Female Elephants Research Articles

Into the large ears: otitis externa associated with nematodes, mites, and bacteria in Asian elephants (Elephas maximus)

BackgroundThe Asian elephant (Elephas maximus), which is an endangered species, harbors several parasites. Among the ectoparasites that it harbors, ear mites of the genus Loxanoetus have the potential to cause external otitis, an inflammation that may also be associated with the presence of other microorganisms. We assessed the relationships between ear mites, nematodes, yeast, bacterial rods, and cocci sampled from the ears of captive Asian elephants in Thailand. In addition, we discuss the possibility that dust-bathing behavior may be triggered by ear mite infestation, and that this in turn may lead to contamination of the ears with soil microorganisms.Methods Legally owned captive Asian elephants (n = 64) were sampled. Ear swabs were individually collected from both ears and microscopically examined for the presence of mites, nematodes, yeast, bacterial rods, cocci, and host cells. Mites and nematodes were identified to species level using morphological and molecular methods.ResultsLoxanoetus lenae mites were present in 43.8% (n = 28/64) of the animals (19 animals with mites in one ear and nine animals with mites in both ears). Nematodes of the genus Panagrolaimus were detected in 23.4% (n = 15/64) of the animals (10 with nematodes in one ear and five with nematodes in both ears). In adult elephants (Fisher’s exact test, P = 0.0278) and female elephants (Fisher’s exact test, P = 0.0107), the presence of nematodes in both ears was significantly associated with the presence of mites. In addition, higher categorical burdens of nematodes were also significantly associated with the presence of mites (Fisher’s exact test, P = 0.0234) and epithelial cells (Fisher’s exact test, P = 0.0108), and marginally significantly associated with bacterial cocci (Fisher’s exact test, P = 0.0499).ConclusionsThe presence of L. lenae mites in the ear canals of the Asian elephants was significantly associated with the occurrence of other microorganisms, such as soil nematodes, bacteria and yeasts. The presence of mites in their ears may increase the dust-bathing behavior of elephants which, if confirmed, represents a further paradigmatic example of a parasitic infestation affecting animal behavior.Graphical

Elephant trunks use an adaptable prehensile grip

Elephants have long been observed to grip objects with their trunk, but little is known about how they adjust their strategy for different weights. In this study, we challenge a female African elephant at Zoo Atlanta to lift 20–60 kg barbell weights with only its trunk. We measure the trunk’s shape and wrinkle geometry from a frozen elephant trunk at the Smithsonian. We observe several strategies employed to accommodate heavier weights, including accelerating less, orienting the trunk vertically, and wrapping the barbell with a greater trunk length. Mathematical models show that increasing barbell weights are associated with constant trunk tensile force and an increasing barbell-wrapping surface area due to the trunk’s wrinkles. Our findings may inspire the design of more adaptable soft robotic grippers that can improve grip using surface morphology such as wrinkles.

Abnormal prolactin secretion is associated with changes in metabolic health biomarkers in acyclic female African elephants (Loxodonta africana)

Circulating prolactin aberrations (chronically high or low concentrations) have been shown to have strong associations with ovarian dysfunction in African female elephants. However, despite the well-established pleiotropic role that prolactin plays in human health, comprehensive metabolic effects from chronically elevated or suppressed prolactin have yet to be investigated in this species. In humans, in addition to amenorrhea, hyperprolactinemic women have shown increased risks for accelerated atherosclerosis, hyperandrogenemia, lowered metabolism, and insulin resistance. The aim of the study was to determine if elephants with long-term abnormal prolactin secretion were also experiencing alterations in metabolic biomarkers. One year of serum samples, collected biweekly, were obtained from female African elephants (n = 74) housed in North American zoos and categorized based on ovarian cyclicity and prolactin status: normal cycling, normal prolactin (NORMAL, n = 25), acyclic, high prolactin (HIGH, n = 25), or acyclic, low prolactin (LOW, n = 24). Each sample was further analyzed for measures of metabolic function, glucose metabolism, and cardiovascular health. Overall, thyroid hormones were significantly lower in both HIGH (TSH, T3, T4) and LOW (TSH) prolactin elephants compared to NORMAL counterparts. Additionally, HIGH prolactin elephants exhibited lower glucose, G:I ratios, and low-density lipoprotein values, but higher cholesterol concentrations compared to normal cycling females. Overall, LOW prolactin elephants exhibited higher body condition scores and G:I ratios, and higher concentrations of insulin, high-density lipoproteins, cortisol and testosterone, but decreased triglyceride values compared to NORMAL elephants in the study. Data suggest that HIGH prolactin elephants may be experiencing hypothyroidism as a comorbidity, whereas LOW prolactin elephants may be exhibiting aspects of insulin resistance, albeit different from human clinical data. Specific studies are suggested that would help elucidate the underlying mechanisms at play and increase our understanding of prolactin’s role in elephant physiology.

Effects of disease on foraging behaviour and success in an individual free-ranging northern elephant seal.

Evaluating consequences of stressors on vital rates in marine mammals is of considerable interest to scientific and regulatory bodies. Many of these species face numerous anthropogenic and environmental disturbances. Despite its importance as a critical form of mortality, little is known about disease progression in air-breathing marine megafauna at sea. We examined the movement, diving, foraging behaviour and physiological state of an adult female northern elephant seal (Mirounga angustirostris) who suffered from an infection while at sea. Comparing her to healthy individuals, we identified abnormal behavioural patterns from high-resolution biologging instruments that are likely indicators of diseased and deteriorating condition. We observed continuous extended (3-30minutes) surface intervals coinciding with almost no foraging attempts (jaw motion) during 2weeks of acute illness early in her post-breeding foraging trip. Elephant seals typically spend ~ 2minutes at the surface. There were less frequent but highly extended (30-200minutes) surface periods across the remainder of the trip. Dive duration declined throughout the trip rather than increasing. This seal returned in the poorest body condition recorded for an adult female elephant seal (18.3% adipose tissue; post-breeding trip average is 30.4%). She was immunocompromised at the end of her foraging trip and has not been seen since that moulting season. The timing and severity of the illness, which began during the end of the energy-intensive lactation fast, forced this animal over a tipping point from which she could not recover. Additional physiological constraints to foraging, including thermoregulation and oxygen consumption, likely exacerbated her already poor condition. These findings improve our understanding of illness in free-ranging air-breathing marine megafauna, demonstrate the vulnerability of individuals at critical points in their life history, highlight the importance of considering individual health when interpreting biologging data and could help differentiate between malnutrition and other causes of at-sea mortality from transmitted data.

Introduction to the Special Section.

Introduction to the Special Section Franklin G. Miller Happy is a female elephant who has been confined at the Bronx Zoo for over 40 years. In 2018 the Nonhuman Rights Project sued the Wildlife Conservation Society, which manages the zoo, seeking habeas corpus for Happy in order to release her to an elephant sanctuary. Numerous amicus curiae briefs were filed in favor and against the petition on behalf of Happy. The case reached the highest court in New York State, which denied the petition of the plaintiff in June 2022. This special section includes views on the case of Happy by David DeGrazia, Martha Nussbaum, and Christine Korsgaard, three distinguished moral philosophers who have made significant contributions to animal ethics. The essays by Martha Nussbaum and Christine Korsgaard are drawn from the amicus briefs that they filed in the legal proceedings, which they agreed could be published here. Professor Nussbaum applies her "capabilities approach" as a foundation for promoting wellbeing and recognizing rights to Happy and to elephants in general. She argues that Happy is a being with a meaningful life and is entitled to be treated with respect and dignity, which is incompatible with her conditions of confinement at the zoo. Professor Korsgaard applies her understanding of the moral philosophy of Immanuel Kant to the case of Happy—a "cognitively sophisticated [End Page 1] animal" which, like human beings, should be treated as an end in herself and not merely as a means to the purposes of human beings. Professor DeGrazia, in an invited essay, analyzes the meanings of "person" and examines the pertinent characteristics of elephants that make them at least "borderline persons," with the moral status of possessing basic rights. While Happy remains confined at the Bronx Zoo, these three incisive contributions challenge readers to reflect on the ethical treatment of nonhuman animals, especially those with complex and rich capacities of intelligence and emotion. [End Page 2] Franklin G. Miller Weill Cornell Medical College, New York Copyright © 2023 Johns Hopkins University Press ...

Immunocontraception of the female African savanna elephant (Loxodonta africana) in South Africa: from pipe dream to policy

Globally, African savanna elephants have been assessed as ‘endangered’. Consequently, additional threats and losses due to human–elephant conflict (HEC) could further exacerbate the species’ decline. In stark contrast, South Africa’s elephant populations are mostly confined within fenced-in reserves that impede natural processes such as migration. As ecosystem engineers, elephant population growth herein should be limited. Within South Africa, elephant management has evolved as differing wildlife philosophies from utilitarian conservation (‘nature for man’) to biocentric preservation (‘nature for nature’) and a combination thereof, have been practiced. Traditionally, both HEC and population control have been largely synonymous with lethal control, i.e. culling. However, with the increase of public or expert input to Policy, lethal control is not favoured by the public. As an alternative, immunocontraception of female African savanna elephants through non-invasive, native porcine zona pellucida (pZP) vaccinations has been employed successfully and is currently adopted in 43 elephant reserves across South Africa. Current legislation now recommends culling as the last population management resort. Newly promulgated legislation calls for wellbeing and welfare to be carefully measured in all biodiversity management decisions taken to minimise threats to biodiversity. As a keystone species, elephant is a direct driver of biodiversity change. Accordingly, and in light of these developments, all population management options, including immunocontraception, must be fully considered in South Africa’s largest national park, the Kruger.

Virtual fencing of captive Asian elephants fitted with an aversive geofencing device to manage their movement

Aversive Geofencing Devices (AGDs) are designed to emit audible warning signals followed by electric shocks when animals reach virtual fences (VFs) with the intent that animals will learn to turn away at audio warnings and thereby avoid receiving shocks. AGDs are a potentially useful tool for mitigating human-elephant conflict, but a greater understanding of captive elephant responses to AGDs is required before they might be confidently used on wild elephants. We conducted experiments with eight, female captive Asian elephants using a modified dog-training collar to deliver mild electric shocks (4 kV) of varying strength (pulse frequencies) to determine the ideal location on the neck to deliver the stimuli and the optimum strength of the shock required to generate desired aversive responses. Ten shocks (<1 s duration) of different strengths were delivered during a 10 min session (i.e., one shock per minute) at two positions on one side of the elephant’s neck. Results indicated that elephants were more likely to display desirable aversive behaviours at the upper position tested on the neck (odds ratio=0.47, 95% CI 0.25–0.87, P = 0.018) and at higher stimuli strengths (odds ratio=1.03, 95% CI 1.01–1.04, P ≤ 0.001). A conditioning experiment was then conducted several months later with five of the same elephants. These were individually trained to walk along a ∼100 m path to a food reward on three consecutive days, wearing a dummy collar. On the next three days and on one other day few months later, the elephants were fitted with a similar shock collar (positioned at the upper neck location, and with the highest strength tested earlier) to determine if the AGD could prevent the elephants from accessing the food reward. Three VFs were established at ∼30 m, ∼50 m and ∼60 m points along the path. As the elephant approached the food, a mild audio warning, a more aggressive audio warning, and an electric shock was administered at the first, second and third VFs respectively. Warnings and shocks were not delivered if elephants heeded earlier warnings. A maximum of five such trials were attempted. The VFs successfully kept elephants from reaching the food 77.8% of the time, with elephants responding to the audio warnings and avoiding electric stimulation 47.2% of the trials. These findings suggest that AGDs are a promising method to manage elephant movement, but further research is needed to develop a reliable approach for wild elephants.

Reproduction record of captive Sumatera elephant (Elephas maximus sumatranus) at Way Kambas National Park, Indonesia

This research aims to determine reproductive data on Sumatran elephants (Elephas maximus sumatranus) in the ETC and ERU of Way Kambas National Park, Indonesia during 1988-2021. Data recorded from the elephant population at both locations (ETC and ERU) includes the number, gender of elephants, elephant calves, ages and birth dates. Calving intervals and service periods were calculated from calving records of cows with a minimum parity of two. Data collection produced data on 47 elephant calves from 13 female elephants with at least twice the parity and 12 primiparous cows. Elephant reproductive records at ETC and ERU were: age (37.44 ± 9.03 vs. 29.75 ± 3.30 years), parity (2.78 ± 1.09 vs. 2.50 ± 0.58), and age at first birth (18, 11 ± 3.92 vs. 17.75 ± 0.50 years). While the calving interval was 1857.56 ± 870.81 vs. 1833.00 ± 305.18 days, and service period respectively 1229.44 ± 846.18 vs. 1210.50 ± 283.59 days, respectively. It can be concluded that the calving interval and service period for captive elephants at ETC and ERU were not much different and were within the normal range. Young cows showed better reproductive efficiency than older cows. Monitoring calves is very important. Further assistance is needed to improve elephant mobile veterinary services, increase diagnostic laboratory capacity, and educate camp managers, veterinary assistants, and mahouts about elephant diseases, their monitoring and treatment. In addition, the use of reproductive technology such as monitoring ovulation using ultrasound and carrying out artificial insemination was expected to increase reproductive efficiency.

Reproduction record of captive Sumatera elephant (Elephas maximus sumatranus) at Way Kambas National Park, Indonesia

This research aims to determine reproductive data on Sumatran elephants (Elephas maximus sumatranus) in the ETC and ERU of Way Kambas National Park, Indonesia during 1988-2021. Data recorded from the elephant population at both locations (ETC and ERU) includes the number, gender of elephants, elephant calves, ages and birth dates. Calving intervals and service periods were calculated from calving records of cows with a minimum parity of two. Data collection produced data on 47 elephant calves from 13 female elephants with at least twice the parity and 12 primiparous cows. Elephant reproductive records at ETC and ERU were: age (37.44 ± 9.03 vs. 29.75 ± 3.30 years), parity (2.78 ± 1.09 vs. 2.50 ± 0.58), and age at first birth (18, 11 ± 3.92 vs. 17.75 ± 0.50 years). While the calving interval was 1857.56 ± 870.81 vs. 1833.00 ± 305.18 days, and service period respectively 1229.44 ± 846.18 vs. 1210.50 ± 283.59 days, respectively. It can be concluded that the calving interval and service period for captive elephants at ETC and ERU were not much different and were within the normal range. Young cows showed better reproductive efficiency than older cows. Monitoring calves is very important. Further assistance is needed to improve elephant mobile veterinary services, increase diagnostic laboratory capacity, and educate camp managers, veterinary assistants, and mahouts about elephant diseases, their monitoring and treatment. In addition, the use of reproductive technology such as monitoring ovulation using ultrasound and carrying out artificial insemination was expected to increase reproductive efficiency.

Age-sex structure of drought-driven African elephant (Loxodonta africana) mortality in Hwange National Park, Zimbabwe

Age and sex determination of 101 lower jaws from drought-driven savanna elephant mortalities was done in Hwange National Park (HNP) using the Age Reference Line (ARL) method. We recorded an overall higher number of female elephant death compared to males. The age at death was skewed towards the young and very old individuals, with an overall gradual decrease in frequency into prime cohorts. Female elephant mortalities were more prevalent in young animals, nursing, and very old individuals. A similar mortality trend was observed for male elephants below the age of 22 years. We did not record any elephant between the age of 45–52.5 years for both sexes. We support the notion that the overall distribution of the female's mortality prevalence compared to males is aligned to and influenced by the social and developmental behaviour of savanna elephants. Our findings suggest a natural selection process at play, facilitated by resource limitation during the period of drought. This study provides evidence for the need to get back to the basic ecological principles and understanding of natural ecological processes in the conservation of key species. Although elephant mortalities due to drought represent a small proportion of the entire population in the study area, more work needs to be done to investigate the influence of drought, novel infections and anthropogenic drivers as they have potential to affect savanna elephant populations in the long term.

Density-dependent habitat selection varies between male and female African elephants

Habitat selection models are the basis of an increasing number of conservation and management programs. Decision-makers rely on accurate models to assess animal distribution over space and time, and to recommend suitable actions that can alleviate human-wildlife conflicts. Despite a rapidly growing number of field studies on habitat selection, there remains a paucity of empirical evidence that selection is a density-dependent process that can impact males and females differently. Based on 11 years of monitoring, we demonstrate that the response of African elephants (Loxodonta africana) to land-cover types varied with population size, and that density-dependent adjustments differed between sexes. Specifically, our longitudinal follow-up of GPS-collared elephants revealed that elephants gradually decrease their selection for open woodlands and forests, as the population increased and the availability of palatable browse species decreased. Both sexes – though males more strongly – increased their travel rate together with their relative probability of selection of roads for travel. Also, elephants displayed a density-dependent increase in their selection of infrastructures, a response that was stronger for males than females. The risk of human-elephant conflicts thus increased with population size, with males being particularly prone to be involved in such conflicts. Overall, we provide rare empirical evidence that density-dependence in fine-grain habitat selection can differ between sexes. This information can be critical to accurately forecast potential human-wildlife conflicts, and for taking targeted and effective conservation and management actions.

Predictors of testosterone in zoo-managed male African elephants (Loxodonta Africana).

Reproductive complications for both male and female zoo-managed African elephants (Loxodonta africana) contribute to the rapidly declining population. In zoo-managed bull elephants, few studies have explored the potential physiological, physical, social, and environmental factors that influence bull fertility, particularly, androgen production. Testosterone is the essential steroid hormone for male sexual maturation and inadequate concentrations can be detrimental for spermatogenesis. Testosterone, fecal glucocorticoid metabolites, leptin, glucose, insulin, and triglycerides were analyzed from weekly fecal and blood serum samples taken over 6 months from six zoo-managed African elephant bulls (10-19 years of age). Testosterone levels were compared to endocrine factors, weekly social and environmental variables, daily musth signs, and body condition scores (BCS). The glucose-to-insulin ratio (G:I) was the only physiological biomarker found to be positively associated with testosterone. Predictive physical variables included Musth Score (+) and Moderate Exercise (+). Bulls with BCSsignifying overweight (BCS 4) had lower testosterone (36.6 ± 1.6 ng/g fecal extraction [FE]) than bulls with healthyBCS 3; 51.2 ± 4.9 ng/g FE). Numerous social variables influenced testosterone concentrations, including Total Contact Day (+), Female Interaction Day (+), Indirect Contact Day (+), Indirect Contact Night (+) and Total No Contact (-). Both percentage of Time Outdoor and Time Mixed positively influenced testosterone, whereas testosterone decreased for percentage of Time Indoors. Each additional daily browse opportunity increased testosterone by approximately 7 ng/g FE. In managed care, the emphasis should be placed on optimizing these predictors of testosterone production to promote bull reproductive health.

Foraging behavior of a mesopelagic predator, the northern elephant seal, in northeastern Pacific eddies

The role of mesoscale features in structuring trophic transfer in the mesopelagic zone is poorly understood. Deploying sensors on marine animals, or “biologging,” is a powerful tool to infer the organism's behavior and simultaneously collect high-resolution oceanographic data to describe physical-biological interactions. We investigated whether mesoscale eddies are used by a mesopelagic predator, the northern elephant seal (Mirounga angustirostris), and if so, what mechanisms might create beneficial foraging conditions in association with eddies. We hypothesized seals would increase their foraging behavior in both cyclonic and anticyclonic eddies due to nutrient enhancement and physical aggregation of prey and that seals would dive deeper in anticyclonic eddies in response to a deeper prey field. We used tracking data and continuous in situ temperature measurements from 221 adult female northern elephant seals collected between 2004 and 2019. These predators primarily targeted myctophid fishes and squid throughout the northeast Pacific mesopelagic zone, foraging between approximately 400–800 m. Eddy encounters were identified using remotely sensed sea level anomaly data and confirmed visually with collocated sea level anomaly, in situ temperature, and in situ temperature anomaly. Over more than 30,000 days of data and >3 million temperature casts collected by seals, we found 129 high confidence encounters with anticyclonic eddies and 83 with cyclonic eddies. Overall, seals traveled more slowly and in a less directed manner while associated with eddies, particularly anticyclonic eddies, suggesting increased foraging behavior, especially in the California Current. Elephant seals spent more time at the edges of cyclonic eddies than their center. In contrast, they utilized both the interior and edge of anticyclonic eddies. This suggests that the aggregation of prey at the frontal region of an eddy is an important mechanism, whereas nutrient upwelling associated with an eddy play a more minor role in enhancing the seals' prey field. Seal foraging behavior was not influenced by eddy age, size, amplitude, or rotational speed. The large sample size in this study showed considerable variation between individual behavioral responses, suggesting caution when extrapolating individual behavior to a population level. Our data show that both cyclonic and anticyclonic eddies can affect the seals' prey field as demonstrated by enhanced foraging behavior. Still, the variation in behavioral responses resulting from individual foraging strategies, eddy histories, and possible spatiotemporal mismatches between eddy physics and biological responses relevant to mesopelagic predators merit further investigation.

Surgical Removal of Urinary Bladder Urolith in Female Asian Elephant (Elephas maximus) by Episiotomy and Urinary Bladder Sphincterotomy

Surgical Removal of Urinary Bladder Urolith in Female Asian Elephant (Elephas maximus) by Episiotomy and Urinary Bladder Sphincterotomy

Prolonged proximity to humans ensures better performance of semi-captive Asian elephants at discriminating between human individuals by voice

To avoid risks, organisms must recognize threatening heterospecies from non-threatening onesviaacoustic cues from a distance. With land-use change, humans have encroached considerably into natural areas. Therefore, it is beneficial to animals to use acoustic cues to discriminate between different levels of threats posed by humans. Our study aims at testing this discriminatory ability in Asian elephants (Elephas maximus), animals that have been for long history subjected to human interaction. We tested whether eighteen semi-captive elephants could discriminate between voices of their own mahouts (i.e., who take care of the elephants exclusively) and of other mahouts (unfamiliar individuals). The results showed that elephants responded successfully to the commands from their own mahouts, with an average response rate as high as 78.8%. The more years the mahouts had been as their caretakers, the more the elephant showed active responses toward the commands. Female elephants responded to the commands more frequently and faster than males. Also younger elephants responded more frequently and faster than older elephants. We argue that Asian elephants can discriminate between familiar and unfamiliar humans by acoustic cues alone. Proximity with humans may be a factor, as fundamental as domestication, for animals to develop heterospecies discriminatory ability.

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

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

Male African Elephant (Loxodonta africana) Behavioral Responses to Estrous Call Playbacks May Inform Conservation Management Tools.

Simple SummaryDuring annual periods of heightened sexual activity (musth), male African elephants expend a significant amount of energy communicating their reproductive status, as well as searching and competing for potential mates. To locate females, musth males may risk venturing outside protected areas and into landscapes shared with humans where conflict between wildlife and people can occur. Adverse interactions between elephants and people can be detrimental to human livelihoods, resulting in negative attitudes towards elephants and, in some cases, retaliatory killings. Interactions with aggressive musth males can also be life-threatening to community members who attempt to confront them. Mitigation strategies that effectively target the reproductive motivations of musth males may offer solutions as the human–elephant interface continues to expand. In this study, we build on earlier research showing that playbacks of female elephant reproductive calls, (i.e., estrous rumbles) can change the movement trajectory and behavior of male elephants in Etosha National Park, Namibia. Individuals belonging to three male groups were opportunistically subjected to playback experiments and evaluated based on their reaction intensity. Our results demonstrate that mature musth adults are more likely to change directions and approach the source of a female’s estrous call than mature, sexually-inactive adult elephants. We also show that post-dispersal young males that were not in musth also respond strongly to the stimulus. These findings support further exploration of mitigation solutions that incorporate elephant behavior, reproductive status, and context-specific vocalizations.Driven by reproductive motives, male African elephants (Loxodonta africana) in musth often expand their home ranges to locate estrous females. This extended range, coupled with heightened aggression often observed in musth males, can be particularly problematic in regions where human-modified landscapes and elephant territories increasingly overlap. Several mitigation tools have been tested to resolve a wide range of human–elephant conflicts with varying degrees of success due to geographical disparities and habituation. We present findings on the potential application of estrous call playbacks in manipulating the behavior and movement of male elephants non-invasively, particularly mature musth adults and younger post-dispersal males, in Etosha National Park. Estrous vocalizations were presented across 26 experimental trials to mature musth adults (n = 5), mature non-musth adults (n = 6), and non-musth males belonging to younger, post-dispersal age classes (n = 8), with behavioral responses scored on a gradient scale from 0–1. Both mature musth adults and younger non-musth elephants were significantly more likely to respond with the highest intensity by approaching the acoustic source compared to mature non-musth adults that avoided the call. However, younger males tested in the presence of an older, higher-ranking male tended to react with a lower intensity than those tested alone. This result likely demonstrates the influence of social hierarchy and associations on male elephant behavior. We also observed a significant increase in physiological response, measured by defecation rate, across all male groups in response to the estrous call playbacks. Our findings suggest that using estrous calls as acoustic deterrents may effectively and non-invasively aid in reducing tension at the human–elephant interface, depending on the age, social context, and reproductive status of the male elephant.

Habitat associations of post-breeding female southern elephant seals (Mirounga leonina) from Península Valdés, Argentina

Research on marine mammal habitat-associations often uses satellite remote sensing of sea surface temperature, chlorophyll concentration, and sea surface height to map mesoscale features, which may indicate areas of enhanced productivity and prey availability. However, for species that feed at depths >400 m, the increased productivity associated with mesoscale features observed near the surface may have little or no immediate effect on habitat-associations at depth. As a result, previous studies have found a weak correlation between mesoscale features and the movements of marine mammals. The advantage of biologging is that hydrographic variables are recorded in situ and at foraging depths using animal-borne instruments with sensors for temperature, conductivity (salinity), and dissolved oxygen. The goal of this study was to characterize the habitat-associations of female southern elephant seals (SES) from Península Valdés, Argentina during the post-breeding foraging trip. Although female SES exhibited significant habitat-associations with sea surface height anomaly and chlorophyll concentrations, the presence or absence of eddies was not predictive of foraging behavior, and the majority of foraging dives (74%) and prey encounters (77%) occurred in the absence of eddies. The strongest habitat-association was with deep (>500 m) and cold (3.73 ± 1.29 °C) subantarctic water, primarily during foraging dives from dusk to dawn. Female SES made most of their foraging dives (68%, mean maximum depth of 539 ± 226 m) and had the most prey encounters (67%) in Antarctic Intermediate Water (AAIW), which is formed near the Subantarctic Front on the northern flank of the Antarctic Circumpolar Current. Our results suggest that AAIW is the principal foraging habitat of female SES from Península Valdés, which may not be directly associated with near-surface mesoscale features. Future research on the habitat-associations for SES and other deep-diving marine mammals should focus on indices of foraging success and the hydrographic features of water masses at foraging depths, not mesoscale features observed near the surface.

How evolutionary biology can explain why human and a few marine mammal females are the only ones that are menopausal

Two fundamental questions related to menopause that have not been answered are: (1) why does menopause even occur? And, (2) of the more than six thousand known mammals extant today, why human and four whale females are the only ones that are menopausal? Answers to both of these basic questions are provided here on the basis of evolutionary biology. From observational data, it was found that there are three elemental criteria that all menopausal species must fulfill: first, it has to be long-lived (average female lifespan of the species has to be forty years or more); second, it must live in groups; and third, the average female-male lifespan differential has to be at least thirty percent or more. In addition, a corollary criterion for menopause was also established: for a species’ females to be menopausal, the Encephalization Quotient (EQ) for the species has to be 2.5 or more. Though humans do not fulfill the third menopausal criterion currently, it has been shown that when the menopausal mechanism first became common in human ancestors, in all likelihood, that principle was conformed to. Of the multitude of mammals around, only a few species satisfy all three menopausal criteria, and hence are the only ones whose females undergo the menopausal process. Many hitherto unanswered questions with respect to menopause, such as, while long and short-finned pilot whales are close to each other both genetically and physiologically, why short-finned females are menopausal while long-finned females are not, why orca females are menopausal while elephant females are not, in spite of both being long-lived, etc., can be answered on the basis of those three criteria. Why there was no selection pressure for males to undergo advanced-age reproductive cessation in those few menopausal species and why the majority of divorces occur in mid-life (40-to-60s) are also explained from a menopausal perspective.

The relationship between distal trunk morphology and object grasping in the African savannah elephant (Loxodonta africana).

BackgroundDuring reach-to-grasp movements, the human hand is preshaped depending on the properties of the object. Preshaping may result from learning, morphology, or motor control variability and can confer a selective advantage on that individual or species. This preshaping ability is known in several mammals (i.e., primates, carnivores and rodents). However, apart from the tongue preshaping of lizards and chameleons, little is known about preshaping of other grasping appendages. In particular, the elephant trunk, a muscular hydrostat, has impressive grasping skills and thus is commonly called a hand. Data on elephant trunk grasping strategies are scarce, and nothing is known about whether elephants preshape their trunk tip according to the properties of their food.MethodsTo determine the influence of food sizes and shapes on the form of the trunk tip, we investigated the morphology of the distal part of the trunk during grasping movements. The influence of food item form on trunk tip shape was quantified in six female African savannah elephants (Loxodonta africana). Three food item types were presented to the elephants (elongated, flat, and cubic), as well as three different sizes of cubic items. A total of 107 ± 10 grips per individual were video recorded, and the related trunk tip shapes were recorded with a 2D geometric morphometric approach.ResultsHalf of the individuals adjusted the shape of the distal part of their trunk according to the object type. Of the three elephants that did not preshape their trunk tip, one was blind and another was subadult.Discussion and perspectivesWe found that elephants preshaped their trunk tip, similar to the preshaping of other species’ hands or paws during reach-to-grasp movements. This preshaping may be influenced by visual feedback and individual learning. To confirm these results, this study could be replicated with a larger sample of elephants.