Tannin animal adaptation

LUa ZA, Mohammed N, Kanda S et al (2003) Effect of a-cyclodextrin allyl isothiocyanate on ruminal microbial methane production in vitro. Anim Sd J 74 321-326 Macheboeuf D, Morgavi DP, Papon Y et al (2008) Dose-response effects of essential oils on in vitro fermentation activity of the rumen microbial population. Anim Feed Sci Technol 145 335-350 Makkar HPS (2003) Effects and fate of tannins in ruminant animals, adaptation to tannins, and strategies to overcome detrimental effects of feeding tannin-rich feeds. Small Rumin Res 49 241-256... 

Tannin levels vary within an acorn. They are more concentrated in the apical (pointed) portion with the embryo. Accordingly, gray squirrels, and also grackles and jays, selectively consume more often the basal part of an acorn than the distal part (Steele et al. 1993). The embryo will still germinate after being left over by a squirrel. The chemical gradient in the acorn may represent an adaptation that results in a compromise animals consume only the part of the acom that contains the least tannin, but the better protected seedling and parts around it will still survive the predation. 

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