Article

Demography of Asian elephants from identified individuals at Uda Walawe National Park, Sri Lanka

May 2011
Biological Conservation 144(5):1742-1752

DOI:10.1016/j.biocon.2011.03.011

Authors:

Shermin de Silva

Unversity of California, San Diego

Ashoka Ranjeewa

University of Colombo

Devaka Weerakoon

University of Colombo

We provide estimates of population size and other demographic variables for individually-identified Asian elephants (Elephas maximus) in Uda Walawe National Park (UWNP), Sri Lanka based on systematic year-round observations. Two hundred and eighty-six adult females and 241 adult males were identified, of which four adults (2% of males) had tusks. Sightings-based demographic models showed seasonal immigration and emigration from the study area. The total population, including non-adults, was between 804 and 1160 individuals. Density ranged from 102 to 116 adult females per 100 km(2) and remains at this level throughout the year. This large, un-fragmented population of Asian elephants should be of high conservation priority. We find that estimates of survivorship and migration rates should be based on long sampling intervals when possible, but estimates of density and population size can still be made when observations are constrained to shorter intervals, if spatial data are available. We offer suggestions to guide census design for other elephant populations or cryptic species. We urge that other locations be systematically surveyed as well using photographic identification.

Day and night camera trap videos are effective for identifying individual wild Asian elephants

Article

Full-text available

Mar 2023

Regular monitoring of wild animal populations through the collection of behavioral and demographic data is critical for the conservation of endangered species. Identifying individual Asian elephants ( Elephas maximus ), for example, can contribute to our understanding of their social dynamics and foraging behavior, as well as to human-elephant conflict mitigation strategies that account for the behavior of specific individuals involved in the conflict. Wild elephants can be distinguished using a variety of different morphological traits— e.g ., variations in ear and tail morphology, body scars and tumors, and tusk presence, shape, and length—with previous studies identifying elephants via direct observation or photographs taken from vehicles. When elephants live in dense forests like in Thailand, remote sensing photography can be a productive approach to capturing anatomical and behavioral information about local elephant populations. While camera trapping has been used previously to identify elephants, here we present a detailed methodology for systematic, experimenter differentiation of individual elephants using data captured from remote sensing video camera traps. In this study, we used day and night video footage collected remotely in the Salakpra Wildlife Sanctuary in Thailand and identified 24 morphological characteristics that can be used to recognize individual elephants. A total of 34 camera traps were installed within the sanctuary as well as crop fields along its periphery, and 107 Asian elephants were identified: 72 adults, 11 sub-adults, 20 juveniles, and four infants. We predicted that camera traps would provide enough information such that classified morphological traits would aid in reliably identifying the adult individuals with a low probability of misidentification. The results indicated that there were low probabilities of misidentification between adult elephants in the population using camera traps, similar to probabilities obtained by other researchers using handheld cameras. This study suggests that the use of day and night video camera trapping can be an important tool for the long-term monitoring of wild Asian elephant behavior, especially in habitats where direct observations may be difficult.

Day and night camera trap video is effective for identifying wild Asian elephants

Preprint

Jul 2021

Camera traps provide a virtual window into the natural world of wild animals, as they provide a noninvasive way to capture anatomical and behavioral information. Regular monitoring of wild populations through the collection of behavioral and demographic data is critical for the conservation of endangered species like the Asian elephant (Elephas maximus). Identifying individual elephants can contribute to our understanding of social dynamics and foraging behavior in this species. Wild elephants can be distinguished using a variety of different morphological traits: variations in ear and tail morphology, body scars and tumors, and tusk presence, shape, and length. However, to our knowledge, there is little explanation in the literature about how remote camera trapping can be used to systematically identify elephants. Thus, this study set out to provide a template for how to provide this information using physical characteristics identified from day and night video footage collected remotely in the Salakpra Wildlife Sanctuary in Thailand between February 2019 and January 2020. We identified 24 morphological characteristics that can be used to identify individual Asian elephants. Using 33 camera traps spread across the protected area within the sanctuary as well as crop fields along its periphery, 107 Asian elephants were identified, for the first time in Thailand, using 475 total day and night videos. In the identified population, there were 72 adults, 11 sub-adults, 20 juveniles, and 4 infants. We predicted that the morphological traits would aid in reliably identifying these individuals with a low probability of misidentification. The results indicated that there were low probabilities of misidentification between elephants in the population using camera traps, and that the elephants in this study were reliably identified. These low probabilities of misidentification are comparable to a previous study using photographic data that were collected through direct observations of wild Asian elephants. This study suggests that the use of day and night video camera trapping can be an important tool for the long-term monitoring of wild Asian elephant behavior, especially in habitats where direct observations may be difficult. This work has important implications for the study of wildlife behavior using remote methods, as well as for endangered species conservation.

Towards a reliable assessment of Asian elephant population parameters: the application of photographic spatial capture–recapture sampling in a priority floodplain ecosystem

Article

Full-text available

Jun 2019

The hitherto difficult task of reliably estimating populations of wide-ranging megafauna has been enabled by advances in capture–recapture methodology. Here we combine photographic sampling with a Bayesian spatially-explicit capture–recapture (SCR) model to estimate population parameters for the endangered Asian elephant Elephas maximus in the productive floodplain ecosystem of Kaziranga National Park, India. Posterior density estimates of herd-living adult females and sub-adult males and females (herd-adults) was 0.68 elephants/km2 (95% Credible Intervals, CrI = 0.56−0.81) while that of adult males was 0.24 elephants/km2 (95% CrI = 0.18−0.30), with posterior density estimates highlighting spatial heterogeneity in elephant distribution. Estimates of the space-usage parameter suggested that herd-adults (

{\hat{\sigma }}_{HA}

= 5.91 km, 95% CrI = 5.18–6.81) moved around considerably more than adult males (

{\hat{\sigma }}_{AM}

= 3.64 km, 95% CrI = 3.09–4.34). Based on elephant movement and age–sex composition, we derived the population that contributed individuals sampled in Kaziranga to be 908 herd-adults, 228 adult males and 610 young (density = 0.46 young/km2, SD = 0.06). Our study demonstrates how SCR is suited to estimating geographically open populations, characterising spatial heterogeneity in fine-scale density, and facilitating reliable monitoring to assess population status and dynamics for science and conservation.

Demographic Tipping Points as Early Indicators of Vulnerability for Slow-Breeding Megafaunal Populations

Article

Full-text available

May 2019

Decisions based on trends in population abundance and distribution may fail to protect populations of slow-breeding, long-lived megafauna from irrevocable decline if they ignore demographic constraints. For such taxa, we urge that effort be directed at understanding the interactions among vital rates governing population growth rates, rather than on predicting probabilities of extinction. The proximity of a population to demographic tipping points, i.e., where growth rate switches from positive to negative, can signal vulnerability to perturbation long before numbers drop below a point of no return. We define the “demographic safe space” as the combination of key vital rates that support a non-negative growth rate and illustrate this approach for Asian elephants. Through simulations, we find that even with optimal reproduction, Asian elephant populations cannot tolerate annual female mortality rates exceeding 7.5%. If adult mortality is very low (3%/year), populations can tolerate high annual mortality in calves below age 3 (up to 31.5%/year), or slow female reproduction (primiparity at 30 years or average inter-birth interval of up to 7.68 years). We then evaluate the potential impact of current threats, showing that near-optimal reproduction and high calf survival is necessary to offset even modestly increased mortality among adult female age classes. We suggest that rather than rely on simple counts or “viability” assessments, conservation planners for slow-breeding megafauna should consider demographic tipping points and strive to keep populations within their safe spaces.

The structure and seasonal habitat use of an Asian elephant (Elephas maximus) population in Nangunhe National Nature Reserve, Yunnan, China.

Thesis

Nov 2017

Lauren Hale

The Asian elephant (Elephas maximus), like several endangered species, is disappearing from this anthropogenic planet. Conservation aims to increase their population size, but this is of little worth if no individuals can adapt to human-induced changes. Elephant conservation should thus be aimed at genetic diversity, for more alleles mean more adaptive behaviours. Generally zoos have tried to sustain genetic diversity, but without success. Focus should therefore be mounted on wild elephant populations, in particular those that hold exclusive alleles. One such population is that in Nangunhe National Nature Reserve (NGH), China. The population exhibits more nucleotide diversity than is recorded in Laos and Vietnam combined, but is vulnerable to stochasticity. With knowledge of the adverse effects of stochasticity, it is surprising that neither management nor scientists have studied elephant demographics in NGH before. This study thus filled the gap in research, generating some startling results. Camera trapping and mark-recapture revealed that the population is very small in NGH (17-33 elephants), emphasising its exposure to stochasticity. The impacts of stochasticity are apparent, with only four calves (≤ 24 months) and two adult males in the population. This age-sex structure is concerning, as it suggests population decline and inbreeding in the coming future. One means of moderating stochasticity is to reconnect NGH with other populations, so facilitating gene flow. Habitat links cannot be established however without a solid understanding of elephant habitat use. This study therefore determined the rainy season habitat use of elephants, previously unknown in NGH. It appears that elephants concentrate in low elevation forests, which are in close proximity to rivers and have dense canopy cover. Their habitat use also increased in forests far from roads (z = 2.474, p < 0.05) while it decreased in forests dominated by dead trees (z = -2.716, p < 0.01). This indicates that Asian elephants avoid both roads and degraded habitats. Overall, this research shows the repercussions of stochasticity for the NGH elephant population. With this information and that on seasonal habitat use, management can expertly intervene to conserve the unique Asian elephant population in NGH. Saving this genetic resource will not only benefit the species provincially, but also globally.

Context-dependent lateralization of trunk movements in wild Asian elephants

Article

Full-text available

May 2017

Asymmetrical trunk use in elephants represents a distinctive example of motor lateralization. Previous studies have shown that trunk movements in the elephant behaviour associated with feeding is lateralized at the individual, but not the population level. The manifestation of lateralized behaviour depends on the nature of the behaviour and is usually more pronounced in social context. Therefore, we hypothesized that population-level lateralization of trunk use in elephants is manifested in social behaviour. One-sided biases in trunk movements were assessed in wild individually-identified Asian elephants during feeding (tearing off a tuft of grass) and social interactions (trunk-to-mouth contacts and trunk-to-genitals contacts between male initiator and female recipient). In feeding, lateralization at the individual and population levels was estimated based on 50 lateral trunk uses per individual. In social interactions, only the population-level bias was assessed using a single trunk contact from each individual. For trunk movements during feeding, elephants showed ro- bust individual preferences, but no population-level lateralization. The distribution of right- and left-trunkers in the present study did not differ significantly from that obtained in previous studies of both the same elephant population and geographically distinct population. No population-level bias in trunk movements during trunk-to-mouth contacts was revealed. In trunk-to-genitals contacts, in contrast, a population-level lateralization was found. Right-sided trunk movements prevailed in males touching females. While individual preferences for feeding, combined with the absence of one-sided population bias, is obviously a species-typical characteristic of Asian elephants, social behaviour, such as male-female socio-sexual contacts, can elicit population-level lateralization of trunk use in this species. The right-sided bias in trunk-to-genitals contacts may reflect lateralization of olfactory perception. If this is the case, the revealed lateralization indicates a right-hemispheric advantage in the processing of social information which is consistent with the general tendency in mammals.

Abundance and social organization of male Asian elephants (Elephas maximus) in Rajaji Tiger Reserve

Thesis

Full-text available

Jul 2024

Abhimanyu Madhusudanan

I employed a polygon-search based spatially explicit capture-recapture framework to estimate the abundance and density of adult male Asian elephants and also looked at what factors influence male association patterns in Rajaji Tiger Reserve in North-western India.

Strategies of protected area use by Asian elephants in relation to motivational state and social affiliations

Article

Full-text available

Nov 2022

Animals’ space requirements may vary according to life-history and social considerations. We observed 516 wild adult Asian elephants from both sexes, over 9 years, to investigate how life-history traits and social behavior influence protected-area (PA) use at Udawalawe National Park, Sri Lanka. Male PA-use, quantified in terms of average between-sightings-interval (BSI), was significantly influenced by the interaction of age class and motivational state (i.e. reproduction vs. foraging). Musth lengthened with age, with a median of 24.5 days for ages 21–30, 32.5 days for ages 31–40, and 45 days for those > 40. A minority (11%) used it exclusively during musth, while others used it exclusively for foraging (44%) or both (45%). Males using it in both states and older musth-only males were more likely to be seen across years. There were 16 social communities containing between 2–22 adult females. Females’ BSI was significantly influenced by social ties, but this relationship was weak, because members of social communities do not necessarily disperse together, resulting in high individual variation in space-use. Inter-annual variability in sightings among individuals of both sexes indicates that around ¾ of the population is likely non-residential across years, challenging the prevailing fortress-conservation paradigm of wildlife management.

Feasibility of using convolutional neural networks for individual-identification of wild Asian elephants

Article

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Jan 2022

View full paper here - https://rdcu.be/cFtQB

The Elephant in the Room: Methods, challenges and concerns in the monitoring of Asian elephant populations

Article

Full-text available

Oct 2020

Increasing anthropogenic pressures has led to the fragmentation of Asian elephant habitats, affecting their numbers, demography and ranging patterns across their range. Baseline information on the demography and population dynamics of free-ranging Asian elephants is often unavailable. Population monitoring at the landscape level has many constraints, including those of visibility, habitat, terrain and field logistics, among several others. While knowing elephant numbers may be important for managing local populations, demographic parameters and distribution patterns are perhaps more crucial to ascertain long-term trends for conservation.

Nocturnal behavior of orphaned Asian elephant (Elephas maximus) calves in Sri Lanka

Article

Jun 2017
ZOO BIOL

Many animals exhibit circadian variation in behavior; thus, studying nocturnal behavior is important to fully understand species activity patterns. The nocturnal behavior of Asian elephants, and specifically calves, has received little previous study. We carried out observational study of the nocturnal behavior of orphaned Asian elephant calves at three age groups: "infant" (0-24 months), "young juvenile" (25-36 months) and "old juveniles" (over 36 months). Project aims were to build a nocturnal activity budget, to investigate key age differences, and whether calves exhibited synchronous behavior patterns. We carried out focal animal sampling and instantaneous group scan sampling on 34 calves for 18 nights using an infra-red camera. Focal results indicated that calves spent the highest percentage of scans in lying rest (46.2%) and feeding (28.4%). There was no significant difference between lying rest in the three age groups. Calves spent the majority of time within 5 m of their nearest neighbor, with infants remaining in closest proximity to conspecifics compared to older calves. Synchronous behavior could not be proved statistically but two distinct lying rest periods between 2300 and 0100, and 0330 and 0530, were noted. We found that calves spent more time in lying rest than previously observed in adult elephants. Activity patterns observed suggest that the orphaned group behavior is similar to that reported in the wild and captive zoological collections, and appears to be in concordance with "natural" behavior patterns, a defining feature of animal welfare. This research provides valuable data as a preliminary study.

Tourism-induced disturbance of wildlife in protected areas: A case study of free ranging elephants in Sri Lanka

Article

Full-text available

Jul 2015

Tourism-induced disturbance is a growing concern in wildlife conservation worldwide. This case study in a key protected area in Sri Lanka, examined the behavioral changes of Asian elephants in the context of elephant watching tourism activities. Observations of different age–sex-group classes of elephants were conducted focusing on the feeding activity of elephants in the presence vs. absence of tourists. Frequency and duration of alert, fear, stress and aggressive behaviors of elephants were significantly high in the presence of tourists and these behaviors occurred at a cost of feeding time. Tourist behavior, vehicle noise, close distances and time of the tours were closely associated with the behavioral changes of elephants. It is important to monitor tourism effects on endangered species such as Asian elephants and to take proper measures including controlled tourist behavior and vehicle activity in protected areas in order to reduce disturbance of wildlife behavior.

Non-Invasive Genotyping of Sumatran Elephants: Implications for Conservation

Article

Full-text available

Sep 2015

Reliable baseline information necessary for the monitoring and conservation of Sumatran elephants is scarce. We here combine non-invasive molecular genetics methods and capture-recapture modeling to estimate elephant population size, distribution, sex ratio, and age structure for the Bukit Tigapuluh landscape in Sumatra, Indonesia. Two separate subpopulations were found, for which we estimated a population size of 99 (95% CI = [86, 125], PCCL = 38.59%) and 44 elephants (95% CI = [37, 56], PCCL = 43.18%), respectively. Low elephant densities are likely the result of patchy habitat usage and anthropogenically increased mortality, the latter assumption being supported by strong skews in both sex ratio and age structure as well as direct evidence of elephant killing. Still, the Bukit Tigapuluh landscape currently holds the largest known population of elephants in central Sumatra, representing one of the most important areas for their conservation in Indonesia. Conservation of both the elephant population and their habitat in this region should thus be of high priority. We identified several threats to the population, including (i) the risk of inbreeding and subsequent loss of genetic diversity, (ii) illegal elephant killing, and (iii) the lack of protected habitat. In order to overcome these challenges we suggest: (i) the implementation of a meta-population management program, (ii) monitoring and safeguarding elephants and improving law enforcement, and (iii) providing sufficient safe habitat to mitigate human-elephant-conflict (HEC) and ensure elephant survival.

Individual identification in Asian Elephants

Article

Full-text available

Jan 2014

Individual identification of animals is the first step in studying elephant behaviour, demography, and conservation, but few studies of Asian elephants (Elephas maximus) are based on individual identification. We describe in detail, traits that can be used to identify individuals, and examine the variability of different traits. Based on fieldwork in Nagarahole National Park, southern India, we scored trait states for 22 traits in 223 individuals. We found that the top fold of the ear and nicks/tears in the ear were useful for identifying both males and females. Tusk features and the presence of warts/ wounds on the body were useful in male identification, and tail characteristics were useful in female identification. The number of marks increased slowly with age, leading to adults having a lower probability of being misidentified than subadults. Analysis of temporal changes in trait states showed that even the fastest changing traits changed only over the course of several years, allowing for reliable identification of animals.

How did the elephant cross the fence? Electric fence crossing by elephants in Udawalawe, Sri Lanka

Article

Full-text available

Sep 2024
ANIM CONSERV

Electric fences are widely used in human–elephant conflict mitigation. However, elephants constantly challenge and overcome fences, which is a growing concern. We studied how elephants crossed the perimeter electric fence around the Udawalawe National Park (UWNP), Sri Lanka. Using camera traps, we monitored 18 fence posts and an open gate in the fence over 605 days from 2016 to 2019. Photographs of 3097 fence crossings were analysed to obtain demographic data for fence crossing elephants, crossing methods, and the daily and seasonal timing of fence crossing. We identified 77 adult males and 12 adult females that crossed the fence, which represent about 17% of the adult elephants in UWNP. Most of the crossings were through the open gate at night. Elephants used a variety of crossing methods, comprised of crossing at the open gate, at previously toppled posts, by crashing through wires and stepping over wires, as well as by using the trunk or forefeet to topple posts. Fence voltage was not a determinant of fence crossing. The frequency and timing of fence crossings varied between locations with later exits and less time spent outside, at crossing points bordering human dominated areas. Our results emphasis on the importance of taking into account the problem solving abilities of elephants in fence design and location, such as energising fence posts and constructing exclosure fences at the boundaries of crop fields and settlements, in employing electric fences to mitigate human‐elephant conflict.

Fernando et al 2022 Age-size classification Gajah

Article

Aug 2022

Experiences and emotional responses of farming communities living with Asian Elephants in Southern Sri Lanka

Article

Full-text available

Dec 2023

Individuals’ tolerance toward wildlife can be based on a combination of tangible benefits and costs (e.g. economic gains and losses) as well as intangible benefits and costs (e.g. shared values and risk perceptions). Asian Elephants (Elephas maximus) potentially present both types of benefits and costs for rural communities. We examined which factors were associated with emotional responses toward wild Asian Elephants among agriculturalists using a questionnaire survey of 300 households situated around the Wetahirakanda sanctuary connecting Udawalawe and Lunugamwehera National Parks, Sri Lanka. Respondents were all from the Sinhala-Buddhist ethno-religious majority with average annual household incomes of Rs. 339,335 LKR (~$2610 USD). We found that none of the surveyed households derived any economic benefits from tourism despite the proximity of two national parks, whereas 171 (57%) had experienced crop damage by Elephants. Though the median annual income lost due to elephants was Rs.50,000 LKR (4%), 21 households (7%) had losses exceeding 100%. Only six individuals (2%) recollected any human fatalities in their communities. Only three individuals reported positive feelings toward elephants, whereas all others had negative or neutral feelings. Economic factors were not significant predictors of feelings toward elephants, whereas fear of elephants and worry about crop damage had the largest and most significant negative effects. Our findings suggest that it might not be sufficient to reduce losses solely at an individual level, but that human-elephant coexistence interventions should target communities as a whole to reduce the spill-over effects of worry and anxiety by association with others who have experienced loss.

Size-Age Class Scale for Asian Elephants

Article

Full-text available

Jan 2022

Population structure provides important information for managing and conserving free ranging Asian elephant populations. A variety of size-age classes, based on estimating height or age and measuring captive animals of known age, have been used previously. Here we propose a simple scale, using the individual’s height relative to an adult female. We also indicate morphological characters of relevance, where determining relative height maybe an issue, as in the case of adult males.

Bottlenose dolphins share fish farm areas while maintaining sexual segregation: Investigating group memberships through spatially and temporally explicit parameters

Article

Dec 2022
AQUAT CONSERV

1. Group membership is a key attribute of animal societies and central to the study of social structure in several taxa. However, social structure analyses are sensitive to the way data are collected and associations defined. 2. In this study, a time–space method was used to investigate the social structure of common bottlenose dolphins Tursiops truncatus observed and photographed across 7 years in the semi-enclosed Gulf of Corinth, Greece. Instead of adopting traditional group definitions, individuals were considered as being members of the same group if photographed within a specific time and space window. This approach can be applied post hoc across studies and can offer advantages under challenging sampling conditions (e.g. when dealing with groups spread over vast areas or when group membership is otherwise hard to assess). 3. Dolphins were mostly found around coastal cage aquaculture facilities farming European sea bass Dicentrarchus labrax and gilthead seabream Sparus aurata. 4. Dolphins formed clusters largely or entirely composed of individuals of the same sex, suggestive of sex-based homophily. Habitat partitioning was not detected: there was substantial spatial overlap among dolphin clusters, with all individuals using a relatively small area in the northern portion of the Gulf, where most of the productive fish farms were located. Associations between females were stronger than those between males, and daughters tended to stay in the group of their mothers. 5. Sex-based social clustering may allow females and calves to limit interactions with potentially aggressive males, while individuals of both sexes benefit from prey concentrated around fish farms. 6. Adaptation to foraging around farms can result in trade-offs between the costs and benefits of nourishment and social interaction. This may have both positive or negative effects on the animals that should be considered in the context of ensuring their favourable conservation status.

Changes in habitat coverage from 2005 to 2019 in the Udawalawe National Park, Sri Lanka

Article

Full-text available

Dec 2021

In protected areas (PAs) designated for the conservation of biodiversity, temporal landscape changes do occur, driven by natural and anthropogenic factors. Such changes may impact on the conservation value of the PA. In a wildlife PA, changes in habitat extents could adversely affect some of the faunal species. Our objective was to assess temporal changes in the cover of three major habitat types in the Udawalawe National Park (UWNP) that have occurred over a short term. Based on the outcome, we aimed to determine the potential impacts such changes would have on the wildlife. Considering that UWNP was established primarily for conserving the nationally threatened and flagship species Elephas maximus, we carried out field studies and decided on three relevant habitat types - forest, scrub, and grassland. We used multi-temporal satellite images with ground truthing for assessing habitat extents in the years 2005, 2010, 2015, and 2019. Habitat cover maps were prepared using supervised classification and changes in the extents of the selected habitats were assessed. Between 2005 and 2019, the areas under forest and scrub had increased. The grassland has considerably decreased, mainly owing to invasion by scrub. Grassland depletion adversely impacts the elephant whose preferred food is grass and the high population of elephants in UWNP aggravates the situation. Depletion of food resources within the park would also lead to an increase in the human-elephant conflicts in border villages. Thus, in this study we highlight the importance of monitoring temporal changes in habitat cover in order to manage the PA and the inhabiting wild elephants. Keywords: Elephas maximus; habitat cover mapping; protected areas; remote sensing.

Assessing population structure and body condition to inform conservation strategies for a small isolated Asian elephant (Elephas maximus) population in southwest China

Article

Full-text available

Mar 2021
PLOS ONE

The Asian elephant (Elephas maximus) population in Nangunhe National Nature Reserve in China represents a unique evolutionary branch that has been isolated for more than twenty years from neighboring populations in Myanmar. The scarcity of information on population structure, sex ratio, and body condition makes it difficult to develop effective conservation measures for this elephant population. Twelve individuals were identified from 3,860 valid elephant images obtained from February to June 2018 (5,942 sampling effort nights) at 52 camera sites. Three adult females, three adult males, one subadult male, two juvenile females, two juvenile males and one male calf were identified. The ratio of adult females to adult males was 1:1, and the ratio of reproductive ability was 1:0.67, indicating the scarcity of reproductive females as an important limiting factor to population growth. A population density of 5.32 ± 1.56 elephants/100 km² was estimated using Spatially Explicit Capture Recapture (SECR) models. The health condition of this elephant population was assessed using an 11-point scale of Body Condition Scoring (BCS). The average BCS was 5.75 (n = 12, range 2–9), with adult females scoring lower than adult males. This isolated population is extremely small and has an inverted pyramid age structure and therefore is at a high risk of extinction. We propose three plans to improve the survival of this population: improving the quality and quantity of food resources, removing fencing and establishing corridors between the east and wet parts of Nangunhe reserve.

The elephant at the fence: almsman, panhandler, friend or foe?

Article

Full-text available

Dec 2020
EUR J WILDLIFE RES

Feeding of wild Asian elephants at the Udawalawe National Park perimeter electric fence by the general public is longstanding. We monitored the elephants and feeding activities, and conducted questionnaire surveys of stakeholders. Over 50 individual adult male elephants engaged in the activity. The exclusive male presence was consistent with a high-risk high-gain male strategy. The elephants were mostly offered fruits and vegetables. Over a thousand people a day watched and fed the elephants. Most people bought food for elephants from roadside stalls and vendors had significantly more sales if elephants were present. The feeding of elephants brought significant economic benefit to communities bordering the park. We found the impacts of feeding on the elephants and environment to be largely neutral. Impacts on people and conservation were mainly positive. Actions taken by authorities to stop the feeding have targeted the elephants and resulted in the decrease of feeding but not its elimination. Managing the activity instead would help increase economic benefits and ensure safe interaction between people and elephants. Such management, by directly benefitting local communities, could make them partners in the conservation process and form the basis of an effective outreach program.

Navigating paved paradise: Evaluating landscape permeability to movement for large mammals in two conservation priority landscapes in India

Article

Jul 2020
BIOL CONSERV

Human land use and activity results in the loss of habitat and biodiversity, and alters how animals move through landscapes. Spatially explicit information on where animal movement is affected at large spatial scales is crucial for prioritizing conservation efforts. We evaluated landscape permeability to movement in two conservation priority landscapes in India, the Western Ghats (WG) and Central India (CI). Using an agent-based model we simulated movement and dispersal of five wide-ranging species in WG (elephant, gaur, leopard, sambar and sloth bear) and four in CI (gaur, leopard, sambar and sloth bear). For each species we compared movement in the presence and absence of land-use land-cover, infrastructure and human population to identify areas where movement is impeded and reduced due to high-resistance features; unrestricted due to relatively low-resistance features; and increased and channelled due to surrounding high-resistance areas. In both landscapes, median movement was reduced. Human land-use, human population and high linear infrastructure density contribute the highest to impeded movement for all species. Natural areas constitute only 20–55% and 50–70% of unrestricted, increased and channelled movement areas in WG and CI respectively. This suggests that a large percentage of the landscape crucial for maintaining movement is not completely permeable. Such areas are often neglected in conservation planning. Our spatially explicit results help identify and prioritize areas where restoration or mitigation should be planned to improve permeability to movement for large mammals. Our approach can be used for other landscapes where data on large mammal movement is lacking.

Influence of the number of calves and lactating adult females in a herd on the adrenocortical activity of free-ranging Asian elephants

Article

Aug 2019

Context: Physiological stress has the potential to influence animal population persistence. The endangered Asian elephant (Elephas maximus) is involved in intense conflict with humans in many parts of its range, which likely leads to stress for individuals and groups, with consequences for population survival. Thus, it is important to understand how the elephants’ stress levels are influenced by socio-ecological factors when not directly exposed to human-induced threats, and to use this understanding to improve conservation and management strategies. Aims: The present study was designed to provide baseline information on the link between socio-ecological factors and stress levels of undisturbed populations of elephants. The main aim was to determine the influence of a number of factors – herd size, season, number of calves and adult females present in a herd and their lactational status and body condition – on the adrenocortical activity of free-ranging adult female Asian elephants living in protected forests (without any direct exposure to human-induced threats), by measuring their faecal glucocorticoid metabolite (fGCM) levels. Methods: A total of 145 fresh faecal samples were collected from 123 identified adult female elephants inhabiting Bandipur and Nagarahole National Parks of southern India, between the years 2013 and 2015. fGCM levels were measured by employing a group-specific standardised 11-oxoetiocholanolone enzyme immunoassay (EIA). A generalised linear mixed-effects model (GLMM) was used to assess the influence of socio-ecological factors on fGCM levels of adult female elephants. Key results: When fGCM levels were analysed with a GLMM, the following patterns were observed: fGCM levels were negatively correlated with the number of adult females (herd size) and positively correlated with the number of calves in a herd and active lactational status of an adult female. fGCM levels of adult female elephants were higher during the dry season (February to May) than wet season (August to December) and negatively correlated with body condition scores. Conclusions: Adrenocortical activity of female elephants is significantly influenced by the number of calves and adult females present in the herd, seasonality and lactational status. Implications: It is important to consider the influence of multiple ecological and social correlates when assessing and interpreting the adrenocortical activity of Asian elephants. Our findings highlight the importance of maintaining the social structure of elephants in the wild to avoid detrimental effects on their physiological health. Insights from such assessments could be used to evaluate the stress in elephants that are involved in direct conflicts with humans to take appropriate management decisions for mitigating conflicts.

Influence of the number of calves and lactating adult females in a herd on the adrenocortical activity of free-ranging Asian elephants

Article

Full-text available

Dec 2019

Context Physiological stress has the potential to influence animal population persistence. The endangered Asian elephant (Elephas maximus) is involved in intense conflict with humans in many parts of its range, which likely leads to stress for individuals and groups, with consequences for population survival. Thus, it is important to understand how the elephants’ stress levels are influenced by socio-ecological factors when not directly exposed to human-induced threats, and to use this understanding to improve conservation and management strategies. Aims The present study was designed to provide baseline information on the link between socio-ecological factors and stress levels of undisturbed populations of elephants. The main aim was to determine the influence of a number of factors – herd size, season, number of calves and adult females present in a herd and their lactational status and body condition – on the adrenocortical activity of free-ranging adult female Asian elephants living in protected forests (without any direct exposure to human-induced threats), by measuring their faecal glucocorticoid metabolite (fGCM) levels. Methods A total of 145 fresh faecal samples were collected from 123 identified adult female elephants inhabiting Bandipur and Nagarahole National Parks of southern India, between the years 2013 and 2015. fGCM levels were measured by employing a group-specific standardised 11-oxoetiocholanolone enzyme immunoassay (EIA). A generalised linear mixed-effects model (GLMM) was used to assess the influence of socio-ecological factors on fGCM levels of adult female elephants. Key results When fGCM levels were analysed with a GLMM, the following patterns were observed: fGCM levels were negatively correlated with the number of adult females (herd size) and positively correlated with the number of calves in a herd and active lactational status of an adult female. fGCM levels of adult female elephants were higher during the dry season (February to May) than wet season (August to December) and negatively correlated with body condition scores. Conclusions Adrenocortical activity of female elephants is significantly influenced by the number of calves and adult females present in the herd, seasonality and lactational status. Implications It is important to consider the influence of multiple ecological and social correlates when assessing and interpreting the adrenocortical activity of Asian elephants. Our findings highlight the importance of maintaining the social structure of elephants in the wild to avoid detrimental effects on their physiological health. Insights from such assessments could be used to evaluate the stress in elephants that are involved in direct conflicts with humans to take appropriate management decisions for mitigating conflicts.

Long-term field studies of elephants: understanding the ecology and conservation of a long-lived ecosystem engineer

Article

Full-text available

May 2018

Hervé Fritz

Elephants may live for > 60 years, so it is obvious that long-term studies are necessary if we are to understand their life histories. Here, I review long-term population studies, most based on individual elephants, to show the wealth of detailed mechanisms that such studies can reveal. This review is biased toward African savanna elephants, a reflection of existing long-term studies on elephants worldwide. Besides life histories, there are 2 aspects of elephant biology that are illuminated by long-term field studies (not necessarily those based on individual elephants). First is knowledge of spatial dynamics of populations that occur in response to environmental change (climatic or anthropogenic), such as density dependence that is associated with the distribution of surface water or responses to specific management decisions, and second is the effects these ecosystem engineers have on habitats, landscapes, other species, and ultimately on ecosystems. I also argue that these long-term data are crucial to inform conservation policies and associated management actions, such as changes in water-pumping strategies, landscape management, and control of elephant populations.

Asian elephants' social structure and mineral lick usage in a Malaysian rainforest using camera traps

Article

Jul 2017

Ning Hii

Elephants (Family Elephantidae) are animals that rely on complex social behavior and organization for survival. The current literature on elephant social organization come from studies in African savannas, an open environment where animals are relatively easy to observe and study. Much less is known, however, about the social behavior of forest elephants, particularly of wild elephants (Elephas maximus) in Southeast Asia. Wild elephants in Malaysian rainforests regularly visit mineral licks to supplement their diet with nutrients and to acquire clay to buffer secondary plant compounds This provides a great opportunity to set up camera traps and regularly observe animals that otherwise would be impossible to study in their natural environment. Thus, the objective of this study is 1) to assess the feasibility of using camera traps to study the social structure of elephants in the wild; 2) to describe their social structure; and 3) to quantify wild Asian elephant patterns of mineral lick usage. Individuals were identified using features on the ears, body and tail, or any other prominent profile; and associations between elephants were recorded. Camera traps were set up at a Sira in the Belum Temenggor Forest Complex from October 2012 till October 2013. Video data were retrieved monthly. In total, we recorded 951 hours of videos representing 165 elephant visits. We were able to identify 55 adult individuals while 21 offspring in the age classes of newborn, infants, and juveniles were unidentified over the course of the study. The identified individuals included 26 female adults, 8 female subadults, 15 male adults and 6 male subadults. Seven female family units and four mother-calf units were identified with a median group size of 6 and 2 individuals, respectively. The results show that forest Asian elephants live in smaller groups than their African savanna counterparts. Among the identified elephants, resident family groups were regularly detected, suggesting that mineral licks are important for the feeding ecology of elephants though the reason is still unclear. This study thus provides a baseline of Asian elephant social structure and mineral lick use in Peninsular Malaysia using camera trapping as a recording technique.

Effects of illegal grazing and invasive Lantana camara on Asian elephant habitat use

Article

Apr 2018
BIOL CONSERV

Protected areas provide some of the last refuges for Asian elephants in the wild. Managing these areas for elephants will be critical for elephant conservation. Scientists know little about elephant habitat use in Asia and how invasive species or livestock grazing influence habitat use. We studied these issues in two protected areas in Sri Lanka, Udawalawe National Park and Hurulu Eco-Park. These areas contain some of Sri Lanka's largest remaining grasslands. These grasslands are threatened by the invasive and toxic shrub, Lantana camara, and are used for illegal livestock grazing. To measure habitat use by elephants and livestock, we conducted dung surveys along over 50 km of transects stratified across grassland, scrub, and forest. We surveyed 159 vegetation plots along these transects to assess plant composition, and mapped habitat types based on satellite images. We used mixed-effect models to determine the relative importance of habitats, livestock presence, and plant associations for elephant use. Elephant presence was greatest in scrub and grassland habitats, positively associated with both livestock presence and short graminoids, and unaffected by L. camara, which was widespread but at low densities. Given the importance of these areas to elephants, we recommend a precautionary management approach that focuses on curbing both illegal grazing and the spread of L. camara.

Wild Sri Lankan elephants retreat from the sound of disturbed Asian honey bees

Article

Full-text available

Jan 2018

Asian elephants (Elephas maximus) are threatened primarily by habitat loss and human-elephant conflict. In addition to establishing protected areas and corridors for wildlife, empowering farmers to protect their crops is crucial for Asian elephant conservation [1,2]. Elephants can habituate to artificial deterrents, hence natural biological alternatives are of great interest [2,3]. African elephants (Loxodonta africana) avoid African honey bees (Apis mellifera scutellata), inspiring 'beehive fences' as a successful means of small-scale crop protection [4,5]. Here, we used a recording of a disturbed hive of cavity-dwelling Asian honey bees (Apis cerana indica) and conducted sound playbacks to 120 wild elephants in 28 different groups resting under trees in Uda Walawe National Park in Sri Lanka. Elephants responded by moving significantly further away from their resting site in bee playback trials compared to controls. Elephants also increased vocalization rates, as well as investigative and reassurance behaviours in response to bee sounds, but did not display dusting or headshaking behaviour.

Decreasing reservoir water levels improve habitat quality for Asian elephants

Article

Oct 2017

Population health and habitat quality are intimately related and seasonal changes in habitat quality are likely to be reflected in the body condition of animals. We studied seasonal variation of body condition in free ranging Asian elephants (Elephas maximus) in Udawalawe National Park, Sri Lanka based on visual scoring of individually identified elephants. We assessed the body condition of 218 adult females and 329 adult males from January 2008 to November 2012 and examined its relation to monthly rainfall and water level of the Udawalawe reservoir. Contrary to expectations, body condition of elephants was higher in the dry season, when primary productivity decreases due to lack of rainfall. However, the body condition showed both a seasonal and inter-annual negative co-relation with reservoir water level. A possible explanation for improved body condition in the dry season is the greater availability of fresh grass due to the emergence of reservoir bed grasslands with the drawdown of water. Our results underscore the importance of water management of large irrigation reservoirs in elephant conservation in Sri Lanka.

A preliminary investigation of seed dispersal by elephants (Elephas maximus maximus) in Kumaragala Forest Reserve, Matale District, Sri Lanka

Article

Full-text available

Sep 2017
Ceylon J Sci Biol Sci

Elephants are capable of dispersing seeds in the wild and hence, have the potential to affect the vegetation dynamics of forests. Only few studies have been conducted in Sri Lanka to study the seed dispersal capability of wild elephants. Thus, this study was initiated to determine the diversity of plant species that are dispersed by the elephants in Kumaragala forest reserve, Central Sri Lanka. Dung piles were searched twice a month and three dung boli were collected randomly from each dung pile. Visible seeds were identified by comparing with a reference seed collection. A total of 84 dung piles were recorded from September 2014 to February 2015. Fifty three dung piles out of 84 (63.1%) contained seeds or seedlings of one or more plant species. Most of the dung piles were found in relatively undisturbed areas of the study site. Twenty two plant species; 15 cultivated (68.2%) and seven non-cultivated (31.8%) plants belonging to nine families were identified from dung boli. Careya arborea, Megathyrsus maximus and Mimosa pudica were the most commonly noted seedlings. The findings of this study prove that elephants assist in dispersing seeds of some plant species in Kumaragala forest reserve area.

Effects of social organization, trap arrangement and density, sampling scale, and population density on bias in population size estimation using some common mark-recapture estimators

Article

Full-text available

Mar 2017
PLOS ONE

Mark-recapture estimators are commonly used for population size estimation, and typically yield unbiased estimates for most solitary species with low to moderate home range sizes. However, these methods assume independence of captures among individuals, an assumption that is clearly violated in social species that show fission-fusion dynamics, such as the Asian elephant. In the specific case of Asian elephants, doubts have been raised about the accuracy of population size estimates. More importantly, the potential problem for the use of mark-recapture methods posed by social organization in general has not been systematically addressed. We developed an individual-based simulation framework to systematically examine the potential effects of type of social organization, as well as other factors such as trap density and arrangement, spatial scale of sampling, and population density, on bias in population sizes estimated by POPAN, Robust Design, and Robust Design with detection heterogeneity. In the present study, we ran simulations with biological, demographic and ecological parameters relevant to Asian elephant populations, but the simulation framework is easily extended to address questions relevant to other social species. We collected capture history data from the simulations, and used those data to test for bias in population size estimation. Social organization significantly affected bias in most analyses, but the effect sizes were variable, depending on other factors. Social organization tended to introduce large bias when trap arrangement was uniform and sampling effort was low. POPAN clearly outperformed the two Robust Design models we tested, yielding close to zero bias if traps were arranged at random in the study area, and when population density and trap density were not too low. Social organization did not have a major effect on bias for these parameter combinations at which POPAN gave more or less unbiased population size estimates. Therefore, the effect of social organization on bias in population estimation could be removed by using POPAN with specific parameter combinations, to obtain population size estimates in a social species.

Road effects on demographic traits of small mammal populations

Article

Full-text available

Jan 2017
EUR J WILDLIFE RES

Recent studies have highlighted the positive effects of road verges on the abundance of small mammals. However, most of these studies occurred in intensively grazed or cultivated areas, where verges were the last remnants of suitable habitats, which could mask the true effects of roads on population traits. We analysed the effects of roads on small mammal populations living in a well-preserved Mediterranean forest. We used the wood mouse (Apodemus sylvaticus) as a model of forest-dwelling small mammals that probably are among the species most affected by road clearings. Our study compared populations in similar habitat areas with and without road influence. We assessed abundance, survival and temporary emigration using extended Pollock’s robust design capture-recapture models. Moreover, we analysed population turnover, sex ratio, age structure and body condition. We found that wood mouse abundance and body condition were lower at the road bisected area, whereas the remaining population traits were similar. This suggests that the reduced habitat availability and quality due to the physical presence of the road and verge vegetation clearing are the main drivers of demographic differences in wood mouse populations between areas. Nevertheless, our results also suggest that in high-quality habitats surrounding national roads, wood mouse populations present similar dynamics to others living in undisturbed areas, despite the decrease in abundance and body condition. Overall, the often-reported increased small mammal abundance in road surroundings should not be generalized independently of habitat quality or to other population traits.

Bleaching patterns and capacity building for Maldives Conservationists during Reef Check expeditions

Conference Paper

Full-text available

Nov 2016

One of the particularly concerning attributes of coral reefs is the potential for ‘phase shifts’ from coral to non-coral dominated assemblages (e.g. Jamaica 25 years ago). The reefs of the Maldives were variously regarded as ‘pristine’ or a ‘wonderland’ by initial visitors with SCUBA such as Cousteau in the 1950s, but profound ecological changes have occurred since then. We have been undertaking Reef Check surveys of the same Maldives sites since 2005 and recorded a variety of ‘states’ of coral reefs, with some shifed from a ‘coral’ to a corallimorph’(non-coral) state. Observations of reef condition of inner to outer reef sites from 2005 to 2015 shows a greater diversity of corals, ascidians, sponges and other benthic invertebrates within the inner atolls, with outer reefs exhibiting much more consistent and higher hard coral cover and bare rock. The 2016 bleaching event was induced by water temperatures of 32 degrees Celcius for two weeks in early May. Surveys in mid-July showed corals in areas of deeper adjacent waters to be (a) either still bleached, some two months after the bleaching event, (b) recovered, or (c) not to have been bleached at all. However, more ‘sheltered’ reefs within the central lagoons showed mass colonisation by algal turfs, encroachment of vulnerable reefs by Discosoma corallimorphs, and Crown-of-Thorns invasions. Observations on the (recent) historical baseline condition of coral communities inside and outside atolls leads us to believe that inner atoll reefs are currently more susceptible to a ‘phase shift’ from a multitude of factors, primarily stimulated by climate change, but exacerbated by local anthropogenic factors. On the other hand, outer reefs appear less affected and indeed could be showing considerable resilience to such impacts.

A Robust Design Capture-Recapture Analysis of Abundance, Survival and Temporary Emigration of Three Odontocete Species in the Gulf of Corinth, Greece

Article

Full-text available

Dec 2016
PLOS ONE

While the Mediterranean Sea has been designated as a Global Biodiversity Hotspot, assessments of cetacean population abundance are lacking for large portions of the region, particularly in the southern and eastern basins. The challenges and costs of obtaining the necessary data often result in absent or poor abundance information. We applied capture-recapture models to estimate abundance, survival and temporary emigration of odontocete populations within a 2,400 km² semi-enclosed Mediterranean bay, the Gulf of Corinth. Boat surveys were conducted in 2011–2015 to collect photo-identification data on striped dolphins Stenella coeruleoalba, short-beaked common dolphins Delphinus delphis (always found together with striped dolphins in mixed groups) and common bottlenose dolphins Tursiops truncatus, totaling 1,873 h of tracking. After grading images for quality and marking distinctiveness, 23,995 high-quality photos were included in a striped and common dolphin catalog, and 2,472 in a bottlenose dolphin catalog. The proportions of striped and common dolphins were calculated from the photographic sample and used to scale capture-recapture estimates. Best-fitting robust design capture-recapture models denoted no temporary emigration between years for striped and common dolphins, and random temporary emigration for bottlenose dolphins, suggesting different residency patterns in agreement with previous studies. Average estimated abundance over the five years was 1,331 (95% CI 1,122–1,578) striped dolphins, 22 (16–32) common dolphins, 55 (36–84) “intermediate” animals (potential striped x common dolphin hybrids) and 38 (32–46) bottlenose dolphins. Apparent survival was constant for striped, common and intermediate dolphins (0.94, 95% CI 0.92–0.96) and year-dependent for bottlenose dolphins (an average of 0.85, 95% CI 0.76–0.95). Our work underlines the importance of long-term monitoring to contribute reliable baseline information that can help assess the conservation status of wildlife populations.

Need for longitudinal studies of Asian wildlife in the face of crises

Article

Full-text available

Apr 2016

Shermin de Silva

Conservation biology is conceived as a discipline that must balance the short-term aim of gathering data on pressing conservation issues with the long-term vision of protecting populations, species, and functional ecosystems. Asian wildlife face imminent threats ranging from hunting to loss of critical habitats, but there are few examples of detailed longitudinal wildlife research in the region. Longitudinal research is essential for protecting populations especially in light of the high volumes of legal and illegal trade, understanding basic population dynamics, notably with respect to long-lived species, as well as accommodating the spatial needs of animals. It is also critical for evaluating the success of conservation or management interventions and adaptively improving outcomes. Such studies, particularly when requiring sustained field work, are impeded by mismatches between needs on the ground vs. the priorities of different stakeholders, the ephemeral and inefficient nature of funding mechanisms, and by the logistics of maintaining sites and personnel. Yet we cannot adequately protect biodiversity in Asia unless the magnitude of human impacts on its species is quantitatively understood and used to inform management.

Patterns and Determinants of Habitat Occupancy by the Asian Elephant in the Western Ghats of Karnataka, India

Article

Full-text available

Jul 2015
PLOS ONE

Understanding species distribution patterns has direct ramifications for the conservation of endangered species, such as the Asian elephant Elephas maximus. However, reliable assessment of elephant distribution is handicapped by factors such as the large spatial scales of field studies, survey expertise required, the paucity of analytical approaches that explicitly account for confounding observation processes such as imperfect and variable detectability, unequal sampling probability and spatial dependence among animal detections. We addressed these problems by carrying out 'detection--non-detection' surveys of elephant signs across a c. 38,000-km(2) landscape in the Western Ghats of Karnataka, India. We analyzed the resulting sign encounter data using a recently developed modeling approach that explicitly addresses variable detectability across space and spatially dependent non-closure of occupancy, across sampling replicates. We estimated overall occupancy, a parameter useful to monitoring elephant populations, and examined key ecological and anthropogenic drivers of elephant presence. Our results showed elephants occupied 13,483 km(2) (SE = 847 km(2)) corresponding to 64% of the available 21,167 km(2) of elephant habitat in the study landscape, a useful baseline to monitor future changes. Replicate-level detection probability ranged between 0.56 and 0.88, and ignoring it would have underestimated elephant distribution by 2116 km(2) or 16%. We found that anthropogenic factors predominated over natural habitat attributes in determining elephant occupancy, underscoring the conservation need to regulate them. Human disturbances affected elephant habitat occupancy as well as site-level detectability. Rainfall is not an important limiting factor in this relatively humid bioclimate. Finally, we discuss cost-effective monitoring of Asian elephant populations and the specific spatial scales at which different population parameters can be estimated. We emphasize the need to model the observation and sampling processes that often obscure the ecological process of interest, in this case relationship between elephants to their habitat.

Reliable monitoring of elephant populations in the forests of India: Analytical and practical considerations

Article

Jul 2015
BIOL CONSERV

Morphometrics and behavior of a wild Asian elephant exhibiting disproportionate dwarfism

Article

Full-text available

Dec 2014
BMC Res Notes

Dwarfism is a condition characterized by shorter stature, at times accompanied by differential skeletal growth proportions relative to the species-typical physical conformation. Causes vary and are well-documented in humans as well as certain mammalian species in captive or laboratory conditions, but rarely observed in the wild. We report on a single case of apparent dwarfism in a free-ranging adult male Asian elephant in Sri Lanka, comparing physical dimensions to those of other males in the population as well as in previous literature. The subject M459 was found to have a shoulder height of approximately 195 cm, is shorter than the average height of typical mature males, with a body length of 218 cm. This ratio of body length to height deviates from what is typically observed, which is approximately 1:1, but was similar to the attributes of a dwarf elephant in captivity documented in 1955. We report on behavior including the surprising observation that M459 appears to have a competitive advantage in intrasexual contests. We discuss how this phenotype compares to cases of dwarfism in other non-human animals. M459 exemplifies a rare occurrence of disproportionate dwarfism in a free-ranging wild mammal that has survived to reproductive maturity and appears otherwise healthy.

Combining dead recovery, auxiliary observations and robust design data to estimate demographic parameters from marked individuals

Article

Sep 2013
Methods Ecol. Evol.

When estimating demographic parameters for wild populations, using multiple data sources can increase robustness through greater precision, reducing bias and permitting the estimation of otherwise confounded parameters. We present a method that combines recapture data from marked individuals, collected at a single study site, under a robust design framework, with dead recoveries and auxiliary resightings collected at any time and place. This model permits the joint modelling of survival, permanent and temporary emigration from the study area. We demonstrate that the usefulness of this model is compelling in the case of long‐lived species with substantial rates of temporary emigration, to mitigate bias in survival at the end of the time series and to permit conservation decisions based on more current information. We use the case of Florida manatees as an example. Our model can easily be extended to account for an arbitrary number of phenotypic states and account for state uncertainty. The increase in precision overall in vital rates, and the mitigation of bias in survival estimation in the final years of a time series, permits managers to base resource decisions on more robust and timely information. The model also provides the ability to adapt monitoring to changing conditions or specific management objectives, via dynamic allocation of effort to auxiliary resightings.

Identifying human elephant conflict hotspots through satellite remote sensing and GIS to support conflict mitigation

Article

Full-text available

Jun 2024

Face to face: human recognition of Asian elephant facial features

Article

Apr 2024

Especially in species with complex social systems, the relatedness between individuals is important information. Visual phenotypic cues present one way to identify closely related conspecifics. Humans are capable of recognizing such visual cues in the faces of their own as well as several primate species, but to which degree this applies to non-primate species is largely unexplored. Here we demonstrate the capability of 110 test persons to recognize faces of 47 male Asian elephants based on 186 photographs. The human examiners were not only able to recognize an individual based on its face after several years, but also to identify, at decreasing accuracy, full brother pairs and paternal kinship. People regularly working with elephants were more successful than laypersons. However, even laypersons recognized 73.3% of the same individuals. The identification of individual elephants by a look at their faces presents a simple approach which can be a valuable tool for in situ research.

Identifying sex and individual from faecal DNA of the Asian elephant using a single multiplex PCR for population monitoring

Article

Full-text available

Sep 2023

Information on the sex- and individual-specific space use by a species elucidates demography, resource selection and individual life history. However, traditional field surveys often lack information on sex and individual identity, thereby not maximizing the potential of the effort put in. Recent advances in genetic non-invasive sampling provide cost-effective approaches to determine identity and sex from faecal DNA with high accuracy, which are advantageous for tracking individuals compared to field observations. Therefore, we describe the first single multiplex-based sex and individual identification protocol using faecal samples of the wild Asian elephant (Elephas maximus) collected from the vicinity of Rajaji Tiger Reserve, Uttarakhand, India. We co-amplified fluorescence-labelled microsatellites (n = 5) and a Y chromosome-linked sex marker in four replicates from faecal DNA extracts (n = 149). The mean per genotype allelic drop-out rate was 0.11 ± 0.02, while the false allele rate was 0.05 ± 0.01. The mean null allele frequency across the markers was 0.15 ± 0.02. We obtained 74.1% consensus genotypes across microsatellites and dropped samples with more than one-locus missing genotype from further analyses. The remaining dataset comprised 105 samples, 30.5% of which were females. We identified 51 unique individuals (25 males and 26 females) with a maximum of one-locus mismatch. With low genotyping error rates and adequate misidentification probabilities (PID = 4.2 × 10⁻⁴; PIDSib = 3.0 × 10⁻²), the described panel provides a cost-effective method (US$ 18/sample) for molecular sexing and individual identification. Hence, the suggested multiplex panel would provide a thorough understanding of individual and sex-specific differences in habitat use across heterogeneous landscapes, facilitating effective conservation strategies.

Proximate nutrients of selected forage and the diet composition of adult elephants in Udawalawe National Park, Sri Lanka, a preliminary study

Article

Full-text available

Jul 2023

Asian Elephants feed predominantly on grass. The comparative nutritional contribution of grasses and other elephant forage is not known. Therefore, the proximate nutrition of food plants selected by elephants, and the relationship of their diet composition to body condition and gender were examined in this study. Proximate analysis was conducted on 11 plant species recognised upon 66h of opportunistic focal animal sampling. Five species among them were grasses, including the invasive Megathyrsus maximus. The micro-histological composition of freshly collected dung from 26 identified elephants was assessed against their body condition and gender. Associations, comparisons, and hypotheses were tested. Dicots were significantly high in dry matter and low in moisture, while monocots were high in moisture and low in dry matter (p <0.001). The average monocot: dicot ratio was 1: 0.73 in elephant diet. However, it was observed that the monocot composition in the male diet was significantly higher than dicots (p <0.001), while there was no significant difference in the female diet composition. Elephant body condition did not show any correlation with the abundance of monocot or dicot plant tissues. The preliminary study implies that dry matter nutrients in dicots and moisture in monocots influence diet selection of elephants. Their diet composition was associated with gender but did not correlate with body condition. M. maximus was not outstanding in nutrition from the selected plant species.

Collective movements during visits to water bodies in wild Asian elephants

Article

Jun 2023

Collective movements feature multiple consecutive processes involving different types of initiative behavior. It remains unclear whether, and to what extent, the same individual consecutively performs different initiative behaviors in a single collective-movement event. We conducted behavioral observations of wild Asian elephants (Elephas maximus) visiting a water body in Udawalawe National Park, Sri Lanka. We analyzed 32 collective-movement events involving 51 individually identified adult females. We used randomization tests to compare the observed and expected frequencies of initiative behavior by a particular individual. We found that adults were more likely to exhibit such behavior than the expected frequencies. We also found that a single female, generally the oldest female, consecutively engaged in three types of initiative behavior more frequently than expected, although their occurrence did not constitute the majority of cases (6/23). This low consecutiveness among Asian elephants may be related to their fission–fusion dynamics and lack of core groups. Our results highlight the importance of analyzing multiple initiative behaviors associated with collective movement.

A brighter future? Stable and growing sea turtle populations in the Republic of Maldives

Article

Full-text available

Apr 2023
PLOS ONE

The Indian Ocean represents a significant data gap in the evaluation of sea turtle population status and trends. Like many small island states, the Republic of Maldives has limited baseline data, capacity and resources to gather information on sea turtle abundance, distribution and trends to evaluate their conservation status. We applied a Robust Design methodology to convert opportunistic photographic identification records into estimates of abundance and key demographic parameters for hawksbill sea turtles (Eretmochelys imbricata) and green sea turtles (Chelonia mydas) in the Republic of Maldives. Photographs were collected ad hoc by marine biologists and citizen scientists around the country from May 2016 to November 2019. Across 10 sites in four atolls, we identified 325 unique hawksbill turtles and 291 unique green turtles—where most were juveniles. Our analyses suggest that, even when controlling for survey effort and detectability dynamics, the populations of both species are stable and/or increasing in the short term at many reefs in the Maldives and the country appears to provide excellent habitat for recruiting juvenile turtles of both species. Our results represent one of the first empirical estimations of sea turtle population trends that account for detectability. This approach provides a cost-effective way for small island states in the Global South to evaluate threats to wildlife while accounting for biases inherent in community science data.

Asian Elephant (Elephas maximus Linnaeus) Population Status and Demography in Tropical Forest of Southern India

Preprint

Full-text available

Mar 2022

The assessment of population dynamics and demography of long-lived species can be challenging due to a longer life span and slow reproduction. The population status and demography of the Asian elephant was studied from Dec 2006 to May 2008 at Mudumalai Tiger Reserves and results were compared with earlier studies carried out in the study area in 1985 and 2000 to understand changes in the population size. The population was estimated using distance sampling and mark-recapture methods during wet and dry seasons. In the line-transect sampling, a total distance of 651.5km was walked. To estimate the population based on the capture-recapture method 17 routes were surveyed consisting of 128.5km surveyed twice per month. The estimated elephant density based on capture-recapture and distance sampling was 3.4/km ² and 3.6/km ² respectively, which was higher than the earlier estimate (1/km ² in 1985 and 2.4/km ² in 2000). Thus, the population of elephants increased significantly when compared to the past. The adult male to adult female ratio was 1:20. Tuskless male Makhnas make up 20% of the male population. Demography data shows that the male population has increased in the population. But lack of older bulls in the population and mortality of males due to retaliatory killing needs further investigation. The major per cent (61%) of mortality was due to natural causes like disease, injuries, and predation by tigers (two calves). There were sex-biased changes in mortalities that have occurred over time; while adult and sub-adult male mortalities were higher (83%) in the earlier study period, adult female mortalities were higher (54.5%) during the present study. Despite the skewed sex ratio elephant population has increased significantly when compared to the past in the study area.

New Framework for Evaluating Ecosystem Quality in Nature Reserves based on Ideal References and Key Indicators

Article

Apr 2022

With increasing numbers and types of nature reserves (NRs), objective evaluation and comparison of the effects of different nature NRs on conservation efforts are of great importance for protecting species diversity, ensuring reasonable national economic input, and adjusting government management schemes. Developing a method for the combined assessment of flagship or umbrella species and ecosystem quality will improve the evaluation of NRs. However, it is also important to establish a new framework for rapid evaluation of ecosystem quality, supported by the advantages of scientific, economic, and regular principles. Here, we proposed a new framework that incorporates the novel concept of ideal references into evaluation systems, which will facilitate the comparison of results from different periods and regions. Furthermore, from the perspective of making the framework as objective, rapid, and economical as possible, we recommended some key ecological indicators, such as net primary productivity, soil organic matter, plant diversity, for use in the new evaluation framework. The new framework, referred to as ideal reference and key indicators (IRKI), can sufficiently meet the requirements for the rapid evaluation of ecosystem quality both regionally and nationally. Furthermore, IRKI can identify the restoration potential and restoration periods of NRs, thus facilitating the rational distribution of resources and enhancing the protective effect. There are many types of NRs in China, and it is necessary to partially alter the assessment methods or parameters for different types of NRs. Overall, IRKI provides a simple, clear, and comparable framework that will strongly enhance the conservation of protected areas (PAs) and facilitate the standardization of management practices.

Social lateralization in wild Asian elephants: visual preferences of mothers and offspring

Article

Full-text available

Jan 2018
BEHAV ECOL SOCIOBIOL

Theoretical and empirical evidence suggest that socio-biological factors determine the expression of behavioural lateralization across species. One would expect the same association at the intraspecific level, that is, that the differences in social strategies of the two sexes entail the sex differences in the lateralized social processing. This study aimed to test whether this hypothesis applies to the lateralized behaviour of offspring towards a mother. The preferences in the use of the lateral visual field of the left and right eye were assessed in wild Asian elephant, Elephas maximus mothers and their young sons and daughters. The spatial positioning relative to a social partner during approach was used as a behavioural indicator of visual lateralization. At the population level, elephant mothers preferred to keep the young in their left visual field during slow travelling. In contrast, young did not display a one-sided bias for the whole sample. The lateralization, however, was pronounced in a sex-specific manner—sons preferentially kept their mothers in the right visual field, while daughters preferred to keep mothers in the left visual field. Intriguingly, both sons and daughters preferentially kept the familiar older young in the left visual field. Sons, thus, showed oppositely directed lateral preferences towards mother and non-mother companion. Presumably, sons aim to approach the mother from her left side (rather than to keep her in the right visual field) and benefit from optimized maternal perception, while daughters facilitate their own perception of the mother by keeping her in the left visual field. These sex-related differences in lateralized behaviour may result from strikingly different social strategies of two sexes. Significance statement Young mammals show robust lateralization in the form of one-sided behavioural preferences in the interactions with their mother. Previous studies suggest that the social lifestyle may serve as a driving force in the evolution of behavioural lateralization. To test this proposition, we investigated behavioural lateralization in young subjects of Asian elephants, a species in which females are more gregarious than males. The lateralized behaviour of offspring towards the mother was found to be strongly sex-specific. In contrast, interactions with older young were lateralized in a similar manner in sons and daughters. Our results suggest that the benefits of a left-sided or right-sided position relative to mother have different significance for sons and daughters because of the distinctive social strategies of two sexes.

Morphometrics of a wild Asian elephant exhibiting disproportionate dwarfism

Article

Full-text available

Jan 2014

Shermin de Silva

Dwarfism is a condition characterized by shorter stature, at times accompanied by differential skeletal growth proportions relative to the species-typical physical conformation. Causes vary and well-documented in humans as well as certain mammalian species in captive or laboratory conditions, but rarely observed in the wild. Here we report on a single case of apparent dwarfism in a free-ranging adult male Asian elephant (Elephas maximus) in Sri Lanka, comparing physical dimensions to those of other males in the same population, males in other populations, and records in previous literature. The subject was found to have a shoulder height of approximately 195cm, is shorter than the average height of typical mature males, with a body length of 218cm. This ratio of body length to height deviates from what is typically observed, which is approximately 1:1. In absolute height the subject was similar to the attributes of a captive elephant documented in 1955 in Sri Lanka, also said to be a dwarf, however the two specimens differed in the relative proportions of height vs. body length. The subject also exhibits a slight elongation of the skull. We discuss how this phenotype compares to cases of dwarfism in other non-human animals.

The human-elephant conflict: A review of current status and mitigation methods

Article

Full-text available

Jan 2009

Buthgamu M A O Perera

Getting to know a population

Article

Full-text available

Jan 1996

Cynthia J Moss

Errors in identification using natural markings: rates, sources, and effects on capturerecapture estimates of abundance

Article

Full-text available

Apr 2011
CAN J FISH AQUAT SCI

The results of a double-marking experiment using natural markings and microsatellite genetic markers to identify humpback whales (Megaptera novaeangliae) confirm that natural markings are a reliable means of identifying individuals on a large scale. Of 1410 instances of double tagging, there were 414 resightings. No false positive and 14 false negative errors were identified. The rate of error increased with decreasing photographic quality; no errors were observed among photographs of the highest quality rating, whereas an error rate of 0.125 was identified in sightings for which only part of the area used for identification was visible. There was also a weaker relationship between error rate and the distinctiveness of markings, which may result from non-independence in coding for image quality and distinctiveness. A correction is developed for the Petersen two-sample abundance estimator to account for false negative errors in identification, and a parametric bootstrap procedure for estimation of variance is also developed. In application to abundance estimates from the North Atlantic, the correction reduces the bias in estimates made using poorer quality photographs to a negligible level while maintaining comparable precision.

Sinking the Flagship: the Case of Forest Elephants in Asia and Africa

Article

Full-text available

Sep 2004
CONSERV BIOL

Application of photographic capture–recapture modelling to estimate demographic parameters for male Asian elephants

Article

Full-text available

Aug 2007
ANIM CONSERV

In addition to the threats of habitat loss and degradation, adult males of the Asian elephant Elephas maximus also face greater threats from ivory poaching and conflict with humans. To understand the impact of these threats, conservationists need robust estimates of abundance and vital rates specifically for the adult male segment of elephant populations. By integrating the identification of individual male elephants in a population from distinct morphology and natural markings, with modern capture–recapture (CR) sampling designs, it is possible to estimate various demographic parameters that are otherwise difficult to obtain from this long-lived and wide-ranging megaherbivore. In this study, we developed systematic individual identification protocols and integrated them into CR sampling designs to obtain capture histories and thereby estimate the abundance of adult bull elephants in a globally important population in southern India. We validated these estimates against those obtained from an independent method combining line-transect density estimates with age–sex composition data for elephants. The sampled population was open to gains and losses between sampling occasions. The abundance of adult males in the 176 km2 study area was N̂(SÊN̂) = 134(14.20) and they comprised 14% (±1%) of the total elephant population. Time-specific abundance estimates for each sampling occasion showed a distinct increase in adult male numbers over the sampling period, explained by seasonal patterns of local migration. CR-based estimates for adult male abundance closely matched estimates from distance-based methods. Thus, while providing abundance data of comparable rigour and precision, photographic CR methods permit estimation of demographic parameters for the Asian elephant that are both urgently needed and difficult to obtain.

Distribution, status and conservation needs of Asian elephant (Elephas maximus) in Lampung Province, Sumatra, Indonesia

Article

Full-text available

Jan 2005
BIOL CONSERV

In the mid 1980s, Asian elephant (Elephas maximus) populations were believed to persist in 44 populations on the Indonesian island of Sumatra. Twelve of these populations occurred in Lampung Province, but our surveys revealed that only three were extant in 2002. Causal factors underlying this decline include human population growth, changes in land use, and human–elephant conflict. Nevertheless, our surveys in the Province’s two national parks, Bukit Barisan Selatan and Way Kambas, produced population estimates of 498 (95% CI = [373, 666]) and 180 (95% CI = [144, 225]) elephants, respectively. The estimate for Bukit Barisan Selatan is much larger than previous estimates; the estimate for Way Kambas falls between previous estimates. The third population was much smaller and may not be viable. These are the first estimates for Southeast Asian elephant populations based on rigorous sampling-based methods that satisfied the assumptions of the models used, and they suggest that elephant numbers in these parks are of international importance. While our results suggest that Sumatra’s remaining elephant populations may be larger than expected, they also suggest that the future for these animals is bleak. Human–elephant conflict was reported around all three areas in Lampung and their elephant populations are currently threatened by habitat loss and poaching. Local solutions are possible, but will require much greater commitment by all stakeholders.

Estimating State-Transition Probabilities for Unobservable States Using Capture-Recapture/Resighting Data

Article

Full-text available

Dec 2002

Temporary emigration was identified some time ago as causing potential problems in capture–recapture studies, and in the last five years approaches have been developed for dealing with special cases of this general problem. Temporary emigration can be viewed more generally as involving transitions to and from an unobservable state, and frequently the state itself is one of biological interest (e.g., ''nonbreeder''). Development of models that permit estimation of relevant parameters in the presence of an unobservable state requires either extra information (e.g., as supplied by Pollock's robust design) or the following classes of model constraints: reducing the order of Markovian transition prob-abilities, imposing a degree of determinism on transition probabilities, removing state specificity of survival probabilities, and imposing temporal constancy of parameters. The objective of the work described in this paper is to investigate estimability of model pa-rameters under a variety of models that include an unobservable state. Beginning with a very general model and no extra information, we used numerical methods to systematically investigate the use of ancillary information and constraints to yield models that are useful for estimation. The result is a catalog of models for which estimation is possible. An example analysis of sea turtle capture–recapture data under two different models showed similar point estimates but increased precision for the model that incorporated ancillary data (the robust design) when compared to the model with deterministic transitions only. This com-parison and the results of our numerical investigation of model structures lead to design suggestions for capture–recapture studies in the presence of an unobservable state.

Predictability of Sri Lankan rainfall based on ENSO

Article

Full-text available

Jun 2007
INT J CLIMATOL

Investigating the year-round rainfall of Sri Lanka provides understanding into the South Asian monsoon system as it compliments studies on the Indian summer monsoon. The El Niño-Southern Oscillation (ENSO) is a primary mode of climate variability of this area. Here, the predictability of Sri Lanka rainfall based on ENSO is quantified based on composite analysis, correlations and contingency tables. The rainfall is modestly predictable based on ENSO during January–March, July–August and October–December. El Niño typically leads to wetter conditions during October to December and drier conditions during January to March and July to August on average. The correlations of ENSO indices with rainfall are statistically significant for October to December, January to March and July to August and an analysis based on contingency tables shows modest predictability. The use of ENSO indices derived from the central Pacific sea surfaces improves the predictability from January to June. The predictability in the mountain regions is diminished when garnering orographic rainfall. The predictability in the east is diminished during the cyclone season. The predictability based on ENSO for October to December rainfall is robust on a decadal scale while the predictability of January to March and July to August rainfall has acquired significance in recent decades. An ENSO-based scheme that is adapted to each season and region, and takes account of decadal variations can thus provide skillful rainfall predictions. Copyright © 2007 Royal Meteorological Society

Estimating abundance for a savanna elephant population using mark-resight methods: A case study for the Tembe Elephant Park, South Africa

Article

Full-text available

Apr 2007
J ZOOL

Elephants living in dense woodlands are difficult to count. Many elephant populations in Africa occur in such conditions. Estimates of these populations based on total counts, aerial counts and dung counts often lack information on precision and accuracy. We use standard mark–recapture field methods to obtain estimates of population size with associated confidence limits. We apply this approach to a closed elephant population in the Tembe Elephant Park (300 km2), South Africa. A registration count completed in 4 months gives a known population size. We evaluate mark–recapture models against the known population size. Individual identification profiles obtained for elephants during the registration count and mark–recapture events indicate that at least 167 elephants live in the park. We consider this value as an estimate of the minimum number alive. We include 189 sightings of bulls and 37 sightings of breeding herds in the mark–recapture modelling. Of the models we test (Petersen, Schnabel, Schumacher, Jolly–Seber, Bowden's, Poisson and negative binomial), Bowden's gives an estimate closest to the registration count. Assumptions of the model are not violated. For all models except one (negative binomial), our estimates improve with increased sampling intensity. Confidence intervals do not improve with increased effort except for the Schnabel model. Mark–recapture methods should be considered as reliable estimators of population size for elephants occurring in dense woodlands and forests when other methods cannot be relied on.

Program MARK: Survival Estimation from Populations of Marked Animals

Article

Full-text available

Jan 1999

MARK provides parameter estimates from marked animals when they are re-encountered at a later time as dead recoveries, or live recaptures or re-sightings. The time intervals between re-encounters do not have to be equal. More than one attribute group of animals can be modelled. The basic input to MARK is the encounter history for each animal. MARK can also estimate the size of closed populations. Parameters can be constrained to be the same across re-encounter occasions, or by age, or group, using the parameter index matrix. A set of common models for initial screening of data are provided. Time effects, group effects, time x group effects and a null model of none of the above, are provided for each parameter. Besides the logit function to link the design matrix to the parameters of the model, other link functions include the log—log, complimentary log—log, sine, log, and identity. The estimates of model parameters are computed via numerical maximum likelihood techniques. The number of parameters that are estimable in the model are determined numerically and used to compute the quasi-likelihood AIC value for the model. Both the input data, and outputs for various models that the user has built, are stored in the Results database which contains a complete description of the model building process. It is viewed and manipulated in a Results Browser window. Summaries available from this window include viewing and printing model output, deviance residuals from the model, likelihood ratio and analysis of deviance between models, and adjustments for over dispersion. Models can also be retrieved and modified to create additional models. These capabilities are implemented in a Microsoft Windows 95 interface. The online help system has been developed to provide all necessary program documentation.

Socioecology, acoustic communication and demography of Asian elephants in Sri Lanka

Article

Full-text available

Aug 2010

Shermin de Silva

SOCIOECOLOGY, ACOUSTIC COMMUNICATION AND DEMOGRAPHY OF ASIAN ELEPHANTS IN SRI LANKA Shermin de Silva (Author) Dorothy L. Cheney (Supervisor) Comparison of behavior across species brings to light the underlying social and ecological factors that have shaped social organization and communication. Elephantids, the only living members of the Proboscidean clade are cognitively sophisticated, long-lived, putatively social mammals. I examine how vocal communication and social organization in Asian elephants (Elephas maximus) compare to African savannah elephants (Loxodonta africana), as well as basic demographic and conservation issues concerning Asian elephants. The first chapter defines fourteen distinct acoustic signals based on their acoustic features, and describes the contexts in which they occur. Most vocalizations are employed in contexts of movement, and some vocalizations are used primarily during movement or non-aggressive social interactions. This suggests that elephants actively seek out association with particular individuals. The second chapter tests the hypothesis that associations among adult female Asian elephants are governed by resourced availability, and describes the temporal structure and strength of bonds. This study population demonstrates fission-fusion social dynamics in which individuals change companions over short time scales, influenced by rainfall, but maintain stable relationships over long time scales. In the third chapter I test the hypothesis that associations are purely the consequence of the spatial distribution of resources, rather than social preference, using a modeling approach based on the spatio-temporal coordinates of individuals. In all seasons, individuals appear to move in a coordinated manner, supporting the interpretation that observed associations reflect true social preference. At the same time, resource distributions do influence the size of social units, and their movements. In the fourth chapter I review the most recent demographic studies of elephant populations in Asia as well as Africa, and highlight the lack of data for much of Asia. I outline methods based on individual identification that may be used to address this challenge to conservation and management. I apply these methods to offer demographic estimates for the study site, and examine what constitutes good practice, in the fifth chapter.

Behavior rather than diet mediates seasonal differences in seed dispersal by Asian elephants

Article

Full-text available

Nov 2008

Digestive physiology and movement patterns of animal dispersers determine deposition patterns for endozoochorously dispersed seeds. We combined data from feeding trials, germination tests, and GPS telemetry of Asian elephants (Elephas maximus) to (1) describe the spatial scale at which Asian elephants disperse seeds; (2) assess whether seasonal differences in diet composition and ranging behavior translate into differences in seed shadows; and (3) evaluate whether scale and seasonal patterns vary between two ecologically distinct areas: Sri Lanka's dry monsoon forests and Myanmar's (Burma) mixed-deciduous forests. The combination of seed retention times (mean 39.5 h, maximum 114 h) and elephant displacement rates (average 1988 m in 116 hours) resulted in 50% of seeds dispersed over 1.2 km (mean 1222-2105 m, maximum 5772 m). Shifts in diet composition did not affect gut retention time and germination of ingested seeds. Elephant displacements were slightly longer, with stronger seasonal variation in Myanmar. As a consequence, seed dispersal curves varied seasonally with longer distances during the dry season in Myanmar but not in Sri Lanka. Seasonal and geographic variation in seed dispersal curves was the result of variation in elephant movement patterns, rather than the effect of diet changes on the fate of ingested seeds.

A Likelihood-Based Approach to Capture-Recapture Estimation of Demographic Parameters under the Robust Design

Article

Full-text available

Apr 1995

The Jolly-Seber method has been the traditional approach to the estimation of demographic parameters in long-term capture-recapture studies of wildlife and fish species. This method involves restrictive assumptions about capture probabilities that can lead to biased estimates, especially of population size and recruitment. Pollock (1982, Journal of Wildlife Management 46, 752-757) proposed a sampling scheme in which a series of closely spaced samples were separated by longer intervals such as a year. For this "robust design," Pollock suggested a flexible ad hoc approach that combines the Jolly-Seber estimators with closed population estimators, to reduce bias caused by unequal catchability, and to provide estimates for parameters that are unidentifiable by the Jolly-Seber method alone. In this paper we provide a formal modelling framework for analysis of data obtained using the robust design. We develop likelihood functions for the complete data structure under a variety of models and examine the relationship among the models. We compute maximum likelihood estimates for the parameters by applying a conditional argument, and compare their performance against those of ad hoc and Jolly-Seber approaches using simulation.

The Proboscidea: Evolution and Palaeoecology of Elephants and Their Relatives

Article

Sep 1996

The Proboscidea, of which only two species of elephant survive today, were one of the great mammalian orders of the Cenozoic. Their success over evolutionary time is reflected by their morphological and taxonomic diversity, their nearly worldwide distribution on every continent except Australia and Antarctica, and their persistence through nearly fifty million years. Their great past ability to migrate and to adapt to changing climatic conditions and interspecific competition provides a unique laboratory for the testing of evolutionary theories and development of new concepts. This is the first complete treatise on the evolution and palaeoecology of this group for half a century. It reviews their classification and phylogeny, the early differentiation of proboscideans, the major adaptive radiations and their evolutionary patterns, and the origins and current status of extant elephant species. Written by leading international experts, this is a major study documenting the record of terrestrial biodiversity.

Getting to know a population. In: K Kangwana. Studying elephants

Article

Jan 1996

Cynthia J Moss

Relationships and social structure of African elephants. In: Hinde RA ed. Primate Social Relationships: An Integrated Approach

Article

Jan 1983

On the use of secondary capture-recapture samples to estimate temporary emigration and breeding proportions

Article

Nov 1995

The use of the Cormack-Jolly-Seber model under a standard sampling scheme of one sample per time period, when the Jolly-Seber assumption that all emigration is permanent does not hold, leads to the confounding of temporary emigration probabilities with capture probabilities. This biases the estimates of capture probability when temporary emigration is a completely random process, and both capture and survival probabilities when there is a temporary trap response in temporary emigration, or it is Markovian. The use of secondary capture samples over a shorter interval within each period, during which the population is assumed to be closed (Pollock's robust design), provides a second source of information on capture probabilities. This solves the confounding problem, and thus temporary emigration probabilities can be estimated. This process can be accomplished in an ad hoc fashion for completely random temporary emigration and to some extent in the temporary trap response case, but modelling the complete sampling process provides more flexibility and permits direct estimation of variances. For the case of Markovian temporary emigration, a full likelihood is required.

Multimodel Inference: understanding AIC and BIC in Model Selection

Article

Jan 2004

The Asian Elephant: Ecology and Management

Article

Jan 1991

The Asian elephant has had a unique cultural association with people. Unfortunately, elephants and people have also been in conflict, resulting in the decline in elephants throughout their former range in Southern Asia. This book provides an ecological analysis of elephant human interaction and its implications for the conservation of elephants. The foraging habits of elephants and their impact on vegetation are considered, along with the interactions that occur between elephants and humans. The ecological data provide the basis for recommendations on elephant conservation and management, keeping in view the socioeconomic imperatives of the Asian region.This first comprehensive account of Asian elephant ecology will be of particular interest to conservation biologists and mammalogists.

Some Practical Aspects of a Conditional Likelihood Approach to Capture Experiments

Article

Jun 1991

R. M. Huggins

The use of conditional likelihood methods in the analysis of capture data allows the modeling of capture probabilities in terms of observable characteristics of the captured individuals and the trapping occasions. The resulting models may then be used to estimate the size of the population. Here the use of conditional likelihood procedures to construct models for capture probabilities is discussed and illustrated by an example.

Estimating Temporary Migration Using the Robust Design

Article

Mar 1997

One of the basic assumptions central to the analysis of capture-recapture experiments is that all marked animals remain in the population under study for the duration of the sampling, or if they migrate out of the population they do so permanently. K. P. Burnham [in J.-D. Lebreton and P. M. North (eds.), Marked Individuals in the Study of Bird Populations, 199-213 (1993)], W. L. Kendall and J. D. Nichols [J. Appl. Stat. 22, 751-762 (1995)], and W. L. Kendall, J. D. Nichols and J. E. Hines (in press) showed that completely random temporary emigration influences only estimates of the probability of capture, these now estimating the product of the temporary emigration rate and the conditional probability of capture given the animal remains in the population. Estimates of abundance or survival that refer to the entire population, including the temporary emigrants, remain unaffected. W. L. Kendall et al. (in press) further showed that K. H. Pollock’s [J. Wildlife Manage 46, 757-760 (1982)] robust design could be used to estimate the temporary emigration rate when the population ws assumed closed during the secondary samples. We generalize this result to allow animals to enter and leave the population during the secondary samples. We apply the results to a study of Grey Seals and perform simulation experiments to assess the robustness of our estimator to errors in field identification of brands and other violations of our assumptions.

Errors in identification using natural markings: Rates, sources, and effects on capture-recapture estimates of abundance

Article

Sep 2001
CAN J FISH AQUAT SCI

Estimating Temporary Emigration Using Capture-Recapture Data with Pollock's Robust Design

Article

Mar 1997

Statistical inference for capture-recapture studies of open animal populations typically relies on the assumption that all emigration from the studied population is permanent. However, there are many instances in which this assumption is unlikely to be met. We define two general models for the process of temporary emigration: completely random and Markovian. We then consider effects of these two types of temporary emigration on Jolly-Seber estimators and on estimators arising from the full-likelihood approach to robust design data. Capture-recapture data arising from Pollock's robust design provide the basis for obtaining unbiased estimates of demographic parameters in the presence of temporary emigration, and for estimating the probability of temporary emigration. We present a likelihood-based approach to dealing with temporary emigration that permits estimation under different models of temporary emigration and yields tests for completely random and Markovian emigration. In addition, we use the relationship between capture probability estimates based on closed and open models under completely random temporary emigration to derive three ad hoc estimators for the probability of temporary emigration. Two of these should be especially useful in situations where capture probabilities are heterogeneous among individual animals. Ad hoc and full-likelihood estimators are illustrated for small-mammal capture-recapture data sets. We believe that these models and estimators will be useful for testing hypotheses about the process of temporary emigration, for estimating demographic parameters in the presence of temporary emigration, and for estimating probabilities of temporary emigration. These latter estimates are frequently of ecological interest as indicators of animal movement and, in some sampling situations, as direct estimates of breeding probabilities and proportions.

Home range and seasonal movement of elephants in the Kunene Region, northwestern Namibia

Article

Jan 2009

Keith Leggett

This paper examines the home ranges and seasonal movements of eight GPS-collared elephants (two females and six males) in the northwestern Kunene region of Namibia. Minimum convex polygon (MCP) and the fixed kernel density estimation (FKDE) methods were used to analyse home ranges. The collared elephants showed defined home and seasonal ranges. In the eastern section of the research area, the elephants generally had smaller home ranges that were at their least during the hot and cold dry seasons, expanding during the wet season. In the western areas, the elephants moved between the Hoanib and Hoarusib Rivers in response to available vegetation that did not necessarily correspond to rainfall. The length of movement of collared elephants varied from 54.5 to 473 km in the eastern section of the research area to between 251 to 625 km in the west, over periods of up to five months.

Fragmentation of Asia's remaining wildlands: Implications for Asian elephant conservation

Article

Nov 2003
ANIM CONSERV

Habitat loss and fragmentation are main causes for Asian elephant population declines. We mapped wildlands - large, unfragmented and undeveloped areas - asking: (1) Where are the largest wildlands that constitute elephant habitats? (2) What proportion of these wildlands is protected? (3) What is their potential for elephant conservation? Our study demonstrates that wildlands constitute only 51% of the Asian elephant range. Myanmar has the largest wildland ([similar]170,000 km2), followed by Thailand and India. In Principal Components Analysis (PCA), the first two components explained 73% of the variation in fragmentation among ranges. We identified three fragmentation clusters from the PCA. Cluster A contains large ranges with unfragmented wildlands; cluster B includes ranges with well-developed transportation networks and large human populations; and cluster C contains ranges with severely fragmented wildlands. In cluster A, we identified four ranges with elephant populations >1000 animals: ARYO, MYUC, BNMH and BITE. Together with ranges that support >1000 elephants in cluster B, these A ranges have great potential for long-term elephant conservation. We propose that fragmentation clusters and population size can be used to identify different elephant monitoring and management zones.

Distribution and Status of the Asian Elephant

Article

Nov 1978
ORYX

Robert Olivier

This comprehensive survey of the Asian elephant is the result of an FPS-sponsored project dating from 1973. The author is Co-Chairman with J.C. Daniel, Curator of the Bombay Natural History Society) of the Survival Service Commission's Asian Elephant Group, created in 1976. He discusses the history of man-elephant relationships in Asia, the animal's status in each country where it occurs, and the reasons both for its disappearance from most of its former range and for its continuing decline. Much of the information is based on reports direct from the field and, in the case of peninsular Malaysia, on the author's own observations while attached to the office of the Chief Game Warden of West Malaysia. He estimates that only 28,000-42,000 Asian elephants remain in the wild.

The problem of precision and trend detection posed by small elephant populations in West Africa

Article

May 2002
AFR J ECOL

Richard F W Barnes

The precision of elephant estimates from aerial sample surveys and dung counts is inversely proportional to abundance. West African elephant populations are already small, and the power of a monitoring programme to detect changes in abundance diminishes as the population shrinks in size. Thus it will be difficult to evaluate the effects on elephant numbers of new management policies in West Africa. The same will be true of monitoring schemes for antelope and primate populations that are hunted for bushmeat. Elephant estimates from dung counts are more precise than those from aerial sample surveys, and changes in elephant numbers are more likely to be detected in the subregion by dung counts than by aerial sample surveys. La précision des estimations des éléphants réalisées à partir de surveillances aériennes échantillons et du comptage des crottes est inversement proportionnelle à leur abondance. Les populations d'éléphants d'Afrique de l'Ouest sont déjà réduites et la capacité qu'a un programme de surveillance continue de détecter des changements de nombre diminue quand la population se réduit. Il sera donc difficile d'évaluer les effets des nouvelles politiques ouest-africaines en matière de gestion sur le nombre d'éléphants. Ce sera aussi le cas des programmes de surveillance des populations d'antilopes et de primates qui sont chassées pour leur viande. Les estimations du nombre d'éléphants réalisées à partir du comptage des crottes sont plus précises que celles qui sont faites à partir de comptages échantillons aériens, et les changements du nombre d'éléphants dans la sous-région seront plus probablement décelés par les comptages des excréments que par des contrôles aériens.

Estimating decay rates of elephant dung piles in forest

Article

Apr 2008
AFR J ECOL

Data from a dropping decay experiment were re-analysed following the finding by other workers that decay is not an exponential process. Methods based on the assumption of constant age-specific decay gave biased estimates of the mean decay rate for the population of droppings. The best estimate was obtained by weighting the decay rate by the frequency of droppings in each age-class. On a réanalysé les résultats d'une expérience sur la décomposition des excréments suite au fait que d'autres chercheurs avaient trouvé que la décomposition n'est pas un processus exponentiel. Les méthodes basées sur l'hypothèse d'une décomposition constante liée à l'âge donnent des estimations biaisées du taux moyen de décomposition pour l'ensemble des excréments. On a obtenu la meilleure estimation en mettant en balance le taux de décomposition et la fréquence des déjections pour chaque classe d'âge.

Hierarchical model for estimating density in camera-trap studies

Article

Nov 2008
J APPL ECOL

Estimating animal density using capture–recapture data from arrays of detection devices such as camera traps has been problematic due to the movement of individuals and heterogeneity in capture probability among them induced by differential exposure to trapping. We develop a spatial capture–recapture model for estimating density from camera‐trapping data which contains explicit models for the spatial point process governing the distribution of individuals and their exposure to and detection by traps. We adopt a Bayesian approach to analysis of the hierarchical model using the technique of data augmentation. The model is applied to photographic capture–recapture data on tigers Panthera tigris in Nagarahole reserve, India. Using this model, we estimate the density of tigers to be 14·3 animals per 100 km ² during 2004. Synthesis and applications. Our modelling framework largely overcomes several weaknesses in conventional approaches to the estimation of animal density from trap arrays. It effectively deals with key problems such as individual heterogeneity in capture probabilities, movement of traps, presence of potential ‘holes’ in the array and ad hoc estimation of sample area. The formulation, thus, greatly enhances flexibility in the conduct of field surveys as well as in the analysis of data, from studies that may involve physical, photographic or DNA‐based ‘captures’ of individual animals.

An ocean-basin-wide mark-recapture study of the North-Atlantic Humpback Whale (Megaptera novaeangliae)

Article

Jan 1999
MAR MAMMAL SCI

A bstract Although much is known about the humpback whale, Megaptera novaeangliae , regional studies have been unable to answer several questions that are central to the conservation and management of this endangered species. To resolve uncertainties about population size, as well as the spatial and genetic structure of the humpback whale population in the North Atlantic, we conducted a two‐year ocean‐basin‐wide photographic and biopsy study in 1992‐1993. Photographic and skin‐biopsy sampling was conducted of animals in feeding and breeding areas throughout most of the range of this species in the North Atlantic, from the West Indies breeding grounds through all known feeding areas as far north as arctic Norway. A standardized sampling protocol was designed to maximize sample sizes while attempting to ensure equal probability of sampling, so that estimates of abundance would be as accurate and as precise as possible. During 666 d at sea aboard 28 vessels, 4,207 tail fluke photographs and 2,326 skin biopsies were collected. Molecular analyses of all biopsies included determination of sex, genotype using six microsatellite loci, and mitochondrial control region sequence. The photographs and microsatellite loci were used to identify 2,998 and 2,015 individual whales, respectively. Previously published results from this study have addressed spatial distribution, migration, and genetic relationships. Here, we present new estimates of total abundance in this ocean using photographic data, as well as overall and sex‐specific estimates using biopsy data. We identify several potential sampling biases using only breeding‐area samples and report a consistent mark‐recapture estimate of oceanwide abundance derived from photographic identification, using both breeding and feeding‐area data, of 10,600 (95% confidence interval 9,300‐12,100). We also report a comparable, but less precise, biopsy‐based estimate of 10,400 (95% confidence interval of 8,000‐13,600). These estimates are significantly larger and more precise than estimates made for the 1980s, potentially reflecting population growth. In contrast, significantly lower and less consistent estimates were obtained using between‐feeding‐area or between‐breeding‐area sampling. Reasons for the lower estimates using the results of sampling in the same areas in subsequent years are discussed. Overall, the results of this ocean‐basin‐wide study demonstrate that an oceanwide approach to population assessment of baleen whales is practicable and results in a more comprehensive understanding of population abundance and biology than can be gained from smaller‐scale efforts.

A global overview of the conservation status of tropical dry forests

Demography of Asian elephants from identified individuals at Uda Walawe National Park, Sri Lanka

Abstract

No full-text available