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.)
---------------------------------------------------------------------------------------------------
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/