Annual Dispersal of Young Bucks Strengthens the Genetic Pool
Story and Photos by Tom Fegely
Hunters have long been under the impression that white-tailed deer are relative homebodies, living their lives in a square mile or so of fields and woodlands on or near their birth places.
Not so, suggests an ongoing study of deer travels being monitored by Penn State’s College of Agricultural Science and being watched by deer biologists across the country. Initial investigations show that young deer — yearling bucks in particular — abandon life with mama and head out on exploratory jaunts that might take them far from their home turf. A few stay in their new surroundings for a short time, then turn tail and head back home. Most, however, leave and never return.
The Penn State study includes tracking young bucks by capturing them in baited cages and fitting them with radio-collars. A select few of the 300-plus study subjects were fitted with global positioning system units (GPS). The computerized collar devices enable biologists to check on a buck’s location at any time by logging onto satellite reception. The units were programmed to download the carrier’s location every 2 1/2 hours during a fall study in north-central Pennsylvania. The collars were programmed to release the GPS devices from the deer on Jan. 31, making them available for downloading data and reuse.
Assistant wildlife professor Duane Diefenbach said it’s common knowledge that male deer disperse. The biological purpose of the act is to prevent them from interbreeding with their sisters or mothers, protecting the integrity of the herd’s gene pool. Few detailed studies have been done anywhere on the intriguing behavior of young bucks.
What is known, however, is that most bucks leave their mothers and female siblings as yearlings, usually setting out on their meandering journeys a year after their birth and as their mother’s dropping time nears. Most of the newfound nomads — at their mother’s urging along with a natural instinct to migrate - may travel five to as far as 15 miles in the first 24 hours. In a few cases, bucks have set up shop more than 26 miles from home, researchers have learned.
Although most travels occur during the spring fawning period, some young bucks await the fall rut before moving out, driven by aggressive older and bigger bucks, which become intolerant of 18-month-old bucks harassing their harems of does.
Penn State doctoral candidate Eric Long has also recorded, via GPS devices, some short-duration yet notable round-trip travels. Satellite signals revealed that at least two bucks in the 2003 study took three-mile trips from their natal ranges, and then returned in a mere 24-hour period. One buck did it three times, as if collecting exploratory real estate studies before making a final decision.
“These journeys took place (in spring) at the same time that other yearling bucks were dispersing and not returning,” Long said. “It looks like they set out to find a new home range but didn’t like what they found and came back.”
According to John Ozoga in “Whitetail Autumn” (Willow Creek Press; 1994), “A [sexually active] yearling male may trail a family group during the early autumn but is not readily accepted into the group. Those that fail to disperse as yearlings [may not] do so until they are 2 1/2 years old.”
Although the continuing Penn State study could be the first time specific travel routes and distances have been pinpointed, biologists have long known that some yearling bucks disperse great distances. Female yearlings, however, will stay closer to their mothers, usually overlapping their home ranges. Of course, yearling males set up shop in the same areas from which other young bucks have departed, replacing them while bringing new genetics to the party.
This documented dispersal of white-tailed bucks helps explain why identifiable individuals seen in early spring or prior to the rut might magically disappear days or weeks later as they seek new turf at birthing and rutting times. The fascinating process assures the biological integrity of the herd by adding new genetic patterns to the mix.
This article was published in the July 2006 edition of Buckmasters Whitetail Magazine. Join today to have Buckmasters delivered to your home.