1. A system for estimating the volume, mass or weight of an individual animal comprising: a representation of an individual animal, generated from an image-capturing machine and comprising a plurality of spatially distributed points, stored on a computer readable medium; a virtual spatial model of a reference object comprising a plurality of spatially distributed points; and a computer particularly programmed with the capability of reshaping the virtual spatial model, the representation of the individual animal, or both, into an approximate fit with each other and with the capability of matching individual points in the representation of the individual animal with individual points in the virtual spatial model; and a camera for capturing the representation of a visible or spatial characteristic of the individual animal, such that the camera and the computer are included in a hand-held unit, wherein the computer is particularly programmed to estimate the mass, weight, or volume of the individual animal as a function of an amount that the virtual spatial model, the representation of the individual animal, or both, were reshaped.