Hyena
| Hyena | |
|---|---|
| |
| Brown hyena Parahyaena brunnea | |
| Scientific classification | |
| Kingdom Information | |
| Domain | Eukaryota |
| Kingdom | Animalia |
| Subkingdom | Bilateria |
| Branch | Deuterostomia |
| Phylum Information | |
| Phylum | Chordata |
| Sub-phylum | Vertebrata |
| Infraphylum | Gnathostomata |
| Class Information | |
| Superclass | Tetrapoda |
| Class | Mammalia |
| Sub-class | Theriiformes |
| Infra-class | Holotheria |
| Order Information | |
| Superorder | Preptotheria |
| Order | Carnivora |
| Sub-order | Feliformia |
| Family Information | |
| Family | Hyaenidae |
| Population statistics | |
The hyenas are Old World terrestrial carnivores of the family Hyaenidae.
Contents
Etymology
The word "hyena" is derived from the Greek ὕαινα, ("hyaina") which in itself is derived from the word ὗς ("hӯs"), "hog" or "sow", a possible reference to comparisons of its bristly back to pigs. The Latin word hyaena inspired both the Old High German ijēna and Old English hyene, from which we get today's word "hyena".[1]
Description
Hyenas are somewhat dog-like in appearance, despite being more closely related to cats. The head-trunk length is 21-62 inches long, depending on the species, and they have a shoulder height of 17-31 inches. The front legs are longer and more powerful than the hind legs, giving the appearance of a sloping back. The tail is relatively short and somewhat bushy. Hyenas have four toes on front and hind legs, except the aardwolf, which bears a fifth dewclaw toe on the front legs. The toe pads bear dull, non-retractable claws, and all species walk with both legs on one side in motion, alternating with the other. The females of the spotted hyena, the largest species, are about 10% larger than the males; in the other species, there is no significant sex dimorphism in size. The actual hyenas weigh 57-121 pounds, with individual spotted hyenas reaching up to 189 pounds. The aardwolf is by far the smallest and lightest species at 17-30 pounds.
The body fur is rather coarse, and three species have a crest of hair extending from the ears to the tail along the spine; this crest can be erected, making the animal appear larger (in spotted hyenas the crest is reduced to guard hairs on top of the neck).
The bite of the actual hyenas is extremely strong. The premolars are adapted to the breaking up of bones and enlarged, especially the third upper and third lower premolars, and these teeth bear a structure which prevents breakage. The fourth upper premolar and the first lower molar are shaped like a blade and serve to cut meat. The molars lying behind these teeth are reduced or are missing completely, which leaves more space for the remaining molars: the premolars become wider and the teeth are thus better protected against abrasion. The tooth formula of the actual hyenas consists of 3/3 I, 1/1 C, 4/3 P and 1/1 M, altogether 34 teeth.
Combined with the strong bite of the actual hyenas is a strong masticatory musculature; The temporal muscle has a high crest at the point of the skull, providing for a better reaction of the biting force. Thanks to their exceptional jaw apparatus, spotted hyenas can develop a bite force of over 1,100 pounds of pressure per square inch. They are able to break the bones of giraffes, rhinos and hippos, which have a diameter of more than 2.75 inches.
Species
Living hyenas are divided into two subfamilies:
- Subfamily Hyaeninae (bone-crushing, or actual hyenas)
- Striped hyena, Hyaena hyaena
- Brown hyena, Parahyaena brunnea
- Spotted hyena, Crocuta crocuta
- Subfamily Protelinae (dog-like hyenas)
- Aardwolf, Proteles cristata
Range and habitat
Hyenas are found in large parts of Africa and in western and southern Asia. In Africa, their distribution ranges from the Atlas Mountains to South Africa, but they are lacking in the pure deserts of the Sahara and the Kalahari. In Asia, they come from Turkey and the Arabian Peninsula via Afghanistan to India. Extinct species were spread over large parts of Eurasia, and a single species (Chasmaporthetes) once occurred in North America.
The striped hyena inhabits northern Africa, the Middle East and eastward into India. The spotted hyena is located in much of sub-Saharan Africa. The aardwolf lives in two separate areas in eastern and southern Africa, and the brown hyena inhabits a relatively small area in the south of the continent.
In general, hyenas inhabit rather dry areas such as semi-desert, savannah, bushsteps and rocky highlands; sometimes they can also be found in wetlands and mountainous forests. In the Ethiopian highlands they can be reached up to 12,000 feet. However, they avoid pure sand deserts as well as lowland rainforests. Hyenas are usually not very selective in terms of their habitat, each of the four species occurs in several habitats. They have little fear of people and occasionally stay close to human settlements.
Social and territorial behavior
Spotted and brown hyenas live in groups called "clans". In both species groups of related females form the nucleus of a clan, the reproductive males have migrated and are not related to the females. The social behavior of the spotted hyenas is unique among the predators, in that it is similar to baboons; the clans can comprise up to 80 animals, which are divided into smaller subgroups. The clan is matriarchal; females are dominant and establish a strict ranking, with the ranks being hereditary as the mothers help their daughters to reach the same position as they do. The males are always subordinate to the females, and their own ranking in the group gets higher the longer they belong in it. With brown hyenas the clans comprise 4-14 animals, and depending on the habitat there is a variance in the way of life, with established ranking orders where high population densities occur. Males and females have their own hierarchies, and both sexes are equally entitled. Various observations have been made in the striped hyena, with reports of loner animals, stable couples, and cohabitation in groups. Probably the social behavior of this species is variable. Aardwolfs have a stable and long-lived relationship with the young, but the young animals are often not fathered by the male. Outside the mating season, aardwolfs show little social behavior: they inhabit separate burrows and go separately for food searches.
Hyenas are territorial, the size of the territory depending on the type and the food supply: the areas of the spotted hyenas in the grassland savannahs of East Africa measure about 12.4 mi², while the areas of spotted and brown hyenas in the dry areas of southern Africa can exceed 620 mi². The territory of aardwolfs covers around 3000 termite mounds and measures 1.2-2 mi². The territories are usually marked with the secretion of their anal bags, which are whitish or yellowish and foul-smelling; this secretion is sprayed on tall grasses, logs, and is used to mark boundaries. Interlopers entering a territory are chased away, sometimes involving violent battles.
Communication
Since hyena territories often have enormous dimensions and the animals often travel alone, olfactory communication - that is, by means of scent - plays an important role. Hyenas can recognize the sex, reproductive status and group affinity of other hyenas by means of an anal bag secretion. Hyenas have a special welcome ritual that show members of the same group when they get together: they sniff at the nose or the anal bag of the other animal or lick its back. In the case of spotted hyenas, the erected sexual organs - both males and females - play a role, which are nibbled or licked by the opposing animal.
Three of the four species of hyenas give only a few sounds. At best, they emit snarling or screeching sounds, which can only be heard over small distances. In contrast, the spotted hyena has a rich repertoire of sound communication, with the most frequently heard sound is a loud wuup, which can be heard over several kilometers and is used to contact other clan members. They also give grunting, weeping, and muted sounds. But the most famous sound is what gives the animal the name "laughing hyena", a cackle that resembles human laughter, and made when an animal accepts a lower rank, or a pack moves in to take over a kill.
Diet
The four species of hyenas have occupied three different ecological niches with regard to nutrition. Spotted hyenas are active hunters who kill 60-95% of their prey, with a dietary range from insects to elephants. However, most of the kills are larger ungulates such as wildebeest, gazelles, and zebras. They hunt individually or in groups; they do not sneak up on their victims, but rely on their stamina and perseverance. They also will scavenge carrion, and they have been observed working in coordinated fashion to drive other predators from their own kills.
The striped and brown hyenas also engage in hunting; small mammals, birds, eggs, insects, are part of their diet, and brown hyenas of the Namib desert on the Atlantic coast have had success hunting and killing the young of Atlantic fur seals. Despite this, both striped and brown hyenas are primarily scavengers, and will wait until a threat was removed from the carcass (such as lions) before moving in to consume the remains. Thanks to their powerful teeth, they can break thick bones; their efficient digestive system utilizes all the body parts of an animal except the hairs, hooves and horns, and powerful bacterial poisons contained in their stomachs further digest the meal.
Aardwolfs feed almost exclusively on termites, especially the insects of the genus Trinervitermes. The termites of this genus move in the night in large groups on the earth's surface and are licked by aardwolfs with their sticky tongue.
Reproduction
The mating behavior of hyenas varies among the species. Frequently there is a promiscuous behavior, that is males and females are propagated with several partners. With striped hyenas polyandry is occasionally practiced, a rarity in mammals; that is, a female has several male mating partners. The choice of the partner is also variable: males of nomadic groups move around the clan outside their own area and are sometimes chosen as partners; this behavior may depend on the food supply. Aardwolfs will sometimes trade an existing male partner for a stronger, more aggressive male in about 40% of the procreations.
Reproduction in most cases is not seasonal, but can be done throughout the year. After a 90 to 110 day gestation period, the female gives birth to one to four young animals, sometimes five. The degree of development of the newborn is different: while in the case of spotted hyenas, the milkteeth are already present and the eyes are opened; striped and brown hyenas are less developed and their eyes still closed. Newborn spotted hyenas are black in color; in the other species, the coloration of the young animals resembles that of the adult animals, but with an added dark streak on the back.
Newborn hyenas spend their first weeks of life in an earthen burrow. In the case of spotted and brown hyenas these borrows are communal in which the young animals of a clan grow together. After a few weeks, the young animals begin to explore the area outside the burrow. After a few months they undertake their first foraging, for the first time in the company of an adult animal, and later on alone. Young hyenas are suckled for a relatively long time, the actual hyenas are finally weaned after 12–16 months. In the second or third year of life, sexual maturity occurs.
Threats
Man is considered the greatest threat to hyenas, for the following reasons: hyenas have on occasion attacked livestock and domestic pets; spotted hyenas have attacked and killed man, and both spotted and striped hyenas have scavenged human corpses from cemeteries. Different body parts of hyenas have also been used in folk healing medicines. A further threat comes from the automobile, as hyenas often eat the carcasses of roadkill animals as they lay directly on the road, and are careless of oncoming vehicles.
With the exception of the aardwolf, the population of hyenas has fallen back. Estimates of the total population of the different types of hyenas range from 27,000-47,000 for spotted hyenas,[2] 5,000-8,000 for brown hyenas,[3] and 5,000-14,000 striped hyenas,[4] and at least several thousand aardwolfs,[5] which may benefit from an increase in the large-scale cattle economy, which in turn has caused an increase in its preferred termite population. However, despite a lack of direct persecution, aardwolfs may be driven away from habitats as a result of farmers destroying termite mounds.
