Whitetail Biology and Behavior
Understanding the Whitetail Rut
By T.R. Michels, Trinity Mountain Outdoors

After spending time with, and talking to, a number of different whitetail hunters, most of them experienced and some of them quite knowledgeable, I realized many of them did not understand the progression of the rut, or the time frame of the rut. Most of them knew that in the upper Midwest rubbing usually begins in September, scraping in mid-October, and that the "peak of the rut" occurs during the second week of November. But there seemed to be a difference of opinion about what the "peak of the rut" meant. To some it meant the time when they most often saw bucks during the day, usually the two weeks before the breeding phase. Others thought the peak of the rut meant peak breeding activity, which it does. Some thought all the breeding activity occurred during the week of the peak of the rut; they resigned themselves to the belief that once the peak of the rut was over no more breeding would occur. If they did not get a buck by the peak of the rut there was no reason to hunt as hard, because there was less activity.

Rubbing, Scraping and Breeding Peaks
Rubbing, scraping and breeding all have their own time frames (which overlap each other), and their own peaks. We've already established that the peak of the rut refers to the peak of breeding activity. Rut related activity in northern areas usually starts when bucks begin rubbing small trees and brush to remove velvet from their antlers, possibly as early as late August or early September. Rubbing may peak in mid-September and generally diminishes throughout the rut, but it may rise again during later breeding phases. Scraping activity may begin as early as the first week of September, but without much activity until mid to late October. Breeding may begin in mid-October, and the breeding curve begins to rise along with the scraping curve in late October. Scraping peaks in mid to late November as bucks continue to make new scrapes and maintain existing scrapes. As breeding activity increases in early November scraping decreases. Breeding in northern areas may be intermittent from mid to late October; fairly continuous throughout November, with peak breeding occurring sometime between the first and the third week of November; and intermittent from early December into January. But, hold on what was that about breeding beginning in mid-October?

Estrus Cycles
My own observations, those of several other writers and photographers, and the studies of Dr. Larry Marchinton in Georgia show that breeding occurs as early as September 24 in northern Minnesota, October 15 in southern Minnesota, October 17 in Georgia, and October 24 in central Wisconsin. Thanks to Marchinton's studies we can actually pinpoint estrus cycles in captive deer. The study was conducted to find out how many estrus cycles unbred does would experience. During the study recurrent estrus ranged from 2 to 7 times. Of the eight does studied one 2.5 year old came into a first estrus on October 17, another on October 24, three 1.5 year olds on November 11, one 2.5 year old on November 19, one 1.5 year old on November 21, and one 5.5 year old on December 1. The last recurrent estrus occurred on April 7.
This shows that, even without recurrent estrus, some does will be in estrus from mid-October to early December, resulting in a breeding period of more than 45 days. In northern areas the breeding period may last in excess of 60 days; from mid-October to late December. In southern areas it may last more than 90 days; into February. In most areas a small portion of the adult does may be bred in October, most of them in November, and a few more in December. This is typical of most deer populations. In northern areas 1.5 year old does may experience their first estrus in December. Doe fawns (5+ months) may experience their first estrus and breed in December, January or February.

Late Breeding Phase
Because of Marchinton's study we know we cannot reliably predict when the late breeding phase may occur. Even if the majority of the does come into estrus at the same time, the research shows that recurrent estrus cycles are variable. Instead of occurring every 28 days as previously thought the cycles ranged from 21 to 30 days. This would make it difficult to pinpoint the late breeding period, especially when coupled with the knowledge that the first estrus of a doe may occur anytime from mid-October to mid-December. Another note of interest is that the does were in estrus from 24 to 48 hours, not the 22-24 hours previously thought. Any buck chasing a doe may spend up to three days with her without returning to its core area.

Moon Phase
There are several theories that suggest that the phase of the moon affects the estrus cycle of whitetail does in the northern states and Canada. One writer claims that peak breeding will occur from 5-7 days before the first new moon following the second full moon after the fall equinox (on September 22). In 1997 that full moon would have occurred on November 30, which would be a very late breeding period. Another writer, and two researchers working together, claim that peak breeding will occur from 5 to 7 days after the second full moon occurring after the fall equinox. In 1997 that would have been November 19-21. This is still fairly late in the upper Midwest. Obviously these predictions can't both be right.
The truth of the matter is that whitetails in different areas may breed at different times, because the breeding dates for deer in each area are dependent on fawn survival; and fawn survival depends on warm weather and green forage. Since the whitetail gestation period is 180-210 days (mean length 197-202), deer in most areas breed approximately 6 2/3 months before warm weather and spring forage appears, which generally occurs in late May. In northern areas May is when temperatures regularly stay above freezing, which allows plants to begin growing, and does to produce enough milk for the fawns.
The two researchers mentioned above do state that although the moon may have some effect on the rut, when the appropriate moon phase occurs outside of the normal breeding period, the deer will breed at the normal time, but there may be a longer breeding period with a less noticeable peak. I have checked with local deer researchers in Minnesota and they tell me that peak breeding invariably occurs in mid-November, not the third week of November, or the last week of November. Two friends of mine who raise deer tell me their does are bred every year from November 1-20.
There is good evidence to show that the moon phase predictions are not right. Several years ago I received the conception dates for 1,600 does in Minnesota between 1980 and 1987. Peak breeding for all years combined occurred on November 11, and peak yearly breeding did not very by more than a few days from year to year. This shows that most breeding in Minnesota generally occurs from the first to the fourth week of November, and that breeding always peaks during the second week of November.
Incidentally, during the years of the study, the second full moon after the fall equinox occurred from as early as October 21 to as late as November 27, and it occurred most frequently during the second week of November, showing no correlation between peak breeding and the week after the full moon. In 2001 Dr. Karl Miller presented a research paper showing that there was no correlation between moon phases and peak breeding of does in Maine, Michigan, Minnesota, Mississippi, Missouri, South Carolina or Texas.

Priming Pheromones
Researchers believe that rubbing and scraping by bucks, and the pheromones left behind at these signposts, help bring the does into estrus and synchronize the rut between the bucks and does. It has been suggested that the pheromones may bring does into what researchers call a "silent ovulation," during which the doe usually cannot conceive. If the priming pheromones at rubs and scrapes cause the does to come into estrus, then the rut should be more synchronized if there are abundant rubs and scrapes in areas where does will come in contact with them. Rub clusters and scrapes often occur in high use doe areas: along travel routes, near doe core areas, in staging areas near food sources, and at the edges of feeding areas, where does are most likely to come in contact with them. When scraping activity begins in mid-October, the pheromones of the scrape may bring the does into this silent ovulation and they experience a normal "estrus ovulation" 21 to 30 days later, from approximately the beginning of the first week to the third week of November, signaling the peak of the breeding period. This scenario makes more sense to me than the moon phase theories.
I have checked my data and found that scrapes regularly appear at or near food sources from October 15 to 21 in my area. Peak breeding in the area regularly occurs from November 7 through the 14; 21-30 days later. Although there may be a correlation between scrape activity and the moon, I don't think the moon is what causes increased scraping in late-October. I believe it is caused by the fact that there are approximately 11 hours of daylight at that time of the year, which affects the hormone levels and breeding related activities of the deer. If you want to know when peak breeding will occur in your area, find out when scraping becomes frequent in doe feeding areas, then expect breeding to occur 21 to 30 days later, or call your local game manager.

Buck To Doe Ratio
The higher the buck to doe ratio is, the more mature bucks there are, and the choicer the habitat is; the more concentrated the deer are, the more priming pheromones there are available to the does, and the more synchronized the rut should be. In ideal conditions there would be one buck for each one or two does in an area. The does would come into contact with the pheromones, the rut would be synchronized, and there would be abundant breeding related activity. Numerous estrus does would be pursued by one or more bucks, and fights would occur regularly. However, in heavily hunted areas the mature buck to doe ratio may be as low as one mature buck for every 4-10 does. The fewer the mature bucks, the less likely the rut will be synchronized, and the less chance peak breeding will occur during any one phase of the moon.

If you are interested in more whitetail hunting tips, or more whitetail biology and behavior, click on Trinity Mountain Outdoor News and T.R.'s Hunting Tips at www.TRMichels.com. If you have questions about whitetails log on to the T.R.'s Tips message board. To find out when the rut begins, peaks and ends in your area click on Whitetail Rut Dates Chart.

This article is an excerpt from the Whitetail Addict's Manual ($19.95 + $5.00 S&H), by T.R. Michels.

T.R. Michels is a nationally recognized game researcher/wildlife behaviorist, outdoor writer and speaker. He is the author of the Whitetail, Elk, Duck & Goose, and Turkey Addict's Manuals. His latest products are the 2003 Revised Edition of the Whitetail Addict's Manual, the 2003 Revised Edition of the Elk Addict's Manual; and the 2003 Revised Edition of the Duck & Goose Addict's Manual. For a catalog of books and other hunting products contact: T.R. Michels, Trinity Mountain Outdoors, PO Box 284, Wanamingo, MN 55983, USA. Phone: 507-824-3296, E-mail: TRMichels@yahoo.com, Internet Site: www.TRMichels.com

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T.R.'s Tips: Understanding The Rut
Rubbing to remove velvet, and scraping, signal the start of the rut, about early September in the north. Although deer "mouth" licking branches at traditional scrapes all year long, bucks may not work these licking branches with their antlers until the velvet is removed.
Most scent marking activity (rubbing and scraping) occurs at night. When scent marking occurs during the day, more activity occurs in the evening than in the morning.
Nighttime scraping often occurs in semi-open and open areas. Scrapes appearing in wooded sites indicate areas bucks may use during the day.
Rubs and scrapes are small dominance areas within a buck's home range. Scrapes near clusters of rubs may be used to attract does and bring them into estrus.
Bucks may make as many as 300 rubs per year, averaging 2.5 rubs per day over a four-month period. During peak rubbing bucks may make as many as 20 rubs per day.
In areas where there are older dominant bucks, yearling bucks make about half as many rubs as older bucks. When there are few older bucks, younger bucks may rub more. Abundant rubs may indicate several dominants, or few dominants.
Rubbing begins as much as two months before the primary breeding phase, and usually peaks about a month before the peak breeding. The decline in rubbing often coincides with a rise in scraping activity; less rubbing, more scraping.
The first rubs (Type 1 Rubs) to appear are usually on small saplings, often leaving the tree broken but with little bark removal. These rubs decrease early in the rut and are replaced by rubs with minor bark removal (Type 2 Rubs). These (Type 2) rubs are usually replaced by rubs with much of the bark removed (Type 3 Rubs), that are often on large trees.
When buck territories overlap, bucks often stamp, paw the ground, and thrash bushes and small trees with their antlers, leaving torn up areas that indicate places frequented by more than one buck.
Low acorn (possibly other food) production may cause a decrease in rubbing and scraping, because bucks spend more time in search of food. Less scent marking activity during some years may not mean fewer bucks, but less forage.
Scraping often begins as soon as bucks shed their velvet, in northern areas as early as the first week of September. Most of these early scrapes appear at/near open area food sources. They are used primarily at night, and may be infrequently used.
Dominant bucks generally begin scraping earlier than younger bucks, and make most of the scrapes. Scrapes prior to the breeding phase suggest a dominant buck, but not necessarily an older or large antlered buck. Dominance is established by a combination of size, fighting ability, and most importantly testosterone level. A small antlered buck with high testosterone levels may be the dominant. The only reliable way to tell the size of the buck's rack is to see it.
Numerous bucks may visit the same scrape, but, while bucks of all ages mark overhanging branches, they may not all scrape. In one study of captive deer only 3.5 year or older dominants scraped; older non-dominant bucks scraped but did not rub-urinate; bucks in the 1.5-2.5 year range did not scrape at all. However, another study of wild deer suggested that all bucks may scrape and rub-urinate at scrapes. The study did show that the majority of scrapes in the last two weeks of October were made or used by 2.5 year old or older bucks. Therefore, scrapes with urine may indicate an older or dominant buck, particularly if the scrape is used during the two weeks prior to peak breeding. The amount of mutilation of the overhanging branch at a scrape may be a better indicator of the importance and frequency of use, than the size of the scrape.
Scrapes in wooded or otherwise secure areas may be used during daylight hours. Bucks usually begin using these secure area scrapes more frequently as the breeding phase approaches. Some of these secure area scrapes are traditional, andmay be used several years in a row.
Traditional scrapes often occur within doe use areas along travel lanes; in protected staging sites near food sources; and near doe core areas. Traditional scrapes are often visited by more than one buck.
Peak scraping usually signals the beginning of breeding. A small percentage of does are usually bred in October. Peak breeding in northern areas (above the 38th parallel) usually occurs during the second week of November. A late breeding phase of fawns (not 1 year olds as previously thought) may occur about a month after the older does have been bred.

T.R. Michels, Trinity Mountain Outdoors
PO Box 284, Wanamingo, MN 55983
507-824-3296 trmichels@yahoo.com
SS 474-54-8219