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Author Topic: Little known blacktail buck body and antler size "facts"  (Read 3657 times)

Offline fishnfur

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Little known blacktail buck body and antler size "facts"
« on: April 09, 2016, 06:43:38 PM »
Scratch your head on this abstract of a study I came across regarding the body size and antler size of blacktail bucks in CA.  While it doesn't seem to have much relevance to mainland deer populations in most areas of Western WA, and the information is not really "facts" but merely observations, it does likely explain the role that weather and deer population density may have in areas such as the islands found in Puget Sound and the San Juans, and perhaps the Kitsap Peninsula.  The study also clearly demonstrates the positive affects of harvesting does in an overpopulated environment.   The abstract, or discussion of the study and results are below.  (To minimize confusion, the definition of "cohort effects" from the paper:  Cohort effects occur when individuals born within the same year experience similar environmental conditions, which may alter the life-history characteristics of that group.)
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Antler and Body Size in Black-Tailed Deer: An Analysis of Cohort Effects
Johanna C. Thalmann,1 R. Terry Bowyer,1 Ken A. Aho,1 Floyd W. Weckerly,2 and Dale R. McCullough3
1Department of Biological Sciences, Idaho State University, 921 South 8th Avenue, Stop 8007, Pocatello, ID 83209, USA
2Department of Biology, Texas State University, 601 University Drive, San Marcos, TX 78666, USA
3Department of Environmental Science, Policy, & Management, University of California, Berkeley, 130 Mulford Hall No. 3114, Berkeley, CA 94720, USA

Received 5 August 2015; Revised 26 October 2015; Accepted 4 November 2015

Academic Editor: Sveinn Are Hanssen

Copyright © 2015 Johanna C. Thalmann et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

For long-lived species, environmental factors experienced early in life can have lasting effects persisting into adulthood. Large herbivores can be susceptible to cohort-wide declines in fitness as a result of decreases in forage availability, because of extrinsic factors, including extreme climate or high population densities. To examine effects of cohort-specific extrinsic factors on size of adults, we performed a retrospective analysis on harvest data of 450 male black-tailed deer (Odocoileus hemionus columbianus) over 19 years in central California, USA. We determined that population density of females had a more dominant effect than did precipitation on body size of males. Harvest of female deer resulted in increases in the overall size of males, even though a 6-year drought occurred during that treatment period. Body size was most influenced by female population density early in life, while antler size was highly affected by both weather early in life and the year directly before harvest. This study provides insights that improve our understanding of the role of cohort effects in body and antler size by cervids; and, in particular, that reduction in female population density can have a profound effect on the body and antler size of male deer.

For those desiring a bit more suffering, here's a bit more from the work:

Understanding how the interaction between climate and population density influences body mass throughout the lifetime of a large herbivore enables biologists to better predict growth, survival, and reproduction within cohorts [13–17]. Extrinsic and intrinsic factors affect body condition, and when resources are limited, important tradeoffs may be made early in life by an individual, or by a mother before parturition, which affects offspring while in utero [18]. Those tradeoffs result in delayed life-history characteristics that can persist into adulthood and even through future generations [4].

In times of severe weather or high population density, tradeoffs are made by the mother when the fetus is in utero [19]. Decreases in maternal investment during periods of low spring precipitation stunt the growth of fetuses, resulting in young that are born small and remain small throughout their lives [20–26]. Furthermore, much of the variation in adult size of ungulates has been linked to conditions experienced during the year of birth [27] and environmental conditions and nutrition of their grandmothers 2 generations previously [3, 28].

Antler size has been positively correlated with warmer temperatures and higher precipitation in spring and autumn during the year of harvest [29]. Discerning the influence of extrinsic factors the year preceding harvest with those that occurred during youth is critical for understanding phenotypic variation in size of antlers. Determining the degree to which weather and population density during youth and adulthood affect antler and body size of ungulates is still poorly understood, although body and antler size are related to a number of life-history characteristics among cervids [30]............

For a full-body lashing, the entire study is here:  http://www.hindawi.com/journals/ae/2015/156041/
“When I die, I want to die like my grandfather who died peacefully in his sleep. Not screaming like all the passengers in his car.”  - Will Rogers

Offline JimmyHoffa

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Re: Little known blacktail buck body and antler size "facts"
« Reply #1 on: April 09, 2016, 06:48:24 PM »
So global warming will make antlers bigger.....be back, need to go burn a tank of fuel.

Offline fishnfur

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Re: Little known blacktail buck body and antler size "facts"
« Reply #2 on: April 09, 2016, 10:48:55 PM »
 :chuckle: :chuckle: :chuckle:
“When I die, I want to die like my grandfather who died peacefully in his sleep. Not screaming like all the passengers in his car.”  - Will Rogers

Offline JDHasty

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Re: Little known blacktail buck body and antler size "facts"
« Reply #3 on: April 09, 2016, 11:41:09 PM »
I have seen some monsters that had fair to middlin racks.  Especially around Manchester Fuel Depot.  They were old and grey and I think were no longer pursuing breeding dominance.  Perhaps the fact that they had shoddy headgear made it so that they were never in the running in breeding season anyway so they just didn't bother.  IDK, just a theory and that may be why they got so big, without chasing does maybe they were not starving themselves out every year for a month.

Ive seen some monster racks come out of that area.  It never occurred to me to ask how big the bucks that grew them were.  I guess that if you have a pretty good rack, you will tend to tell the audience how massive the buck's body was. On the islands I hunt - really big bucks are sportin' big racks. 

It is uncanny just how big a really big island BT buck is when seen next to mature does, spikes and forkies.  Half again as big or bigger and built like a brick outhouse.  Hey, when you hunt the islands 95% of the property is off limits and you get to see some really tame monster BT bucks just hanging out - waiting for the apples to fall.  Where they are hunted, like where I have access to I know they are there, but are in grey ghost mode.   We get nice ones every year, and every year friends get one or two of these monsters, and they are as big and studly in body as their racks are impressive. 

But then again, around Manchester Fuel Depot, I see big bodied BT bucks come out of there that are pretty common.  I will have to ask how much the ones with nice racks weighed at the butcher. 

I shot a nice island buck that was really grey and old, he had a lot of horn, and I was able to drag him field dressed to the tailgate of the truck, and there was no way, no how, that I could load him without help.  I tried.  We didn't weigh that one, he was butchered at home, but he was solid.  I can normally drag a mediocre three point out and toss him in the truck whole.       
« Last Edit: April 09, 2016, 11:48:35 PM by JDHasty »

Offline fishnfur

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Re: Little known blacktail buck body and antler size "facts"
« Reply #4 on: April 10, 2016, 10:05:24 PM »
- There's plenty of past discussion by many authors that state that poor genetics in regards to number of antler points, tine length and overall mass can't be overcome by good nutrition.  Then again, there are also a couple of studies on penned/domesticated bucks that showed a balanced nutritious diet can produce two-year-old bucks with 4x4 antlers and that weighed something like 50% more than the average two-year-old wild bucks (or something like that - substantially bigger anyways). 

The thing that struck me about the study was the fact that the number of does in a deer population and health of those does was found to have an immediate impact on the future size of bucks born in that and possibly the subsequent year, for the entire lifespan of those bucks.  It makes sense when you consider that an over-browsed area cannot support an unlimited number of does in total health.  The pregnant does bodies steal the nutrition from a developing deer fetus, which when born, will be smaller than normal and forced to survive in the same environment that the maternal doe was doing poorly in.  The issue of rain/weather vs. drought was factored in as well, but non surprisingly, years of rain with normal snow pack (vs. periods of drought) resulted in more food, better nutrition, healthier does and yielded bigger bucks once fully mature.   Nothing mind-shattering in the study, just a plausible explanation for the diminished size of deer in an over-browsed environment, and something to think about while we wait for the upcoming hunting season.  I don't remember any discussion about global warming in the study, but we can always hope that that will somehow help us out as well.

- RE: The big old grey bucks with small headgear - I think it was Scott Haugen's book that suggested that bucks past their prime and well in decline are likely more interested in just surviving the next winter and may not participate in the rut.  They stick tight to their core zones and count the days.  My understanding of the regressive antlers in these deer is that they will loose points over the years but continue to have substantial antler mass.  I would assume that they, like humans, loose some body mass in old age as they become less active, so that doesn't quite fit your observations, (and certainly may be inaccurate) - so it is hard to guess what that situation really was.  Perhaps they do use less reserves by not chasing does and maintain their body mass long into senescence.  My gut tells me though that a huge buck blessed with only small-medium antlers still did some serious breeding during it's prime years.  I think antler size is probably very important in bucks of similar size and age when exerting dominance.  Body size and mass must somehow get factored into that dominance equation as well.  A young small-bodied four-point would likely still turn tail and run from a massive fork horned brute that was courting a doe if the big buck challenged him.
“When I die, I want to die like my grandfather who died peacefully in his sleep. Not screaming like all the passengers in his car.”  - Will Rogers

 


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