Aardwolf
| Aardwolf | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Aardwolf ( Proteles cristata ) |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name of the subfamily | ||||||||||||
| Protelinae | ||||||||||||
| Flower , 1869 | ||||||||||||
| Scientific name of the genus | ||||||||||||
| Proteles | ||||||||||||
| I. Geoffroy Saint-Hilaire , 1824 | ||||||||||||
| Scientific name of the species | ||||||||||||
| Proteles cristata | ||||||||||||
| ( Sparrman , 1783) |
The aardwolf ( Proteles cristata , Syn .: Proteles cristatus ) is a species of predator from the hyena family (Hyaenidae). With a weight of 8 to 14 kilograms, it is the smallest representative of the hyenas. In body structure and with the small molars it differs greatly from the other hyena species, the real hyenas (Hyaeninae), and it is therefore placed in its own subfamily, Protelinae.
Aardwolves tend to inhabit arid regions in eastern and southern Africa . They live shy and reclusive and nocturnal , daytime they withdraw into their building back. Their diet consists mainly of termites of the genus Trinervitermes . They inhabit territories in pairs, but the pairs hardly interact with one another outside of the mating season. The two to four young animals are often not conceived by the male who lives with the female. The aardwolf is not an endangered species.
features
General build and coat
Aardwolf are by far the smallest species of hyena. They reach a head body length of 55 to 80 centimeters, the bushy tail measures an additional 20 to 30 centimeters. Your shoulder height is 45 to 50 centimeters. The weight is subject to seasonal fluctuations and varies between 8 and 12 kilograms in southern Africa and up to 14 kilograms in the east of the continent. There is no such thing as sexual dimorphism , the sexes are the same size.
As with all hyenas, their physique is characterized by their sloping back: the front legs are longer than the rear legs, and generally the legs are long and slender. The front paws have five toes and the rear paws four - in the other hyena species the first toe of the front paw is missing. Like all hyenas, aardwolves are digitigrad (toe walkers), the toes have strong, non-retractable claws .
The basic color of the fur is yellow-gray, but it can vary from whitish-yellow to reddish-brown. There are several dark, vertical stripes on the back and on the flanks, and diagonal stripes run across the front and rear legs. There are irregular horizontal stripes on the lower parts of the legs, the paws themselves are dark. Sometimes there are stripes or spots on the neck as well; the throat is light gray or whitish in color. With their stripes, aardwolves are similar to the stripe hyena , but they are half the size and their stripes are much more regular. A long mane runs along the back from head to tail. This hair can be up to eight inches long on the shoulders. In the event of danger or threat, wolves can straighten their manes, making them appear significantly larger.
Aardwolves have a well-developed anal pouch , the secretion of which is used to mark territory. As with all hyenas , the males lack a penis bone , the females have two pairs of mammary glands located in the groin region . In contrast to other hyenas, they do not show any special features in the structure of the urinary and sexual apparatus .
Head and teeth
The slender head sits on an elongated neck. The ears are large and pointed, the eyes are also enlarged and have a tapetum lucidum for better night vision. In particular, the sense of hearing and smell are well developed. As with many other inhabitants of dry regions, the tympanic bladder (bulla tympanica) is noticeably enlarged. The jaws are strongly developed - presumably as an adaptation to fights with conspecifics.
The teeth show the clearest differences to the other hyena species. The molars are much smaller, they have receded into tiny, widely spaced pins, and their number is irregular. The canine teeth , which are used for defense and fighting with conspecifics, are well developed, but in old animals they are often worn. The incisors are inconspicuous as with all hyenas. The tooth formula is I 3/3 - C 1/1 - P 3 / 1-2 M 1 / 1-2, so they have a total of 28 to 32 teeth. In its mouth, there are further adaptations to the termite diet: the broad palate houses a broad, spatula-shaped tongue, which is covered with large, conical papillae . The salivary glands produce large amounts of sticky saliva.
distribution and habitat
Aardwolves are native to two geographically separated areas of Africa ; the two distribution areas are separated from each other by a gap of around 1500 kilometers. The northern part of their range is in eastern Africa. It runs from the extreme southeast of Egypt along the coast of the Red Sea in Sudan and Eritrea via Ethiopia , Somalia to Kenya and into central Tanzania . The second part is in the south of the continent. It stretches from southwestern Angola and southern Zambia to South Africa .
Aardwolves prefer open, rather dry habitats ; their habitats have an annual rainfall of 100 to 800 millimeters. They are primarily found in grasslands and bush-lined savannas, but are absent in forests and pure deserts. In Ethiopia they occur up to an altitude of 2000 meters . Nowhere in their range are they particularly common, in favorable habitats the average population density is one adult per square kilometer.
Way of life
Activity time and social behavior
Aardwolves are mostly nocturnal; depending on the availability of the food, they sometimes start looking for food in the late afternoon. In the summer in South Africa, their activity begins half an hour to an hour after sunset and ends one to two hours before sunrise, which means that they are active for a total of eight to nine hours. In winter, they often return to the burrow after three to four hours. In summer, they cover around eight to twelve kilometers per night, in winter, with three to eight kilometers, significantly less.
During the day or during rest breaks at night, they withdraw into burrows . These burrows are often expanded hare burrows , sometimes taken over by aardvarks or porcupines or dug themselves. The burrows have a single entrance, consist of a narrow tunnel up to five meters long and end in a chamber. A building is used for around six to eight weeks, after which a new one is sought out. Six to eighteen months later, an old building can be moved into again.
Aardwolves live together in pairs; a couple lives in a common territory with last year's offspring . These pair ties are relatively stable for two to five years. Outside of the mating season, the social behavior of the aardwolves is poor: they live in separate burrows and go foraging alone. When they meet, they ignore each other; unlike other hyenas, they do not have any welcoming rites.
The areas are around 1.5 to 4 km² in size, the size varies according to the number of termites: One area contains around 3000 termite mounds. Aardwolves mark their territories by rubbing their anal region on tufts of grass or other objects. The anal bag secretes an orange-yellow secretion that turns black when exposed to the air. Both the male and the female attach their markings, but the males more often - up to twice at 100 meters. These markings are mostly found along the territorial boundaries, less often at the entrances to the burrows. If a strange conspecific is discovered in its own territory, the aardwolf straightens its mane and tries to chase the intruder away. Females are tried to drive away by the resident females and males by the resident males, the hunts always end at the territorial border. Sometimes there is a fight, however, in which both opponents kneel and try to bite the other in the neck.
Communication takes place primarily olfactory , i.e. by means of smells. On the basis of the scent traces, wolves can recognize the sex, the reproductive status and, in the case of animals living close together or in the same territory, also the individual identity. Earth wolves are acoustically inconspicuous animals, they rarely make noises . In the case of aggressive encounters, verbal statements are made. Depending on the intensity, this is a clicking sound that is generated by opening and closing the mouth, or a deep-throated growl. During a fight or when caught by surprise, they let out a surprisingly loud and explosive roar. In addition, a wailing sound, which is believed to be used to appease, and a squeak are known that only the young animals in search of their mother.
Like all hyenas, aardwolves defecate in specially created pits. These pits are often made in sandy soil and are one to two meters in diameter. There can be up to 20 such pits in one district; those located near the territorial boundaries are used much more frequently. The wolves also usually go to these pits to urinate; only when there is a great deal of food they only interrupt their food intake for a short time, crouch down and urinate on the spot.
food
In contrast to the other hyenas, aardwolf feed almost exclusively on termites . Unlike other insectivorous mammals, such as pangolins or aardvarks , with whom they share the settlement area, they do not have powerful claws for breaking termite mounds; rather, the broad, sticky tongue is ideally suited to licking prey off the ground. Aardwolves specialize in termites of the genus Trinervitermes , with Trinervitermes bettonianus in East Africa, T. rhodesiensis in Zimbabwe and Botswana and T. trinervoides in South Africa being the preferred species. These termites are spurned by most other insectivorous mammals because the soldiers secrete poisonous terpenoids , which aardwolves are one of the few species to be tolerant of. The Trinervitermes termites are nocturnal and search for food in groups of 2,000 to 4,000 animals on the earth's surface, making them easier to capture than other genera that move in underground passages.
An aardwolf eats up to 300,000 termites per night, which is one to two kilograms. During the nightly forays it moves in a zigzag course and covers around one kilometer per hour. He keeps his head down and his ears bent forward - the termites are presumably located by smell or hearing. Young animals are often seen vomiting after eating. This is a sign that tolerance to the poison increases with age.
When termites of the genus Trinervitermes are not or not sufficiently available, for example in winter in South Africa or in the rainy season in East Africa, aardwolves also eat other termite genera such as Hodotermes , Microhodotermes , Odontotermes or Macrotermes . However, these genera swarm out in much smaller groups, often only 10 to 20 animals. Very rarely do wolves eat other insects or spiders . It is known from studies from South Africa that they only consume a fifth of the normal amount of food in winter, and their weight can drop by up to 20%. In winter the mortality of the young animals is also highest. One reason for the dependence on the genus Trinervitermes is that these termites are the only insects in the habitat that regularly swarm in high density on the earth's surface throughout the year. Most other termite species either live in underground tunnels or their schools are much more irregular.
As a rule, aardwolves do not need to drink, but rather take in the liquid they need with their prey. Exceptions are very cold winters, when there are few termites. Then the animals sometimes cover considerable distances to get to water sources.
Reproduction
pairing
In southern Africa, the mating season is in the last weeks of June or the first two weeks of July, in the warmer regions further north, reproduction is probably less seasonal.
Despite the monogamous way of life, the young are often not conceived by the male with whom the female shares the territory. The females remain in their own territory all year round, while the males begin to invade foreign territories around a month before the mating season. At first this is purely an observation, probably to assess the males and females in the neighboring areas. After that, the alien male begins to penetrate more aggressively and intensively mark the alien territory with his own scent traces. The resident male also marks his territory until the weaker of the opponents loses this "betting mark". If the resident male turns out to be the weaker, the intruder has a good chance of breeding with the resident female.
During this time, the females often roam along the territorial boundaries, obviously to attract strange males. The strange males show a conspicuous courtship behavior : They run to the female, then turn away and stalk past with their tails raised. This is associated with chasing away or fighting the resident male. In around 40% of the cases, a foreign and not the resident male reproduces with the female.
The oestrus lasts one to three days. If a female has not been fertilized during this time, a fertile period can occur again within two weeks. The copulations last around one to four hours, with multiple ejaculations . It can also happen that an invading male interrupts copulation, drives away the mating male and immediately mates with the female.
This "blatant cheating" is likely to be an established aspect of the breeding of aardwolves. While the young animals are in the female's den, they are guarded by the resident male. This is time-consuming and costs a lot of energy, since the males only have to search for food 2 to 3 hours before sunrise, while the females have at least 6 hours available. This means that the males will also help raise young animals that were not conceived by them. As far as is known, this is unique among mammals. The evolutionary reasons behind this strategy could be that the stronger and more aggressive males pass on their genes more frequently, but the intensive guarding of the young is taken over by many males.
Birth and rearing of young
The gestation period is around 90 days; in South Africa, births fall in early October (spring). The litter size is two to four newborns, in human care it can be up to five.
The young are born in the female's den. They come out for the first time after about a month, and at six to nine weeks they play outside, but no more than 30 meters away from the entrance. When they are nine to twelve weeks old, they accompany adult animals on the raids for the first time, but they still remain no more than 100 meters away from the burrow. At twelve to sixteen weeks they roam the entire territory of the adult, but are still accompanied by the male or female. At the end of this period - around four months - they are finally weaned. In contrast to the other hyena species, the young grow quickly and reach their full weight at four months. This is presumably an adjustment to minimize the high puppy mortality in the first winter, the time when there was little food available.
Up to the age of around seven months, the young animals are sometimes accompanied by an adult in search of food, after which they go on their forays alone. At around a year old, her forays lead ever further away from her parents' territory. At the latest when the next year's young animals leave the den for the first time, they completely remove themselves and try to establish their own territory. Sexual maturity occurs at around 1.5 years.
In a study carried out in South Africa between 1981 and 1984, 68% of the young survived the first year of life. The maximum age of an animal in human care was 15 years and life expectancy in the wild is unknown but is undoubtedly lower.
Natural enemies and food competitors
.jpg)
The most important predator of the aardwolves is the black-backed jackal ( Canis mesomelas ). It often tears off young animals and is the main reason the males watch over the females. Sometimes careless adult animals also fall victim to it. According to Philip D. Gingerich , the stripes are a form of mimicry to simulate a resemblance to the striped hyena and thus deter predators such as the leopard . Other researchers reject this view because of the size difference, among other things. It is sometimes reported that the aardwolf also uses its musk- smelling secretion from the anal pouch for defense , but there are very few observations about it. The aardwolf parasites have hardly been researched; only the jaw louse Protelicola intermedia is known.
Due to the specialization in the termite genus Trinervitermes , which is mostly inedible for other insectivorous mammals, aardwolves have only few direct food competitors. There are sympathetic termite eaters such as the spoonbill - which even has a similar two-part distribution area - but these switch to other termite genera. There is a special relationship with the aardvark , which also obtains a large proportion of its food from Trinervitermes termites. In contrast to the aardvark, the aardvark has an excellent physical adaptation to breaking up the hard termite burrows. Especially in winter, when the termites retreat into their nests, the termite genus forms an essential basis of the aardvark's diet due to the higher concentration of individuals in the nests. According to observations in southern Africa, the aardwolf follows the aardvark at this time of the year at a distance of less than 50 m and, after the latter has left its feeding site, benefits from the termite burrows that were previously opened.
Aardwolves and humans
Although aardwolves do not eat vertebrates , they were sometimes persecuted by farmers who accused them of killing their sheep and chickens. But this practice has declined. Some animals also fall victim to domestic dogs that are actually trained to hunt foxes or jackals or die in traffic accidents. Some African tribes hunt aardwolves to eat their meat and use their body parts for medicinal purposes. None of these practices endanger the general aardwolf population to any great extent. The greatest danger comes from insecticides : toxins used to control locusts or termites can significantly decimate populations or even lead to local extinction.
In some places, the destruction of their habitat is also a threat. On the other hand, large-scale grazing leads to an increase in the Trivervitermes termites, so that the conversion of forests and savannahs into pastures has a positive effect on the population of aardwolves.
The IUCN estimates the total population as stable and lists the species as not endangered ( least concern ). Estimates of the total population are at least several thousand individuals; due to their shy, nocturnal way of life, the species may be more common than previously thought.
Systematics
The aardwolf is the only living member of the genus Proteles . It is classified within the hyenas in its own subfamily, Protelinae, which is opposite to the real hyenas (Hyaeninae) and forms its sister taxon . Some systematists consider the differences in physique and way of life to be so great that they place the aardwolf in a family of their own , Protelidae. However, this division is not adopted in more recent taxonomic publications.
On the basis of the two-part distribution area, two subspecies are distinguished: The nominate form Proteles cristata cristata includes the animals of southern Africa and P. c. septentrionalis that of eastern Africa. There are no studies of any genetic or morphological differences between the two subspecies, so this classification is questionable.
Older writers believed the aardwolf to be an early side branch of the hyenas. According to the morphological studies of Werdelin and Solounias, the Protelinae and the Hyaeninae separated 18 to 20 million years ago, as a result of which the aardwolves evolved from primeval hyena species such as Plioviverrops . The molecular studies by Koepfli et al. In 2005, however, came to the conclusion that the two lines diverged around 10.6 million years ago; therefore it is conceivable that aardwolves developed from a hyena branch that already had the strong teeth typical of the real hyenas. The aardwolves could have occupied an ecological niche that was previously hardly filled by predators.
With Proteles transvaalensis a fossil ancestor of the aardwolf is known, the approximately 1.5 million year old remains of which were found in Swartkrans in South Africa. It was larger than the animal it is today, and its molars were even larger. There are also other finds from South Africa, around a million years old, which can no longer be distinguished from today's species.
literature
- Kay E. Holekamp and Joseph M. Kolowski: Family Hyaenidae (Hyenas). In: Don E. Wilson, Russell A. Mittermeier (eds.): Handbook of the Mammals of the World. Volume 1: Carnivores. Lynx Edicions, 2009, ISBN 978-84-96553-49-1 , pp. 234-261.
- CE Koehler and PRK Richardson: Proteles cristatus. In: Mammalian Species 363 (1990), pp. 1-6. PDF
- Ronald M. Nowak: Walker's Mammals of the World. 2 volumes. 6th edition. Johns Hopkins University Press, Baltimore MD et al. 1999, ISBN 0-8018-5789-9 .
Individual evidence
- ↑ Figures from Holekamp & Kolowski (2009), p. 252.
- ^ Koehler & Richardson (1990), p. 2.
- ↑ a b c d Holekamp & Kolowski (2009), p. 253.
- ↑ WRJ Dean, W. Roy Siegfried: Orientation of Diggings of the Aardvark . In: Journal of Mammalogy . 72, No. 4, 1991, ISSN 0022-2372 , pp. 823-824, p. 824.
- ↑ a b Koehler & Richardson (1990), p. 3.
- ↑ "overt cuckoldry": Holekamp & Kolowski (2009), p. 253.
- ↑ a b c Koehler & Richardson (1990), p. 4.
- ↑ Aardwolf ( Proteles cristata ) at Hyaena Specialist Group ( Memento of the original from April 17, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. , accessed September 2, 2009
- ^ Philip D. Gingerich: Is the aardwolf a mimic of the hyaena? In: Nature , 253 (1975), pp. 191-192.
- ^ Koehler & Richardson (1990), p. 6.
- ↑ PJ Apps, HW Viljoen, PRK Richardson, V. Pretorius: Volatile components of anal secretion of aardwolf (Proteles cristatus) . In: Journal of Chemical Ecology , Vol. 15, No. 5, 1989, p. 1683.
- ↑ Koehler & Richardson (1990), pp. 2-3.
- ^ W. Andrew Taylor and John D. Skinner: Associative feeding between Aardwolves (Proteles cristatus) and Aardvarks (Orycteropus afer). Mammal Review 30 (2), 2000, pp. 141-143
- ↑ Proteles cristata in the IUCN Red List of Threatened Species . Retrieved August 28, 2009.
- ^ "A minimum of several thousand individuals": Holekamp & Kolowski (2009), p. 250.
- ↑ e.g. Koehler & Richardson (1990)
- ↑ for example: WC Wozencraft: Order Carnivora. In: DE Wilson and DM Reeder, (Eds.) Mammal Species of the World : a taxonomic and geographic reference. Washington, Smithsonian Institution Press 1993, pp. 279-344. or Holekamp & Kolowski (2009).
- ↑ Holekamp & Kolowski (2009), p. 252.
- ↑ L. Werdelin and N. Solounias: The Hyaenidae: Taxonomy, systematics and evolution. In: Fossils and Strata 30 (1991), 1-104.
- ↑ Klaus-Peter Koepfli, Susan M. Jenks, Eduardo Eizirik, Tannaz Zahirpour, Blaire Van Valkenburgh and Robert K. Wayne: Molecular systematics of the Hyaenidae: Relationships of a relictual lineage resolved by a molecular supermatrix. In: Molecular Phylogenetics and Evolution 38 (2006) 603-620.
