H a b i t a t

Natively, giraffe inhabit both the arid and dry African Savannah and the open Acacia woodlands south of the Sahara. Giraffe are still prevalent in East Africa, however poaching and encroachment on their habitat has caused giraffe numbers to decrease in the western parts of the country. As a result, many giraffe now live in Reserves and National Parks.

Predators

The giraffe's size renders it immune to nearly all predation. When danger threatens, giraffe make no effort to conceal themselves amidst vegetation. Lions, the only giraffe predator for life, pose only a minor threat to mature giraffe; giraffe can outdistance a lion with their giant stride and can use their hoof (which weighs between 50 and 60 pounds) to administer a fatal blow to any predator. Because of their smaller size, giraffe young are, on occasion, the victims of crocodiles, cheetahs, and leopards.
Humans pose a significant threat to giraffe. Poaching and encroachment on giraffe habitat has had a detrimental effect on giraffe populations (Dagg 1976).

SOCIAL ORGANIZATION

Giraffe live mostly as solitary adults and occasionally as members of single sex groups (young bachelor herds or females and their calves). They form loose, open herds, void of leaders. A herd consists of up to 10 members that may be as far as ½ of a mile apart from each other. The giraffe's height, excellent eyesight, and freedom from predation allow them to maintain such distance between individuals. Because giraffe need to spend the majority of their time feeding and moving independently between trees and because their size makes the 'selfish herd' unnecessary for security, minimum coordination of herd movement exists. Moreover, individuals freely move between herds and can leave and join a herd at any time. Thus a herd usually does not consist of kin. In fact, giraffe only cluster together if attracted to the same tree or, occasionally, in the presence of a lion (Nje 1983).

Giraffe are non-territorial. They possess home ranges that vary in size depending on the abundance of food. The average home range is 44 square miles (150 square kilometers), however in regions in which food remains abundant throughout the year, giraffe can spend their entire lives in 1.5 square miles (5 square kilometers)!
Unlike males, females tend to stay in their natal ranges. Immature males tent to wander the farthest but dramatically decrease the size of their range as they mature (Leuthold 1979).

Giraffe are not considered territorial because they do not defend any particular area of land. They require too much food to inhabit a defensible area.

INTER-GIRAFFE RELATIONSHIPS:

Male-Male Relationships
Male - male interaction, aside from necking competitions, which begin at age 1 month or less, to establish dominance rank, is rare. (See also establishment of dominance rank.) As males grow older, they become more and more solitary.

Male-Female Relationships(See Mating).

Cow-calf relationships

Parturition
The female leaves the herd to give birth and usually does so in the same location every year. Dawn is the best time for parturition because an early morning entry into the world maximizes the calf's strength by night when more predators are active. Additionally, birth during daylight hours allows for successful imprinting.
Calving generally lasts between 1 and 2 hours and culminates when the mother licks her calf free of the fetal membrane; she may or may not eat the afterbirth that she expels up to 9 hours later. At the time of delivery, the calf is 6 feet (1.8 m) tall and weighs between 45 and 70 kg. After five minutes the giraffe can stand. It can nurse after 20 minutes and can follow its mother after an hour.
Because a calf's vulnerability stems from its small size, giraffe calves grow very quickly to 'remedy the condition;' a calf may grow as fast as 1 m in the first 6 months and may nearly double its size in its first year. Their daily activity saves energy for growth that results in immunity to predation.
For the first four to five months, calves congregate in nursery groups called crèches to rest and socialize while their mothers drink and forage in the distance - up to 1 km away. Distance between mother and calf varies seasonally; in the green season, with plenty of food outside the riverine forest, the females are usually within 200 m of their calves. However, during the dry season, the distance may be greater than 1km; the females feed in the forest and the calves remain outside. It is at these times that calves are often left in crèche groups.

Lying-out
Lying out, either single-lying out or group lying-out, involves "infant or juvenile giraffe lying or standing in an area without any adult giraffe within .5 km" (Langman 1976). As is typical of hiders, animals who remain hidden and separated from their mother except during nursing periods, neither infant nor juvenile giraffe left the lying out area "unless grossly disturbed" (Langman 1976). Newly born calves tended to practice single lying out. When following their mother, calves practiced 'heeling;' they walked at her side. Group lying out proved similar to calving pools except that the calves were left on their own without a mother cow. As with calves in a pool, the calves in a group lying out session were visited by their mothers periodically throughout the day to nurse. Regardless of disturbances, the calves remained in the same area throughout the day. The distance traveled from the lying out position by the cow ranged from 20 m to 3 km.
Adaptive advantages of lying out - First, a lactating cow under physiological stress may concentrate on feeding rather than on protecting her calf. Second, by lying all day a calf conserves energy and body water. Calves have a smaller mass and higher surface to volume ratio than adults and thus necessitate a higher expenditure of metabolic water for thermoregulation. Third, because of size differences, while searching for browse and water, the cow may cross terrain impossible for the calf to traverse (Langman 1976).

Nursery Herds
Behaviorists define nursery herds as "two or more infants and/or juveniles and their cows moving or browsing together." The nursery herds observed by Langman ranged in numbers from 4 to 13 members with 6.8 as the average number of giraffes per herd. The herds were loose and fluid and the associations of a short duration (Langman 1976).

Calving Pools
Calving pools exist when cows of nursery herds leave all of their calves with one female, usually the mother of the youngest, while they travel to other areas for browse or water. The average size calving pool observed by Langman, in his study of cow-calf relationships in the Timbavati Private Nature Reserve, contained 4.25 giraffe, with a ratio of 1: 2.33 cows to calves. The giraffe repeatedly formed the pools in the same relatively open areas, on high ground rather than amidst dense riverine bush. As with the group laying out behavior, the pools tended to be on route of travel for giraffe. Mother cows returned periodically during the day to nurse their calves that did not leave their group until nudged by their mother. The pools lasted for a single day; by nightfall his mother collected each calf (Langman 1976).

Nursing
Cows let only their own calves suckle. For the first three weeks of life, the calf nurses between 2 and 4 times a day for periods of 45 seconds to 2 minutes. The mother possesses ultimate control over the duration of suckling sessions. As age increases, so do the intervals between nursing periods. Once rumination is possible, by age 6 months, nursing is essentially complete (Pratt 1979).

Calf-calf relationships

Observation of calf- calf relationships suggests that each calf possesses a peer group of one to four peers. The consistency of these relationships reflected both associations between the calves' mothers and "mutual attraction and attachment quite aside from their mothers' affiliations" (Pratt 1982). The calves also demonstrated a lot of "deliberate physical contact" including nosing, rubbing, sniffing, licking, kicking, gamboling, and 'naso-frontal greeting' (Pratt 1982).

MATING:

Giraffe are a hierarchically promiscuous species; a female bases her mating preferences on the male's dominance rank, which he achieves through 'necking' competitions with other males. It is likely that hierarchical promiscuity evolved, rather than monogamy or polygyny, because females do not require male help in rearing the young.

Males wander in search of females in estrous, a phenomenon that occurs approximately once every two weeks. A successful male will mate with a mature, receptive female whenever and wherever he finds one. After approaching a group of females, a male giraffe will sniff each female's vulva, incite each to urinate and then perform Flehmen. If he finds that the female is in estrous, the male giraffe will 'guard' her (by intimidating other subservient males who approached) and follow her for hours before mounting her. The two remain together for the next 1 to 2 days and mate repeatedly until the female becomes pregnant.
Males and females become sexually mature at age 3.5 years - though males rarely mate before age 7 due to the dominance hierarchy. Gestation last approximately 15 months and females can continue to reproduce until age 20 and can thus have a maximum of 10 young during their lifetimes. Because of the female's foraging efficiency, no particular calving season exists (see also diet).

MORE ON NECKING AND THE ESTABLISHMENT OF A DOMINANCE RANK

Male sparring bouts, "necking," begin with pushing and shoving and can escalate to the point where male giraffe use their heads as 'hammers' to attack the opposing male. The intent of such action is not to hurt but to establish dominance. In fact, giraffe never resort to kicking or biting.
Several morphological adaptions have resulted from this behavior; giraffe possess blunt horns, thick hide, and have a special cavity in their head that helps to minimize the effect of impact. Moreover, several researchers contend that the giraffe's long neck has evolved from sexual selection pressures. Males with longer, stronger necks win 'necking' competitions, achieve dominance, and thus have increased reproductive success (Simmons 1996).
Biologists have observed necking at all times of day and during every season. While studying giraffe in East Tsavo National Park in Kenya, Barbara Leuthold found that sub-adult males engaged in play fighting, 'necking,' for up to 2 hours a day (Leuthold 1979).

Controversial Theories and Possible Future Studies:

Evolutionary Force Driving Lengthening of the Neck: Competition for Food or Sexual Selection?

Conflicting theories exist regarding the evolution of the giraffe's elongated neck. Some behaviorists agree with Darwin's assertion that the giraffe's long neck evolved as a result of the adaptive advantage of feeding at higher levels, beyond the reach of competing species. However, Robert E. Simmons and Lue Scheepers provide evidence to suggest that the giraffe's neck did not evolve specifically for feeding at higher levels but in fact evolved as a sexually selected trait. They disagree with Darwin's proposition that competition with other mammalian browsers drove the neck's evolution. Simmons and Scheepers provide statistics which point to the fact that, during the dry season when feeding competition ought to be most intense, giraffe feed from low shrubs rather than tall trees. Increased neck length, they contend, has been driven by sexual selection; because males fight for females by clubbing opponents with "well-armored heads on long necks," larger - necked males are dominant and gain the greatest access to females (Simmons 1996).

Simmons and Scheepers provide detail about "necking" and "sparring" and the victor's (dominant male's) subsequent right to females. Because the energy delivered by a club (the head) increases in proportion to the mass of the head and length of the neck, Simmons and Scheepers expected and found giraffe's with longer and more massive necks to dominate. If such theory is valid, then males should use only their necks and heads for intrasexual combat, male giraffes should exhibit more distinct morphological adaptations than females, males with larger necks and heads should dominate over others, and fossil records should point to disproportionate lengthening of the neck (versus that of all the limbs). Simmons and Scheepers found all to be true (Simmons 1996).

Possible Future Studies

Simmons and Scheepers hope that their paper, suggesting that sexual selection drove the evolution of the giraffe's long neck, will instigate others to conduct more studies regarding giraffe neck length in order to gather more data that will either support or reject their own proposal (Simmons 1996).

In their book, The Giraffe: Its Biology, Behavior, and Ecology, Dagg and Anne Innis Dagg and J. Bristol Foster suggest that behaviorists will most likely partake in more research regarding the giraffe's hearing capability (Dagg 1976).

For some more pictures:

• http://www.wildlife-nature.com/giraffe001.html
• http://www.giraffehaven.com/giraf003.html

For all the basics:

• http://www.123spot.com/AnimalDirectory/giraffes.html
• http://www.zoo.org/educate/fact_sheets/savana/giraffe.htm

For a brief summary:

• http://www.wildlifeafrica.co.za/girafebehavior.html

Anything you could ever want à la giraffe theme:

• http://home.earthlink.net/~jeffh4/giraffe.html

Works Cited