A possible solution for this problem could be to establish/use general links between certain biological traits and contact and transmission patterns . The shape of the transmission–density function is determined by a combination of infection and host characteristics, so based on these characteristics, it should theoretically be possible to a priori predict the shape of the function, at least roughly. Knowledge of density-dependent changes in home range size and overlap could, for example, be a useful proxy for the contact–density function. For male brushtail possums (Trichosurus vulpecula), it has been established that contacts increase with density according to a positive power function , which fits with the fact that this species is not territorial, and with the observation that home ranges are larger at low densities which may result in the maintenance of contacts. Such an inverse correlation between home range size and density was also observed for M. natalensis , and this may have similar results on contact rates at low densities, as the maintenance of contacts even at very low densities was also observed for this species . This pattern would be expected to be different for territorial species. In an enclosure experiment, movements of meadow voles (Microtus pennsylvanicus), which are strongly territorial, decrease significantly with density , and although the effect of density on contacts was not measured, it is not unlikely that this decrease in movement distance corresponds with a contact–density function that does not increase, or at least not linearly. As a final example, consider the experimental study of the transmission of the parasitic mite Coccipolipus hippodamiae in populations of the two-spot ladybird (Adalia bipunctata) . The mite is transmitted sexually, and although sexual contacts are typically assumed to be frequency-dependent, the authors observed that the transmission–density function was closer to linear density-dependence and therefore concluded that the common assumption that sexual transmission is frequency-dependent is not always true. Their study species (A. bipunctata), however, is known to be highly promiscuous, which means that sexual contacts are not limited to one or a few mates, but instead increase with density. A priori use of this knowledge about host and infection biology would have resulted in the more accurate prediction that sexual transmission of C. hippodamiae is density- rather than frequency-dependent.