Changes in age‐structure over four decades were a key determinant of population growth rate in a long‐lived mammal

1. A changing environment directly influences birth and mortality rates, and thus population growth rates. However, population growth rates in the short term are also influenced by population age‐structure. Despite its importance, the contribution of age‐structure to population growth rates has rarely been explored empirically in wildlife populations with long‐term demographic data. 2. Here we assessed how changes in age‐structure influenced short‐term population dynamics in a semi‐captive population of Asian elephants Elephas maximus . 3. We addressed this question using a demographic dataset of female Asian elephants from timber camps in Myanmar spanning 45 years (1970–2014). First, we explored temporal variation in age‐structure. Then, using annual matrix population models, we used a retrospective approach to assess the contributions of age‐structure and vital rates to short‐term population growth rates with respect to the average environment. 4. Age‐structure was highly variable over the study period, with large proportions of juveniles in the years 1970 and 1985, and made a substantial contribution to annual population growth rate deviations. High adult birth rates between 1970 and 1980 would have resulted in large positive population growth rates, but these were prevented by a low proportion of reproductive‐aged females. 5. We highlight that an understanding of both age‐specific vital rates and age‐structure is needed to assess short‐term population dynamics. Furthermore, this example from a human‐managed system suggests that the importance of age‐structure may be accentuated in populations experiencing human disturbance where age‐structure is unstable, such as those in captivity or for endangered species. Ultimately, changes to the environment drive population dynamics by influencing birth and mortality rates, but understanding demographic structure is crucial for assessing population growth

Efficacy of daratumumab combination regimen in patients with multiple myeloma : A combined analysis of phase III randomized controlled trials

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Males have more aggressive and less sociable personalities than females in semi-captive Asian elephants

Personality, i.e. consistent between-individual differences in behaviour, has been documented in many species. Yet little is known about how males and females of long-lived, highly social species differ in their measures of personality structure. We investigated sex differences in the mean, variance, and covariance of three previously reported personality traits (Attentiveness, Sociability, Aggressiveness) in 150 female and 107 male Asian elephants (Elephas maximus) from a semi-captive population in Myanmar. These three personality traits were obtained by performing exploratory factor analysis on 28 behavioural items that had been rated by experienced elephant handlers. We found that males scored significantly higher on Aggressiveness and tended to score lower on Sociability than females. However, no sex difference was found in the mean scores of Attentiveness. Variances for the three personality traits did not differ between the sexes, suggesting that male and female elephants share the same range of personality variation. Likewise, trait covariances were similar between the sexes. While both sexes show complex sociality in the wild, female Asian elephants typically live in highly social family units, whereas male elephants' social bonds are weaker. Males usually form dominance ranks by aggressive interactions, especially during musth. Our results on a large sample of individuals living in their natural environment are thus in agreement with elephant life-histories and parallel the findings of sex differences in other long-lived highly social species with similar life-histories

Asian elephants exhibit post-reproductive lifespans

Background The existence of extended post-reproductive lifespan is an evolutionary puzzle, and its taxonomic prevalence is debated. One way of measuring post-reproductive life is with post-reproductive representation, the proportion of adult years lived by females after cessation of reproduction. Analyses of post-reproductive representation in mammals have claimed that only humans and some toothed whale species exhibit extended post-reproductive life, but there are suggestions of a post-reproductive stage for false killer whales and Asian elephants. Here, we investigate the presence of post-reproductive lifespan in Asian elephants using an extended demographic dataset collected from semi-captive timber elephants in Myanmar. Furthermore, we investigate the sensitivity of post-reproductive representation values to availability of long-term data over 50 years. Results We find support for the presence of an extended post-reproductive stage in Asian elephants, and that post-reproductive representation and its underlying demographic rates depend on the length of study period in a long-lived animal. Conclusions The extended post-reproductive lifespan is unlikely due to physiological reproductive cessation, and may instead be driven by mating preferences or condition-dependent fertility. Our results also show that it is crucial to revisit such population measures in long-lived species as more data is collected, and if the typical lifespan of the species exceeds the initial study period

Investigating associations between nematode infection and three measures of sociality in Asian elephants

Frequent social interactions, proximity to conspecifics, and group density are main drivers of infections and parasite transmissions. However, recent theoretical and empirical studies suggest that the health benefits of sociality and group living can outweigh the costs of infection and help social individuals fight infections or increase their infection-related tolerance level. Here, we combine the advantage of studying artificially created social work groups with different demographic compositions with free-range feeding and social behaviours in semi-captive Asian elephants (Elephas maximus), employed in timber logging in Myanmar. We examine the link between gastro-intestinal nematode load (strongyles and Strongyloides spp.), estimated by faecal egg counts, and three different aspects of an elephant's social world: individual solitary behaviour, work group size, and work group sex ratio. Controlling for sex, age, origin, time since last deworming treatment, year, human sampler bias, and individual identity, we found that infection by nematodes ranged from 0 to 2720 eggs/g between and within 26 male and 45 female elephants over the 4-year study period. However, such variation was not linked to any investigated measures of sociality in either males or females. Our findings highlight the need for finer-scale studies, establishing how sociality is limited by, mitigates, or protects against infection in different ecological contexts, to fully understand the mechanisms underlying these pathways. Significance statement Being social involves not only benefits, such as improved health, but also costs, including increased risk of parasitism and infectious disease. We studied the relationship between and three different sociality measures-solitary behaviour, group size, and the proportion of females to males within a group-and infection by gut nematodes (roundworms), using a unique study system of semi-captive working Asian elephants. Our system allows for observing how infection is linked to sociality measures across different social frameworks. We found that none of our social measures was associated with nematode infection in the studied elephants. Our results therefore suggest that here infection is not a large cost to group living, that it can be alleviated by the benefits of increased sociality, or that there are weak infection-sociality associations present which could not be captured and thus require finer-scale measures than those studied here. Overall, more studies are needed from a diverse range of systems that investigate specific aspects of social infection dynamics.Peer reviewe

Evaluating the reliability of non-specialist observers in the behavioural assessment of semi-captive Asian elephant welfare

Recognising stress is an important component in maintaining the welfare of captive animal populations, and behavioural observation provides a rapid and non-invasive method to do this. Despite substantial testing in zoo elephants, there has been relatively little interest in the application of behavioural assessments to the much larger working populations of Asian elephants across Southeast Asia, which are managed by workers possessing a broad range of behavioural knowledge. Here, we developed a new ethogram of potential stress- and work-related behaviour for a semi-captive population of Asian elephants. We then used this to collect observations from video footage of over 100 elephants and evaluated the reliability of behavioural welfare assessments carried out by non-specialist observers. From observations carried out by different raters with no prior experience of elephant research or management, we tested the reliability of observations between-observers, to assess the general inter-observer agreement, and within-observers, to assess the consistency in behaviour identification. The majority of ethogram behaviours were highly reliable both between- and within-observers, suggesting that overall, behaviour was highly objective and could represent easily recognisable markers for behavioural assessments. Finally, we analysed the repeatability of individual elephant behaviour across behavioural contexts, demonstrating the importance of incorporating a personality element in welfare assessments. Our findings highlight the potential of non-expert observers to contribute to the reliable monitoring of Asian elephant welfare across large captive working populations, which may help to both improve elephant wellbeing and safeguard human workers

How Big Is It Really? Assessing the Efficacy of Indirect Estimates of Body Size in Asian Elephants

Information on an organism's body size is pivotal in understanding its life history and fitness, as well as helping inform conservation measures. However, for many species, particularly large-bodied wild animals, taking accurate body size measurements can be a challenge. Various means to estimate body size have been employed, from more direct methods such as using photogrammetry to obtain height or length measurements, to indirect prediction of weight using other body morphometrics or even the size of dung boli. It is often unclear how accurate these measures are because they cannot be compared to objective measures. Here, we investigate how well existing estimation equations predict the actual body weight of Asian elephants Elephas maximus, using body measurements (height, chest girth, length, foot circumference and neck circumference) taken directly from a large population of semi-captive animals in Myanmar (n = 404). We then define new and better fitting formulas to predict body weight in Myanmar elephants from these readily available measures. We also investigate whether the important parameters height and chest girth can be estimated from photographs (n = 151). Our results show considerable variation in the ability of existing estimation equations to predict weight, and that the equations proposed in this paper predict weight better in almost all circumstances. We also find that measurements from standardised photographs reflect body height and chest girth after applying minor adjustments. Our results have implications for size estimation of large wild animals in the field, as well as for management in captive settings.</p

Cross-species reactivity of antibodies against Plasmodium vivax blood-stage antigens to Plasmodium knowlesi

Funding: FM would like to thank Indonesia Government Fund for Education for the financial support of his scholarship. This study was supported by Indonesia Government Fund for Education (LPDP/20140812021475) (FM), by the National Research Foundation of Korea (NRF) grant funded by the Korea government (MSIP) (NRF-2017R1A2A2A05069562) (ETH), by the Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Science, ICT and Future Planning (2015R1A4A1038666) (ETH). RM is supported by a UK Medical Research Council Career Development Award Fellowship (MR/M021157/1).Malaria is caused by multiple different species of protozoan parasites, and interventions in the pre-elimination phase can lead to drastic changes in the proportion of each species causing malaria. In endemic areas, cross-reactivity may play an important role in the protection and blocking transmission. Thus, successful control of one species could lead to an increase in other parasite species. A few studies have reported cross-reactivity producing cross-immunity, but the extent of cross-reactive, particularly between closely related species, is poorly understood. P. vivax and P. knowlesi are particularly closely related species causing malaria infections in SE Asia, and whilst P. vivax cases are in decline, zoonotic P. knowlesi infections are rising in some areas. In this study, the cross-species reactivity and growth inhibition activity of P. vivax blood-stage antigen-specific antibodies against P. knowlesi parasites were investigated. Bioinformatics analysis, immunofluorescence assay, western blotting, protein microarray, and growth inhibition assay were performed to investigate the cross-reactivity. P. vivax blood-stage antigen-specific antibodies recognized the molecules located on the surface or released from apical organelles of P. knowlesi merozoites. Recombinant P. vivax and P. knowlesi proteins were also recognized by P. knowlesi- and P. vivax-infected patient antibodies, respectively. Immunoglobulin G against P. vivax antigens from both immune animals and human malaria patients inhibited the erythrocyte invasion by P. knowlesi. This study demonstrates that there is extensive cross-reactivity between antibodies against P. vivax to P. knowlesi in the blood stage, and these antibodies can potently inhibit in vitro invasion, highlighting the potential cross-protective immunity in endemic areas.Publisher PDFPeer reviewe

Demographic and reproductive associations with nematode infection in a long-lived mammal

Infection by macroparasites, such as nematodes, varies within vertebrate host systems; elevated infection is commonly observed in juveniles and males, and, for females, with different reproductive states. However, while such patterns are widely recognized in short-lived model systems, how they apply to long-lived hosts is comparatively understudied. Here, we investigated how infection varies with host age, sex, and female reproduction in a semi-captive population of individually marked Asian elephants Elephas maximus. We carried out 1,977 faecal egg counts (FECs) across five years to estimate nematode loads for 324 hosts. Infection patterns followed an established age-infection curve, whereby calves (5 years) exhibited the highest FECs and adults (45 years) the lowest. However, males and females had similar FECs across their long lifespan, despite distinct differences in life-history strategy and clear sexual dimorphism. Additionally, although mothers invest two years in pregnancy and a further three to five years into lactation, nematode load did not vary with four different measures of female reproduction. Our results provide a much-needed insight into the host-parasite dynamics of a long-lived host; determining host-specific associations with infection in such systems is important for broadening our knowledge of parasite ecology and provides practical applications for wildlife medicine and management.</p

Faecal Glucocorticoid Metabolites and H/L Ratio are Related Markers of Stress in Semi-Captive Asian Timber Elephants

Animals are kept in captivity for various reasons, but species with a slower pace of lifemay adapt to captive environments less easily, leading to welfare concerns and the need to assessstress reliably in order to develop effective interventions. Our aim was to assess welfare of semicaptivetimber elephants from Myanmar by investigating the relationship between twophysiological markers of stress commonly used as proxies for welfare, faecal glucocorticoidmetabolite concentrations (FGM) and heterophil/lymphocyte ratios (H/L), and link these measuresto changes in body condition (determined by body weight). We further assessed how robustly thesetwo markers of stress performed in animals of different age or sex, or in different ecological contexts.We measured FGM concentrations and H/L ratios between 2016 and 2018 from 316 samples of 75females and 49 males ranging in age from 4 to 68. We found a positive and consistent link betweenFGMs and H/L ratios in Asian elephants, irrespective of their sex, age, or ecological context. Ourresults will help to inform managers of (semi-) captive elephants about using heterophil/lymphocyteratio data from blood smears on site as a potentially cheaper and faster alternative to determiningstress than measuring faecal glucocorticoid metabolite concentrations in the laboratory.</p