Still other evidence that the quantity of forage, by 

 itself, was not influencing deer population dynamics was 

 provided by examination of interactions between fawn survival, 

 antler size (condition) of yearling males, and numbers /density 

 of deer on the area. Although fawn survival and antler size 

 of yearling males were correlated to estimates of forage 

 production, neither was correlated with the number of deer 

 eating that forage. If deer and their forage supply 

 interacted in a density-dependent manner we should have 

 observed a significant interaction between fawn survival and 

 antler size of yearling males with estimates of forage 

 quantity and deer numbers. Addition of deer numbers to 

 multiple regressions did not add significantly to the observed 

 relationship. 



There also was no evidence that browsing by deer 

 subsequently reduced important browse plant populations or 

 browse forage production. Deer utilization of rubber 

 rabbitbrush, an important autumn-winter forage species, 

 remained near 100% annually throughout the study, regardless 

 of deer population level. Despite this and 2 deer population 

 "peaks and crashes", rabbitbrush plant populations at least 

 remained stable, and may have increased on the study area. 

 Some plant species, perhaps because of their biology and 

 season of use, tolerate browsing far above levels previously 

 considered to be "over browsing" while maintaining 

 productivity (Pellew 1984). 



Similarly, the number and size of fragrant sumac plants 

 was at least stable to increasing on most transects despite 

 heavy use by deer during some years and severe girdling by 

 microtine rodents during other years . The degree of use of 

 current annual growth for fragrant sumac was not directly 

 related to deer numbers. Relatively light use occurred at 

 both low and high deer populations. Relatively heavy use was 

 often but not always associated with drought conditions. The 

 number of snowberry and rose plants declined as forest 

 succession closed the canopy, but these plants increased in 

 some areas following fires. The major shrub species used by 

 deer during winter, big sagebrush and Rocky Mountain juniper, 

 were essentially unlimited in abundance and did not show 

 "classical" signs of heavy use such as "highlining" or 

 "clubbing" . 



Overall, trends in forage plant abundance and production 

 did not appear influenced measurably by deer browsing. Any 

 annual or long-term changes that occurred were influenced more 

 by climatic factors and/or successional changes related to 

 forest maturation and periodic wildfires. 



We also found no relationship between "key" browse plant 

 abundance, production, utilization, and condition trends and 



280 



