Evidence of pregnancy failure in the wild meadow vole, Microtus pennsylvanicus

1977 ◽  
Vol 55 (1) ◽  
pp. 1-17 ◽  
Author(s):  
F. F. Mallory ◽  
F. V. Clulow
Keyword(s):  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Corpora Lutea ◽  
Wild Stock ◽  
Density Dependent ◽  
Pregnancy Failure ◽  
Laboratory Conditions ◽  
In The Wild

Normal and blocked pregnancy were studied in the meadow vole, Microtus pennsylvanicus (Ord), in the laboratory, on individuals bred from wild stock caught near Sudbury, Ontario. The results were then compared with those obtained from wild voles trapped from quadrats during the summers of 1969 and 1970.Criteria were found for distinguishing between individuals in which pregnancy had been blocked and those in which it had not, under laboratory conditions. Nursing females were not found to be susceptible to male-induced blockage and the second set of corpora lutea in the ovaries was not observed to increase the rate of involution of the first set. Females were found to be susceptible to blockage on the 2nd and 5th days after coitus.Some indication of pregnancy failure in the wild was found and the incidence of this phenomonon appears to increase in populations with a higher density. Thus it seems reasonable to hypothesize that pregnancy failure is one of the density-dependent factors that decreases reproduction and ultimately the recruitment of young animals to the population.

Ovaries of meadow voles, Microtus pennsylvanicus, after copulation with a series of males

1974 ◽  
Vol 52 (2) ◽  
pp. 265-267 ◽  
Author(s):  
F. V. Clulow ◽  
F. F. Mallory
Keyword(s):  
Microtus Pennsylvanicus ◽  
Clethrionomys Glareolus ◽  
Vaginal Smear ◽  
Corpora Lutea ◽  
Meadow Voles ◽  
Ovarian Weight ◽  
Pregnancy Failure ◽  
Suggestive Evidence ◽  
Microtus Spp

Female meadow voles, Microtus pennsylvanicus, were paired with a series of four males. Each male, except the first, interrupted the pregnancy caused by the preceding male and initiated a further ovulation and pregnancy. These events were reflected in vaginal-smear patterns. The ovaries of these voles were compared with those obtained from primiparous and multiparous females killed after copulation. No significant differences in ovarian weight were observed among the three groups. The number of corpora lutea per vole varied from 20.0 ± 1.3, in the repeatedly mated group, to 5.6 ± 0.4 and 5.9 ± 0.5, respectively, in the primiparous and multiparous groups. The data are compared with published information on ovaries of wild microtines. High numbers of corpora lutea in the ovaries of wild microtines, such as Microtus spp. and Clethrionomys glareolus. which nave been shown to be induced ovulators, may be taken as suggestive evidence of pregnancy failure in nature.

Similarities between female meadow voles mating during post-partum oestrus and raising two concurrent litters and females raising only one litter

2006 ◽  
Vol 18 (7) ◽  
pp. 751 ◽  
Author(s):  
Javier delBarco-Trillo ◽  
Michael H. Ferkin
Keyword(s):  
Sex Ratio ◽  
Maternal Care ◽  
Post Partum ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Gestation Length ◽  
Meadow Voles ◽  
Litter Weight ◽  
In The Wild ◽  
Males And Females

In many species of small mammals, females undergo post-partum oestrus soon after delivering a litter, becoming pregnant while suckling the previous litter. Females raising two concurrent litters need to allocate many more resources to reproduction than females raising only one litter. Consequently, there may be differences between litters raised concurrently or singly. We investigated this issue in the meadow vole, Microtus pennsylvanicus, a species in which most females in the wild reproduce during post-partum oestrus. Specifically, we tested the hypothesis that the development of pups in two concurrent litters differs from that of pups in a single litter. To test this hypothesis, we measured the following variables for concurrent and singly reared litters: gestation length; litter size; sex ratio; bodyweight of males and females at different ages; total litter weight at weaning; growth rates; and intra-litter variation in body mass. Except for bodyweight of males at 60 days of age, which was higher in the first of the concurrent litters, none of the variables differed among the litters. These results indicate that females are able to adjust to differing loads of maternal care to provide equivalent resources to concurrent litters and singly reared litters.

Winter coexistence of voles in spruce forest: relevance of seasonal changes in aggression

1975 ◽  
Vol 53 (8) ◽  
pp. 1004-1011 ◽  
Author(s):  
Brian N. Turner ◽  
Michael R. Perrin ◽  
Stuart L. Iverson
Keyword(s):  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Breeding Period ◽  
Spruce Forest ◽  
Vole Population ◽  
Reproductive Condition ◽  
Interspecific Aggression ◽  
Meadow Voles ◽  
Nonbreeding Season ◽  
Short Period

Beginning in November 1973, numerous meadow voles (Microtus pennsylvanicus) moved onto a spruce forest grid occupied by red-backed voles (Clethrionomys gapperi). A resident meadow vole population resulted, the two species coexisting until April 1974, when most meadow voles disappeared from the grid during a relatively short period. Interspecific aggression levels, as determined from voles temporarily removed from the populations and tested in paired encounters in a laboratory arena, were low during the winter, but increased when males of both species entered reproductive condition in the spring. Microtus was generally dominant in early breeding period encounters, but this dominance declined concurrently with the meadow voles' disappearance from the forest. It is argued that meadow voles did not leave the forest to breed, or because the snow cover melted, since this species will live and reproduce in forest in the absence of Clethrionomys. The results are interpreted as support for an earlier hypothesis that competitive habitat exclusion varies seasonally with reproduction-related aggression. Thus, these species apparently may coexist in either of their preferred habitats when interspecific aggression is low (the nonbreeding season), but this relationship terminates when interspecific aggression levels increase with the resumption of breeding in the spring.

Effect of Orthene® on an unconfined population of the meadow vole (Microtus pennsylvanicus)

1986 ◽  
Vol 64 (1) ◽  
pp. 243-250 ◽  
Author(s):  
David A. Jett ◽  
James D. Nichols ◽  
James E. Hines
Keyword(s):  
Survival Rate ◽  
Population Size ◽  
Weight Change ◽  
Relative Weight ◽  
Reproductive Activity ◽  
Microtus Pennsylvanicus ◽  
Field Application ◽  
Meadow Vole ◽  
Old Field ◽  
Insecticide Treatment

The possible impact on Microtus pennsylvanicus of ground applications of Orthene® insecticide was investigated in old-field habitats in northern Maryland during 1982 and 1983. The treatment grids in 1982 and 1983 were sprayed at 0.62 and 0.82 kg active ingredient/ha, respectively. A capture–recapture design robust to unequal capture probabilities was utilized to estimate population size, survival, and recruitment. Data on reproductive activity and relative weight change were also collected to investigate the effect of the insecticide treatment. There were no significant differences in population size or recruitment between control and treatment grids which could be directly related to the treatment. Survival rate was significantly lower on the treatment grid than on the control grid after spraying in 1983; however, survival rate was higher on the treatment grid after spraying in 1982. Significantly fewer pregnant adults were found on the treatment grid after spraying in 1982, whereas the proportions of voles lactating or with perforate vaginas or open pubic symphyses were slightly higher or remained unchanged during this period. Relative weight change was not affected by the treatment. Results do not indicate any pattern of inhibitory effects from the insecticide treatment. Field application of Orthene® did not have an adverse effect on this Microtus population.

Iodine-131 in Thyroids of the Meadow Vole (Microtus pennsylvanicus) in the Vicinity of the Three Mile Island Nuclear Generating Plant

1981 ◽  
Vol 41 (2) ◽  
pp. 297-301 ◽  
Author(s):  
William R. Field ◽  
Elizabeth H. Field ◽  
David A. Zegers ◽  
Guy L. Steucek
Keyword(s):  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Iodine 131

scholarly journals PREGNANCY-BLOCK IN THE MEADOW VOLE, MICROTUS PENNSYLVANICUS

Reproduction ◽  
1971 ◽  
Vol 24 (2) ◽  
pp. 275-277 ◽  
Author(s):  
F. V. CLULOW ◽  
P. E. LANGFORD
Keyword(s):  
Microtus Pennsylvanicus ◽  
Meadow Vole

Paleoecological implications of Late Pleistocene and Holocene microtine rodents from the Bluefish Caves, northern Yukon Territory

1989 ◽  
Vol 26 (1) ◽  
pp. 149-156 ◽  
Author(s):  
Richard E. Morlan
Keyword(s):  
Late Pleistocene ◽  
Growing Season ◽  
Microtus Pennsylvanicus ◽  
Yukon Territory ◽  
Meadow Vole ◽  
Tooth Size ◽  
Microtine Rodents ◽  
Clethrionomys Rutilus ◽  
Tundra Vole ◽  
Dicrostonyx Torquatus

Bluefish Caves 1, 2, and 3 have produced tens of thousands of vertebrate remains among which at least nine species of microtine rodents are represented: red-backed vole, Clethrionomys rutilus; collared lemming, Dicrostonyx torquatus; brown lemming, Lemmus sibiricus; singing vole, Microtus miurus; tundra vole, Microtus oeconomus; meadow vole, Microtus pennsylvanicus; yellow-cheeked or taiga vole, Microtus xanthognathus; muskrat, Ondatra zibethicus; and northern bog lemming, Synaptomys borealis. Late Pleistocene and Holocene components are clearly distinguishable from one another in each of the three caves, and each component can be subdivided within cave 1. This paper discusses (i) variations in taxonomic abundance through time and between site areas, (ii) contrasts in microhabitat between north-facing cave 1 and south-facing cave 2, and (iii) decreases in tooth size that may reflect a reduction in the length of the growing season. A general decrease in diversity is shown to involve increased dominance and decreased species richness and evenness. These changes are attributed to postglacial zonation of habitat.

scholarly journals On Realistically Attacking Tor with Website Fingerprinting

2016 ◽  
Vol 2016 (4) ◽  
pp. 21-36 ◽  
Author(s):  
Tao Wang ◽  
Ian Goldberg
Keyword(s):  
Background Noise ◽  
Laboratory Tests ◽  
Training Data ◽  
Web Traffic ◽  
Training Set ◽  
Data Set ◽  
Laboratory Conditions ◽  
Testing Data ◽  
In The Wild ◽  
New Algorithms

Abstract Website fingerprinting allows a local, passive observer monitoring a web-browsing client’s encrypted channel to determine her web activity. Previous attacks have shown that website fingerprinting could be a threat to anonymity networks such as Tor under laboratory conditions. However, there are significant differences between laboratory conditions and realistic conditions. First, in laboratory tests we collect the training data set together with the testing data set, so the training data set is fresh, but an attacker may not be able to maintain a fresh data set. Second, laboratory packet sequences correspond to a single page each, but for realistic packet sequences the split between pages is not obvious. Third, packet sequences may include background noise from other types of web traffic. These differences adversely affect website fingerprinting under realistic conditions. In this paper, we tackle these three problems to bridge the gap between laboratory and realistic conditions for website fingerprinting. We show that we can maintain a fresh training set with minimal resources. We demonstrate several classification-based techniques that allow us to split full packet sequences effectively into sequences corresponding to a single page each. We describe several new algorithms for tackling background noise. With our techniques, we are able to build the first website fingerprinting system that can operate directly on packet sequences collected in the wild.

scholarly journals Population Genomic Analyses of Wild and Farmed Striped Catfish Pangasianodon Hypophthalmus in the Lower Mekong River

2020 ◽  
Vol 8 (6) ◽  
pp. 471
Author(s):  
Nguyen Thanh Vu ◽  
Tran Thi Thuy Ha ◽  
Vo Thi Bich Thuy ◽  
Vu Thi Trang ◽  
Nguyen Hong Nguyen
Keyword(s):  
Genetic Diversity ◽  
Mekong River ◽  
Effective Population ◽  
Wild Stock ◽  
Pangasianodon Hypophthalmus ◽  
Population Genomic ◽  
Diversity Assessment ◽  
Genomic Analyses ◽  
In The Wild ◽  
Striped Catfish

The striped catfish Pangasianodon hypophthalmus is an important freshwater fish cultured in many countries where the collection of wild brooders is still widely practiced. Global farming development of this species makes use of significant natural resources that pose challenges for the genetic diversity of striped catfish. Hence, this study aims to conduct a systematic genetic diversity assessment of wild and farmed catfish stocks collected from four major pangasius-farming countries, using a new genotyping by sequencing platform known as DArT-seq technology. Our population genomic analyses using 7263 single-nucleotide polymorphisms (SNPs) after high-quality-control showed that there were two distinct populations of striped catfish in the lower Mekong river: (i) wild catfish from Thailand and (ii) catfish from Cambodia and Vietnam. The genetic diversity was greatest (0.363) in the wild stock from Thailand, but it was lower in farmed and wild stocks in other countries (0.049 to 0.088). The wild stocks were more genetically diverse than the farmed animals (0.103 vs. 0.064). The inbreeding coefficient ranged from 0.004 and 0.109, with the lowest value (−0.499) in the wild animals from Thailand. Molecular inference methods revealed high degree of historical effective population size (1043.9–1258.4), but there was considerable decline in the contemporary estimates in all populations (10.8 to 73.6). Our additional analyses calculating divergent times and migration patterns showed that the wild catfish from Thailand stand out as separate lineages, while those from Cambodia and Vietnam are genetically identical. Our results also indicated that the cultured stock in Bangladesh originated from the lower part of the Mekong river. These findings have significant practical implications in the context of genetic selection and conservation of striped catfish in the region. Collectively, they will contribute to the sustainable development of the striped catfish sector in these countries.

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