Bull African elephants are among the most physically imposing and behaviorally complex land animals alive. A mature male can stand over 3.5 meters at the shoulder, outweigh females by several tonnes, and continue growing well into middle age. But sheer size is only the beginning of what makes these animals remarkable. Bulls cycle through a hormonally driven state called musth that transforms their behavior for weeks at a time, they navigate landscapes using spatial memory that can pinpoint water sources from dozens of kilometers away, and their social lives are far more structured than the old image of a solitary wanderer would suggest.
How Big Bulls Get, and How Long They Keep Growing
Male African elephants grow faster than females from birth onward, and the gap widens steadily. By about ten years of age the size difference is already obvious, and it keeps increasing because males continue growing for much longer than females do. By around 65 years of age, bulls are on average 60 to 70 centimeters taller at the shoulder than cows of the same age.1Journal of Zoology. Statural growth in known‐age African elephants That prolonged growth trajectory has consequences for everything from how bulls compete with one another to why older males carry such outsized ecological influence. A 45-year-old bull in good condition is a substantially larger animal than a 25-year-old, and body size directly affects who wins fights and who gets to mate.
Interestingly, body size in male elephants is not determined by genetics and food supply alone. Research comparing crop-raiding bulls with non-raiders found that males who raided agricultural fields ended up larger as adults, even though they were not any bigger or smaller than their peers when young. The risk-taking appears to pay off nutritionally, accelerating growth rates and ultimately producing bigger adults.2Behavioral Ecology. No risk, no gain: effects of crop-raiding and genetic diversity on body size in male elephants This matters for understanding conflict between elephants and farming communities: the bulls most likely to raid crops are the ones gaining the most from it in reproductive terms, since larger males dominate breeding.
Tusks and Laterality
Tusks are elongated upper incisors, and in African elephants they grow continuously throughout life. In males, both the length and circumference of tusks increase steadily, and because the circumference keeps expanding too, the rate at which dentine accumulates actually accelerates with age. An old bull’s tusks are not just longer than a young bull’s; they are disproportionately heavier.3Pachyderm. Growth characteristics of tusks of elephants in Kruger National Park
Most elephants are not symmetrical in their tusk use. The vast majority of individuals studied, about 94%, showed measurable differences in weight between their left and right tusks. On average the left tusk was slightly heavier, and elephants with larger overall tusk pairs showed a greater degree of asymmetry. The explanation is behavioral rather than anatomical: elephants appear to favor one tusk for digging, stripping bark, and sparring, wearing it down more on one side, much the way humans are right- or left-handed.4Journal of Zoology. Tuskedness in African elephants – an anatomical investigation of laterality One Kruger National Park study found a slight lean toward right-tuskedness in its sample, suggesting the pattern varies across populations.3Pachyderm. Growth characteristics of tusks of elephants in Kruger National Park
Decades of poaching have left a measurable mark on tusk size. In one well-documented regional population, tusk length declined by roughly 21% in males born during a period of population recovery following heavy illegal harvest. Tusk circumference dropped by about 5% in those same males. Among surviving individuals who had lived through the worst poaching years, the declines were even steeper: 22% in length and 8% in circumference.5PubMed Central. Illegal tusk harvest and the decline of tusk size in the African elephant The selective removal of large-tusked individuals over generations appears to be shifting the trait distribution in the population, a textbook case of human-driven selection pressure playing out in real time.
Musth, the Defining Male State
Musth is a periodic condition unique to elephant bulls, and it dominates the reproductive biology of the species. During musth, a bull’s testosterone production surges dramatically, his temporal glands (located on either side of the head, between the eye and ear) swell and secrete a viscous fluid, and he dribbles pungent urine almost continuously. His behavior shifts toward heightened aggression and active mate-seeking.6PubMed Central. Characterization of Longitudinal Testosterone, Cortisol, and Musth in Male Asian Elephants (Elephas maximus), Effects of Aging, and Adrenal Responses to Social Changes and Health Events Females generally prefer musth males as mates, and bulls in musth have a well-documented fighting advantage over non-musth males even of similar size.7PubMed. The impact of competition on elephant musth strategies: A game-theoretic model
The hormonal picture during musth is more complex than just a testosterone spike. Studies across both African and Asian elephants have found that musth is also associated with increases in luteinizing hormone, follicle-stimulating hormone, and cortisol, alongside a decrease in thyroid hormones.8PubMed. Variation in metabolic factors and gonadal, pituitary, thyroid, and adrenal hormones in association with musth in African and Asian elephant bulls The cortisol picture is not entirely settled, though. At least one study focused specifically on African elephant bulls found that cortisol metabolites were not elevated during musth, suggesting the stress-hormone response may differ between species or measurement methods.9General and Comparative Endocrinology. Non-invasive assessment of adrenocortical function in the male African elephant (Loxodonta africana) and its relation to musth Whether musth is genuinely “stressful” in the cortisol sense for African bulls, or whether it just looks that way in Asian elephants and cross-species comparisons, remains an open question.
Musth episodes tend to be annual and can last from a few weeks to several months, with duration generally increasing as a bull ages and reaches his physical prime. The timing matters because it creates a rotating dominance system: a relatively smaller bull in musth can displace a larger one who is not, shuffling the competitive hierarchy throughout the year.
Social Lives of Bull Elephants
The popular image of bull elephants as loners is incomplete at best. After leaving their natal family group in adolescence, males do spend time alone, but they also form loose all-male groups and maintain social bonds that matter for survival and behavior. Research tracking movements of these all-male groups in savannah populations has found clear age-based structure. Older adults are significantly more likely to travel at the front of a moving group, while adolescents cluster in the middle. No age class showed a particular tendency to bring up the rear, but the front-of-group pattern was strong, suggesting that experienced bulls lead and younger ones follow.10Scientific Reports. Importance of old bulls: leaders and followers in collective movements of all-male groups in African savannah elephants (Loxodonta africana)
These groups are not random aggregations. Studies of vocal coordination during group departures found that the low-frequency rumbles elephants use to initiate and coordinate movement occur between closely bonded individuals, not between loose acquaintances. Pairs of bulls who participated in coordinated group departures had significantly higher association indices than pairs who did not, indicating that these departure events are socially structured rather than haphazard.11PubMed Central. The use of vocal coordination in male African elephant group departures: evidence of active leadership and consensus
The regulatory role of older bulls is perhaps the most striking aspect of male elephant sociality. A well-known case in South Africa’s Pilanesberg Game Reserve illustrated what happens when that regulation is absent. Young orphaned males, translocated without older males present, began killing rhinoceroses, a behavior essentially unheard of in normal elephant populations. When six older bulls were introduced from Kruger National Park, the killings stopped. The older males suppressed the premature and prolonged musth episodes the young bulls had been entering, restoring something closer to normal behavior.12Nature. Older bull elephants control young males This case became a landmark example of how social disruption, particularly the loss of mature males from a population, can produce cascading behavioral problems.13Ethology. How Elephants are Opening Doors: Developmental Neuroethology, Attachment and Social Context
Chemical Communication and Mate Detection
Bulls rely heavily on chemical signals to find mates and to broadcast their own reproductive status. During musth, males secrete copious temporal gland fluid and produce strongly odoriferous urine, both of which convey information about the male’s condition to other elephants. Females appear to use these chemical cues when choosing mates and show greater chemosensory interest in the urine of musth males compared with non-musth males.14PubMed. Chemical signals in the reproduction of Asian (Elephas maximus) and African (Loxodonta africana) elephants
Bulls also actively investigate females’ reproductive state using their trunks. The flehmen response, a curling of the upper lip that draws scent molecules toward a specialized sensory organ in the roof of the mouth, is one of the characteristic behaviors males perform when assessing whether a cow is in estrus. Researchers have isolated chemical components from the urine of estrous females that reliably trigger flehmen responses in bulls.15PubMed. Asian bull elephants: Flehmen-like responses to extractable components in female elephant estrous urine In practice, bulls combine direct genital inspection (touching the female’s urogenital area with the trunk tip) with sniffing urine deposits. Both methods allow bulls to detect estrus at rates better than chance, though neither is perfectly accurate on its own.16PubMed. Use of genital inspection and female urine tests to detect oestrus in captive Asian elephants This chemical toolkit helps explain how bulls roaming over vast distances can locate receptive females efficiently.
Built for the Job
Supporting the mass of a large bull requires some unusual engineering. African elephant feet contain large subcutaneous cushions made of fibrous connective tissue organized into compartments filled with fat. These cushions distribute weight during each step and absorb mechanical forces, functioning somewhat like built-in shock absorbers.17PubMed Central. The structure of the cushions in the feet of African elephants (Loxodonta africana) Pressure studies show that the front feet bear higher peak pressures than the hind feet, consistent with the observation that roughly 60% of an elephant’s body weight rests on the forelimbs.18PubMed Central. Foot pressure distributions during walking in African elephants (Loxodonta africana)
Thermoregulation is another challenge for an animal this large, since volume increases faster than surface area as body size goes up. Elephants dump excess heat through their large, highly vascularized ears. Flapping and spreading the ears increases airflow across the blood-rich surface, and the calculated heat loss from the ears represents a substantial fraction of the total metabolic heat an elephant needs to shed.19South African Journal of Zoology. Why do elephants flap their ears?20Journal of Mammalogy. The Functional Significance of Movements and Positions of the Pinnae of the African Elephant, Loxodonta africana But ears are not the only cooling mechanism. Infrared thermography of African zoo elephants has revealed “thermal windows” across the entire body surface: sharply defined patches of skin where blood flow increases to radiate heat. These windows become more frequent as ambient temperature and body weight rise, suggesting they act as a fine-tuning system for heat management beyond what the ears provide.21Journal of Thermal Biology. Thermal windows on the body surface of African elephants (Loxodonta africana) studied by infrared thermography
Elephant dentition is also unusual. Rather than replacing baby teeth with a permanent set the way most mammals do, elephants cycle through six sets of molars over a lifetime, with each new tooth larger than the last, pushing forward in the jaw as the preceding one wears down and breaks apart. Each replacement lasts roughly 10 to 15 years. When the final set wears out, usually in old age, the animal can no longer chew effectively, which is a common limiting factor on lifespan.
How Bulls Navigate the Landscape
Bull elephants move across enormous home ranges, and they do not wander randomly. Studies using GPS tracking and movement modeling have shown that elephants make goal-oriented decisions about where to go, particularly when heading for water. On average, the decision to move toward a specific waterhole was initiated about 4.6 kilometers away, but in some cases elephants appeared to begin navigating toward a waterhole from nearly 50 kilometers out. They chose the closest available water source about 90% of the time, but this selectivity dropped when they were switching to a different waterhole than the one they last visited or during the dry season.22PubMed Central. Elucidating the significance of spatial memory on movement decisions by African savannah elephants using state-space models Males made their water-seeking decisions from somewhat shorter distances than female groups, possibly because bulls tend to range closer to known water resources in general.
The movements of bulls have outsized effects on the landscapes they cross. Elephants are well known for knocking over, stripping, and breaking trees, and research in the Serengeti has found that this chronic damage is a stronger driver of tree mortality than either fire or rainfall variation. The key word is chronic: repeated low-intensity browsing damage over time kills more trees than occasional severe events.23Journal of Ecology. Elephant damage, not fire or rainfall, explains mortality of overstorey trees in Serengeti Bulls contribute disproportionately to this kind of damage because of their size and their tendency to push over large trees that cows cannot. In this way, bull elephants function as ecosystem engineers, maintaining the open structure of savannahs and creating habitat heterogeneity that benefits other species.
Contraception and the Challenge of Managing Bulls
In fenced reserves where elephant populations can grow beyond what the habitat supports, wildlife managers sometimes turn to reproductive control. One approach that has been tested on bulls is vaccination with GnRH (gonadotropin-releasing hormone) vaccines, which suppress the hormonal cascade that drives reproduction. The results are dramatic. After repeated vaccinations, bulls showed a roughly 58% reduction in testis size, and after five to eight injections, half the treated post-pubertal bulls produced only small numbers of immotile sperm while the rest produced none at all. Androgen metabolites dropped significantly, and none of the treated males entered musth during the study.24PubMed Central. Effects of GnRH vaccination in wild and captive African Elephant bulls (Loxodonta africana) on reproductive organs and semen quality
This kind of intervention is effective at reducing births, but it comes with behavioral side effects that managers need to consider. When even one dominant bull in a small population is treated with a GnRH suppressant, the dominance hierarchy among males can shift, and treated males may spend unusually large amounts of time associating with female herds. In one fenced reserve, association indices between certain males and female groups were notably elevated compared with what would be expected in a normal population where musth cycles drive males to alternate between solitary ranging and herd contact.25Global Ecology and Conservation. The impact of male contraception on dominance hierarchy and herd association patterns of African elephants (Loxodonta africana) in a fenced game reserve Whether these altered social patterns have downstream effects on female group behavior or calf development is not yet well understood, but the finding underscores that suppressing reproduction in a bull changes more than just his fertility. It rewrites his social role in ways that ripple through the population.