Elephant Development

Elephants have a complex social structure that heavily revolves around the presence of an old matriarch. Elephant herds comprise of multiple generations of mothers and children that move together in groups. Once males reach adulthood, they leave their herd and tend to travel alone. However, some males may move in smaller groups outside of breeding periods ¹⁾ . This leaves the females to travel together under the direction of the matriarch. The matriarch of the group is a female elephant that is over 30 years of age²⁾ The matriarch is a crucial part of an elephant herd, as she is responsible for most decisions of the group. Matriarchs decide responses to environmental threats, and decide the best course of action in grazing of the group. It was also found that the effectiveness of matriarch decision making increases with age ³⁾ .

In order to measure levels of stress in elephants, fecal samples are taken to quantify glucocorticoid levels. The most common glucocorticoids released in elephants are cortisol and corticosterone. These chemicals are a product of the adrenal gland when an elephant experiences stress.

While glucocorticoids can be measured through saliva or blood samples, fecal samples are used more often in order to prevent excess stress when handling elephants to retrieve these samples. Although fecal samples may be more difficult to tie to specific elephants, it is the least invasive method and provides the most reliable data ⁴⁾ .

(A chart showing glucocorticoid levels of different elephant herds)⁵⁾

Related studies have used glucocorticoids to measure stress related to other environmental factors such as poaching. Elephants are one of the few animals that actively express distress when other elephants of a group show illness or death ⁶⁾ . Due to the disruption of the matriarchal social structure, elephants that have lost family members, especially old matriarchs, to poaching have consistently higher glucocorticoid levels. ⁷⁾

(An elephant bull secreting from his temple while in musth)⁸⁾

Musth is a period of elevated testosterone in adult male elephants which causes a change in normal behavior to switch to a focus towards mating. Musth causes males to move from their normal home ranges in search of a mate. During this period, males are much more aggressive and willing to stand off with other males in order to secure a mate. During musth, males secrete a liquid from their temporal glands. This liquid gives a strong odor that signals to other elephants that the male is in musth. When two musth males meet, there is often aggression between the two in order to secure a female nearby. Most often, older males will win because they are often of a larger size than younger bulls. Younger bulls (25-35 years of age) can usually only breed successfully during the beginning or end of estrus cycles in females because they are able to avoid competition with an older, stronger male. Males will also exhibit guarding behavior of a female while in musth, which prevents other males from trying to mate with the same female ⁹⁾ ) .

Elephants exhibit competitive mating behaviors that are polygynous and often involve female choice of mate. Females are more likely to choose the largest males that are in musth. Many females begin mating at 7 years of age, and nearly all females have mated by the time they reach 11 years old. Fertility of female elephants begins to decline at about 45 years of age ¹⁰⁾ . These males are chosen as they are often strongest and will deter other males from trying to mate with the female. Large males in musth may also be more likely to impregnate a female, and when they are larger, males tend to be older so they may be able to pass on traits that encourage longevity to the offspring ¹¹⁾ . While males may guard a female for a mating season, the relationship does not persist for an extended period of time ¹²⁾ . When a bull finds a female herd, he will use the Flehmen test to find any females that are in estrus. If multiple males are present when a female is fertile, the larger male will win the ability to mate. Most conceptions occur during the wet season, but conception can happen year round ¹³⁾ .

The gestation period of an elephant is 22 months, and they will often raise their calves for up to 5 years after birth. An elephant calf typically weighs 120 kg at birth, and the weight of the calf at birth causes the placenta to rip off the uterine wall which causes observable blood clots. The trauma caused by birth can be used as a tool to tell how long it has been since a female elephant last gave birth ¹⁴⁾ . Female elephants will raise a calf for 3-5 years before being ready to reproduce again ¹⁵⁾ .

(A poster chart showing the stages of elephant birth)¹⁶⁾

Elephant calves are born into large herd structures. These herds often contain multiple females that range over first, second and third generations. Usually, these females are lead by a matriarch. The matriarch is the eldest female elephant that decides how the herd operates. Herds that are missing this key part of the structure often experience higher levels of stress among members. Females in a group are often relatives of one another, but this is less common¹⁷⁾ . Due to the herd structure, elephants often have allomothering of their young. The allomothers tend to be juvenile females that are not at reproductive age. While all members of a herd tend to interact and greet calves, allomothers will often display comforting and protective behaviors of a calf. However, in times of direct threat, all members of a herd will move into a defensive stance in order to protect the young calf. Allomothers are more common in herds that have family members present ¹⁸⁾ .

An elephant calf will typically nurse during the entire rearing period as they are often weaned by three years of age, but they can be weaned as early as two years. An elephant’s milk is similar to that of a cow’s, but it has a much higher fat content. This content is crucial to the growth of the calf as they grow very quickly over the first few years ¹⁹⁾ . Nursing of male calves tends to be more demanding than that of females. This is likely caused by more growth in males who will eventually grow to be much bigger than females. This demand for milk from a nursing mother causes a stronger maternal bond to males than females early in development, but this will eventually decrease with age ²⁰⁾ .

Elephants rely on communication that can come from chemical signals (as seen in Musth), touch or vocalization. Elephants have high vocal recognition that is able to recognize calls from over 1 km away. However, these calls tend to be a very low frequency (often between 10 and 20 Hz) and some calls are considered to be infra-sound. From these calls, elephants are able to deduce characteristics such as age, sex, location, sexual and physical status ²¹⁾ .

Elephants also utilize visual cues in order to communicate. By using certain stances, elephants can convey attitude to other elephants and other animals. During musth, bulls tend to stand with their head held higher to assert dominance and warn any challengers that may be nearby. Elephants can also assist their visual communication by using their trunk, as some animals have been observed to show apprehension or understanding by touch their trunk to their mouth or face. This signal can also be used as a greeting or a sign of submission to other elephants ²²⁾ .

(An adult elephant and calf intertwining trunks)²³⁾

Elephants show complex communication in the way they use touch with one another. The trunk of the elephant contributes to this complexity as the trunk is a very useful tool for elephants to discern information about their environment. An elephant’s trunk is able to differentiate touch with sensitivity that is similar to a finger tip, so touch is often used in order to learn more about other elephants. Elephants will often intertwine their trunks as a form of greeting, and they may continue to conduct a mouth check in order to learn more about each other. It is currently unknown exactly why elephants perform this act, but some speculate that it may teach elephants about physical status (such as being in musth or estrus) or about the food that another elephant may have access too. Touch is commonly used in the development of calves in a herd, and they will often receive more touching from other members of a herd than its own mother. Elephants will use touch during play, socialization, and to comfort calves. However, a calf also relies on touch to communicate with its mother. In order to initiate nursing with its mother, a calf will touch its mother’s hind leg or breast. However, if the calf may be tired and wants the herd to stop moving so it can rest, it will push on the mother’s front leg to signal a desire to slow down. Touch is not always limited to positive social interactions though, and it can be used as a punishment when raising offspring. Mother elephants have been known to use their trunks to slap offspring or poke them when they misbehave ²⁴⁾ .