Figure 3. — Squirrels severed 

 this ponderosa pine shoot 

 to harvest the mature 

 cones. The small aonelet 

 that would mature the 

 next year, and the ovulate 

 buds that would mature in 

 2 years (not shown here), 

 are destroyed by such 

 cutting. 



First Year of Cone Development 



Red squirrels were the only animals affecting the cones during the first year of 

 cone development. These annual losses ranged from to 8 percent, averaging less than 

 2 percent for the four cone crops. Because of the immaturity of the cones in the first 

 year, it is unlikely the squirrels were specifically seeking them in their food forays. 

 Rather, the cutting of immature cones was more likely due to their being located nearer 

 the tip of the shoot beyond mature cones of the current season (Squillace 1953) . In 

 most cases, squirrels severed the entire cone-bearing shoots just below the current 

 mature cone; thus, immature cones and ovulate buds were accidentally destroyed. Such 

 indiscriminate cutting by the squirrels can adversely affect 3 years of cone production 

 represented by the ovulate bud, immature cone, and mature cone (fig. 3). Squirrels also 

 sever the ends of pine branches in the winter to feed on the cambium and, in the process 

 destroy some of the partially developed cones (Adams 1955). 



Second Year of Cone Development 



Of the cones that survived the first year of development, only about one- fourth 

 survived the second year (fig. 4). Squirrels were responsible for most of the cone 



Figure 4. — Factors affecting the 

 survival of ponderosa pine cones 

 during their second year of 

 development. 



SECOND-YEAR DEVELOPMENT 



6 



