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Social Spacing and Organization of the Giraffe
Photograph of a giraffe herd. Photograph courtesy of Dr. Case.
Social Spacing and Organization
Giraffes live in very loose and open herds that lack leaders and coordination and are non-territorial animals (Anderson, 1985). Giraffes are found alone, in groups of two and threes, and in groups from ten to fifty giraffes, but most often they are found in groups of two to ten individuals (Leuthold, 1979). Males are often found to be solitary (Leuthold, 1979; Anderson, 1985). It is difficult for researchers to define a herd since giraffes are so tall and have good vision and therefore, can maintain visual contact over long distances (over about 1/2 mile region) (Nature-Wildlife, 2002). Group sizes vary with environment and season as giraffes in different areas have different group sizes, while other aspects of behavior remain constant (Le Pendu, 2000).
The homerange for a giraffe averages about 63 square miles and there are conflicting reports as to whether males or females have larger homeranges (Ciofolo, 2002; Moss, 1975). Homeranges have been observed at sizes anywhere from 2 to 252 square miles (Nature-Wildlife, 2002; Moss, 1975). The composition of giraffe herds changes continuously and can be composed of all males, all females, females and their young, or a mixture of both sexes (Van der Jeugd, 2000). Although adult giraffes don't seem to form bonds with each other, female giraffes are often found in herds (Leuthold, 1979; Van der Jeugd, 2000). Although adult females also don't appear to form bonds with each other because they change groups, they do appear to be more sociable than male giraffes (Leuthold, 1979). Female giraffes remain near their natal range while male giraffes remain in their mother's herd until they become sexually mature at the age of 4 years, when they leave to join bachelor herds (Nature-Wildlife, 2002).
Female giraffes don't appear to have a hierarchy system, but there does appear to be a dominance hierarchy order for males (Moss, 1975). If one male is feeding at a tree and a more dominant male approaches, the subordinate male will leave (Moss, 1975). If the subordinate male does not leave, the dominant male exhibits threat behavior by holding his head and neck high and if the subordinate male still does not leave, the two male giraffes will fight in what is termed "necking" (Moss, 1975). The details of this behavior will be discussed in the section on mating behavior since that is the main time that male giraffes fight.
Why do giraffes have homeranges?
Giraffes live in homeranges because their food is widely and variably scattered, found in clumps, and abundant. Therefore, it is not economical for a giraffe to attempt to defend an area and form a territory because it would not be much different from another giraffe's territory and and it would take too much energy and probably be impossible to defend an area large enough to provide enough food for the giraffes (Le Pendu, 1999). Therefore the main reason that giraffes have homeranges is because they are constantly moving to find food, even a small group needs a large amount of food to survive, and enough food is available in the region as long as they move to find it. The size of giraffe homeranges depends on the spacing of the trees they eat that are located in the region (Leuthold, 1979).
Why do giraffes have a loose and open social system?
The fluid social organization of the giraffe reflects the giraffes need to be constantly moving to find food, since its food is spread unevenly over a large area (Nature-Wildlife, 2002). Since man is the only main predator for adult giraffes and their food is plentiful, yet clumped, what is the function of a giraffe group? Some researchers suggested that maybe the giraffe group functions as a protective arrangement, but predation isn't much of a problem for adult giraffes due to their large size and height and excellent vision, which allows them to see predators approaching from large distances. Also, when a giraffe is in danger, it may or may not give a warning snort and even if it does, the other giraffes may or may not respond to his call (Moss, 1975). It is not really known why giraffes are not solitary, since they don't gain much from being in a group, but young male giraffes live in bachelor herds so that they can move up in the dominance hierarchy and gain dominance status that will allow them to breed with females at some point in their life. Also, giraffes do appear to utilize the many eyes of the group for watching predators at night time because they sleep little and in a circle formation with all of the giraffes facing in a different direction (Moss, 1975). Females seem to be sociable even when they are not caring for young, but a social group is especially important when females have newborns because during the day, they leave their newborn with the other newborns in a creche often with one adult female for predator protection while they search for food (Moss, 1975).
Maternal Care
Females with calves appear to have the closest associations, although the female's maternal functions and bonds are being debated by researchers (Anderson, 1985). Foster observed female giraffes in Nairobi and watched female giraffes leave their young for days (Moss, 1975). In the Serengeti, Mejia observed the interactions of female giraffes with their calves from immediately following birth to months later. Female giraffes return to the same location each time they give birth, which is usually a secluded spot away from the herd (Anderson, 1985). Amazingly, the female giraffe stands to give birth and the calves survive the 5 1/2 foot fall to the ground (Moss, 1975). During the first few days after birth, the mother stays secluded with her calf and spends a great deal of time nosing and licking the calf (Moss, 1975). This time is vital because the mother and the young calf are imprinting on each other, so that when they return to the group they will be able to recognize each other (Moss, 1975).
After a few days, the mother and calf leave the secluded spot and join other females with new calves (Moss, 1975). The females form maternity groups called creches or kindergarten groups of about 9 calves and the calves begin to form strong bonds with each other (Moss, 1975). Calves are born throughout the year, but there are peak times for birth. Therefore, a female giraffe with a newborn can usually find other new mothers to form creche groups (Leuthold, 1979). Backhaus observed that in Zaire, one female stayed with the creche group during the day while the other females went in search of food, while Mejia observed that in the Serengeti, the females left the calves in the creche group alone during the day on the top of a hill, but return at night (Ginnett, 1999). Female giraffes look for an area with good vegetation that provides them the ability to see long distances to stay with their young (Ginnett, 1999). The young giraffes play during the day, but the females must return in the evening to protect them from predators such as lions, hyenas, leopards, and wild dogs (Ginnett, 1999). Adult giraffes are very good at warding of predators as they kick them with their hind legs, but the mortality rate of young calves is still high around 50-75% (Moss, 1975). Young giraffes also must nurse about twice a day, but the duration of nursing has been debated. The consensus seems to be that the young nurse regularly until they are one year old and sporadically until they are 16 months old (Moss, 1975). After about four months, the calves begin to go with their mothers to feed (Moss, 1975). Giraffe calves become independent around the age of 16-18 months and both male and female calves leave their mother (Leuthold, 1979). Female calves join other females in their natal range while male calves join bachelor herds (Moss, 1975).