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Phacochoerus aethiopicusdesert warthog

By Ian Winkelstern

Geographic Range

Desert warthogs are found in the Horn of Africa, in central and eastern Kenya, western Somalia, and southeastern Ethiopia. They were also known from South Africa, but are now extinct there. (d'Huart and Grubb, 2001)

Habitat

Desert warthogs are primarily a savannah species, though they have higher tolerance for dry conditions than common warthogs, Phacochoerus africanus, and so can live in more arid and desert-like conditions. They generally stay away from heavily forested zones and areas with thick undergrowth. Most of their grazing area is at low elevations as they have a low tolerance to cold. Phacochoerus aethiopicus is currently a tropical species, though populations that are now extinct may have extended into temperate zones. (Estes, 1991; Kingdon, 1979)

  • Range elevation
    0 to 1000 m
    0.00 to 3280.84 ft
  • Average elevation
    300 m
    984.25 ft

Physical Description

At over 1 m long and generally more than 0.5 m tall at the shoulder, desert warthogs are large. They have a stocky build and a large, somewhat flattened head. There is significant sexual dimorphism, males are significantly larger than females. The characteristic "warts" that give Phacochoerus species their common name also differ between the sexes; males have much larger and more protrusive warts, which are paired masses of dense facial tissue. Males also have larger tusks (elongated canine teeth) than females. Juvenile desert warthogs are like adults, but smaller with much reduced "warts" and no tusks. Tusks gradually appear after the onset of puberty. Most desert warthogs are brown to dark brown with short and sparse hairs covering much of the body. A crest of much longer hair runs along the back of the neck of males and females. A portion of this crest is sometimes whitish in color. (d'Huart and Grubb, 2001; Estes, 1991; Kingdon, 1979; Randi, et al., 2002)

The clearest morphological trait that separates desert warthogs from common warthogs (Phacochoerus africanus) is the lack of functional incisors. These two species are quite distinct genetically and common warthogs are usually slightly larger than desert warthogs. Desert warthogs are distinguishable from closely related bushpigs (Potamochoerus porcus) and giant hogs (Hylochoerus meinertzhageni) by their distinctive facial warts and larger tusks. (d'Huart and Grubb, 2001; Estes, 1991; Kingdon, 1979; Randi, et al., 2002)

  • Sexual Dimorphism
  • male larger
  • sexes shaped differently
  • ornamentation
  • Range mass
    45 to 130 kg
    99.12 to 286.34 lb
  • Average mass
    75 kg
    165.20 lb
  • Range length
    100 to 145 cm
    39.37 to 57.09 in
  • Average length
    125 cm
    49.21 in

Reproduction

During the mating period, female desert warthogs urinate quite frequently, up to 10 times more than males. Male warthogs can smell the urine from a significant distance and will investigate the urine to determine female reproductive state. During estrus females secrete a discharge from the vulva which changes the color of her hindquarters. The act of copulation lasts from 1 to 10 minutes, generally followed by the separation of the couple. Females and boars (males) mostly live in separate groups, but these groups interact more frequently and can even temporarily join in the mating season. Males and females may have several mates during a mating season, but females stop mating when they become pregnant. (Delany and Happold, 1979; Estes, 1991; Kingdon, 1979)

The timing of desert warthog mating is in part determined by climate. They inhabit areas with distinct dry and rainy seasons and tend to breed towards the end of the wet season (peaking around early April). Desert warthog females are polyestrous, with estrous periods lasting for about 72 hours and occurring once every 6 weeks (if her egg was not fertilized). Births occur between August and December, with most occurring in late September. Desert warthogs give birth to 2 to 3 offspring per year. Young emerge from the burrow to feed on grasses at about 3 weeks of age, though they are not fully weaned until they are about 6 months old. Offspring follow the mother wherever she goes, suckling as much as every 40 minutes, using her as shade from the hot sun, and sometimes using her feces as a food source. Desert warthogs are thought to become sexually mature slightly earlier than common warthogs, which mature at 1.5 years. (d'Huart and Grubb, 2001; Delany and Happold, 1979; Estes, 1991; Kingdon, 1979)

  • Breeding interval
    Desert warthogs breed once yearly.
  • Breeding season
    Desert warthogs breed from March to May, in general.
  • Range number of offspring
    1 to 8
  • Average number of offspring
    2 to 3
  • Range gestation period
    160 to 175 days
  • Average gestation period
    170 days
  • Range weaning age
    2.5 to 6 months
  • Average weaning age
    3 months
  • Range time to independence
    1.5 to 2 years
  • Average time to independence
    2 years
  • Range age at sexual or reproductive maturity (female)
    1.0 to 1.5 years
  • Range age at sexual or reproductive maturity (male)
    1.0 to 1.5 years

Because it takes desert warthog piglets over a year to fully mature, parental investment is significant. Males generally contribute very little to parenting as they more or less leave the group after mating season. Therefore, females must both provide food for the offspring as well as teach them how to find food and avoid predation. Also, because juveniles take so long to become independent, females may have two sets of young for a period of time, older young and newly born piglets. Birth takes place in a burrow, where females remain for long periods with newborns to nurse them for about a week. After that she will return often after short feeding periods for more nursing. Several months later, when offspring are ready for sustained excursions outside of burrows, the mother (along with other females in her group) must constantly be aware of predators and sound the alarm when one is spotted. Usually females will defend their young with great vigor, though there is a reported case of mothers standing idly by while a hyaena killed and ate a juvenile. (Estes, 1991; Kingdon, 1979)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • provisioning
      • female
    • protecting
      • female
  • pre-weaning/fledging
    • provisioning
      • female
    • protecting
      • female
  • pre-independence
    • provisioning
      • female
    • protecting
      • female
  • post-independence association with parents
  • extended period of juvenile learning

Lifespan/Longevity

Warthogs have an average lifespan between 7 and 18 years. However, no study on lifespan has been done specifically on desert warthogs. Among juveniles, warthog mortality in the wild is about 50% per year, with adult mortality dropping to around 15% per year. The main limit on longevity in the wild is predation. Boars often have higher mortality rates than females due to a tendency to sleep out in the open (not in a burrow), especially during and after the mating season. (d'Huart and Grubb, 2001; Estes, 1991; Kingdon, 1979)

  • Typical lifespan
    Status: wild
    7 to 18 years
  • Average lifespan
    Status: wild
    10 years

Behavior

Desert warthogs create deep burrows or steal them from other burrowing species. These burrows mainly provide protection from predators, especially for the young. Warthogs may use up to 10 different burrows when moving throughout their home range, ensuring that one is always nearby if they are threatened. Desert warthogs live in social groups known as "sounders." These groups are primarily made up of females and their offspring, with males rarely drifting in an out when it is not the mating season. All members of the group, including adult males if present, usually follow the oldest and largest female. Often the home ranges of different sounders will overlap and the groups will at different times occupy the same burrows. A sounder that finds a burrow already taken will seek out a different one. Members of different groups rarely interact otherwise and almost never exchange members. On very hot days warthogs will stay in the shade for much of the time. In cooler weather they spend much of their time grazing on grasses or digging for roots and tubers. They are strongly diurnal, retreating to burrows when it becomes dark. However, in areas where human persecution is more intense many groups have started to forage later into the night. (d'Huart and Grubb, 2001; Estes, 1991; Kingdon, 1979)

  • Range territory size
    2 to 4 km^2

Home Range

Desert warthogs are generally sedentary at times, typically staying within a home range 3 to 4 km wide, but they may travel over 7 km in a day. Home ranges are often centered around a watering hole of some kind. (d'Huart and Grubb, 2001; Kingdon, 1979)

Communication and Perception

Smell is the most important and keen sense that desert warthogs have. Much of warthog communication is though scent marking, through tusk and preorbital glands and urination. Males use urination to temporarily mark a burrow as his own. Sound is also very important, as they have a variety of warning calls used to alert the group to the presence of a predator. Because they have comparatively weaker sight, smell and hearing are the main ways by which desert warthogs are alerted to danger. Sight can be important in various social displays to signify dominance, submissiveness, or an imminent attack. Desert warthogs have a "strutting" behavior, consisting of walking deliberately around a more submissive warthog with the crest of hair and tail fully erect. Submissive displays include lying flat against the ground or even rolling over to expose the belly. Male warthogs fight to establish dominance, including pushing with the snout and horizontal strikes with tusks. (Estes, 1991; Kingdon, 1979)

Food Habits

Warthogs are herbivores which feed mainly on grasses and roots. Because of their harsh environments, desert warthogs are probably less picky eaters than common warthogs, which tend to feed only on select plants. Warthogs eat a variety of grasses and shrubs, and occasionally fruits and some insects in hard times. An important element in their diet is underground rhizomes, bulbs, and tubers, all of which are dug up with the tusks and snout. They sometimes eat their own dung and the dung of other animals. During times of little food, they have been known to eat carrion. Plants eaten by warthogs include Sporobolus pellucida, Microchloa kunthii, Brachiaria, Cynodon dactylon, Chrysochloa orientalis, Bothriochloa, Cenchrus, Panicum maximum, Eragrostis tenuifolia, Harpachne schimperi, and Digitaria macrobole. They eat the fruit of Balanites, Sclerocarya, and Ficus species. (d'Huart and Grubb, 2001; Estes, 1991; Kingdon, 1979)

  • Plant Foods
  • leaves
  • roots and tubers
  • wood, bark, or stems
  • fruit
  • flowers
  • Other Foods
  • dung

Predation

The main predators of desert warthogs are large cats, including lions, leopards, and cheetahs. Hyaenas have also been known to hunt warthogs. Adult and juvenile warthogs run to the nearest burrow when threatened. All but the youngest individuals enter the hole tail-first, enabling them to use their tusks against the attacking predator. Though they can run at 55 km/hr, warthogs do not have the speed or endurance that many other prey animals have in sub-Saharan Africa, and so must get to a burrow as fast as possible. Lions pose an especially great threat to desert warthogs because they can dig warthogs out of their burrows. Desert warthogs have specific warning grunts and sounds that cause all members of a group to be on high alert. Juvenile warthogs, upon hearing a specific sound from the mother, will freeze in place then dash to the nearest burrow as fast as possible. (Estes, 1991; Kingdon, 1979)

Ecosystem Roles

All warthogs consume large amounts of grass and may influence plant communities through their foraging. Their ability to take and use the burrows of other animals (such as aardvarks) has a negative ecological impact on those species. Because they are a host for the tick Ornithodoros moubata, warthogs are a reservoir for African swine fever. They also serve as a preferred host for tsetse flies. (Estes, 1991; Estes, 1991; d'Huart and Grubb, 2001; Estes, 1991)

Commensal/Parasitic Species

Economic Importance for Humans: Positive

Warthogs are iconic animals of the African savanna, so they can contribute to ecotourism. They also can be hunted and used as a source of food. (Estes, 1991)

Economic Importance for Humans: Negative

Warthogs can be agricultural pests, causing damage to bean, rice, or wheat fields. Their burrowing can cause problems for livestock or machinery. In the past warthog elimination campaigns were established to control warthogs as reservoirs for African swine fever, which can be transmitted to domesticated pigs. These campaigns are less common now as it is known that the disease is transmitted by ticks and thus removing the original wild host will do little to stop its spread. Rarely, and only when threatened, warthogs have attacked humans. This has lead to injury and, in a few cases, death. (Kingdon, 1979)

Conservation Status

Desert warthogs are not considered threatened, as they have a large distribution and are adaptable. However, populations are considered in decline and face continued threats through human persecution in the form of hunting and competition for foraging habitat with domestic livestock. In areas where human persecution is intense many populations have become somewhat nocturnal- a change from their normal diurnal lifestyle. (Kingdon, 1979)

Other Comments

For most of the last century, African warthogs were considered a single species, Phacochoerus aethiopicus. It was only in the last decade that desert warthogs (Phacochoerus aethiopicus) and common warthogs (Phacochoerus africanus) were recognized as two distinct species. This recognition was based mainly on genetic evidence. As a result there is little specific research that has been done on the behavior, ecology, and life history of desert warthogs. Nearly all available information on warthogs, especially from prior to 2001, may or may not be applicable to what is now known as Phacochoerus aethiopicus. However, the two species are similar in appearance, ecological impact, and behavior and much of the above information is based on a combination of studies on both species of African warthogs. Information may change as further scientific research is completed. (d'Huart and Grubb, 2001; Randi, et al., 2002)

Contributors

Ian Winkelstern (author), University of Michigan-Ann Arbor, Phil Myers (editor, instructor), Museum of Zoology, University of Michigan-Ann Arbor, Tanya Dewey (editor), Animal Diversity Web.

Glossary

Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

World Map

acoustic

uses sound to communicate

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carrion

flesh of dead animals.

causes or carries domestic animal disease

either directly causes, or indirectly transmits, a disease to a domestic animal

chemical

uses smells or other chemicals to communicate

crepuscular

active at dawn and dusk

desert or dunes

in deserts low (less than 30 cm per year) and unpredictable rainfall results in landscapes dominated by plants and animals adapted to aridity. Vegetation is typically sparse, though spectacular blooms may occur following rain. Deserts can be cold or warm and daily temperates typically fluctuate. In dune areas vegetation is also sparse and conditions are dry. This is because sand does not hold water well so little is available to plants. In dunes near seas and oceans this is compounded by the influence of salt in the air and soil. Salt limits the ability of plants to take up water through their roots.

diurnal
  1. active during the day, 2. lasting for one day.
dominance hierarchies

ranking system or pecking order among members of a long-term social group, where dominance status affects access to resources or mates

ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

fertilization

union of egg and spermatozoan

folivore

an animal that mainly eats leaves.

food

A substance that provides both nutrients and energy to a living thing.

herbivore

An animal that eats mainly plants or parts of plants.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

pheromones

chemicals released into air or water that are detected by and responded to by other animals of the same species

polygynandrous

the kind of polygamy in which a female pairs with several males, each of which also pairs with several different females.

scent marks

communicates by producing scents from special gland(s) and placing them on a surface whether others can smell or taste them

scrub forest

scrub forests develop in areas that experience dry seasons.

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

visual

uses sight to communicate

viviparous

reproduction in which fertilization and development take place within the female body and the developing embryo derives nourishment from the female.

year-round breeding

breeding takes place throughout the year

young precocial

young are relatively well-developed when born

References

Delany, M., D. Happold. 1979. Ecology of African Mammals. New York: Longman Inc..

Estes, R. 1991. The Behavior Guide to African Mammals. Berkeley, Los Angeles, and London: University of California Press.

Honacki, J., K. Kinman, J. Koeppl. 1982. Mammal Species of the World: a Taxonomic and Geographic Reference. Lawrence, Kansas: Allen Press Inc. and The Association of Systematics Collections.

Kingdon, J. 1979. East African Mammals. Chicago: University of Chicago Press.

Randi, E., J. D'Huart, V. Lucchini, R. Aman. 2002. Evidence of two genetically divergent species of warthog, Phacochoerus africanus and P. aethiopicus (Artiodactyla: Suiformes) in East Africa. Mammalian Biology, 67/02: 92-96.

d'Huart, J., P. Grubb. 2001. Distribution of the common warthog (Phacochoerus africanus) and the desert warthog (Phacochoerus aethiopicus) in the Horn of Africa. African Journal of Ecology, 39: 156-169.

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