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Matt asked a great question regarding what triggers the elk rut, so I figured I'd put it in the next blog rather than just the latest comment line...
First, we need to define what we mean by "the rut?" For some, they are referring to the entire period a bull bugles in the fall - from mid-August all the way into, and through, October. For me, however, I define "the rut" as the time period encompassing actual active breeding of cows. While some may say this is a relatively narrow view of "the rut," I believe there is a definite period, defined by very clear behaviors, that separate elk activities into the pre-rut, rut, and post-rut phases.
For breeding of cows, there is one primary trigger - the estrous cycle of cows, dictated by the cycling of hormones in the cow, triggered by the ratio between daylight and darkness (photoperiod). The cycling of the photoperiod each year is relatively constant (i.e. fall equinox being roughly the 23rd each year, +/- a day or two), so the cycling of hormones each year is relatively constant. The full moon definitely plays into the animal's perceived daylight/darkness ratio, but the jury is still out on whether or not the full moon actually affects the TRIGGERING of hormone changes and ultimately active breeding, or whether it just heightens the observed behavior of the animals in question (similar to how the full moon supposedly brings out the craziness in certain people... i.e. why ERs can often see increased activity around the full moon). I'm doing some research/investigating of my own right now on that very question.
Weather definitely affects the observed behavior (i.e. Hot, dry weather can see little to no bugling activity, but bring on the first really cold morning, or the next beautiful morning after bad weather, and bulls can go absolutely nuts!), but make no mistake about it, the ratio of daylight to darkness is the primary factor affecting my definition of "the rut." You can see this by the fact that year in and year out, regardless of the weather and regardless of the full moon cycle, most cow elk show up on the summer ranges with their calves like clock-work pretty much the same time each year, with most calves being relatively the same age – meaning they all conceived their calves within roughly the same time-period each year. How many times over the years have you heard someone say – or you’ve said - “there didn’t seem to be any rut this year...” yet every year, cows give birth to calves. Regardless of whether or not we observer rutting behavior, “rut happens!” :-)
For the "broader" definition of the rut, then all of the above plays a part. Photoperiod again is responsible for the cycling of hormones in bulls, but – for the pre-rut phase – weather, spring/summer moisture, full moon cycles, the ratio of bulls to cows, the presence/absence of other bulls, etc. all conspire to create a certain scenario for how bulls engage one another (early bugling and sparring) and their environment (wallows, rubs, etc.). Some years, like this year it seems – at least in the areas I hunted – pre-rut activity was crankin! We had great summer moisture in most areas of the mountains, we had cool weather early (i.e. Late August), and rubs and wallows were everywhere! In past years, however, you couldn’t buy a bugle if you drove to the store; with hot, dry weather, very little moisture, and other factors resulting in almost no observed pre-rut activity.
For the post-rut phase, it is heavily dependent upon the bull:cow ratio and whether or not the bulk of the cows were bred during their first estrous cycle. If not, then the odor and pheromones of cycling cows can keep testosterone high in bulls, and thus keep “the rut” going well into October – and in some areas, November. If all the available cows in an area are bred during the first estrous cycle, testosterone can diminish relatively quickly as animals move into October, and observed “rut” activity can drop to near zero.
For you whitetail hunters out there, this isn’t too far off for you either. Although the whitetail rut is later in November, nearly all the above is true for those sneaky little suckers as well! For us elk hunters, a lot of people get excited about the middle to later part of September for classic “rutting” behavior, whereas for whitetail hunters, I believe it’s the period encompassing roughly the 9th through the 15th of November. Although the dates are different, the reasons are the same... Photoperiod, photoperiod, photoperiod.
Hope everyone has (or had) a great season! Click below to see what I came up with during CO elk season this year!
Chris Roe
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