A mother giraffe nudging her calf.
Image taken with permission from Ralf Schmode
Female giraffes care for their calves from birth until around 13-16 months, when young become more independent and are classed as subadults. Because giraffes are promiscuous, males take no part in parental care of young. Early scholars such as Dagg (1976) characterized maternal care in giraffe as minimal, even negligent. These authors noted that mother giraffes left their infants for hours at a time over distances of up to 1 km while they browsed elsewhere, concluding that giraffe maternal care was uninvolved. However, later authors such as Pratt (1982) found that although females frequently left their young to browse, they returned regularly to nurse and check on them, and that infants were typically left in groups with other calves rather than alone.
According to Dagg (1976), infant giraffes are very precocious. Newborns are around six feet tall, and they can walk as early as an hour after birth. For the first few months of their life, giraffe infants nurse regularly, but they may also begin to browse at ages as early as three weeks. Infants nurse until they are around six to nine months old (Langman 1977).
Overall, parental care in giraffe consists of nursing, protection, and to some extent, socialization. Mothers are often found to investigate potential threats, and they defend their calves from predators by placing themselves in between the predator and the infant, and by kicking the predator (Dagg 1976; Pratt 1979). No evidence of kin or reciprocal altruistic is found among giraffes: mothers only nurse their own young, and calving groups are ultimately formed for selfish herd reasons (Langman 1977).
A mother giraffe nudging her calf.
Image taken with permission from Ralf Schmode
Adult giraffes, like most large mammals, need a constant supply of high quality browse to stay healthy. Adult male giraffes tend to spend much of their time alone in wooded areas, where many trees and shrubs are available for browsing. However, female giraffes with young are more often found in open areas, where the quality of browse is lower. Young (1991) and Ginnett (1999) both observed this phenomenon, and came to the following conclusions:
Because male giraffes do not contribute to the care of young, they maximize their reproductive success by attaining the best browse possible. Their large body size aids them in competing for mates (see mating system). Therefore, when males are not looking for mates, they are typically feeding in heavy vegetation. Though wooded areas often contain the richest food sources, they provide less visibility of predators, and mothers must maintain higher levels of vigilance in underbrush than in open plains. For females, the reproductive gains attained by browsing in heavy vegetation are offset by greater predation risk for offspring, and a resulting higher need for vigilance. Female giraffes exhibit a compromise strategy: they sacrifice some nutritional benefits by spending more time in the open with their young. However, in open areas, they are less vigilant, and can spend more time browsing. Ultimately, the reproductive success of female giraffes is enhanced by this strategy, in the greater survival of their offspring. Female giraffes also leave their infants in groups with other calves, which allows them to browse on rich, thick vegetation for part of the day without dramatically increasing the predation pressure on their young.
This "reproductive strategy hypothesis," that giraffe mothers gravitate more toward open areas for predator protection, is supported by evidence from female giraffes without young. Like males, these females without young are found most often in the woodlands and tend to avoid open floodplain areas. Further, Ginnett found that male giraffes are most selective in their choice of browse, whereas females choose their food mostly based on availability. This difference in selectivity supports the reproductive strategy hypothesis: males can apparently be more selective in their feeding, since they do not also have to care for young.
Young also observed that dominant males seemed to sacrifice their foraging efficiency when they were in groups with female giraffes. In the presence of female groups, dominant males often fed at heights above their optimum foraging level. Young attributed this behavior to the reproductive strategy hypothesis, noting that the male giraffes maintained this erect position even when they were not browsing. The authors concluded that these dominant males were exhibiting increased vigilance against competing males. Feeding at higher-than-optimum height allowed the males to spot nearby competitors, and to maximize their own visibility, thereby "warning" other males to stay away. Thus, Young concluded that both males and females occasionally compromised their quality of feeding in order to obtain higher reproductive success.
A giraffe infant among shrubs. Infants are most vulnerable to predation in wooded areas.
Image taken with permission from Hedweb
Though parental care in giraffe is characterized by an exclusive bond between cow and calf, mother and infant are often separated for hours at a time. The formation of calving pools (creche groups) and the use of lying out behavior increases the survival of calves while allowing mothers to browse away from their infants. Nursery herds, calving pools, and group lying out are all used in giraffe to protect young from predation through the selfish herd (Langman 1977; Pratt 1979).
Langman (1977) defines nursery herds and calving pools in the following way:
Sometimes, all of the mothers in the calving pool may leave the group of calves. Groups of calves with no adults present are observed fairly often among giraffe-- this phenomenon is known as group lying out. Calves benefit from the selfish herd while remaining in clustered groups rather than lying out alone, so group lying out is more common than single lying out in most ages of giraffe infants. The one exception is seen in giraffe infants less than three weeks old, which are often left alone by their mothers (single lying out), but rarely in groups.
Why the difference?
Langman postulates that infant giraffes may be kept isolated during their first one to three weeks of life in order to aid in the process of imprinting between the mother and calf. In fact, female giraffes purposefully isolate their newborn infants from other adults or calves during the first few weeks postpartum, leading their infants away from other giraffe and threatening or even chasing away curious conspecifics. Both Langman and Pratt (1979) note that newborns left alone by their mothers spend the majority of their time lying down hidden in underbrush, and that they rarely move. Giraffe infants may rely on crypticity rather than selfish herd for predator protection during the first one to three weeks of life. Mothers of newborn calves return several times throughout the day to nurse and to check on their infants.
An infant giraffe lying out. Newborn giraffe infants spend much of their time lying down.
Image taken with permission from Hedweb
Pratt found that infants in between the age of 16 days and two months spent most of their time with their mothers rather than lying out alone or in peer groups. This finding has not been replicated in other studies, and further evidence would be necessary to support or refute it.
In conclusion, the conflict between the nutritional needs of female giraffes and their infants' needs for protection is resolved in several ways throughout infancy. During the first one to three weeks of an infant's life, single lying out is used to maximize browsing time for mothers, while allowing infants to hide from predators in thick underbrush. During this time, the mother-infant bond is cemented through isolation from other giraffes. Between one and three weeks postpartum (or after two months, according to Pratt), female giraffes and their young aggregate in small groups for selfish herd reasons. Nursery herds, calving pools, and group lying out are all observed as mothers leave and return to the groups of calves throughout the day. These groups are typically found in open areas where adults can spot predators most easily. At night, when predation risk is highest, mother giraffes remain with their infants (Langman 1977; Leuthold 1979; Pratt 1979).
Home | Introduction | Social Spacing | Social Interactions | Mating System | Parental Care | Bibliography
Animal Behavior | Davidson Biology Department | Davidson Home