Male Common Voles Research Articles

Effects of an Anti-Fertility Product on Reproductive Structures of Common Vole Males and Residues of Compounds.

Some rodent species cause significant damage to agriculture and forestry, and some can transmit pathogens to humans and livestock. The common vole (Microtus arvalis) is widespread in Europe, and its population outbreaks have resulted in massive crop loss. Bait-based fertility control could contribute to rodent pest management. Bait containing 4-vinylcyclohexene diepoxide (VCD) and triptolide (TP), registered as ContraPest®, was delivered to male common voles for 14 or 28 consecutive days. The effects on reproductive structures and residues in the liver and testes were assessed. There was no effect on testis weight, sperm viability, sperm motility and oxidative stress in sperm cells. Results regarding the mitochondrial membrane potential of sperm, DNA fragmentation and progressively motile sperm cells were inconclusive. However, there was an increase in morphological sperm defects in voles treated for 14/28 days and fewer normal sperm cells in voles treated for 28 days. There were no TP residues in the testes, few and low TP residues and no VCD residues in liver tissues, making considerable secondary exposure to non-target species unlikely. Treatments with VCD + TP seemed to have minor effects on the reproductive organs of males. Further studies should evaluate the effect of VCD + TP on females and on the reproductive success of common voles and other pest rodent species.

The Influence of Sire Presence on Survival and the Growth Rate of Juvenile Common Voles Microtus arvalis

Pup survival and growth rates were monitored to determine whether paternal care potentially contributes to reproductive success of male common voles Microtus arvalis Pallas, 1779. The subjects were 258 pups from 47 litters obtained from adult voles trapped in the wild. Reproducing pairs were formed and divided onto two groups in accordance with the age and parental experience of the reproducing individuals: group I included pairs with subadult males and nulliparous females; group II included pairs with adult males and multiparous females. Each of the groups was divided into two subgroups: in subgroups Iа (n = 13) and IIа (n= 11), litters were raised by females without sires; in subgroups Ib (n = 12) and IIb (n = 11), litters were raised by both parents. The litter size was recorded at parturition and again when the young were 12, 21, and 30 days old. Pups in each litter were weighed at parturition and also again when the young were 12, 21, and 30 days old. This study has shown that the presence of the sire may negatively affect both survival and growth rates of the pups, but this effect is dependent on the age of the reproducing individuals.

High prevalence of Rickettsia helvetica in wild small mammal populations in Germany

Since the beginning of the 21st century, spotted fever rickettsioses are known as emerging diseases worldwide. Rickettsiae are obligately intracellular bacteria transmitted by arthropod vectors. The ecology of Rickettsia species has not been investigated in detail, but small mammals are considered to play a role as reservoirs.Aim of this study was to monitor rickettsiae in wild small mammals over a period of five years in four federal states of Germany. Initial screening of ear pinna tissues of 3939 animals by Pan-Rick real-time PCR targeting the citrate synthase (gltA) gene revealed 296 rodents of seven species and 19 shrews of two species positive for rickettsial DNA. Outer membrane protein gene (ompB, ompAIV) PCRs based typing resulted in the identification of three species: Rickettsia helvetica (90.9%) was found as the dominantly occurring species in the four investigated federal states, but Rickettsia felis (7.8%) and Rickettsia raoultii (1.3%) were also detected. The prevalence of Rickettsia spp. in rodents of the genus Apodemus was found to be higher (approximately 14%) than in all other rodent and shrew species at all investigated sites. General linear mixed model analyses indicated that heavier (older) individuals of yellow-necked mice and male common voles seem to contain more often rickettsial DNA than younger ones. Furthermore, rodents generally collected in forests in summer and autumn more often carried rickettsial DNA. In conclusion, this study indicated a high prevalence of R. helvetica in small mammal populations and suggests an age-dependent increase of the DNA prevalence in some of the species and in animals originating from forest habitats. The finding of R. helvetica and R. felis DNA in multiple small mammal species may indicate frequent trans-species transmission by feeding of vectors on different species. Further investigations should target the reason for the discrepancy between the high rickettsial DNA prevalence in rodents and the so far almost absence of clinical apparent human infections.

Effect of plant secondary metabolites on feeding behavior of microtine and arvicoline rodent species

Rodents are among the most damaging pests in agriculture worldwide. High-density populations of rodent pests can kill plants or diminish their growth, and reduce both fruit size and the number of seeds. Therefore, rodent pests can lead to considerable crop loss and require management actions to minimize damage. Optimal management of pest rodents is usually based on the combination of methods to reduce damage. Although rodenticides are usually the most commonly deployed approach, they have undesirable side effects. Consequently, more environmentally benign approaches such as repellents or attractants to lure rodents away from fields are gaining traction. The dispersal of a large number of juvenile males at certain times of year has prompted us to focus on male rodents for our experiments. We used laboratory feeding experiments to measure how the odor of plant secondary metabolites (PSMs) affects two pest rodents: common voles (Microtus arvalis, Pallas) and house mice (Mus musculus, L.). We tested eighteen different PSMs or combinations thereof with voles. Four PSMs reduced feeding and seven PSMs increased feeding of male common voles. Five of six tested odors were effective as repellents against house mice. However, we assume a species-specific response to volatile PSMs repellents. This study demonstrated that four repellents reduced feeding in both rodent species. Our results contribute to the development of non-lethal management tools for rodent pest species that are potentially more suitable than traps and rodenticides. This approach could be applicable to a variety of crops if effective at field conditions.

Urine marking in male common voles: Does behavioural activity matter?

Rodent urine provides animals with a large amount of information, from the identity of the animal through its physical condition to social status. Many studies therefore focus on rodent urine-marking behaviour and use marking frequency as an indicator of social status or competitive ability. However, marking, like many other aspects of rodent behaviour, may be affected by individual behavioural activity, a factor that has not been examined so far. We therefore studied a relationship between male urine-marking in reaction to another male's marks (standard opponent) and individual personality profile, characterised by behavioural activity in an open field test (OFT). The marking appeared to be consistent and specific for particular individuals as there was a significant positive relationship between individual markings in two different phases of the experiment. The linkage between behavioural activity in the OFT and urine-marking frequency was non-linear (quadratic), which suggested that males with intermediate activity marked more intensively than males from the extremes of the behavioural spectra. The relationship between the opponent's and the tested males' markings was positive, however, we found no statistically significant evidence that the voles would attempt to overmark the opponent. Marking thus seems to have more of a self-advertising than a competitive function in the common vole. Further, as high marking activity is under strong intra- or intersexual selection, the result might suggest a stabilising selection of the personality trait described as behavioural activity in our study.

Parental care, aggressiveness, and testosterone secretion in male common voles (Microtus arvalis) and steppe lemmings (Lagurus lagurus)

Parental care, aggressiveness, and testosterone secretion in male common voles (Microtus arvalis) and steppe lemmings (Lagurus lagurus)

Flea infestation reduces the life span of the common vole

Parasitism is often a source of variation in host's fitness components. Understanding and estimating its relative importance for fitness components of hosts is fundamental from physiological, ecological and evolutionary perspectives. Host-parasite studies have often reported parasite-induced reduction of host fecundity, whereas the effect of parasitism on host survival has been largely neglected. Here, we experimentally investigated the effect of infestation by rat fleas (Nosopsyllus fasciatus) on the life span of wild-derived male common voles (Microtus arvalis) bred in captivity. We found that the mean life span of parasitized voles was reduced by 36% compared to control voles. Parasitized voles had a smaller body size, but a relatively larger heart and spleen than control voles. These results indicate an effect of flea infestation on host life span and our findings strongly suggest that ectoparasites should be taken into account in the studies of host population dynamics.

Developmental, metabolic and immunological costs of flea infestation in the common vole

Summary 1Parasites use resources from their hosts, which can indirectly affect a number of host functions because of trade-offs in resource allocation. In order to get a comprehensive view of the costs imposed by blood sucking parasites to their hosts, it is important to monitor multiple components of the development and physiology of parasitized hosts over long time periods. 2The effect of infestation by fleas on body mass, body length growth, haematocrit, resistance to oxidative stress, resting metabolic rate and humoral immune response were experimentally evaluated. During a 3-month period, male common voles, Microtus arvalis, were either parasitized by rat fleas (Nosopsyllus fasciatus), which are naturally occurring generalist ectoparasites of voles, or reared without fleas. Then voles were challenged twice by injecting Keyhole Limpet Haemocyanin (KLH) to assess whether the presence of fleas affects the ability of voles to produce antibodies against a novel antigen. During the immune challenge we measured the evolution of body mass, haematocrit, resistance to oxidative stress and antibody production. 3Flea infestation negatively influenced the growth of voles. Moreover, parasitized voles had reduced haematocrit, higher resting metabolic rate and lower production of antibodies against the KLH. Resistance to oxidative stress was not influenced by the presence of fleas. 4During the immune challenge with KLH, body mass decreased in both groups, while the resistance to oxidative stress remained stable. In contrast, the haematocrit decreased only in parasitized voles. 5Our experiment shows that infestation by a haematophageous parasite negatively affects multiple traits like growth, energy consumption and immune response. Fleas may severely reduce the survival probability and reproductive success of their host in natural conditions.

Movement patterns of male common voles (Microtus arvalis) in a network of Y junctions: role of distant visual cues and scent marks

Common voles (Microtus arvalis) use networks of runways around their burrows, which are dug in meadows. Their orientation among such networks could be based on rigid "egocentred" routes (possibly through the use of olfactory "trails") or on more general, "allocentred" spatial representations (with distant visual cues). In this 5-day study, male voles should reach food in the centre of a maze of three-way (Y) junctions offering similar local views but surrounded by distant visual cues. I tested whether the animals navigated using olfactory trails, implying one main direct foraging route, or allocentered representations, allowing flexibility among equivalent routes. Males quickly marked their environment, preferentially at the periphery, where they moved the most. However, during most direct trips between the nest and the food, they used one of the central shortest routes, which included the least scent-marked zones. Moreover, the voles preferred different shortest routes to go to the food and return from it, showing a bias in favour of the side where the distant goal (food or nest) was situated. This suggests that male common voles base their choices on the general direction of their goal rather than on trails. Finally, there was no major difference in initial exploration between a clean and a scent-marked maze.

Movement patterns of male common voles (<i>Microtus arvalis</i>) in a network of Y junctions: role of distant visual cues and scent marks

Common voles (Microtus arvalis) use networks of runways around their burrows, which are dug in meadows. Their orientation among such networks could be based on rigid egocentred routes (possibly t...

Role of female aggression in prevention of infanticidal behavior in male common voles,Microtus arvalis (Pallas, 1779)

Infanticidal behavior of male common voles (Microtus arvalis) was investigated in relation to the age of unfamiliar pups. Sires from 18 pairs were removed after parturition of their offspring and replaced by unfamiliar males at different ages of the neonates. In group 1, containing six females with their offspring, the new male was introduced into the females' cages on day 1 after the parturition. In group 2 the new male was introduced on day 5 after parturition and in group 3 on day 9 after parturition. The male was removed after 3 days and the neonates recounted. Male common voles killed up to 100% of the neonates in litters containing neonates younger than 9 days by rapid bites to the head of the neonates (groups 1 and 2, mortality rates of 0.86 and 0.38). However, with older pups, a mortality rate of 0.06 was observed while 33% of the intruder males showed signs of injuries (group 3). These findings show that infanticidal behavior of male common voles represents one factor of pup mortality. The results are discussed in relation to changes in the degree of maternal aggression and in the context of the social system of the common vole for solving the conflict between postpartum estrous mating and infanticidal behavior of male common voles. Aggr. Behav. 23:293–298, 1997. © 1997 Wiley-Liss, Inc.

Unusual heteromorphic bivalents in the common vole (Microtus arvalis) from Belorussia.

Electron microscopic analysis was carried out on the synaptonemal complexes of 10 male common voles (Microtus arvalis) caught in 1990 in Belorussia. In the early pachytene stage of spermatocytes of four males, a heteromorphic bivalent has been found in one of five large autosomes. In the central region of the bivalent one of the lateral elements is in the form of a D-loop, characteristic of insertion/deletion heterozygotes. However, high-resolution G-band staining of mitotic chromosomes from fibroblasts shows no significant differences in the G-band pattern between homologs.