A comparison of time-specific and cohort-specific life tables for Belding's ground squirrels, Spermophilus beldingi

1986 ◽  
Vol 64 (3) ◽  
pp. 602-605 ◽  
Author(s):  
Richard M. Zammuto ◽  
Paul W. Sherman
Keyword(s):  
Life Table ◽  
Survival Data ◽  
Life Tables ◽  
Ground Squirrels ◽  
Age Classes ◽  
Free Living ◽  
Female Population ◽  
Spermophilus Beldingi ◽  
Time Specific ◽  
Combined Data

Eight years of age-specific survival data and 6 years of fecundity data from a free-living population of Belding's ground squirrels (Spermophilus beldingi) at Tioga Pass, California, were used to test the hypothesis that time-specific life tables, based on data from individual years, were different from the cohort-specific life table, based on the combined data from all years. The results indicated that neither the age structure of the male nor the female population significantly differed among years (all P > 0.05). Furthermore, the means and the variances in the sizes of weaned litters did not differ among years either in the population at large or within individual age-classes (all P > 0.05). A 27-day snowstorm that occurred in the spring of 1977 increased mortality and reduced reproduction, but it did not change the ground squirrels' age-specific survival or fecundity patterns. Taken together, our analyses revealed that each time-specific life table provided age-specific survival and fecundity estimates that were statistically indistinguishable (P > 0.05) from the composite, cohort-specific life table for each sex, regardless of severe environmental conditions. This is the first demonstration of the equivalence of time- and cohort-specific life tables for a free-living population of mammals.

Seasonal effects of food provisioning on body fat, insulin, and corticosterone in free-living juvenile Belding's ground squirrels (Spermophilus beldingi)

2002 ◽  
Vol 80 (2) ◽  
pp. 366-371 ◽  
Author(s):  
Scott Nunes ◽  
Eva-Maria Muecke ◽  
Kay E Holekamp
Keyword(s):  
Body Fat ◽  
Plasma Insulin ◽  
Plasma Concentrations ◽  
Plasma Corticosterone ◽  
Ground Squirrels ◽  
Seasonal Effects ◽  
Free Living ◽  
Active Season ◽  
Extra Food ◽  
Spermophilus Beldingi

We evaluated the relationship between body fat and the metabolic hormones insulin and corticosterone in free-living juvenile Belding's ground squirrels (Spermophilus beldingi). Some free-living juveniles were provisioned with extra food high in fat and calories, and unprovisioned juveniles were used as controls. Body fat (as a percentage of body mass) of squirrels was regularly evaluated using non-invasive methods. Blood samples were also regularly collected from juveniles and assayed for plasma concentrations of insulin and corticosterone. Provisioned juveniles were fatter than unprovisioned juveniles during most of the active season, but differences in body fat disappeared near the end of summer as juveniles began fattening for hibernation. Thus, our data indicate that although body fat may fluctuate with energy availability early in the active season, it is regulated at precise levels as squirrels prepare for winter. Plasma corticosterone concentrations did not differ between provisioned and unprovisioned juveniles. However, plasma insulin concentrations were greater in provisioned than in unprovisioned juveniles early in the summer. Differences in insulin concentrations disappeared later in the active season, just prior to the disappearance of differences in body fat. Moreover, plasma insulin concentrations were significantly correlated with subsequent changes in body fat. Thus, our data suggest a link between insulin and seasonal regulation of body fat in juvenile S. beldingi.

Time-Specific and Cohort Life Tables for Belding's Ground Squirrels

Ecology ◽  
1993 ◽  
Vol 74 (7) ◽  
pp. 2168-2169
Author(s):  
Paul W. Sherman ◽  
Richard M. Zammuto
Keyword(s):  
Life Tables ◽  
Ground Squirrels ◽  
Time Specific

Estimating Housing Mortality with Standard Loss Curves

1986 ◽  
Vol 18 (11) ◽  
pp. 1521-1530 ◽  
Author(s):  
M E Gleeson
Keyword(s):  
Survival Data ◽  
Statistical Models ◽  
Life Tables ◽  
Time To Failure ◽  
Truncated Data ◽  
Mobile Homes ◽  
Analytical Work ◽  
Tests Of Fit

Tests of fit using one set of data on mobile homes and another on conventional housing indicate that standard loss curves, such as the Pearl-Reed and Weibull curves, can be used to approximate housing survivorship functions. This finding opens up the possibility of analytical work using standard curves and the application of time-to-failure statistical models that are based on such curves. Tests of fit of standard curves to the two housing survivorship functions using truncated data are also encouraging, suggesting means of estimating housing mortality and computing life tables with incomplete cohort survival data.

Scottish Life Tables, 1921

1925 ◽  
Vol 10 ◽  
pp. 1-38
Author(s):  
James Craufurd Dunlop
Keyword(s):  
Life Tables ◽  
Male Population ◽  
Female Population ◽  
General Table

I Have the honour to submit to the Faculty six Life Tables based on the population of Scotland as ascertained at the Census of 1921 and on the deaths registered during the years 1920 to 1922. Of the six Tables three deal with the male population and three with the female population, the three of each sex consisting of a general Table, a Table applicable to the married, and one applicable to the unmarried. The widowed population and deaths of widowers and of widows are included with those of the married.

Weight in relation to sex, age, and season in Columbian ground squirrels (Sciuridae: Rodentia)

1981 ◽  
Vol 59 (6) ◽  
pp. 999-1004 ◽  
Author(s):  
D. A. Boag ◽  
J. O. Murie
Keyword(s):  
Weight Gain ◽  
Ground Squirrels ◽  
Full Potential ◽  
Age Classes ◽  
Adult Weight ◽  
Spermophilus Columbianus ◽  
Large Colony ◽  
Potential Weight ◽  
Columbian Ground Squirrels

Annual weight gain in Columbian ground squirrels (Spermophilus columbianus) was studied over a period of 7 years in a large colony in southwestern Alberta. Juveniles approximately tripled their weight during the period from emergence to immergence, achieving about 60% of adult weight at onset of their first hibernation. Males were heavier than females and the weight gain in both sexes varied significantly among years. The weight characteristics of the age-classes up to 3 years were different from one another. Full potential weight was not achieved until squirrels were in their fourth summer. Males were always significantly heavier than females in nonjuvenile squirrels and the amount of weight gained by these classes varied significantly among years.

Body fat influences sexual maturation in captive male Belding's ground squirrels

1988 ◽  
Vol 66 (7) ◽  
pp. 1620-1625 ◽  
Author(s):  
Warren G. Holmes
Keyword(s):  
Body Fat ◽  
Sexual Maturation ◽  
Serum Testosterone ◽  
Ground Squirrels ◽  
Constant Darkness ◽  
Physiological Indicators ◽  
Abundant Food ◽  
Cold Room ◽  
Fat Stores ◽  
Spermophilus Beldingi

The influence of white adipose tissue on sexual maturation was investigated in captive-born male Belding's ground squirrels (Spermophilus beldingi). Juveniles were given abundant food during the summer and by fall achieved prehibernation body masses approximating those of sexually mature males. Immediately before being placed in a cold room (5–8 °C, constant darkness) for a 7-month hibernation period, fat was surgically removed (lipectomy) or left intact (sham lipectomy). The following spring, paired testes mass, serum testosterone, and spermatogenesis were monitored, mating tests were conducted, and body fat levels were determined. All three physiological indicators of reproductive status were significantly higher in sham-lipectomized than in lipectomized males, only sham-lipectomized males inseminated females, and body fat levels were significantly higher in sham-lipectomized than in lipectomized males. Thus, sexual maturation was accelerated in male Belding's ground squirrels by providing juveniles abundant food so they achieved body masses typical of adults; body fat was essential for accelerated development. In nature, males may forego reproductive development until they can acquire adequate fat stores to survive hibernation and activate their reproductive system and until they gain social experience important in male–male competition for mates.

scholarly journals Data granularity in mid-year life table construction

2020 ◽  
Author(s):  
Jose M Pavia ◽  
Natalia Salazar ◽  
Josep Lledo
Keyword(s):  
Big Data ◽  
Life Table ◽  
Death Rate ◽  
Life Tables ◽  
Population Estimates ◽  
Substantial Influence ◽  
Pension Systems ◽  
Insurance Policies ◽  
Statistical Agencies ◽  
Data Granularity

Life tables have a substantial influence on both public pension systems andlife insurance policies. National statistical agencies construct life tables fromhypotheses death rate estimates to the (mx aggregated ), or death figures probabilities of demographic (q x ), after applying events (deaths, variousmigrations and births). The use of big data has become extensive acrossmany disciplines, including population statistics. We take advantage of thisfact to create new (more unrestricted) mortality estimators within the familyof period-based estimators, in particular, when the exposed-to-riskpopulation is computed through mid-year population estimates. We useactual data of the Spanish population to explore, by exploiting the detailedmicrodata of births, deaths and migrations (in total, more than 186 milliondemographic events), the effects that different assumptions have oncalculating death probabilities. We also analyse their impact on a sample ofinsurance product. Our results reveal the need to include granular data,including the exact birthdate of each person, when computing period mid-year life tables.

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