scholarly journals The spring decline in the meadow vole, Microtus pennsylvanicus: the effect of density

1984 ◽  
Vol 62 (8) ◽  
pp. 1464-1473 ◽  
Author(s):  
F. Helen Rodd ◽  
Rudy Boonstra
Keyword(s):  
Survival Rates ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Breeding Period ◽  
Home Ranges ◽  
Adult Males ◽  
Long Distance ◽  
Mature Adults ◽  
Female Survival ◽  
Reproductive Rates

The densities of six Microtus pennsylvanicus populations were reduced by removing large, sexually mature adults 6 months prior to (fall removal manipulation) and just prior to (spring removal manipulation) anticipated spring declines. When the spring decline on the control grid was a result of short distance dispersal, the manipulations had no effect; when it was a result of in situ mortality and (or) long distance dispersal, the fall removal manipulation produced a significant improvement in the survival rates of adult males. Adult female survival rates were high and unaffected by the manipulations. Adult reproductive rates were high and similar on all grids. The onset of the females' breeding season was advanced by the manipulations in two trials. Home range sizes were similar for all animals during the nonbreeding period. During the breeding period, males and females on the experimental grids had larger home ranges than those on the control grids.

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.

Population size, survival and reproductive rates of northern Norwegian killer whales (Orcinus orca) in 1986–2003

2013 ◽  
Vol 94 (6) ◽  
pp. 1277-1291 ◽  
Author(s):  
Sanna Kuningas ◽  
Tiu Similä ◽  
Philip S. Hammond
Keyword(s):  
Population Size ◽  
Killer Whale ◽  
Survival Rates ◽  
Clupea Harengus ◽  
Orcinus Orca ◽  
Adult Males ◽  
Killer Whales ◽  
Apparent Survival ◽  
Photo Identification ◽  
Reproductive Rates

A long-term photo-identification study of killer whales (Orcinus orca) in northern Norway was initiated in 1986, when their prey the Norwegian spring-spawning herring (Clupea harengus) started to winter in a complex fjord system. The aim of this work was to estimate population size and apparent survival rates in this killer whale population using photo-identification and mark–recapture techniques with data collected during October–December 1986–2003. Total population size was estimated to be highest in 2003: 731 individuals (SE = 139, 95% CI = 505–1059) using a model taking heterogeneity of capture probabilities into account. Apparent survival of adult males and adult females was estimated using the Cormack–Jolly–Seber model as 0.971 (SE = 0.008) and 0.977 (SE = 0.009), respectively. Calving intervals ranged from 3 to 14 years (mean = 5.06, SE = 0.722). These are the first estimates of northern Norwegian killer whale population parameters, allowing their dynamics to be investigated and comparisons to be made with killer whale populations globally.

scholarly journals Demography of Microtus pennsylvanicus in Southern Ontario: enumeration versus Jolly–Seber estimation compared

1985 ◽  
Vol 63 (5) ◽  
pp. 1174-1180 ◽  
Author(s):  
Rudy Boonstra
Keyword(s):  
Population Size ◽  
Breeding Season ◽  
Survival Rates ◽  
Microtus Pennsylvanicus ◽  
Meadow Vole ◽  
Vole Population ◽  
Maternal Condition ◽  
Southern Ontario ◽  
Almost All

A meadow vole population near Toronto went through a cycle in numbers from July 1978 to May 1982. The population never reached a density less than 96 voles/ha or greater than 630 voles/ha. Jolly–Seber estimates differed from total enumeration counts by an average of 10.6% in population size and by less than 0.03 per 2 weeks in survival rates for almost all periods. Sharp spring declines occurred in both sexes in both the increase and the peak years, but only among females in the decline year. Dispersal occurred more frequently during the spring of the increase and peak than of the decline, was associated with maturation, and was biased towards males. The breeding season lasted 9 months in the increase and decline but only 5 months in the peak. Survival of adults during the decline summer was no different from that in other years. Survival of young during the increase and peak was moderately high, but was extremely poor during the decline. Since most young failed to be captured in either pitfalls or live-traps, I conclude that they died shortly before or after weaning and suggest that maternal condition was impaired by prior events in the peak and that this may apply to other cyclic microtine populations.

scholarly journals Management implications derived from long term re-sight data: annual survival of the Maui Parrotbill Pseudonestor xanthophrys

2013 ◽  
Vol 24 (3) ◽  
pp. 316-326 ◽  
Author(s):  
HANNA L. MOUNCE ◽  
KELLY J. IKNAYAN ◽  
DAVID L. LEONARD ◽  
KIRSTY J. SWINNERTON ◽  
JIM J. GROOMBRIDGE
Keyword(s):  
Management Strategies ◽  
Survival Rates ◽  
Adult Survival ◽  
Accurate Estimation ◽  
Limited Information ◽  
Adult Males ◽  
Apparent Survival ◽  
As Species ◽  
Female Survival ◽  
Species Specific

SummaryThe accurate estimation of key demographic parameters is invaluable for making decisions about the management of endangered wildlife but such estimates are often difficult to obtain. Parameters such as species-specific apparent survival rates are an important component in understanding population ecology and informing management decisions. The Maui Parrotbill Pseudonestor xanthophrys is a ‘Critically Endangered’ Hawaiian honeycreeper endemic to the Island of Maui. We used an 18-year encounter history dataset comprising 146 marked individuals to estimate apparent survival between sexes and age classes (juvenile, adult). A difference in survival rates between sexes was strongly supported; 0.72 ± 0.04 for adult females and 0.82 ± 0.03 for adult males. This difference may be a reflection of either reproductive costs or additional risks of incubation and brooding, such as depredation. We also found support for age-biased survival, but limited information for juveniles did not provide a well-supported model fit for our data (juvenile survival = 0.17 ± 0.15; adults = 0.78 ± 0.02). However, apparent adult survival was similar to that of other Hawaiian passerines (mean 0.78 ± 0.03, n = 16). These results suggest that efforts to prevent the extinction of this species may benefit from future management strategies focused on increasing female survival such as predator reduction.

Demographic characteristics of an unexploited population of fox squirrels (Sciurus niger)

1986 ◽  
Vol 64 (2) ◽  
pp. 512-521 ◽  
Author(s):  
Charles M. Nixon ◽  
Lonnie P. Hansen ◽  
Stephen P. Havera
Keyword(s):  
Population Change ◽  
Survival Rates ◽  
Breeding Period ◽  
Adult Males ◽  
Sciurus Niger ◽  
Recruitment Success ◽  
Adult Females ◽  
Fox Squirrels ◽  
Young Of The Year ◽  
Central Illinois

Demographic changes in an unexploited population of fox squirrels (Sciurus niger) were studied between 1971 and 1978 on 45.2 ha of upland forest in east-central Illinois. Known numbers of squirrels varied between 69 and 142. Adult squirrels (>15 months old) comprised >50% of the known population during the study, with annual survival exceeding 60%. Young-of-the-year made up <20% of the livetrapped population. Increasing populations were characterized by increases (P < 0.05) in numbers of yearling–adult males and young-of-the-year of both sexes. Recruitment depended on both immigration and on production of young by resident females. Recruitment success (proportion of new squirrels resident at least 6 months after initial capture) of immigrants was best for adults and yearlings and poorest for subadults. Adult female breeding success was highest in the winter and correlated negatively with the number of females conceiving the previous breeding period. The size and composition of the seed crop of trees in autumn had no effect (P > 0.05) on recruitment, conception, survival rates, or changes in overall density when at least some winter-storable tree seed was available. In most years, adult females were dispersed evenly, but adult males and young of both sexes showed an aggregated or random dispersion. Breeding rates for yearling females, recruitment success of immigrants and of juveniles born on the study area, and overall changes in squirrel densities between trapping periods correlated negatively (P < 0.05) with the number of adult females but not with the number of males or younger females. Interpretation of dispersion of adult females and the relationship of numbers of adult females to population change suggest that fox squirrels stabilize their numbers in the absence of obvious environmental stresses through aggressive interactions between adult females and resident young and immigrants of all ages.

Life history characteristics and movements of the woodland jumping mouse, Napaeozapus insignis, in Nova Scotia

1988 ◽  
Vol 66 (8) ◽  
pp. 1752-1762 ◽  
Author(s):  
Kristiina Ovaska ◽  
Thomas B. Herman
Keyword(s):  
Life History ◽  
Nova Scotia ◽  
Survival Rates ◽  
Home Ranges ◽  
Adult Males ◽  
Active Season ◽  
The North ◽  
Adult Females ◽  
Napaeozapus Insignis ◽  
Overwintering Survival

We examined abundance, reproduction, movements, and adult–juvenile interactions of Napaeozapus insignis in a 5-year mark–recapture study in Nova Scotia. Densities of N. insignis varied greatly between years, mainly as a result of variation in overwintering survival of juveniles and breeding success of females. Year-to-year survival rates of adults were relatively constant (approximately 26%), whereas those of juveniles fluctuated widely. Adult females produced only one litter per season, and no juvenile reproduced in the summer of her birth. Length of the active season was 12–17 weeks, and timing of emergence from hibernation varied little from year to year. Males emerged from hibernation 15–33 days earlier than females, and their captures were clustered along portions of the transects adjacent to steep slopes, which may have provided well-drained hibernation sites. The overall sex ratio did not differ from 1:1, but in May it was biased towards males, and in July and August adult females outnumbered adult males. Distances moved by adult males and females within 24 h were similar (mean for males = 97 m, for females = 61 m), but home ranges of males between June and August were greater than those of females (mean distance between two farthest captures for males = 447 m, for females = 175 m). Results from a removal experiment, as well as examination of trapping records, indicated that adult females inhibited early capture of juveniles when densities of adults were high. We suggest that the suite of life history traits (long life-span, late maturity, infrequent reproduction) that northern zapodids exhibit relative to southern zapodids is best explained by a bet-hedging hypothesis. Long winters and short summers in the north contribute to low and unpredictable overwintering survival of juveniles. By directing energy from reproduction into accumulation of hibernation fat, adults increase their chances of surviving to breed again the next summer and thus decrease the probability of leaving no young at all.

scholarly journals Factors Influencing the Post-Release Movements of Translocated Fishers: Implications for Translocation Success

2021 ◽  
Author(s):  
Jeffrey Lewis ◽  
Patricia J. Happe ◽  
Kurt J. Jenkins ◽  
David J. Manson
Keyword(s):  
Home Range ◽  
Release Site ◽  
Home Ranges ◽  
Adult Males ◽  
Long Distance ◽  
Pekania Pennanti ◽  
Key Factor ◽  
Process Factors ◽  
High Level ◽  
Juvenile Males

Long distance, post-release movements of translocated wildlife can be a key factor limiting translocation success.  Yet, for many species, we have little or no understanding of factors that influence post-release movements.  Translocations have been important for recovering fisher Pekania pennanti populations across the southern portion of their North American range.  However, little is known about the post-release movements of translocated fishers and how these movements may be influenced by demographic or translocation-process factors.  To restore fishers in Washington State, we moved 90 fishers from central British Columbia and released them at nine sites in the Olympic Fisher Recovery Area on the Olympic Peninsula of Washington from 2008 to 2010. We evaluated post-release movements of 48 fishers to determine both the distance and duration of movements prior to home range establishment.  Fishers moved extensively following their release.  Multi-model selection indicated a high level of support for the hypothesis that post-release movements differed by fisher sex and age; whereas, year of release had no apparent effect on movements, and release date had only a marginal influence on male movements.  Mean distance (± 95% CI) from a release site to a home range was greater for adult males (62.0 ± 19.6 km) than for juvenile males (31.4 ± 16.0 km), adult females (30.9 ± 21.1 km), and juvenile females (29.0 ± 13.5 km).  Mean number of days from release until home range establishment was similar for the sexes, however the variance in movement duration was greater for females.  Twenty-six of 27 females established home ranges over an 11-month period (December-October), while 19 of 21 males did so within a 4-month period (April-July).  Mean home range sizes differed between males (128.3 ± 21.1 km2) and females (63.5 ± 9.0 km2) and were among the largest reported for the species.  A greater proportion of females (18 of 27; 67%) than males (8 of 21; 38%) established home ranges within or partially within the recovery area.  Six females left a previously established home range during the breeding season, presumably to find breeding males.  Given the large distances that fishers can move following release, translocation success could be furthered by releasing individuals at fewer sites in the interior of large reintroduction areas to facilitate greater exposure to a recovery area and greater opportunity to interact with conspecifics and potential mates.

Spacing, movements, and habitat selection of the river otter in boreal Alberta

1994 ◽  
Vol 72 (7) ◽  
pp. 1314-1324 ◽  
Author(s):  
D. G. Reid ◽  
T. E. Code ◽  
A. C. H. Reid ◽  
S. M. Herrero
Keyword(s):  
Lontra Canadensis ◽  
Home Ranges ◽  
Adult Males ◽  
Movement Rates ◽  
River Otters ◽  
Aquatic Mammal ◽  
Adult Females ◽  
Two Factors ◽  
Bog Lakes ◽  
Selection Of

Seasonal spacing patterns, home ranges, and movements of river otters (Lontra canadensis) were studied in boreal Alberta by means of radiotelemetry. Adult males occupied significantly larger annual home ranges than adult females. Males' ranges overlapped those of females and also each other's. In winter, home ranges of males shrank and showed less overlap. Otters often associated in groups, the core members typically being adult females with young, or adult males. Otters tended to be more solitary in winter. In winter, movement rates of all sex and age classes were similar, and much reduced for males compared with those in other seasons. These data indicated a strong limiting effect of winter ice on behaviour and dispersion. We tested the hypothesis that otters select water bodies in winter on the basis of the suitability of shoreline substrate and morphology for dens with access both to air and to water under ice. Intensity of selection was greatest in winter, with avoidance of gradually sloping shorelines of sand or gravel. Adults selected bog lakes with banked shores containing semi-aquatic mammal burrows, and lakes with beaver lodges. Subadults selected beaver-impounded streams. Apart from human harvest, winter habitats and food availability in such habitats are likely the two factors most strongly limiting otter density in boreal Alberta.

Dispersal patterns in a regional koala population in south-east Queensland

2003 ◽  
Vol 30 (3) ◽  
pp. 281 ◽  
Author(s):  
David S. Dique ◽  
Jim Thompson ◽  
Harriet J. Preece ◽  
Deidré L. de Villiers ◽  
Frank N. Carrick
Keyword(s):  
Urban Areas ◽  
Home Ranges ◽  
Adult Males ◽  
Dispersal Patterns ◽  
Young Males ◽  
Straight Line ◽  
The Social ◽  
Straight Line Distance ◽  
Males And Females ◽  
Natal Home

Koala dispersal was investigated as part of a detailed ecological study of a nationally significant koala population located 20 km south-east of Brisbane, Queensland. From 1996 to 2000, 195 koalas from three sites were captured and fitted with radio-collars. A total of 40 koalas (23 males and 17 females) dispersed from these sites. Most (93%) dispersing individuals were 20–36 months of age. Three adult females (more than 36 months old) dispersed and no adult males dispersed during the study. A significantly higher proportion of young males dispersed than females. Dispersal occurred between June and December, with most dispersal of males commencing in July and August and that of females commencing between September and November prior to, and early in, the annual breeding season. The mean straight-line distance between the natal and breeding home ranges for males and females was similar and was measured at 3.5 km (range 1.1–9.7 km) and 3.4 km (range 0.3–10.6 km) respectively. Dispersing males and females tended to successfully disperse south and west of their natal home ranges and were generally unable to successfully disperse to urban areas within the study area, as a high proportion of the mortality of dispersing koalas was associated with attacks by domestic dogs and with collisions with vehicles on roads. Information from other studies indicates that most young koalas disperse from their natal areas. It is likely that the social behaviour and mating systems of koala populations provide mechanisms for young koalas to disperse. The potential role of dispersal in the dynamics of regional koala populations is discussed.

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.

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