Seismic waves — vibrations within and along the Earth’s surface — are ubiquitous sources of information. During propagation, physical factors can obscure information transfer via vibrations and influence propagation range . Here, we explore how terrain type and background seismic noise influence the propagation of seismic vibrations generated by African elephants. In Kenya, we recorded the ground-based vibrations of different wild elephant behaviours, such as locomotion and infrasonic vocalisations , as well as natural and anthropogenic seismic noise. We employed techniques from seismology to transform the geophone recordings into source functions — the time-varying seismic signature generated at the source. We used computer modelling to constrain the propagation ranges of elephant seismic vibrations for different terrains and noise levels. Behaviours that generate a high force on a sandy terrain with low noise propagate the furthest, over the kilometre scale. Our modelling also predicts that specific elephant behaviours can be distinguished and monitored over a range of propagation distances and noise levels. We conclude that seismic cues have considerable potential for both behavioural classification and remote monitoring of wildlife. In particular, classifying the seismic signatures of specific behaviours of large mammals remotely in real time, such as elephant running, could inform on poaching threats.
Repeated use of the same areas may benefit animals as they exploit familiar sites, leading to consistent home ranges over time that can span generations. Changing risk landscapes may reduce benefits associated with home range fidelity, however, and philopatric animals may alter movement in response to new pressures. Despite the importance of range changes to ecological and evolutionary processes, little tracking data have been collected over the long-term nor has range change been recorded in response to human pressures across generations. Here, we investigate the relationships between ecological, demographic and human variables and elephant ranging behaviour across generations using 16 years of tracking data from nine distinct female social groups in a population of elephants in northern Kenya that was heavily affected by ivory poaching during the latter half of the study. Nearly all groups—including those that did not experience loss of mature adults—exhibited a shift north over time, apparently in response to increased poaching in the southern extent of the study area. However, loss of mature adults appeared to be the primary indicator of range shifts and expansions, as generational turnover was a significant predictor of range size increases and range centroid shifts. Range expansions and northward shifts were associated with higher primary productivity and lower poached carcass densities, while westward shifts exhibited a trend to areas with higher values of primary productivity and higher poached carcass densities relative to former ranges. Together these results suggest a trade-off between resource access, mobility and safety. We discuss the relevance of these results to elephant conservation efforts and directions meriting further exploration in this disrupted society of a keystone species.
In the southern Bago Yoma mountain range in Myanmar, Asian elephants are being killed at a disturbing rate. This emerging crisis was identified initially through a telemetry study when 7 of 19 of collared elephants were poached within a year of being fitted with a satellite-GPS collar. Subsequent follow up of ground teams confirmed the human caused death or disappearance of at least 19 elephants, including the seven collared individuals, within a 35 km2 area in less than two years. The carcasses of 40 additional elephants were found in areas located across south-central Myanmar once systematic surveys began by our team and collaborators. In addition to the extreme rate of loss, this study documents the targeting of elephants for their skin instead of the more common ivory, an increasing trend in Myanmar. Intensive research programs focused on other conservation problems identified this issue and are now encouraging local authorities to prioritize anti-poaching efforts and improve conservation policies within the country. Myanmar represents one of the last remaining countries in Asia with substantial wildlands suitable for elephants. Increasing rates of human-elephant conflict and poaching events in this country pose a dire threat to the global population.
1. Development of transportation corridors has accelerated globally, with infrastructure projects being implemented across remote ecosystems, particularly in the tropics. Such developments can have negative impacts on wildlife and their ecosystems. The importance of wildlife crossing structures to mitigate adverse effects of such features is widely recognized, but the siting of and investment in crossing structures is contentious. Data on animal movement provide valuable, highly specific information for such processes, but can present analytical challenges and remain underutilized in planning mitigation efforts.
2. We develop two algorithms based on Integer Linear Programming to prioritize crossing points based on frequency of use or breadth of coverage among tracked individuals. These scenarios represent metrics likely to guide the planning of crossing structures, where the former may relate to the objective of minimizing vehicle‐animal collisions and the latter on maintaining ecosystem connectivity. We exemplify the algorithms through application on a tracking dataset from over 150 African elephants living near the proposed Lamu Port‐South Sudan‐Ethiopia‐Transport corridor. We explore the influence of sampling bias on outcomes and discuss considerations to guide the application process.
3. Given the generally open, unfenced nature of this ecosystem, recorded movements occurred throughout the system and a third of the corridor length in the ecosystem was intersected by recorded elephant movements. The selection of crossing structure locations and their impacts on elephants varied whether we used a subsample of elephant representative of local population density or total sample of monitored individuals. The two algorithms also selected for different crossing structure locations.
4. Synthesis and applications. Our work shows some of the challenges of using Global Positioning System telemetry in deciding where to put crossing structures and demonstrates the need to identify the type of constraints in the system and desired crossing structure characteristics a priori. We recommend managers carefully evaluate the presence of potential biases in their data. High‐resolution data combined with objective prioritization methods allow reasoned planning actions, but are often lacking during critical infrastructure planning stages. Given the limited budget already allocated to mitigation measures in most proposed developments, the tools developed and applied here can facilitate effective spatial planning.
Network (graph) theory is a popular analytical framework to characterize the structure and dynamics among discrete objects and is particularly effective at identifying critical hubs and patterns of connectivity. The identification of such attributes is a fundamental objective of animal movement research, yet network theory has rarely been applied directly to animal relocation data. We develop an approach that allows the analysis of movement data using network theory by defining occupied pixels as nodes and connection among these pixels as edges. We first quantify node-level (local) metrics and graph-level (system) metrics on simulated movement trajectories to assess the ability of these metrics to pull out known properties in movement paths. We then apply our framework to empirical data from African elephants (Loxodonta africana), giant Galapagos tortoises (Chelonoidis spp.), and mule deer (Odocoileous hemionus). Our results indicate that certain node-level metrics, namely degree, weight, and betweenness, perform well in capturing local patterns of space use, such as the definition of core areas and paths used for inter-patch movement. These metrics were generally applicable across data sets, indicating their robustness to assumptions structuring analysis or strategies of movement. Other metrics capture local patterns effectively, but were sensitive to specified graph properties, indicating case specific applications. Our analysis indicates that graph-level metrics are unlikely to outperform other approaches for the categorization of general movement strategies (central place foraging, migration, nomadism). By identifying critical nodes, our approach provides a robust quantitative framework to identify local properties of space use that can be used to evaluate the effect of the loss of specific nodes on range wide connectivity. Our network approach is intuitive, and can be implemented across imperfectly sampled or large-scale data sets efficiently, providing a framework for conservationists to analyze movement data. Functions created for the analyses are available within the R package moveNT.
Living in Harmony with Elephants (LIHWE) is a four-part manual
developed by Save the Elephants in collaboaration with Disney’s Animal
Kingdom that teaches students conservation education with the aims to
future wildlife ambassadors. Since it’s inception in 2012, LIHWE has
reached out to over 500 students within the Samburu Isiolo Conservation
Area (SICA). LIHWE is one of Save The Elephants (STE) Education
Program’s approaches that introduce young minds into the world of
elephants, delighting them in the species’ intelligence and diversity, and
we remain indebted to Disney’s Animal Kingdom educators for all the help
they provided to develop this manual.
The first lesson equips students with knowledge on elephant ecology,
exploring the species physiology, social interaction and its role in
modifying the savannah. Next, learners are introduced to the importance
of and threats to elephant habitats. The third lesson teaches learners how
to protect themselves, their livestock, manyattas from elephants and
while at it, securing a future for elephants and other wildlife.
The present thesis investigates aspects of the reproductive strategy of male African savannah elephants (Loxodonata africana). The existence of, and differences between alternative conditional dependent reproductive tactics are evaluated using a combination of behavioural, endocrinological
and GPS tracking data and the age and tactic related success is measured using genetic paternity
Hidden Markov Models were used as a probabilistic framework for analysing temporal changes in reproductively active and inactive periods based on shifts in association preferences of individuals. Distinct shifts between active and inactive periods were evident well before the onset of
the aggressive reproductive tactic of musth, seen in older dominant males, hence providing the first quantitative evidence for the previously suggested sexually active periods in non-musth males. The link between hormones and reproductive status and tactics were investigated using a new technique for non-invasive faecal analysis of hormones. A combined analysis of androgens (Epiandrosterone) and glucocorticoid (3a,11-oxo-CM) hormones in relation to age, reproductive state and musth signals confirmed previously reported elevated levels of androgens during periods
with temporal gland secretion and urine dribbling (Musth) but further showed that this increase is indeed linked to the presence of musth signals and not to the age of the individual. Androgen levels were generally increased during sexually active periods with a two-fold increase seen in active non-musth bulls and a four to six-fold increase in musth bulls. Contrary to expectations, increased glucocorticoids outputs were not seen in musth bulls but slightly elevated outputs were seen in active non-musth bulls. Brief peaks in glucocorticoids occurred immediately after physical fights and during periods of injuries. A general elevation of glucocorticoids was seen towards the end of the long dry season, a likely effect of ecological conditions. Behavioural changes and onset of musth signals occurred after an initial change in androgen levels suggesting that sex steroids may play an activiational role of sexually active periods as well as activation of the musth tactic within sexually active periods. Some evidence was found for increased androgen levels following encounters with receptive females, suggesting that such encounters may act as a “boosters vaccine” on androgen levels and hereby prolong active periods at times with high numbers of receptive females.
Both musth and sexually active non-musth (SAN) bulls reduced their foraging and walked more than sexually inactive bulls. However musth bulls had a higher time specific investment in reproduction compared to SAN bulls with musth bulls doubling their daily walking distance
compared to a 50% increase in SAN bulls. The (younger) non-musth bulls spent a larger part of the year sexually active (70%) compared to musth bulls (20%) hence SAN bulls have a tactic of prolonged low investment compared to the short and high investment seen in musth bulls,
emphasising the need for evaluating the duration of reproductive bouts when comparing overall investments between tactics. The youngest (non-musth) bull to sire offspring was 21 years but older musth bulls above 35 years had a much higher age specific reproductive success compared to bulls below 30 years.
However on a population level, bulls less than 30 years contributed 30% of the reproduction and 20-25% could be attributed to non-musth bulls.
Compensatory social behavior in nonhuman animals following maternal loss has been documented, but understanding of how orphans allocate bonding to reconstruct their social networks is limited.
Successful social integration may be critical to survival and reproduction for highly social species and, therefore, may be tied to population persistence. We examined the social partners involved in affiliative interactions of female orphans and non-orphans in an elephant population in Samburu, northern Kenya that experienced heightened adult mortality driven by drought and intense ivory poaching. We contrasted partners across different competitive contexts to gain insight to the influence of resource availability on social interactions. Though the number of partners did not differ between orphans and non-orphans, their types of social partners did. Orphans interacted with sisters and matriarchs less
while feeding than did non-orphans, but otherwise their affiliates were similar.
While resting under spatially concentrated shade, orphans had markedly less access to mature adults but affiliated instead with sisters, bulls, and age mates. Orphan propensity to strengthen bonds with non-dominant animals appears to offer routes to social integration following maternal loss, but lack of interaction with adult females suggests orphans may experience decreased resource access and associated fitness costs in this matriarchal society.
Conservation managers are concerned about the impact that African elephants (Loxodonta africana) have on large tree species, necessitating the need for mitigation methods. Elephants actively avoid contact with African honeybees (Apis mellifera subsp. scutellata), staying clear of crop fields surrounded by beehive fence-lines and moving away from the sounds of swarming honeybees. Therefore, our objectives were to test whether the presence of beehives in trees influenced the likelihood of the tree receiving elephant impact, and compare these results to wire-netted (method used to prevent bark-stripping) and control (no treatment) trees. We selected a tree highly sought after by elephant, the marula tree (Sclerocarya birrea subsp. caffra), as our study species. We also assessed whether elephants avoided areas with marula trees containing beehives. Finally we provide a comparison of the financial costs of the beehive and wire-netting mitigation methods. We hung 50 active beehives in 50 trees, with 50 dummy beehives hung from branches on the opposite ends of each tree's main stem. We wire-netted another 50 trees and then assigned 50 trees as a control. Elephant impact on all 150 trees was measured prior to the addition of treatments and then post-treatment addition for 9 months. 54% of the control trees received some form of elephant impact, in comparison to 28% of the wire-netted trees and only 2% of the beehive trees. Wire-netting protected trees against bark-stripping but did not prevent elephants from breaking branches. Beehives proved to be the more effective mitigation method for elephant impact on large trees, although the presence of beehives did not prevent elephants from moving through the study site. The financial cost and maintenance required for the beehive mitigation method are greater than that of wire-netting, but the beehives can provide honey as an additive benefit on a small-scale usage level.
Animal movement is fundamental for ecosystem functioning and species survival, yet the effects of the anthropogenic footprint on animal movements have not been estimated across species. Using a unique GPS-tracking database of 803 individuals across 57 species, we found that movements of mammals in areas with a comparatively high human footprint were on average one-half to one-third the extent of their movements in areas with a low human footprint. We attribute this reduction to behavioral changes of individual animals and to the exclusion of species with long-range movements from areas with higher human impact. Global loss of vagility alters a key ecological trait of animals that affects not only population persistence but also ecosystem processes such as predator-prey interactions, nutrient cycling, and disease transmission.
Introduction and background
This joint report by Save the Elephants and Kenya Wildlife Service summarizes preliminary findings of a long-term study on the effects of the Standard Gauge Railway (SGR), the Mombasa - Nairobi highway, the Voi - Taveta highway and other infrastructural developments on elephant movements and ecosystem connectivity in the Tsavo ecosystem. The extent of the utilization of the wildlife crossing structures, examples of exceptional elephant movements, the effect of water distribution on elephant movements, the effects of a recently constructed fence-line along the SGR are assessed and reported on here. The report concludes by listing several management recommendations. The study began in March 2016 when 10 elephants were fitted with satellite tracking collars for monitoring their movements in relation to these new infrastructure projects.
From 2013 to 2016, Laos’s retail ivory market has expanded more rapidly than in any other country surveyed recently.
■ Laos has not been conforming with CITES regulations that prohibit the import and export of ivory. Since joining CITES in 2004, only one ivory seizure into Laos has been reported to the Elephant Trade Information System (ETIS).
■ Almost no arrests, let alone prosecutions and punishments, have been made of smugglers with ivory coming in or out of the country.
■ Most worked ivory for sale in Laos originates from elephants poached in Africa.
■ Ivory has also been entering Laos illegally from Thailand, as Thai traders have been offloading their ivory following the imposition of much stricter regulations there.
■ In late 2013 the average wholesale price of raw ivory sold by Lao traders peaked at about USD 2,000/kg.
■ By late 2016, the average wholesale price of raw ivory in Laos had declined to USD 714/kg, in line with prices elsewhere in the region. This price was much higher than in African countries, such as Sudan (Omdurman/Khartoum), where the average wholesale price of ivory was USD 279/kg in early 2017. This price differential is due to the extra expenses incurred in transport and bribes to government officials on the long journey to Asia.
■ In Laos, the decline in the wholesale price of raw ivory between 2013 and 2016, as elsewhere in the region, was mainly due to the slowdown in China’s economy, that resulted in an oversupply of illegal ivory, relative to demand.
■ Ivory items seen for sale in Laos are carved or machine-processed in Vietnam by Vietnamese and smuggled into Laos for sale, or are processed by Chinese traders in Laos on new computer driven machines. Ivory carving by Lao people is insignificant.
■ In Laos, the survey found 81 retail outlets with ivory on view for retail sale, 40 of which were in the capital, Vientiane, 21 in Luang Prabang, 8 in Kings Romans, 5 in Oudom Xay, 3 in Pakse, 2 in Dansavanh Nam Ngum Resort and 2 in Luang Nam Tha.
Poaching has escalated in recent years and is becoming the greatest immediate threat to elephants' survival. There is an urgent need to develop innovative and cost-effective methods for monitoring changes in elephant poaching levels remotely to complement the existing traditional field-based ground surveys. Since elephants are known to respond to anthropogenic risks by alterations in their speed of travel, we quantified this alteration as a ratio of night time speed to the day time speed (night-day speed ratio) and examined its relationship with poaching levels. Our hypothesis here is that poaching is a clear daytime risk, and thus an increase in night time movement rates over those seen during the day will support this hypothesis. Using elephant GPS tracking and mortality data collected in the Laikipia-Samburu ecosystem of northern Kenya between 2002 and 2012, we calculated the mean night-day speed ratio for collared elephants that utilised any of 13 contiguous land units, each under different ownership and management status, and related this ratio to the corresponding poaching levels before and during a poaching surge.
Our study shows that the mean night-day speed ratio of both male and female elephants did not vary significantly by month, ruling out possible seasonal effect. However, both male and female elephants moved more at night than during the day where and when poaching levels were high. The relationship between poaching levels and night-day speed ratios was stronger for females than for males. We concluded that the variation in the night-day speed ratio of elephants might be used as an effective indicator for changes poaching levels on a near real-time basis. We recommend its adoption as a complimentary anti-poaching tool, where GPS tracking data is already available, because it would increase the geographical range for monitoring of poaching levels. The significant alteration in movement behaviour by elephants in response to poaching also has potential implications for their foraging strategy, reproduction and ultimate survival, all of which are not yet fully understood.
Kenya is endowed with an extraordinary wealth of mammals, birds and other biodiversity, a unique
heritage for the people of Kenya. Kenya’s development blueprints on ensuring environmental sustainability –
the Constitution (2010), Vision 2030, and Sustainable Development Goals (SDG) – recognize the importance
of sustainable resource use, reducing biodiversity loss, and maintenance of ecosystems processes. In the Vision
2030, under the conservation strategic thrust, the flagship project on securing wildlife dispersal areas and migratory
corridors features prominently as one of the economic and social pillars.
All over the country, wildlife populations have declined dramatically over the last few decades. Ecosystems
are failing to provide ecological services such as water storage, soil protection and climate moderation. At the
same time, human-wildife conflict has increased. To reduce and reverse this trend, it is urgent to assess and
secure Kenya’s wildlife dispersal areas and migratory corridors as a way to restore balance to our country’s
The new Standard Gauge Railway (SGR) linking Mombasa to Nairobi became officially operational in June 2017. It is a flagship project for Kenya under Kenya’s blue print Vision 2030, whose goal is to transform Kenya into a middle-income industrialized economy by 2030. More than a quarter i.e., 135 km of the 487 km railway is through the Tsavo Conservation Area, bisecting the range of Kenya’s largest surviving single elephant population of 12,800 animals, as well as many other wildlife species. This presents a challenge.
While the old railway line lay level with the ground, the new SGR is elevated up to 10 metres in some sections and fenced on either side, creating a substantial barrier to wildlife movement with likely negative consequences. The contractor of the SGR, the China Roads and Bridges Cooperation, built six official wildlife passages to connect Tsavo East to Tsavo West National Parks and Tsavo East to the Taita Ranches to allow animals to travel in search of food, water and mates. The 2 km Tsavo River super bridge, the Kenani and the Maungu railway crossing bridges makes a total of nine wildlife passages.
Save the Elephants in partnership with the Kenya Wildlife Service has been tracking elephants to understand the effectiveness of these passages. We fitted ten elephants (eight along the SGR and two along the Voi – Taveta road) with GPS satellite radio transmitters in March 2016. In June 2016, we initiated systematic vehicle and foot monitoring along the SGR of elephants and other species, not fitted with radio transmitters, by using their signs such as footprints and dung. Some elephants have used them effortlessly, with families in tow, while others have preferred to use the culverts and bridges that perforate the line but which have not officially been classed as wildlife passages. Even though the details of other wildlife species crossings are not reported here, it is important to highlight here that giraffes generally avoided any form of underpasses with only one footprint recorded on 13th March 2017 at culvert DK234+062. Generally, however the culverts offer an opportunity for wildlife crossing points between the two sides of Tsavo National Park and adjoining ranches keeping genetic diversity open and a flow of inter-seasonal movements.
Dominance hierarchies are expected to form in response to socioecological pressures and competitive regimes. We assess dominance relationships among free-ranging female Asian elephants (Elephas maximus) and compare them with those of African savannah elephants (Loxodonta africana), which are known to exhibit age-based dominance hierarchies. Both species are generalist herbivores, however, the Asian population occupies a more productive and climatically stable environment relative to that of the African savannah population. We expected this would lower competition relative to the African taxon, relaxing the need for hierarchy. We tested whether 1) observed dominance interactions among individuals were transitive, 2) outcomes were structured either by age or by social unit according to 4 independent ranking methods, and 3) hierarchy steepness among classes was significant using David’s score. Elephas maximus displayed less than a third the number of dominance interactions as observed in L. africana, with statistically insignificant transitivity among individuals. There was weak but significant order as well as steepness among age-classes but no clear order among social units. Loxodonta africana showed significant transitivity among individuals, with significant order and steepness among age-classes and social units. Elephas maximus had a greater proportion of age-reversed dominance outcomes than L. africana. When dominance hierarchies are weak and nonlinear, signals of dominance may have other functions, such as maintaining social exclusivity. We propose that resource dynamics reinforce differences via influence on fission–fusion processes, which we term “ecological release.” We discuss implications of these findings for conservation and management when animals are spatially constrained.
Understanding the spatial structuring of animal behaviors and how they link landscapes can be critical for conservation management. This emerging field has been greatly facilitated by technologically advanced acquisition and analysis of data on animal movements. The framework of graph theory, which directly quantifies network connectivity properties, provides a useful addition to this tool set. Using a novel application of graph theory, we investigate the structure and patterning of African elephant Loxodonta africana rest sites, a potentially critical feature structuring spatial properties of animal populations. Elephants in the study rested intermittently and for short durations (1–3 rests d–1, lasting 3–5 h total). They switched circadian rest patterns according to landscape attributes, resting more during the day and further from permanent water in areas with high human density outside protected areas. Within protected areas and during the dry season, elephants showed clustering and sequential use of rest nodes (repeated motifs). Repeated use of specific rest nodes (self-looping) was more frequent than expected if rest nodes were chosen at random, particularly when outside protected areas further from water, indicating the importance of preferred rest sites. Our results suggest that elephants adjust resting behavior when in human-dominated areas, using preferred resting sites presumably in locations that reduce the risk of interactions. This study demonstrates how graph theory may be used practically to gain novel insight into behaviours, such as resting, that are discrete in time and space. Furthermore, analysis of the spatial and network properties of rest sites, given an individual's susceptibility when engaged in rest behavior, allowed characterization of spatio-temporal risk perception, providing a powerful behavioral based means to quantify the landscape of fear.
Monitoring anthropogenic impacts on wildlife can be challenging, particularly when human activities affecting wildlife are cryptic. Using anti-predator behaviors as proxies for perceived pressure is appealing because of the relative ease with which they can be recorded and the presumed relationship between the threat of interest and a predator stimulus. However, behaviors are plastic and affected by factors unrelated to human activity. Consequently, it is critical to assess the relationship between behavioral indicators and their context before interpretation. In this study we used a combination of behavior, movement and demography from a threatened population of African elephants in northern Kenya to determine whether reaction to research vehicles was indicative of poaching pressure. We used mixed-effects models predicting reaction of elephants to observer vehicle approaches in which we treated individuals as random effects and included ecological, anthropogenic, spatial, social and demographic predictor variables. Contrary to our hypothesis, recorded levels of reactive behavior did not increase with poaching levels in either a population-level dataset or a data subset of individuals whose spatial behavior was precisely known via radio-tracking. Rather, primary productivity positively predicted reactive behavior in both datasets. This relationship was heightened by the presence of musth males in the radio-collar dataset. Reactivity was not related to the time since entering the protected areas, but increased among groups that spent less time in the protected areas. Inter-individual differences were apparent, suggesting the importance of inherent differences (e.g. personality) across groups. In our study, elephants plagued by a severe human threat did not react defensively to humans in another context, suggesting nuanced discrimination of threats. Our study demonstrates the caution that should be taken in designing studies that use behavioral indices to represent threat and contributes to a growing body of literature employing behavioral indicators to monitor wildlife populations of conservation concern.
Despite increased awareness, China continues to be the world’s major concern in the consumption
of illegal ivory. Media attention and support from international NGOs have drawn attention to the
poaching crisis currently facing elephants in Africa; there has been growing involvement and dialogue
with China from Western leaders and other prominent gures about this. President Obama of
the US and Prince William of the UK both spoke in 2015 on Chinese television addressing fears of
the ongoing elephant poaching to meet demand for ivory in China. Within China certain celebrities have
been involved in campaigns with NGOs, drawing further attention to the elephant-poaching crisis.
There has been less awareness about ivory from the woolly mammoth as its tusks are legal, being from an extinct species; many people in China and around the world remain ignorant about the extent of the use of mammoth ivory in China
Determining underlying demographic population processes is fundamental for the management and monitoring of wildlife species (Caughley & Sinclair 1994). Data on demographic processes (fecundity, survival, age of first reproduction, etc.) allow quantification of population trajectories, the identification of population sectors to which growth is most sensitive and determinations of the mechanisms driving population trends (Caswell 2001). In particular, when animal populations have suffered severe declines, demographic data are critical for evaluating what conservation measures might be effective and estimating time to recovery (Beissinger & Westphal 1998). Such information is fundamental to policy debates regarding the viability and benefits of species trade.
Carbon-14 measurements on 231 elephant ivory specimens from 14 large ivory seizures (?0.5 ton) made between 2002 and 2014 show that most ivory (ca. 90%) was derived from animals that had died less than 3 y before ivory was confiscated. This indicates that the assumption of recent elephant death for mortality estimates of African elephants is correct: Very little “old” ivory is included in large ivory shipments from Africa. We found only one specimen of the 231 analyzed to have a lag time longer than 6 y. Patterns of trade differ by regions: East African ivory, based on genetic assignments of geographic origin, has a much higher fraction of “rapid” transit than ivory originating in the Tridom region of Cameroon–Gabon–Congo. Carbon-14 is an important tool in understanding patterns of movement of illegal wildlife products.
Dominance hierarchies are expected to form in response to socioecological pressures and competitive regimes. We assess dominance relationships among free-ranging female Asian elephants (Elephas maximus) and compare them with those of African savannah elephants (Loxodonta africana), which are known to exhibit age-based dominance hierarchies. Both species are generalist herbivores, however, the Asian population occupies a more productive and climatically stable environment relative to that of the African savannah population. We expected this would lower competition relative to the African taxon, relaxing the need for hierarchy. We tested whether 1) observed dominance interactions among individuals were transitive, 2) outcomes were structured either by age or by social unit according to 4 independent ranking methods, and 3) hierarchy steepness among classes was significant using David’s score.