Because Microtus californicus is a small rodent, it makes for an easy target of many predators. They play a key role in the food web which is known as being a keystone prey species. This is because their populations are generally high in density and they reproduce rapidly (ADW 2002). Large mammalian predators have been found to greatly reduce populations of M. californicus by 88% in a given cycle of reproduction (Cudworth and Koprowski 2010). One explanation as to why mammalian predators like feral cats and coyotes are such successful predators when compared to avian predators like hawks and owls is the amount of vegetative cover that shields M. californicus. It was also found that though this species is heavily predated, mammalian and avian predators do not play a role in the major decline in vole numbers between breeding seasons (Baker and Brooks 1982). Some major predators include:
·         American Kestrel
·         Harrier Hawk
·         White-Tailed Kites
·         Red-Tailed Hawk
·         Barn Owl
·         Great Horned Owl
·         Long-Tailed Weasel
·         Coyotes
·         Grey Fox
·         Multiple species of snakes
·         Herons
·         Egrets
·         Feral Cats
Not only is M. californicus prey to much larger animals, but is also greatly known to be a carrier to many transmittable diseases, endoparasites, and ectoparasites (Cudworth and Koprowski 2010, ADW 2002). These include:
·         Sin Nombre Hantavirus
·         Isla Vista Virus
·         Plague
·         Granulocytic anaplasmosis
·         Tularemia
·         Lyme Disease
·         Pneumocustis carnii (pulmonary fungal parasite)
·         Chrysosporium (lung parasite)
·         Hepatozoon (protozoan)
·         Lice
·         Fleas
·         Ticks
·         Mites
                With regards to humans, M. californicus is widely known to be a pest in gardens,  agricultural fields, vineyards and orchards affecting the growth of vegetation and damaging the land, bark and roots of plants (Cudwork and Koprowski 2010). The most severe damage to pastures and croplands occurs when populations of M. californicus is at very high densities. However, M. californicus tends to avoid already heavily grazed grasslands and mowed fields (Batzli and Pitelka 1970). Typical plants that these voles consume and damage include artichokes, beets, carrots, potatoes, lilies and dichondra. They also damage the bark of many fruit trees by gnawing at the base of the trunk either just above or below the ground (Salmon and Gorenzel 2012).

Next, read some Fun Facts about the California Meadow Vole.