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Voles are small that are relatives of and , but with a stouter body; a longer, hairy tail; a slightly rounder head; smaller eyes and ears; and differently formed molars (high-crowned with angular cusps instead of low-crowned with rounded cusps). They are sometimes known as meadow mice or field mice.
Vole species form the subfamily Arvicolinae with the and the . There are approximately 155 different vole species.
Voles outwardly resemble several other small animals. Moles, , mouse, and even have similar characteristics and ethology tendencies.
Voles thrive on small plants yet, like Shrew, they will eat dead animals and, like mice and rats, they can live on almost any nut or fruit. In addition, voles target plants more than most other small animals, making their presence evident. Voles readily girdling small trees and ground cover much like a porcupine. This girdling can easily kill young plants and is not healthy for trees and other shrubs.
Voles often eat succulent root systems and burrow under plants and eat away until the plant is dead. are another favorite target for voles; their excellent burrowing and tunnelling skills give them access to sensitive areas without clear or early warning. The presence of large numbers of voles is often identifiable only after they have destroyed a number of plants. However, like other burrowing rodents, they also play beneficial roles, including dispersing nutrients throughout the upper soil layers.Dickman, Chris R. "Rodent–Ecosystem Relationships: a Review" in Singleton G, Hinds L, Leirs H, Zhang Z. ed. 1999. "Ecologically-based management of rodent pests". ACIAR Monograph No. 59, 494p Retrieved on 2018-03-28
The behavior is influenced by the number of repetitions of a particular string of microsatellite DNA. Male prairie voles with the longest DNA strings spend more time with their mates and pups than male prairie voles with shorter strings. Summarized in However, other scientists have disputed the gene's relationship to monogamy, and cast doubt on whether the human version plays an analogous role. Physiologically, pair-bonding behavior has been shown to be connected to vasopressin, dopamine, and oxytocin levels, with the genetic influence apparently arising via the number of receptors for these substances in the brain; the pair-bonding behavior has also been shown in experiments to be strongly modifiable by administering some of these substances directly.
Voles have a number of unusual chromosomal traits. Species have been found with 17 to 64 chromosomes. In some species, males and females have different chromosome numbers, a trait unusual in mammals, though it is seen in other organisms. Additionally, genetic material typically found on the Y chromosome has been found in both males and females in at least one species. In another species, the X chromosome contains 20% of the genome. All of these variations result in very little physical aberration; most vole species are virtually indistinguishable. In one species, the creeping vole Microtus oregoni, it was discovered the Y chromosome has been lost entirely; the male-determining chromosome is actually a second X that is largely identical to the female X, and both the maternally inherited and male-specific sex chromosomes carry vestiges of the ancestral Y. This is quite unusual in mammals, as the XY system is fairly stable across a number of mammal species.
Male voles are territorial and tend to include territories of several female voles when possible. Under these conditions polygyny exists and males offer little parental care. Males mark and aggressively defend their territories since females prefer males with the most recent marking in a given area.
Voles prefer familiar mates through olfactory sensory exploitation. Monogamous voles prefer males who have yet to mate, while non-monogamous voles do not. Mate preference in voles develops through cohabitation in as little as 24 hours. This drives young male voles to show non-limiting preference toward female siblings. This is not inclusive to females' preference for males which may help to explain the absence of interbreeding indicators.
Although females show little territoriality, under pair bonding conditions they tend to show aggression toward other female voles. This behavior is flexible as some Microtus females share dens during the winter months, perhaps to conserve heat and energy. Populations which are monogamous show relatively minor size differences between genders compared with those using polygamous systems.
The grey-sided vole ( Myodes rufocanus) exhibits male-biased dispersal as a means of avoiding incestuous matings. Among those matings that involve inbreeding, the number of weaned juveniles in litters is significantly fewer than that from noninbred litters, due to inbreeding depression.
Brandt's vole ( Lasiopodomys brandtii) lives in groups that mainly consist of close relatives. However, they show no sign of inbreeding. The mating system of these voles involves a type of polygyny for males and extra-group polyandry for females. This system increases the frequency of mating among distantly related individuals, and is achieved mainly by dispersal during the mating season. Such a strategy is likely an adaptation to avoid the inbreeding depression that would be caused by expression of deleterious recessive alleles if close relatives mated.
This type of empathetic behavior has previously been thought to occur only in animals with advanced cognition, such as humans, apes, and elephants.
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