what we’re seeing right now is preliminary, we are starting to get a sense of whether the rose petal hypothesis holds true for mule deer.

Thinking back to Deer 96, we do see that daughters tend to set up shop right next to their mothers. One of 96’s surviving daughters, FMO, birthed her first fawn this past summer. FMO gave birth under a half a mile away from where she was born herself. In most of the mother-daughter pairs we’re studying, this tends to be the pattern: daughters develop a home range close to their mom and close to where they were born. This lends support to the rose petal hypothesis.

But the story isn’t so cut and dry. There are some offspring, such as F309, who don’t follow what we would expect from the rose petal hypothesis, instead finding their own patch of summer range. In our sample so far, these rogue deer tend to be less frequent, but they still occur. In all, mule deer look like they’re falling in line with the rose petal hypothesis, for the most part.

In talking about mule deer behavior, we’ve gone a long way from whether your favorite hunting spot might have dried up, so let’s bring it back. Depending on what has happened on a landscape, your favorite hunting hole certainly could have dried up. If enough petals of a rose, or even an entire rose itself, was wiped out for some reason, that pocket won’t have females producing offspring. If there aren’t females around, there aren’t likely to be bucks nearby either.

Given the tendency to display philopatry and faithfulness, deer tend to be satisfied with where they are and don’t frequently go looking to establish new home ranges. To reestablish a family group in a pocket that has been emptied, you need an explorer such as F309. But, because those explorers are relatively rare, getting females into that pocket will probably take a few generations, even if it’s perfectly good deer habitat. Our research is still ongoing but at least so far we are seeing that the arrangement of family members on their summer ranges plays an important part in whether there are deer in a given pocket of a landscape.

Depending on the ecological context of a given area, there is a chance that your favorite hunting spot dried up, especially if something happened that wiped out an entire family group. Bad winters, increased predators, disease, or heavy hunting pressure can, in fact, clear an area of deer for years. Or, maybe you just got skunked.