Grasshopper
Grasshoppers eat large quantities of foliage both as adults and during their development, and can be serious pests of arid land and prairies. Pasture, grain, forage, vegetable and other crops can be affected. Grasshoppers often bask in the sun, and thrive in warm sunny conditions, so drought stimulates an increase in grasshopper populations. A single season of drought is not normally sufficient to stimulate a major population increase, but several successive dry seasons can do so, especially if the intervening winters are mild so that large numbers of nymphs survive. Although sunny weather stimulates growth, there needs to be an adequate food supply for the increasing grasshopper population. This means that although precipitation is needed to stimulate plant growth, prolonged periods of cloudy weather will slow nymphal development.
Field vole
The field vole is a herbivore and feeds on grasses, herbs, root tubers, moss and other vegetation and gnaws bark during the winter (it does not hibernate). It occasionally eats invertebrates such as insect larvae. Among the plants it favours are the grasses "Agrostis" spp. and "Festuca rubra", the yarrow ("Achillea millefolium"), clover ("Trifolium" spp.), dandelion ("Taraxacum officinale") and buttercups ("Ranunculus" spp.). The voles choose species with high digestibility where possible and avoid some common plants amongst which they live such as the tufted hairgrass ("Deschampsia cespitosa") and rosebay willowherb ("Chamerion angustifolium"). The animals have low energy reserves and these are only able to sustain them for five to fourteen hours. Because of the low availability of food in the winter, drier habitats are unable to sustain populations of much over two hundred animals per hectare. The number of voles expands rapidly with the arrival of spring and the better availability of food supplies.