Prey animals must attempt to optimize foraging success while reducing the probability of being captured. Within social prey groups, intrinsic differences in bold-shy personality among individuals influence their respective risk-taking tendencies. We examined the foraging and refuge use behaviour of mixed groups of goldfish (Carassius auratus) containing half bold individuals and half shy individuals under variable levels of predation risk from a live avian predator (Egretta garzetta). At the group level, the fish groups significantly decreased their foraging time by spending more time under the refuge when the predator spent more time at the focal pool. As expected, the bold fish tended to be the first to leave the refuge, and foraged outside the refuge more often than shy fish under control conditions and at lower risk levels. However, the behavioural differences between bold and shy fish disappeared under higher risk conditions. In terms of mortality, the predator captured significantly more bold fish than shy fish. Our study illustrates how bold individuals in social groups often take greater risks to achieve foraging success, but demonstrates that innate differences in boldness can be diminished in times of elevated predation risk.

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Although jojoba (Simmondsia chinensis) has been cultivated for years, information on its N re-quirements is limited. A 6-year study of mature jojoba plants grown under field conditions with an intensive management regime evaluated the effect of N-application rate on plant nutrient status, growth and productivity, and nitrate accumulation in the soil. Five levels of N application were tested: 50, 150, 250, 370 and 500 kg N ha-1. The fertilizers were provided all along the growing season via subsurface drip irrigation system. Leaf N concentration, in both spring and summer, reflected the level of N applied. Diagnostic leaf (youngest leaf that has reached full size) concentration of 1.3% N was identified as the threshold for N deficiency. Increasing rates of N application resulted in higher P levels in young leaves. Plant K status, as reflected by leaf analysis, was not affected by N treatment but was strongly affected by fruit load. Vegetative growth was inhibited when only 50 kg N ha-1 was applied. Soil analysis at the end of the fertilization season showed substantial accumulation of nitrate for the two highest application rates. Considering productivity, N costs, and environmental risk, 150 kg N ha-1 is the recommended dosage for in-tensively grown jojoba. N deficiencies can be identified using leaf analysis and excess N can be detected by soil sampling toward the end of the growing season. These results and tools will fa-cilitate precise N fertilization in intensive jojoba plantations.