Deer Dispersal: Bucks VS. Does

by Ralph Scherder

A strange phenomenon is happening in the deer woods right now, but 90% of hunters don’t even know what’s going down. Over the three-month period of May thru July, many landowners and whitetail managers will have lost roughly 13% of their female deer herd. No, not to predation. These deer are looking for the proverbial greener pastures.

In a sport where bucks get all the glory, the whitetail doe often gets overlooked. With no impressive headgear to set them apart from the crowd, they all tend to look similar. Unless they have unusual coloration or markings on their hide, or some other distinctive trait, it’s almost impossible to tell one from another if they’re the same age and size. This, perhaps, is their greatest asset, and allows them to slip off unnoticed and never come back.

doe standing deer dispersal

Where will she go? And will there be others to take her place?

Dispersal among female deer is not a new revelation. The first known study of female dispersal was done in Illinois in 1970. In recent years, the availability and affordability of radio collars have resulted in more extensive research, but many of them often discover similar patterns. Come summer, a percentage of the female population will have relocated – anywhere from 4-49% (with an average of 13%) depending on habitat and population density.

Males disperse for two reasons – to minimize inbreeding and establish new areas where there’s less competition during the rut. Females, however, have their own agenda. The goal of most relocating females is to find solitude while giving birth and raising their fawns. A 1982 study by John Ozoga found that when a female population in an area is too high it effects maternal behavior as well as makes them more susceptible to predators (Journal of Wildlife Management). In other words, instinct tells these females to isolate themselves from the rest of the herd in order to achieve maximum fawn survival. An added benefit to isolation is a stronger mother/fawn bonding experience, which is also proven to increase offspring fitness.

For that reason, most of the females that disperse tend to be from an older age bracket. Whereas males typically disperse as yearlings, females often do it a year later, about the same time their first fawns are due. There have also been cases where mothers relocated with their fawns later in the summer. In fact, a 1992 Minnesota study found that one mother and fawn didn’t finish relocating until first week of August. How females disperse is just as intriguing as why, though. Studies have shown that when males decide to move, they do it quickly, often walking in a straight line until they reach a suitable destination, an average of one to five miles from their place of birth. Not so with females, which do plenty of window shopping along the way.

deer dispersal fawns on trail camera

Doe dispersal tends to be directly related to their effort to isolate themselves for raising fawns.

Researchers at Penn State University have been tracking whitetails since 2005. According to their Deer-Forest Blog, between 2005 and 2011, they radio-collared 277 eight-month-old females and found that the average dispersal distance was 11.2 miles “as the crow flies” from their origin of birth. However, those females actually traveled almost 32 miles in order to end up 11 miles away.

Also interesting to note is that, in the PSU study, females took an average of 14.5 days to relocate. The longest took 55 days! By comparison, males relocate in an average of just a couple of days.

The time and duration of dispersal can have a negative effect on the mortality of dispersing females. With so many roads crisscrossing the countryside, the farther a whitetail ventures into unfamiliar territory, the more likely it will be to end up in the wrong place at the wrong time. Because of that, dispersing females have a mortality rate of about 7%, compared to males which is less than 1%. It stands to reason that, although many areas will be losing approximately 13% of their female whitetail population this summer, they’ll also be gaining an equal amount that will infiltrate from outlying areas. These newcomers should be welcomed and their presence not taken for granted. After all, who knows how far they had to travel to get there.

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