What causes different rut timing?

[ghosthunter]

I hear so much about daylight deceasing triggering the rut and the moon and all that, but late rutters ignore that, yet just a few miles away the deer play by the magazine rules. It really seems to me that that the above stated rut triggering factors aren't the actual causes of the rut. Maybe these are more of observed coincidences of timing than fact. I've also heard that environment plays a role, and this seems to make more sense to me than anything else, but I know the terrain 5 miles away in some cases can't be that differnt to cause a 1 to nearly 2 month differnce in the rut timing. Is it possible that where these deer were stocked from play a strong role in rut timing?

 

[Mike Belt]

The genetic dispostion of the timing of the rut can very well and does differ from area to area. I don't buy into the stocking of different deer. The later breeders are either deer that didn't get bred on their first heat and recycle 28 days later or they're those early born doe fawns that are entering estrus for the first time.

 

[BSK]

ghosthunter,

The length of the nights is the basic triggering mechanism, but what length of the nights that triggers estrus will be different from location to location, and this night-length trigger is hereditary (genetic). The different estrus dates in different locations is driven by Natural Selection, with the best time for newborn fawn survival being the driving force; i.e. those breeding dates that produce the highest survival rate of fawns born 200 days later become genetically ingrained into the local population.

The big question is why do specific fawning dates produce higher fawn survival rates, hence influence best breeding dates? In some locations, that question is easy to answer. The seasonal timing of environmental factors that have obvious links to fawn survival drive the local breeding/fawning dates. But in many locations, these surival influences are very subtle, and not easily decipherable. For instance, why is an early June birthing date (mid-November breeding) advantageous near Nashville, but an early to mid-July fawn birthing date (mid-December breeding) more advantageous near Memphis?

 

[woodsman87]

I have read somewhere that in Florida the rut is like in August-October so that the fawns are born and old enough for when all the rain during the summer comes they are big enough to not drown. Correct me if I am wrong, and I don't know what for fact, just saying I read that before.

 

[Bucket]

So if the rut timing trigger is genetic, is it possible that stocked deer cause variations in that timing? I ask that because that's what D&DH (Charlie Alshimer) is pushing these days. In one episode of their show I watched they basically drew a line horizontally through the center of Tennessee and said deer south of that line had "trickle rut" traits because so many were stocked from various other areas.

I did think it was funny that they (D&DH) had a rut discussion without once mentioning moon phase!

 

[BSK]

So if the rut timing trigger is genetic, is it possible that stocked deer cause variations in that timing?

Bucket,

That would make logical biological sense. However, you have to imagine exactly what the rut would look like if it were being driven by restocked genetics. Considering that deer were restocked into TN from areas with vastly different rut timings, and those restocking efforts were fairly hodge-podge all over the state, you would end up with rut timings that mimicked these restocking efforts--a hodge-podge of very different dates scattered all over the state. But we don't see that. We see a fairly smooth transtition in dates, from the earliest in the northcentral part of the state and getting later the farther south and southwest you travel. This strongly suggests a cause for these different dates independent of restocking. In fact, with the exception of AL, all the Deep South states display these smooth trasitions in dates from one region to another, with some locations displaying very unusual dates due to localized conditions (these can be seen most pronounced in coastal regions of the Deep South).

Natural Selection is the driving force in fine-tuning the genetic rut timing of each localized deer population. But again, the question is, why is the particular timing in a given location the most advantageous? Sometimes that is easy to ascertain and sometimes it isn't.

 

[BSK]

I have read somewhere...

Probably right here. I use that example all of the time for how Natural Selection can produce what appear to be freakish peak breeding dates.

Interestingly, where the climate never varies (tropical Central America), whitetailed deer have no peak breeding dates. Deer can be found in virtually every state of the breeding cycle at any time of year. There is no climate-driven advantage for birthing at any time of year, hence nothing for natural Selection to select against, and the result is no favored genetic timing.