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PubMed2006

The elephant knee joint: morphological and biomechanical considerations.

Elephant limbs display unique morphological features which are related mainly to supporting the enormous body weight of the animal. In elephants, the knee joint plays important roles in weight bearing and locomotion, but anatomical data are sparse and lacking in functional analyses. In addition, the knee joint is affected frequently by arthrosis. Here we examined structures of the knee joint by means of standard anatomical techniques in eight African (Loxodonta africana) and three Asian elephants (Elephas maximus). Furthermore, we performed radiography in five African and two Asian elephants and magnetic resonance imaging (MRI) in one African elephant. Macerated bones of 11 individuals (four African, seven Asian elephants) were measured with a pair of callipers to give standardized measurements of the articular parts. In one Asian and three African elephants, kinematic and functional analyses were carried out using a digitizer and according to the helical axis concept. Some peculiarities of healthy and arthrotic knee joints of elephants were compared with human knees. In contrast to those of other quadruped mammals, the knee joint of elephants displays an extended resting position. The femorotibial joint of elephants shows a high grade of congruency and the menisci are extremely narrow and thin. The four-bar mechanism of the cruciate ligaments exists also in the elephant. The main motion of the knee joint is extension-flexion with a range of motion of 142 degrees . In elephants, arthrotic alterations of the knee joint can lead to injury or loss of the cranial (anterior) cruciate ligament.

Animals↗

PubMed2003

DNA analysis indicates that Asian elephants are native to Borneo and are therefore a high priority for conservation.

The origin of Borneo's elephants is controversial. Two competing hypotheses argue that they are either indigenous, tracing back to the Pleistocene, or were introduced, descending from elephants imported in the 16th-18th centuries. Taxonomically, they have either been classified as a unique subspecies or placed under the Indian or Sumatran subspecies. If shown to be a unique indigenous population, this would extend the natural species range of the Asian elephant by 1300 km, and therefore Borneo elephants would have much greater conservation importance than if they were a feral population. We compared DNA of Borneo elephants to that of elephants from across the range of the Asian elephant, using a fragment of mitochondrial DNA, including part of the hypervariable d-loop, and five autosomal microsatellite loci. We find that Borneo's elephants are genetically distinct, with molecular divergence indicative of a Pleistocene colonisation of Borneo and subsequent isolation. We reject the hypothesis that Borneo's elephants were introduced. The genetic divergence of Borneo elephants warrants their recognition as a separate evolutionary significant unit. Thus, interbreeding Borneo elephants with those from other populations would be contraindicated in ex situ conservation, and their genetic distinctiveness makes them one of the highest priority populations for Asian elephant conservation.

Alleles↗

PubMed1985

Effects of yohimbine on combined xylazine-ketamine-induced sedation and immobilization in juvenile African elephants.

Twenty-two juvenile African elephants were given a combination of xylazine (mean +/- SD = 0.14 +/- 0.03 mg/kg of body weight) and ketamine (1.14 +/- 0.21 mg/kg) as a single IM injection; one elephant was immobilized twice, 77 days apart. After injection, 14 elephants were immobilized, 4 were sedated deeply, 2 were sedated moderately, and 2 were sedated minimally. Immobilized elephants had a mean immobilization time of 11.6 +/- 6.9 minutes. At the conclusion of a variety of clinical procedures, 12 of the 14 elephants immobilized with a single dose combination of xylazine and ketamine were given yohimbine (0.13 +/- 0.03 mg/kg) IV, and the remaining 2 elephants were allowed to recover spontaneously; the elephants given yohimbine had a mean standing time of 2.4 +/- 1.1 minutes. Of the 8 sedated elephants, 5 were given an additional dose of combined xylazine (0.08 +/- 0.03 mg/kg), and ketamine (0.61 +/- 0.19 mg/kg) IM, and 1 elephant was given ketamine (0.47 mg/kg) IV. After injection, 4 of the 8 elephants were recumbent laterally within 17 minutes and 2 remained standing, under deep sedation. Seven of the 8 elephants were given yohimbine (0.13 +/- 0.03 mg/kg) IV; all were ambulatory in 2 minutes. Results indicated that yohimbine may be useful in controlling duration of xylazine-ketamine sedation and immobilization in juvenile African elephants.

Anesthesia, General↗

PubMed2006

Elephant brain. Part I: gross morphology, functions, comparative anatomy, and evolution.

We report morphological data on brains of four African, Loxodonta africana, and three Asian elephants, Elephas maximus, and compare findings to literature. Brains exhibit a gyral pattern more complex and with more numerous gyri than in primates, humans included, and in carnivores, but less complex than in cetaceans. Cerebral frontal, parietal, temporal, limbic, and insular lobes are well developed, whereas the occipital lobe is relatively small. The insula is not as opercularized as in man. The temporal lobe is disproportionately large and expands laterally. Humans and elephants have three parallel temporal gyri: superior, middle, and inferior. Hippocampal sizes in elephants and humans are comparable, but proportionally smaller in elephant. A possible carotid rete was observed at the base of the brain. Brain size appears to be related to body size, ecology, sociality, and longevity. Elephant adult brain averages 4783 g, the largest among living and extinct terrestrial mammals; elephant neonate brain averages 50% of its adult brain weight (25% in humans). Cerebellar weight averages 18.6% of brain (1.8 times larger than in humans). During evolution, encephalization quotient has increased by 10-fold (0.2 for extinct Moeritherium, approximately 2.0 for extant elephants). We present 20 figures of the elephant brain, 16 of which contain new material. Similarities between human and elephant brains could be due to convergent evolution; both display mosaic characters and are highly derived mammals. Humans and elephants use and make tools and show a range of complex learning skills and behaviors. In elephants, the large amount of cerebral cortex, especially in the temporal lobe, and the well-developed olfactory system, structures associated with complex learning and behavioral functions in humans, may provide the substrate for such complex skills and behavior.

Animals↗

PubMed2006

Results of vaccination of Asian elephants (Elephas maximus) with monovalent inactivated rabies vaccine.

OBJECTIVE: To evaluate the humoral immune response of Asian elephants to a primary IM vaccination with either 1 or 2 doses of a commercially available inactivated rabies virus vaccine and evaluate the anamnestic response to a 1-dose booster vaccination. ANIMALS: 16 captive Asian elephants. PROCEDURES: Elephants with no known prior rabies vaccinations were assigned into 2 treatment groups of 8 elephants; 1 group received 1 dose of vaccine, and the other group received 2 doses of vaccine 9 days apart. All elephants received one or two 4-mL IM injections of a monovalent inactivated rabies virus vaccine. Blood was collected prior to vaccination (day 0) and on days 9, 35, 112, and 344. All elephants received 1 booster dose of vaccine on day 344, and a final blood sample was taken 40 days later (day 384). Serum was tested for rabies virus-neutralizing antibodies by use of the rapid fluorescent focus inhibition test. RESULTS: All elephants were seronegative prior to vaccination. There were significant differences in the rabies geometric mean titers between the 2 elephant groups at days 35, 112, and 202. Both groups had a strong anamnestic response 40 days after the booster given at day 344. CONCLUSIONS AND CLINICAL RELEVANCE: Results confirmed the ability of Asian elephants to develop a humoral immune response after vaccination with a commercially available monovalent inactivated rabies virus vaccine and the feasibility of instituting a rabies virus vaccination program for elephants that are in frequent contact with humans. A 2-dose series of rabies virus vaccine should provide an adequate antibody response in elephants, and annual boosters should maintain the antibody response in this species.

Analysis of Variance↗

PubMed2001

A variant of the endotheliotropic herpesvirus in Asian elephants (Elephas maximus) in European zoos.

Newly discovered, lethal elephant endotheliotropic herpesviruses (EEHV) have been identified in both Asian (Elephas maximus) and African (Loxodonta africana) elephants. Carried by otherwise healthy African elephants they can be fatal mainly for young Asian elephants. Since zoos often harbour both elephant species, we conducted a survey on the presence of EEHV in Asian elephants from 12 European zoos, 3 circuses and 1 Israeli zoo. Here, we demonstrate that all EEHV that have affected Asian elephants so far belong to the EEHV1 group. We also describe the detection and the partial sequencing of an endotheliotropic herpesvirus variant (named EEHV1b) in Asian elephants, being either an EEHV endogenous to Asian elephants or indicating different sources (African elephants) of infection.

2-Aminopurine↗

PubMed2001

Phylogeography of the asian elephant (Elephas maximus) based on mitochondrial DNA.

Populations of the Asian elephant (Elephas maximus) have been reduced in size and become highly fragmented during the past 3,000 to 4,000 years. Historical records reveal elephant dispersal by humans via trade and war. How have these anthropogenic impacts affected genetic variation and structure of Asian elephant populations? We sequenced mitochondrial DNA (mtDNA) to assay genetic variation and phylogeography across much of the Asian elephant's range. Initially we compare cytochrome b sequences (cyt b) between nine Asian and five African elephants and use the fossil-based age of their separation (approximately 5 million years ago) to obtain a rate of about 0.013 (95% CI = 0.011-0.018) corrected sequence divergence per million years. We also assess variation in part of the mtDNA control region (CR) and adjacent tRNA genes in 57 Asian elephants from seven countries (Sri Lanka, India, Nepal, Myanmar, Thailand, Malaysia, and Indonesia). Asian elephants have typical levels of mtDNA variation, and coalescence analyses suggest their populations were growing in the late Pleistocene. Reconstructed phylogenies reveal two major clades (A and B) differing on average by HKY85/gamma-corrected distances of 0.020 for cyt b and 0.050 for the CR segment (corresponding to a coalescence time based on our cyt b rate of approximately 1.2 million years). Individuals of both major clades exist in all locations but Indonesia and Malaysia. Most elephants from Malaysia and all from Indonesia are in well-supported, basal clades within clade A. thus supporting their status as evolutionarily significant units (ESUs). The proportion of clade A individuals decreases to the north, which could result from retention and subsequent loss of ancient lineages in long-term stable populations or, perhaps more likely, via recent mixing of two expanding populations that were isolated in the mid-Pleistocene. The distribution of clade A individuals appears to have been impacted by human trade in elephants among Myanmar, Sri Lanka, and India, and the subspecies and ESU statuses of Sri Lankan elephants are not supported by molecular data.

Animals↗

PubMed1999

Contraceptive potential of the porcine zona pellucida vaccine in the African elephant (Loxodonta africana).

Immunocontraception has been successful in controlling free-roaming equids; however, what is the potential for the immunocontraceptive control of the African elephant (Loxodonta africana)? The porcine zona pellucida (pZP) glycoproteins share antigenic domains with the African elephant zona pellucida (elZP) glycoproteins, and anti-zona pellucida serum antibodies have been successfully stimulated. To determine the cross-reactivity of the pZP and elZP, immunocytochemistry was evaluated by light and electron microscopy. Specifically, the binding of polyclonal antibodies against total heat-solubilized-porcine zona pellucida to fixed elephant ovary sections was evaluated. The elZP of primary, secondary and tertiary follicles was recognized by the rabbit-anti-pZP serum, but there was no apparent recognition of the primordial follicles. The ability of anti-pZP antibodies to recognize the elZP demonstrates that there is molecular homology between the pZP and elZP glycoproteins. This homology makes the African elephant a candidate for pZP immunocontraception. Three captive elephants were vaccinated with 400 micrograms pZP with a synthetic trehalose dicorynomycolate (S-TDCM) adjuvant. The elephants received 2 boosters of 600 micrograms pZP at 4 wk and 10 m.o. after the primary vaccination. The vaccinated female elephants developed significant (P < 0.05) titers to pZP over prevaccination levels. These levels persisted for 12 to 14 m.o. after the third vaccination. This preliminary evidence shows that the female elephant can develop significant serum antibody levels to pZP. These levels of antibodies are comparable to those required in horses for successful immunocontraception. Thus, porcine zona pellucida immunocontraception might be used to control elephant populations.

Animals↗

PubMed2001

Post-bottleneck genetic diversity of elephant populations in South Africa, revealed using microsatellite analysis.

Widespread hunting had fragmented and severely reduced elephant populations in South Africa by 1900. Elephant numbers increased during the 1900s, although rates of recovery of individual populations varied. The Kruger National Park elephant population increased rapidly, to more than 6000 by 1967, with recruitment boosted by immigration from Mozambique. The Addo Elephant National Park population was reduced to 11 elephants in 1931 and remains relatively small (n = 325). Loss of genetic variation is expected to occur whenever a population goes through a bottleneck, especially when post-bottleneck recovery is slow. Variation at nine polymorphic microsatellite loci was analysed for Kruger and Addo elephants, as well as museum specimens of Addo elephants shot prior to the population bottleneck. Significantly reduced genetic variation and heterozygosity were observed in Addo in comparison to Kruger (mean alleles/locus and H(E): Addo 1.89, 0.18; Kruger 3.89, 0.44). Two alleles not present in the current Addo population were observed in the museum specimens. Addo elephants represent a genetic subset of the Kruger population, with high levels of genetic differentiation resulting from rapid genetic drift. The Kruger population is low in genetic diversity in comparison to East African elephants, confirming this population also suffered an appreciable bottleneck.

Animals↗

PubMed2003

Studies on feed digestibilities in captive Asian elephants (Elephas maximus).

In order to test the suitability of the horse as a nutritional model for elephants, digestibility studies were performed with six captive Asian elephants on six different dietary regimes, using the double marker method with acid detergent lignin as an internal and chromium oxide as an external digestibility marker. Elephants resembled horses in the way dietary supplements and dietary crude fibre content influenced digestibility, in calcium absorption parameters and in faecal volatile fatty acid composition. However, the absolute digestibility coefficients achieved for all nutrients are distinctively lower in elephants. This is because of much faster ingesta passage rates reported for elephants. No answer is given to why elephants do not make use of their high digestive potential theoretically provided by their immense body weight. Differences in volatile fatty acid concentrations between these captive elephants and those reported from elephants from the wild are in accord with a reported high dependence of free-ranging elephants on browse forage.

Animal Feed↗

PubMed2002

The evolution and phylogeography of the African elephant inferred from mitochondrial DNA sequence and nuclear microsatellite markers.

Recent genetic results support the recognition of two African elephant species: Loxodonta africana, the savannah elephant, and Loxodonta cyclotis, the forest elephant. The study, however, did not include the populations of West Africa, where the taxonomic affinities of elephants have been much debated. We examined mitochondrial cytochrome b control region sequences and four microsatellite loci to investigate the genetic differences between the forest and savannah elephants of West and Central Africa. We then combined our data with published control region sequences from across Africa to examine patterns at the continental level. Our analysis reveals several deeply divergent lineages that do not correspond with the currently recognized taxonomy: (i) the forest elephants of Central Africa; the forest and savannah elephants of West Africa; and (iii) the savannah elephants of eastern, southern and Central Africa. We propose that the complex phylogeographic patterns we detect in African elephants result from repeated continental-scale climatic changes over their five-to-six million year evolutionary history. Until there is consensus on the taxonomy, we suggest that the genetic and ecological distinctness of these lineages should be an important factor in conservation management planning.

Africa↗

PubMed2004

Neuroleptanalgesia in wild Asian elephants (Elephas maximus maximus).

OBJECTIVE: To evaluate the suitability of etorphine with acepromazine for producing prolonged neuroleptanalgesia in wild Asian elephants. ANIMALS: Ten adult wild elephants (four males, six females), free-roaming in the jungles of the north-western province of Sri Lanka. MATERIALS AND METHODS: Ten wild elephants were tranquilized for attachment of radio transmitter collars from September to November 1997, using Large-Animal Immobilon (C-Vet Veterinary Products, Leyland, UK), which is a combination of etorphine (2.45 mg mL(-1)) and acepromazine (10 mg mL(-1)). This was injected using projectile syringes fired from a Cap-Chur gun (Palmer Chemical Co. Inc., Atlanta, USA). A volume of 3.3 (2.5-4.5) mL Immobilon (6.12-11.02 mg of etorphine and 25-45 mg acepromazine) was injected intramuscularly after body mass estimation of individual elephants. RESULTS: The body condition of all darted elephants was good, and the mean (minimum-maximum) shoulder height was 225 (180-310) cm. The average approximate distance to elephants at firing was 26 (15-50) m. The average time to recumbency after injection was 18 (15-45) minutes. Nine out of 10 elephants remained in lateral recumbency (and did not require additional dosing) for a period of 42 (28-61) minutes. The respiratory and heart rates during anaesthesia were 7 (4-10) breaths and 52 (40-60) beats minute(-1), respectively. An equal volume (8.15-14.67 mg) of diprenorphine hydrochloride (Revivon, 3.26 mg mL(-1) diprenorphine; C-Veterinary Products, Leyland, UK) was given intravenously when the procedure was completed. Recovery (return to standing position) occurred in 6 (2-12) minutes after diprenorphine injection. Immediately afterwards, all elephants slowly retreated into the jungle without complications. Continuous radio tracking of the animals involved in this study indicated no post-operative mortality for several months after restraint. CONCLUSIONS/CLINICAL RELEVANCE: Etorphine-acepromazine combinations can be used safely in healthy wild Asian elephants for periods of restraint lasting up to 1 hour.

Acepromazine↗

PubMed2005

Simultaneous visual discrimination in Asian elephants.

Two experiments explored the behavior of 20 Asian elephants (Elephas aximus) in simultaneous visual discrimination tasks. In Experiment 1, 7 Burmese logging elephants acquired a white+/black- discrimination, reaching criterion in a mean of 2.6 sessions and 117 discrete trials, whereas 4 elephants acquired a black+/white- discrimination in 5.3 sessions and 293 trials. One elephant failed to reach criterion in the white+/black- task in 9 sessions and 549 trials, and 2 elephants failed to reach criterion in the black+/white- task in 9 sessions and 452 trials. In Experiment 2, 3 elephants learned a large/small transposition problem, reaching criterion within a mean of 1.7 sessions and 58 trials. Four elephants failed to reach criterion in 4.8 sessions and 193 trials. Data from both the black/white and large/small discriminations showed a surprising age effect, suggesting that elephants beyond the age of 20 to 30 years either may be unable to acquire these visual discriminations or may require an inordinate number of trials to do so. Overall, our results cannot be readily reconciled with the widespread view that elephants possess exceptional intelligence.

Aging↗

PubMed2005

Pharmacokinetics of a single dose of enrofloxacin administered orally to captive Asian elephants (Elephas maximus).

OBJECTIVE: To determine the pharmacokinetics of enrofloxacin after oral administration to captive elephants. ANIMALS: 6 clinically normal adult Asian elephants (Elephas maximus). PROCEDURE: Each elephant received a single dose of enrofloxacin (2.5 mg/kg, PO). Three elephants received their complete diet (pellets and grain) within 2 hours after enrofloxacin administration, whereas the other 3 elephants received only hay within 6 hours after enrofloxacin administration. Serum concentrations of enrofloxacin and ciprofloxacin were measured by use of high-performance liquid chromatography. RESULTS: Harmonic mean half-life after oral administration was 18.4 hours for all elephants. Mean +/- SD peak serum concentration of enrofloxacin was 1.31 +/- 0.40 microg/mL at 5.0 +/- 4.2 hours after administration. Mean area under the curve was 20.72 +/- 4.25 (microg x h)/mL. CONCLUSIONS AND CLINICAL RELEVANCE: Oral administration of enrofloxacin to Asian elephants has a prolonged elimination half-life, compared with the elimination half-life for adult horses. In addition, potentially therapeutic concentrations in elephants were obtained when enrofloxacin was administered orally at a dosage of 2.5 mg/kg. Analysis of these results suggests that enrofloxacin administered with feed in the manner described in this study could be a potentially useful antimicrobial for use in treatment of captive Asian elephants with infections attributable to organisms, such as Bordetella spp, Escherichia coli, Mycoplasma spp, Pasteurella spp, Haemophilus spp, Salmonella spp, and Staphylococcus spp.

Administration, Oral↗

PubMed1998

Plasma vitamin E and other analyte levels in Nepalese camp elephants (Elephas maximus).

Plasma concentrations of alpha-tocopherol (vitamin E) and other analytes in Asian elephants (Elephas maximus) in Nepal were determined during typical work camp management of the elephants. Elephants foraged for food for 4-6 hr each day under the control of mahouts and were also provided daily with cut forage and supplements of unhusked rice, cane molasses, and salt. Blood samples were taken monthly for 1 yr without chemical restraint from 26 female elephants in four camps. Elephants were 6-60+ yr of age. Mean (+/-SEM) alpha-tocopherol concentration was 0.77+/-0.047 microg/ml, with a range of 0.23-1.57 microg/ml. Subadults had lower concentrations than did older elephants, and there were significant differences in mean concentrations from different camps and in mean monthly concentrations. Plasma alpha-tocopherol concentration appears to vary widely between individuals, and a single value of <0.3 microg/ml is not sufficient to diagnose incipient vitamin E deficiency. Mean (+/-SEM) plasma retinol (vitamin A) concentration was 0.063+/-0.003 microg/ml with a range of 0.01-0.12 microg/ml. Subadults had higher concentrations than did older elephants, and mean retinal values differed significantly among camps. Beta-carotene was not found in plasma. Twenty-five other analytes determined or derived were generally similar to those reported in other Asian and African (Loxodonta africana) elephants. Estimates of nutrient intake, based upon diet composition, suggested that dietary concentrations of zinc and sodium may have been marginal, but the absence of signs of any nutrient deficiencies indicates that dietary husbandry in these elephant camps was generally satisfactory.

Aging↗

PubMed1990

Elephant pituitary gonadotropins.

We describe for the first time the purification and some properties of luteinizing hormone (LH) and follicle-stimulating hormone (FSH) isolated from anterior pituitary tissue of the African elephant (Loxodonta africana). Methodology previously applied to equine and donkey pituitaries was used to obtain purified preparations of elephant LH and FSH in yields of 8.8 and 0.48 mg, respectively, per 10 g pituitary powder. The preparations were characterized by HPLC gel filtration and amino acid analysis, both of which showed the elephant LH and FSH to be very similar to ovine LH and FSH. The preparations were also characterized by radioimmunoassays and bioassays for LH and FSH and a radioreceptor assay for FSH. Results showed virtually no cross-contamination of hormonal activities in the elephant LH and FSH preparations. Elephant LH potencies ranged from 50 to 66% of highly purified ovine LH and elephant FSH potencies ranged from 21 to 52% of highly purified ovine FSH in the various assays employed. No evidence was found for any demonstrable intrinsic FSH activity in elephant LH. The assays employed suggest possible usage for making physiological measurements of gonadotropins in the elephant.

Amino Acids↗

PubMed2004

Species and fetal gender effects on the endocrinology of pregnancy in elephants.

Quantitative and temporal progestin profiles vary during gestation in the elephant, sometimes making it difficult to determine if a pregnancy is progressing normally. The aim of the present study was to determine if circulating progestin variability was related to species or fetal gender effects. A similar comparison also was conducted for secretory profiles of prolactin, relaxin, and cortisol. Overall mean progestin concentrations during gestation in Asian (n = 19) and African (n = 8) elephants were similar; however, the temporal profiles differed (P < 0.001). Concentrations were higher in African elephants during the first half of pregnancy, but then declined to levels below those observed in Asian elephants (P < 0.05). There also was a fetal gender effect in Asian, but not African elephants. Progestin concentrations were higher in Asian cows carrying male calves (n = 9) as compared to those carrying females (n = 10) (P < 0.001). Overall prolactin concentrations were higher in Asian than in African elephants between 8 and 15 months of gestation ( P< 0.001). There were no species differences in the secretory patterns of relaxin. Cortisol was relatively stable until the end of gestation when significant surges were observed, mainly between 8 and 11 days before parturition, and again on the day of birth. In sum, a comparison of progestin patterns between Asian and African elephants identified notable differences related to species and fetal gender. A role for cortisol in the initiation of parturition also was inferred from these data. From a practical standpoint, understanding the factors affecting gestational hormone characteristics and recognizing what the species differences are will help ensure that data used in diagnosing and monitoring elephant pregnancies are properly interpreted.

Analysis of Variance↗

PubMedDate not supplied

Temporary ovarian inactivity in elephants: relationship to status and time outside.

The captive elephant population in North America is in reproductive decline and, without importation from the wild, may cease to be viable within the next several decades. The estrous cycle of three captive, reproductive-age African elephants was monitored for 3 years by measuring serum progesterone concentrations. Each elephant experienced one or more episodes of extended low progesterone (>12 weeks), analogous to supposed terminal cessation of estrous cyclicity or 'flatlining' that has been described in some captive Asian and African elephants. Other studies have reported lengthy non-luteal (follicular) phases that indicate extended episodes of ovarian inactivity; however, this phenomenon has not been examined in detail. In this study, total duration of temporary ovarian inactivity or acyclicity followed a social rank pattern, with the most subordinate female having the longest and the dominant female the shortest duration. During periods of acyclicity, the number of hours the elephants spent outside was significantly less than during non-luteal or luteal phases of the cycle. Except in one instance, behavioral data recorded by elephant keepers during their interactions with the elephants showed no change in handling during periods of ovarian inactivity. Further study is necessary to distinguish the causative agent for temporary cessation of estrous cyclicity. Understanding this phenomenon is imperative for the future reproductive viability of captive elephant populations.

Animals↗