Comparing survey and multiple recruitment–mortality models to assess growth rates and population projections

Estimation of population trends and demographic parameters is important to our understanding of fundamental ecology and species management, yet these data are often difficult to obtain without the use of data from population surveys or marking animals. The northeastern Minnesota moose (Alces alces Linnaeus, 1758) population declined 58% during 2006–2017, yet aerial surveys indicated stability during 2012–2017. In response to the decline, the Minnesota Department of Natural Resources (MNDNR) initiated studies of adult and calf survival to better understand cause‐specific mortality, calf recruitment, and factors influencing the population trajectory. We estimated population growth rate (λ) using adult survival and calf recruitment data from demographic studies and the recruitment–mortality (R‐M) Equation and compared these estimates to those calculated using data from aerial surveys. We then projected population dynamics 50 years using each resulting λ and used a stochastic model to project population dynamics 30 years using data from the MNDNR's studies. Calculations of λ derived from 2012 to 2017 survey data, and the R‐M Equation indicated growth (1.02 ± 0.16 [SE] and 1.01 ± 0.04, respectively). However, the stochastic model indicated a decline in the population over 30 years (λ = 0.91 ± 0.004; 2014–2044). The R‐M Equation has utility for estimating λ, and the supporting information from demographic collaring studies also helps to better address management questions. Furthermore, estimates of λ calculated using collaring data were more certain and reflective of current conditions. Long‐term monitoring using collars would better inform population performance predictions and demographic responses to environmental variability.     

Calculation of longevity and life expectancy in captive elephants

The concepts of longevity (longest lived) and life expectancy (typical age at death) are common demographic parameters that provide insight into a population. Defined as the longest lived individual, longevity is easily calculated but is not representative, as only one individual will live to this extreme. Longevity records for North American Asian elephants (Elephas maximus) and African elephants (Loxodonta africana) have not yet been set, as the oldest individuals (77 and 53 years, respectively) are still alive. One Asian elephant lived to 86 years in the Taipei Zoo. This is comparable to the maximum (though not typical) longevity estimated in wild populations. Calculation of life expectancy, however, must use statistics that are appropriate for the data available, the distribution of the data, and the species' biology. Using a simple arithmetic mean to describe the non‐normally distributed age at death for elephant populations underestimates life expectancy. Use of life‐table analysis to estimate median survivorship or survival analysis to estimate average survivorship are more appropriate for the species' biology and the data available, and provide more accurate estimates. Using a life‐table, the median life expectancy for female Asian elephants (Lx=0.50) is 35.9 years in North America and 41.9 years in Europe. Survival analysis estimates of average life expectancy for Asian elephants are 47.6 years in Europe and 44.8 years in North America. Survival analysis estimates for African elephants are less robust due to less data. Currently the African elephant average life expectancy estimate in North America is 33.0 years, but this is likely to increase with more data, as it has over the past 10 years. Zoo Biol 23:365–373, 2004. © 2004 Wiley‐Liss, Inc.     

Spatial distribution of young forests and carbon fluxes within recent disturbances in Russia

Forest stand age plays a major role in regulating carbon fluxes in boreal and temperate ecosystems. Young boreal forests represent a relatively small but persistent source of carbon to the atmosphere over 30 years after disturbance, while temperate forests switch from a substantial source over the first 10 years to a notable sink until they reach maturity. Russian forests are the largest contiguous forest belt in the world that accounts for 17% of the global forest cover; however, despite its critical role in controlling global carbon cycle, little is known about spatial patterns of young forest distribution across Russia as a whole, particularly before the year 2000. Here, we present a map of young (0–27 years of age) forests, where 12‐ to 27‐year‐old forests were modeled from the single‐date 500 m satellite record and augmented with the 0‐ to 11‐year‐old forest map aggregated from the 30 m resolution contemporary record between 2001 and 2012. The map captures the distribution of forests with the overall accuracy exceeding 85% within three largest bioclimatic vegetation zones (northern, middle, and southern taiga), although mapping accuracy for disturbed classes was generally low (the highest of 31% for user's and producer's accuracy for the 12–27 age class and the maximum of 74% for user's and 32% for producer's accuracy for the 0–11 age class). The results show that 75.5 ± 17.6 Mha (roughly 9%) of Russian forests were younger than 30 years of age at the end of 2012. The majority of these 47 ± 4.7 Mha (62%) were distributed across the middle taiga bioclimatic zone. Based on the published estimates of net ecosystem production (NEP) and the produced map of young forests, this study estimates that young Russian forests represent a total sink of carbon at the rate of 1.26 Tg C yr^?1.     

Acid‐insoluble ash as a measure of dry matter digestibility in captive African elephants (Loxodonta africana)

There are limited data on the diet dry matter digestibility (DMD) of captive African elephants. Although the total fecal collection method is the standard for determining DMD, it is labor‐intensive, time‐consuming, and expensive. The acid‐insoluble ash (AIA) marker technique has been used successfully to determine DMD in ruminants and monogastrics. The objective of this study was to assess how accurately the AIA marker technique could estimate the DMD of captive African elephants (Loxodonta africana). Three mature male African elephants at Disney's Animal Kingdom in Florida were used in this study. The animals were offered a Bermuda grass hay‐based ration, and the total dry matter intake (DMI) and total fecal output were measured daily over a 7‐day period to determine the total collection DMD. The feed ingredients and fecal samples were also analyzed for AIA. Although there were differences (P<0.05) in total DMI and total fecal outputs, the DMD values did not (P>0.05) differ (35.1±0.72 vs. 37.1±0.72 for total collection and AIA, respectively). There was a linear (y=0.9461x; R²=0.74) relationship between the total collection and AIA marker technique DMD values. These results suggest that AIA can be used to accurately estimate the DMD of captive African elephants. Zoo Biol 0:1–5, 2005. © 2005 Wiley‐Liss, Inc.     

Fine‐scale group structure and demography of African savanna elephants recolonizing lands outside protected areas

Aim Dispersal is a critical component of animal ecology that is poorly understood for most species. In particular, savanna elephants (Loxodonta africana) have been studied for decades in national parks across Africa, but little is known about their dispersal into new or unused habitats or their population dynamics in human‐dominated landscapes. We capitalized on a natural dispersal event of savanna elephants recolonizing communal land in southern Kenya to document their demographic characteristics and genetic relationships. Location Rift Valley province of Kenya. Methods We collected faecal samples and used genetic methods to identify individuals, estimate the sex ratio and evaluate the patterns of relatedness within the female groups and male aggregations. We also measured dung bolus circumference to assign age classes to individuals and estimate the age structure. Results We identified 112 individuals with a sex ratio not different from one (1.32:1.00). The age structure was skewed towards younger elephants (71%), suggesting the potential for rapid growth from reproduction. We detected significantly higher kinship levels within female groups (R = 0.124 ± 0.023), suggesting that family groups colonized the site, but found little support for higher‐order genetic relationships among female groups. Males detected together were unrelated (R = 0.003 ± 0.030). Main conclusions Our results suggest that highly social mammals, such as savanna elephants, disperse into unoccupied habitat as family groups and that a young demographic structure and a large number of males might be expected in establishing populations. These findings highlight the potential value of indirect, non‐invasive methods for assessing elephant herd and demographic characteristics when direct observations are difficult.     

Long‐term Successful Weight Loss Improves Vascular Endothelial Function in Severely Obese Individuals

Obesity is associated with increased cardiovascular risk. Although short‐term weight loss improves vascular endothelial function, longer term outcomes have not been widely investigated. We examined brachial artery endothelium‐dependent vasodilation and metabolic parameters in 29 severely obese subjects who lost ≥10% body weight (age 45 ± 13 years; BMI 48 ± 9 kg/m²) at baseline and after 12 months of dietary and/or surgical intervention. We compared these parameters to 14 obese individuals (age 49 ± 11 years; BMI 39 ± 7 kg/m²) who failed to lose weight. For the entire group, mean brachial artery flow‐mediated dilation (FMD) was impaired at 6.7 ± 4.1%. Following sustained weight loss, FMD increased significantly from 6.8 ± 4.2 to 10.0 ± 4.7%, but remained blunted in patients without weight decline from 6.5 ± 4.0 to 5.7 ± 4.1%, P = 0.013 by ANOVA. Endothelium‐independent, nitroglycerin‐mediated dilation (NMD) was unaltered. BMI fell by 13 ± 7 kg/m² following successful weight intervention and was associated with reduced total and low‐density lipoprotein cholesterol, glucose, hemoglobin A_1c, and high‐sensitivity C‐reactive protein (CRP). Vascular improvement correlated most strongly with glucose levels (r = ?0.51, P = 0.002) and was independent of weight change. In this cohort of severely obese subjects, sustained weight loss at 1 year improved vascular function and metabolic parameters. The findings suggest that reversal of endothelial dysfunction and restoration of arterial homeostasis could potentially reduce cardiovascular risk. The results also demonstrate that metabolic changes in association with weight loss are stronger determinants of vascular phenotype than degree of weight reduction.     

Changes in Body Weight and Waist Circumference Affect Incident Hypercholesterolemia During 7 Years of Follow‐up

Objective: To assess whether changes in total and regional adiposity affect the odds for becoming hypercholesterolemic. Methods and Procedures: Changes in BMI and waist circumference were compared to self‐reported physician‐diagnosed hypercholesterolemia in 24,397 men and 10,023 women followed prospectively in the National Runners' Health Study. Results: Incident hypercholesterolemia were reported by 3,054 men and 519 women during (mean ± s.d.) 7.8 ± 1.8 and 7.5 ± 2.0 years of follow‐up, respectively. Despite being active, men's BMI increased by 1.15 ± 1.71 kg/m² and women's BMI increased by 0.96 ± 1.89 kg/m². The odds for developing hypercholesterolemia increased significantly in association with gains in BMI and waist circumferences in both sexes. A gain in BMI ≥2.4 kg/m² significantly (P < 0.0001) increased the odds for hypercholesterolemia by 94% in men and 129% in women compared to those whose BMI declined (40 and 76%, respectively, adjusted for average of the baseline and follow‐up BMI, P < 0.0001). A gain of ≥6 cm in waist circumference increased men's odds for hypercholesterolemia by 74% (P < 0.0001) and women's odds by 70% (P < 0.0001) relative to those whose circumference declined (odds increased 40% at P < 0.0001 and 49% at P < 0.01, respectively adjusted for average circumference). BMI and waist circumference at the end of follow‐up were significantly associated (P < 0.0001) with the log odds for hypercholesterolemia in both men (e.g., coefficient ± s.e.: 0.115 ± 0.011 per kg/m²) and women (e.g., 0.119 ± 0.019 per kg/m²) when adjusted for baseline values, whereas baseline BMI and circumferences were unrelated to the log odds when adjusted for follow‐up values. Discussion: These observations are consistent with the hypothesis that weight gain acutely increases the risk for hypercholesterolemia.     

Strategies to estimate national forest carbon stocks from inventory data: the 1990 New Zealand baseline

An estimate of live tree carbon stored in New Zealand forests at 1990 was made to partially satisfy New Zealand's international obligations under the Framework Convention for Climate Change. A national database was compiled of 4956 forest inventory plots measured as recently as possible to 1990. Plot biomass estimates were obtained by applying species allometric relationships derived from harvested stands. Forest areas and classes were taken from a 1987 national map of vegetation cover. Regularly spaced grids, based on an initial 1 km × 1 km grid, were overlaid on the total forest area and plots were tested for bias against site characteristics at the grid points. As grid point density and sample size increased, bias was minimal in regional sampling intensity and in total annual precipitation. Differences in mean elevation and annual temperature remained stable as grid point density increased, and showed little correlation with stem biomass. This sampling method gave a measure of precision not available from previous estimates. An efficient sample size to estimate the mean within a 5% level of precision (at 95% probability) required a sample of 574 plots selected from a 4‐km grid. This strategy generated a mean estimate for the 1990 New Zealand forest carbon biomass of 179.3 ± 4.9 Mg ha^?1 (± SE), totalling 919.1 ± 25.1 Mt for the 5.1 million ha mapped forest area. The mean was 6–10% lower than previous estimates, and was within the range reported for other countries. Within forest classes, mean carbon biomass ranged from 105 Mg ha^?1 in pure podocarp forest to 215 Mg ha^?1 in mixed lowland podocarp–broadleaved–beech forest. Of the major taxa groups throughout the forest estate, beech (Nothofagus) contributed 60% of the national forest carbon biomass reservoir, 26.7% was in other hardwoods, 13.2% in conifers, and 0.1% in other taxa (e.g. tree ferns).     

African elephant age determination from teeth: validation from known individuals

We assess tooth‐based age criteria for African elephants developed by Laws in relation to known‐aged individuals in the Amboseli elephant population. Laws’s technique remains a robust and useful mechanism for age determination, although we suggest revisions to the oldest age categories. Blind age assignment to jaws of unknown sex using the Laws criteria resulted in misclassification of M4 and M5; measures overlapped too much to differentiate these teeth by sex. Sexes could be reliably distinguished after age 30 or XIX in tooth category by two measures: mandible thickness and width of the ascending ramus, but individuals of the same known age differed in tooth wear and progression rates. Such variation needs to be incorporated in the error assigned to tooth age categories. Ages at death of found jaws (n = 266) were similar to results of survival analysis from all demographic data (n = 2455), excluding calves whose jaws decompose because of weathering and scavengers. Jaw‐based models of age at death need correction for the inability to detect this early mortality, which artificially extends mean longevity by up to 6 years.     

普洱市亚洲象栖息地适宜度评价

亚洲象(Elephas maximus)属于我国Ⅰ级保护动物,在中国仅分布于云南省西双版纳国家级自然保护区、普洱市的思茅区、澜沧县和江城县,以及临沧南滚河国家级自然保护区。将普洱全境作为研究区域,利用野外调查数据,结合遥感与地理信息系统技术,运用生态位因子分析(ENFA)模型对普洱市亚洲象的栖息地适宜度进行了评价,并预测了适宜栖息地的分布。发现:普洱市亚洲象栖息地的边际值为0.991,表明亚洲象在普洱市境内对环境变量的选择不是随机的;耐受值为0.315,表明亚洲象在普洱市境内生态位较窄,受环境条件的制约。根据模型计算得到的栖息地适宜度指数,将普洱市的亚洲象栖息地分为最适栖息地,较适栖息地,边际栖息地和非栖息地4个等级,面积分别为409.32、574.32、2909.48、38722.32 km2。最适栖息地仅占全市面积的0.96%,而非栖息地占90.86%。利用GIS和Biomapper 4.0生成亚洲象栖息地分布图,发现普洱境内最适栖息地和较适栖息地面积狭小。对最适栖息地、较适栖息地和边际栖息地进行景观格局分析的结果表明,3种类型的栖息地破碎化均十分严重,连通度较低,栖息地内受到较大程度的人类活动的干扰。因此建议在普洱和西双版纳间尽快建立野生动物生态廊道,以加强亚洲象各种群间的交流。     

Effects of Sibutramine Plus Orlistat in Obese Women Following 1 Year of Treatment by Sibutramine Alone: A Placebo‐Controlled Trial

Objective: This study assessed whether adding orlistat to sibutramine would induce further weight loss in patients who previously had lost weight while taking sibutramine alone. Research Methods and Procedures: Patients were 34 women with a mean age of 44.1 ± 10.4 years, weight of 89.4 ± 13.8 kg, and body mass index (BMI) of 33.9 ± 4.9 kg/m² who had lost an average of 11.6 ± 9.2% of initial weight during the prior 1 year of treatment by sibutramine combined with lifestyle modification. Patients were randomly assigned, in double‐blind fashion, to sibutramine plus orlistat or sibutramine plus placebo. In addition to medication, participants were provided five brief lifestyle modification visits during the 16‐week continuation trial. Results: Mean body weight did not change significantly in either treatment condition during the 16 weeks. The addition of orlistat to sibutramine did not induce further weight loss as compared with treatment by sibutramine alone (mean changes = +0.1 ± 4.1 kg vs. +0.5 ± 2.1 kg, respectively). Discussion: These results must be interpreted with caution because of the study's small sample size. The findings, however, suggest that the combination of sibutramine and orlistat is unlikely to have additive effects that will yield mean losses ≥15% of initial weight, as desired by many obese individuals.     

PHYLOGEOGRAPHY OF THE ASIAN ELEPHANT (ELEPHAS MAXIMUS) BASED ON MITOCHONDRIAL DNA

Abstract Populations of the Asian elephant (Elephas maximus) have been reduced in size and become highly fragmented during the past 3000 to 4000 years. Historical records reveal elephant dispersal by humans via trade and war. How have these anthropogenic impacts affected genetic variation and structure of Asian elephant populations? We sequenced mitochondrial DNA (mtDNA) to assay genetic variation and phylogeography across much of the Asian elephant's range. Initially we compare cytochrome b sequences (cyt b) between nine Asian and five African elephants and use the fossil‐based age of their separation (～5 million years ago) to obtain a rate of about 0.013 (95% CI = 0.011–0.018) corrected sequence divergence per million years. We also assess variation in part of the mtDNA control region (CR) and adjacent tRNA genes in 57 Asian elephants from seven countries (Sri Lanka, India, Nepal, Myanmar, Thailand, Malaysia, and Indonesia). Asian elephants have typical levels of mtDNA variation, and coalescence analyses suggest their populations were growing in the late Pleistocene. Reconstructed phylogenies reveal two major clades (A and B) differing on average by HKY85/Γ‐corrected distances of 0.020 for cyt b and 0.050 for the CR segment (corresponding to a coalescence time based on our cyt b rate of ～1.2 million years). Individuals of both major clades exist in all locations but Indonesia and Malaysia. Most elephants from Malaysia and all from Indonesia are in well‐supported, basal clades within clade A, thus supporting their status as evolutionarily significant units (ESUs). The proportion of clade A individuals decreases to the north, which could result from retention and subsequent loss of ancient lineages in long‐term stable populations or, perhaps more likely, via recent mixing of two expanding populations that were isolated in the mid‐Pleistocene. The distribution of clade A individuals appears to have been impacted by human trade in elephants among Myanmar, Sri Lanka, and India, and the subspecies and ESU statuses of Sri Lankan elephants are not supported by molecular data.     

Age and growth of pallid sturgeon in the free-flowing Mississippi River

Trotlines were used to capture pallid sturgeon in the free‐flowing Mississippi River, which extends from the Gulf of Mexico to the mouth of the Missouri River. Trotlines were baited with worms, and set overnight usually along the channel border. The pectoral fin rays of 165 pallid sturgeon caught in the Mississippi River were aged; 118 were from the lower Mississippi River (LMR) between the Gulf and mouth of the Ohio River, and 47 were from the middle Mississippi River (MMR) between the mouths of the Ohio and Missouri rivers. Initial agreement within ±1 year between two readers ranged from 53% for the LMR specimens, which were read first, to 84% for the MMR. Final age was agreed upon by both readers. For LMR pallid sturgeon, final age estimates ranged from 3 to 21 years with a mean (±SD) of 11.0 ± 4.7. For MMR pallid sturgeon, final age estimates ranged from 5 to 14 years with a mean of 9.5 ± 2.1. Seven pallid sturgeon marked with coded wire tags (CWT), indicating hatchery origin, were collected in the MMR. Age estimates for CWT fish were 7–8 years representing 1997 stocked fish, and 11–12 years representing 1992 progeny stocked in 1994. Von Bertalanffy growth equations for length indicated that pallid sturgeon in the MMR had higher growth rates for a given age than pallid sturgeon in the LMR. However, there were no significant differences (anova , P > 0.5) in the length–weight relationships between reaches. In the LMR, pallid sturgeon fully recruited to trotlines at age 11 and instantaneous total mortality (Z; slope of catch curve) was estimated at −0.12 (n = 10 year classes, r² = 0.55, P = 0.01). Of the 118 sectioned rays from the LMR, 28 could not be reliably aged (only one section from the MMR could not be aged). Therefore, age was predicted from length using the von Bertalanffy equation. The catch curve was re‐calculated using the predicted ages of the 28 pallid sturgeon in the LMR resulting in Z = −0.07. In the MMR, pallid sturgeon fully recruited to trotlines at age 9 and Z was estimated at −0.36 (n = 6 year classes, r² = 0.67, P = 0.04), which was significantly higher (anova , P = 0.04) than the LMR estimate. Higher mortality in the MMR may be due to habitat limitations compared to a larger, more diverse channel in the LMR, and incidental take of larger, older individuals during commercial harvesting of shovelnose sturgeon. Commercial take of shovelnose does not occur in the LMR except in the northern portion of the reach. Considering the presence of pallid sturgeon with CWT, recruitment of older individuals in the MMR may have been influenced by stocking a decade earlier. Management strategies for this endangered species should consider the differences in mortality rates among reaches, the impacts of commercial fishing on recovery of pallid sturgeon in the MMR, and the long‐term effects of hatchery fish now recruiting into the free‐flowing Mississippi River.     

Maternal obesity is associated with younger age at obesity onset in U.S. adolescent offspring followed into adulthood

Objective: The objective was to test the hypothesis that maternal obesity is associated with younger age of offspring's obesity onset. Research Methods and Procedures: We used prospective, nationally representative, longitudinal data collected across Waves I (1995; 12 to 20 years), II (1996; 13 to 20 years), and III (2001; 18 to 28 years) of the National Longitudinal Study of Adolescent Health (N = 14,654; 49% female). Interval regression analysis was used to assess the association between maternal obesity and age at offspring's obesity onset (International Obesity Task Force BMI ≥30 equivalent age‐ and sex‐specific cut‐off points for adolescents and BMI ≥30 for young adults) using self‐reported heights and weights, adjusting for race/ethnicity, sex, parental education, and family income, accounting for complex sampling design. Results: The net effect of having an obese mother varied by race/ethnicity and was associated with a significantly earlier age at obesity onset (p = 0.0001) for whites [β= ?8.1 year, 95% confidence interval (CI), ?9.3; ?6.9)], blacks (β = ?10.8 years, 95% CI, ?12.4; ?9.2), Hispanics (β = ?7.0 years, 95% CI, ?9.2; ?4.8), and Asians (β = ?8.6 years, 95% CI, ?13.3; ?3.9). Earlier obesity onset (<18 years) was associated with increased severity at young adulthood (mean BMI, 36.0 ± 0.3 kg/m²) vs. onset after age 18 (mean BMI, 34.4 ± 0.2 kg/m²; p = 0.0001). There were no sex differences in the association of maternal obesity to age at obesity onset. Conclusions: Having an obese mother was associated with earlier age at obesity onset across all race/ethnic groups, particularly non‐Hispanic blacks. Early obesity onset has important health consequences because of its association with more severe adult obesity.     

Application of harmonic radar technology to monitor tree snail dispersal

Abstract. Planned conservation efforts for tree snails of the endangered genus Achatinella, endemic to the island of O'ahu, Hawai'i, will include translocations among the remaining wild and captive‐bred populations. In order to establish optimal levels of artificial migration among neighboring groups of snails within fragmented populations, efforts to determine natural dispersal rates through direct observation were initiated. Capture–mark–recapture (CMR) efforts have proved inadequate for obtaining the requisite dispersal estimates, due to low recapture probabilities. In addition, snail dispersal beyond the boundaries of a finite CMR study site was indistinguishable from mortality. In the preliminary study reported here, both the low recapture probability and dispersal detection problems of past CMR efforts were addressed by using harmonic radar tracking. This approach yielded rough dispersal estimates that were unattainable using CMR alone by providing 100% recapture rates even beyond the normal survey area boundaries. Extensive snail movements within clusters of connected trees were frequently observed after tracking for merely a few hours, although movements between unconnected trees were rare and recorded only after monthly survey intervals. Just 11 out of 40 tracked snails made between‐tree movements (average distance of 4.94±1.52 m) during the entire 7‐month study, and provided the only data utilizable for inferring gene flow in and out of subpopulations. Meteorological data loggers were deployed when tracking began to look for an association between such snail movement and weather fluctuations. The resultant data indicate that increases in both wind gusts and humidity facilitate dispersal (R²=0.77, p‐value <0.001), and that passive wind dispersal alone may be responsible for many snail movements (R²=0.59, p‐value=0.0014). Despite having provided coarse estimates of short‐term dispersal and corresponding wind influences, the limitations of the radar method can be substantial.     

Scale and uncertainty in modeled soil organic carbon stock changes for US croplands using a process‐based model

Process‐based model analyses are often used to estimate changes in soil organic carbon (SOC), particularly at regional to continental scales. However, uncertainties are rarely evaluated, and so it is difficult to determine how much confidence can be placed in the results. Our objective was to quantify uncertainties across multiple scales in a process‐based model analysis, and provide 95% confidence intervals for the estimates. Specifically, we used the Century ecosystem model to estimate changes in SOC stocks for US croplands during the 1990s, addressing uncertainties in model inputs, structure and scaling of results from point locations to regions and the entire country. Overall, SOC stocks increased in US croplands by 14.6 Tg C yr^?1 from 1990 to 1995 and 17.5 Tg C yr^?1 during 1995 to 2000, and uncertainties were ±22% and ±16% for the two time periods, respectively. Uncertainties were inversely related to spatial scale, with median uncertainties at the regional scale estimated at ±118% and ±114% during the early and latter part of 1990s, and even higher at the site scale with estimates at ±739% and ±674% for the time periods, respectively. This relationship appeared to be driven by the amount of the SOC stock change; changes in stocks that exceeded 200 Gg C yr^?1 represented a threshold where uncertainties were always lower than ±100%. Consequently, the amount of uncertainty in estimates derived from process‐based models will partly depend on the level of SOC accumulation or loss. In general, the majority of uncertainty was associated with model structure in this application, and so attaining higher levels of precision in the estimates will largely depend on improving the model algorithms and parameterization, as well as increasing the number of measurement sites used to evaluate the structural uncertainty.     

Estimating elephant density using motion-sensitive cameras: challenges,opportunities, and parameters for consideration

With extinction rates far exceeding the natural background rate, reliable monitoring of wildlife populations has become crucial for adaptive management and conservation. Robust monitoring is often labor intensive with high economic costs, particularly in the case of those species that are subject to illegal poaching, such as elephants, which require frequent and accurate population estimates over large spatial scales. Dung counting methods are commonly employed to estimate the density of elephants; however, in the absence of a full survey calibration, these can be unreliable in heterogeneous habitats where dung decay rates may be highly variable. We explored whether motion-sensitive cameras offer a simple, lower cost, and reliable alternative for monitoring in challenging forest environments. We estimated the density of African savanna elephants (Loxodanta africana) in a montane forest using the random encounter model and assessed the importance of surveying parameters for future survey design. We deployed motion-sensitive cameras in 65 locations in the Aberdare Conservation Area in Kenya during June to August in 2015 to 2017, for a survey effort of 967 days, and a mean encounter rate of 0.09 ± 0.29 (SD) images/day. Elephants were captured in 16 locations. Density estimates varied between vegetation types, with estimates ranging from 6.27/km² in shrub, 1.1/km² in forest, 0.53/km² in bamboo (Yushania alpine), and 0.44/km² in the moorlands. The average speed of animal movement and the camera detection zone had the strongest linear associations with density estimates (R = −0.97). The random encounter model has the potential to offer an alternative, or complementary method within the active management framework for monitoring elephant populations in forests at a relatively low cost.     

Importance of disturbance history on net primary productivity in the world's most productive forests and implications for the global carbon cycle

Analysis of growth and biomass turnover in natural forests of Eucalyptus regnans, the world's tallest angiosperm, reveals it is also the world's most productive forest type, with fire disturbance an important mediator of net primary productivity (NPP). A comprehensive empirical database was used to calculate the averaged temporal pattern of NPP from regeneration to 250 years age. NPP peaks at 23.1 ± 3.8 (95% interquantile range) Mg C ha^?1 year^?1 at age 14 years, and declines gradually to about 9.2 ± 0.8 Mg C ha^?1 year^?1 at 130 years, with an average NPP over 250 years of 11.4 ± 1.1 Mg C ha^?1 year^?1, a value similar to the most productive temperate and tropical forests around the world. We then applied the age‐class distribution of E. regnans resulting from relatively recent historical fires to estimate current NPP for the forest estate. Values of NPP were 40% higher (13 Mg C ha^?1 year^?1) than if forests were assumed to be at maturity (9.2 Mg C ha^?1 year^?1). The empirically derived NPP time series for the E. regnans estate was then compared against predictions from 21 global circulation models, showing that none of them had the capacity to simulate a post‐disturbance peak in NPP, as found in E. regnans. The potential importance of disturbance impacts on NPP was further tested by applying a similar approach to the temperate forests of conterminous United States and of China. Allowing for the effects of disturbance, NPP summed across both regions was on average 11% (or 194 Tg C/year) greater than if all forests were assumed to be in a mature state. The results illustrate the importance of accounting for past disturbance history and growth stage when estimating forest primary productivity, with implications for carbon balance modelling at local to global scales.     

Body weight as an effective tool for determination of onset of puberty in captive female Nile hippopotami (Hippopotamus amphibious)

Profiles of fecal progestogens and body weight from the early juvenile to the peri‐pubertal period are presented for eight captive female Nile hippopotami housed at Disney's Animal Kingdom in Florida. Average growth rate in juveniles was 0.85±0.03 kg/day (r²=0.913). Progestogen elevations were detectable as early as 16.8 months of age, and elevations indicative of ovulation and luteal activity were identified in seven of eight females by 30.3±1.6 months of age and body weight of 829.3±49.4 kg. Progestogen patterns before the onset of puberty were highly variable within and between females. Some females remained at baseline concentrations, whereas in others the progestogen pattern was characterized by infrequent, transient elevations of low amplitude and shortened duration. Four females were monitored through onset of puberty, conception, and first pregnancy. Onset of puberty was defined as the first luteal phase from the series of consecutive ovarian cycles culminating in conception and was observed at 34.9±2.2 months of age and 963.6±39.4 kg, however, the quality and number of cycles varied among females before conception. Females conceived between 2.7–3.9 years of age after attaining an approximate threshold body weight of 1,000 kg (1,070.5±39.5 kg). The age at first conception in captivity occurs at a younger age than has been reported for wild populations. Body weight may be an effective tool for approximating the state of reproductive maturity and facilitate collection management in zoos. Zoo Biol. 0:1–13, 2005. © 2005 Wiley‐Liss, Inc.     

Calcium and body fat in peripubertal girls: cross-sectional and longitudinal observations

Objective: The objective was to investigate whether calcium intake is independently associated with body fat in peripubertal girls. Research Methods and Procedures: A total of 45 healthy premenarcheal girls (initially 10.5 ± 0.6 years of age) completed a 2‐year prospective observational study. Percent body fat and trunk fat (by DXA), height, weight, maturational stage, and eating attitudes (children's Eating Attitudes Test [EAT]) were measured at baseline and at 1 and 2 years. Physical activity (by questionnaire) and calcium intake (by calcium‐specific food frequency questionnaire and 3‐day food records) were assessed at 6‐month intervals. Results: Girls with 2‐year mean calcium intake below and above the median had similar age, height, lean mass, and maturational stage at baseline, but girls below the median had significantly higher baseline percentage body fat (29.3 ± 10.3% vs. 22.0 ± 6.8%, p < 0.01) and trunk fat (24.2 ± 10.6% vs. 15.8 ± 6.8%, p < 0.01). However, differences were no longer significant when covariates (most notably children's EAT dieting score) were considered. Regression analysis revealed that dieting score was a consistent positive predictor of percentage body and trunk fat at all cross‐sectional time‐points, accounting for >20% of the variance, but did not predict 2‐year change in percentage fat. Calcium intake did not enter longitudinal regression equations for 2‐year change in percentage fat. Discussion: In this group of girls, an inverse cross‐sectional association between calcium intake and body fat appeared to result from avoidance of foods high in calcium by girls who were concerned about their body weight or shape. Calcium intake was not associated with change in fat over time.