Pygmy hippopotamus

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Pygmy hippopotamus
Two pygmy hippos

Two pygmy hippos

Systematics
Subclass : Higher mammals (Eutheria)
Superordinate : Laurasiatheria
Order : Artiodactyla (Artiodactyla)
Family : Hippos (Hippopotamidae)
Genre : Choeropsis
Type : Pygmy hippopotamus
Scientific name
Choeropsis liberiensis
( Morton , 1849)

The pygmy hippo ( Choeropsis liberiensis or Hexaprotodon liberiensis ) is one of two still occurring species from the family of hippos . The nocturnal and rare pygmy hippopotamus is native to the forests and swamps of western Africa. The species name liberiensis for "coming from Liberia" reflects this.

The pygmy hippopotamus exhibits a number of adaptations for life on land. Similar to the (large) hippopotamus , however, it depends on being near water: Pygmy hippos spend hours in the water, thereby keeping their skin elastic and their body temperature low. Both the mating of the parent animals and the birth of the young can take place on land or in the water. The pygmy hippopotamus is a herbivore whose food spectrum includes ferns, deciduous trees and shrubs as well as grasses and fruits. It lives mostly solitary and is only occasionally observed in groups of three animals.

discovery

Until the 19th century, the existence of this species was unknown outside of West Africa. The pygmy hippopotamus was first scientifically processed by the American doctor and race theorist Samuel George Morton , who received two exceptionally small hippopotamus skulls from Liberia in 1843 , which he described a year later as hippopotamus minor . However, this name had already been given to a fossil hippopotamus, so that Morton described the species again in 1849 as Hippopotamus liberiensis . Morton was Vice President of the Philadelphia Academy at the time and passed the skulls on to Joseph Leidy , who worked there as an anatomist and paleontologist . He recognized the differences to the well-known large hippopotamus and classified it in a new genus Choeropsis . It stayed that way until the Dublin Zoo received a young hippo from Liberia in 1870, weighing 30 pounds less than a newborn hippo . The Irish zoologist Mac Allister, who examined the animal, which died a few weeks later, was able to identify it as Choeropsis liberiensis . The pygmy hippopotamus was a recent species. The conservator at the Reichsmuseum in Leiden, Johann Büttikofer , who undertook two expeditions through Liberia between 1877 and 1887 , brought the first serious information about the habitat . He mainly collected skeletons and skins and learned from local hunters that the pygmy hippopotamus does not live in groups, but as solitary animals and is very rare. In 1885, the Hamburg animal dealer and zoo founder Carl Hagenbeck received the second pygmy hippopotamus sent to Europe alive, which also did not last long. There was no further evidence until 1910 and the species was again declared extinct. Hagenbeck did not want to believe in that. He hired Hans Schomburgk, then living in Africa as a white hunter, for a Liberia expedition. On July 13, 1911, Schomburgk sighted the first pygmy hippopotamus on the Duquea River , but did not shoot. A year later, with the support of some members of the Gola , he succeeded in catching five pygmy hippos in pitfalls, which he was able to bring safely to Hamburg. His telegram to Hagenbeck is about the history of zoology: "Dwarf Hippo caught, a nice little animal".

The first pygmy hippos were kept in zoos at the beginning of the 20th century. They reproduce well in captivity and much of the knowledge about the behavior of this species is based on observations on zoo animals. The survival of the species is considered endangered overall. The IUCN estimates that there are only 3,000 pygmy hippos alive in the wild. The pygmy hippopotamus population is threatened by the loss of their habitats as the forests are increasingly being cleared and converted into agricultural land. The fact that pygmy hippos are still being hunted and that their habitats are repeatedly the scene of armed conflicts also contributes to the decline in the population.

Appearance

Skull of a pygmy hippopotamus
Resting pygmy hippopotamus

The physique of the pygmy hippopotamus is basically the same as that of the large hippopotamus and, with its four short and stocky legs, appears similarly massive and stocky. With a shoulder height between 75 and 83 centimeters, pygmy hippos are only half the size of large hippos and, with a weight of 245 to 275 kilograms, reach less than a quarter of the body weight of their relatives. Their head-torso length is between 150 and 177 centimeters.

The skeletal structure of the pygmy hippopotamus is more delicate compared to that of the large hippopotamus, as their bones are proportionally thinner. While the backbone of the large hippopotamus is horizontal, it drops forward in the pygmy hippopotamus. Presumably this is an adaptation to the densely vegetated habitat, because it makes it easier to move to the dense undergrowth. Compared to the large hippopotamus, the legs and neck are longer and the head is significantly narrower and less massive. The eyes, ears, and nostrils are high up on the head, and ears and nostrils can be closed by muscle contraction so that water does not get in when you are submerged. The eye openings and nostrils of the pygmy hippopotamus, however, are less raised than those of the large hippopotamus, which often resides in deeper waters and, thanks to the shape of its eye and nostril openings, only needs to lift its head slightly out of the water in order to be able to see, smell and breathe. The feet of the pygmy hippopotamus are narrower compared to the large hippopotamus. However, it can spread its toes wider and webbed feet are reduced, making it easier to get around on land.

The pygmy hippopotamus has a black-greenish to black-brownish skin. The epidermis is thin and easily dries up on land. The dermis, on the other hand, is several centimeters thick. Similar to large hippos, pygmy hippos also have glands that release a slimy substance, which often makes the body shimmer reddish. This substance is sometimes called "blood sweat" even though it is neither sweat nor blood. The strongly alkaline mucus presumably has an antiseptic effect and protects the skin from strong sunlight. However, it does not prevent the skin from tearing if it is not regularly moistened with mud or water.

Distribution, habitat and population

Distribution area of ​​the pygmy hippopotamus (red = extinct)
A small population of pygmy hippos lives in the dense forests on Tiwai Island in Sierra Leone .

Pygmy hippos live along the rivers of the West African rainforests of Liberia , Sierra Leone , Guinea, and the Ivory Coast . Most of the pygmy hippos still living in the wild today can be found in Liberia. The populations in the other three countries are mostly close to the border with Liberia. Due to the decline in populations over the last few decades, these are isolated populations, between which there is no longer any exchange. The subspecies C. l. heslopi , which occurred in the Niger Delta , appears to have become extinct in the last few decades.

The largest population of pygmy hippos in Liberia can be found in the Sapo National Park , Liberia's largest nature reserve in terms of area. There are also said to be additional populations in Grand Kru County , Grand Cape Mount County , Grand Bassa County , Grand Gedeh County , Lofa County , Maryland County , Nimba County, and Sinoe County . In recent years, however, Liberia has repeatedly been the scene of military conflicts and unrest (see also Liberian Civil War ). More detailed surveys have therefore hardly been carried out in this region.

In the Ivory Coast, the pygmy hippopotamus is found in several rainforests, including those in Taï National Park . In Guinea, the distribution is mainly limited to the protected area Reserve de Ziama . In Sierra Leone, several isolated populations live in the Gola Rainforest National Park , on Tiwai Island in the Moa River and in the Loma Mountains .

Way of life

behavior

While the large hippopotamus is adapted to the living conditions of the open grass steppe, the pygmy hippopotamus is more at home in the damp to swampy jungle thicket. It avoids mountain forests as it is sensitive to the cold. Pygmy hippos can swim and dive well, but they are nowhere near as tightly bound to the water as large hippos. In contrast to its big cousin, the pygmy hippopotamus flees inland instead of in the direction of the water when attacked and is also unable to dive for more than one to three minutes. Many behaviors are more similar to those of tapirs , but this is a convergent development.

Pygmy hippos need to be in the water regularly to avoid tearing their skin.

The nocturnal pygmy hippopotamuses live individually in their territory, which they roam on permanent alternations. The pygmy hippopotamus only has contact with other conspecifics during the rut and when rearing young. When pygmy hippos meet, they are more likely to ignore each other than to fight with each other. Field investigations have shown that the territory of a pygmy hippopotamus bull is 185 hectares in size and the territory of a cow is between 40 and 60 hectares.

Pygmy hippos tend to be in the rivers during the day. They usually stay in one place for several days before moving on to another place. Some pygmy hippopotamuses have been observed to seek cover in washed-out hollows in the bank walls and in sandbanks of rivers. It is not yet known whether pygmy hippos dig these caves themselves or whether the use of such hiding places is typical for all pygmy hippos.

Food and subsistence

Similar to the hippopotamus, the pygmy hippopotamus leaves the water at dusk to look for food. It mainly uses fixed changes that lead through the dense undergrowth of the rainforests. The changes are marked by pygmy hippopotamuses distributing the feces with quick and vigorous tail movements during the dropping process. The animals spend about six hours a day looking for food.

Pygmy hippos are herbivores whose diet consists mainly of ferns, leaves of trees and shrubs, tubers, shoots and fallen fruits and, to a lesser extent, of aquatic plants, herbs and grasses. The wide range of food plants used suggests that hippos do not select their food, but that the respective availability determines the proportion of individual plants in it. Overall, the food plants they use are more energetic than those eaten by large hippos.

Reproduction

A family group of pygmy hippos. The front animal is a young pygmy hippopotamus

To date, no studies have been done on the reproductive habits of pygmy hippos in the wild. All findings are based on observations of pygmy hippos in zoos and may differ from those of wild pygmy hippos.

Pygmy hippos reach sexual maturity between three and five years of age. The youngest female to have given birth so far lived at Basel Zoo and was three years and three months old when her cub was born. The sexual cycle of a female pygmy hippopotamus lasts an average of 35.5 days. It is ready for conception for a period of 24 to 48 hours.

How long a bull stays with the cow ready to mate is unknown. In zoos, they are usually kept in pairs permanently. Mating takes place both on land and in the water, and the animals mate one to four times during the time the cow is ready to conceive. The animals kept in zoos show no dependence on the season of the year in terms of reproduction. They father and give birth to offspring every month of the year. A single calf is usually born around 190 to 210 days after mating. Twin births occur occasionally. Of the calves born in captivity since 1919, 41 percent were bulls. It is not known whether this gender ratio also applies to wild animals.

Pygmy hippos can give birth to their offspring both on land and in water. Newborn pygmy hippopotamus calves can swim shortly after birth. The calves weigh between 4.5 and 6.2 kilograms at birth. They suckle from their mother until they are six to eight months old. During this time they remain in the water when the pygmy hippopotamus leaves it to forage. About three times during the day the cow returns to the place where the calf is hiding and lets the calf suckle. The cow lies on its side.

Population, predators and life expectancy

Pygmy Hippopotamus, Berlin Zoological Garden

In the already small distribution area, the pygmy hippopotamus is nowhere common. In 2010 the IUCN estimated the number of pygmy hippopotamuses living in the wild at 2000 to 3000 animals, with Sierra Leone having the smallest population with 150 animals. In view of the ongoing chaos of war in Liberia, the IUCN has assumed since 2006 that the population will decline. The IUCN names the decline in suitable habitats as the main factor reducing the population. The forests in which pygmy hippopotamuses can still be found are increasingly being used heavily for forestry purposes, without major efforts being made to make the logging sustainable. Forest areas are also converted into agricultural areas. Due to the shrinking forest areas, the pygmy hippopotamus populations are increasingly being isolated, so that there is a risk of inbreeding degeneration . How the unrest and civil wars in this region affected the population figures is unknown.

Because of their hidden way of life, pygmy hippos were usually not specifically hunted. However, they are shot by the locals when the opportunity arises, as their meat, which is said to taste similar to that of wild boar, is highly valued. Unlike the great hippopotamus, the pygmy hippo's teeth have no commercial value.

Potential predators of pygmy hippos are leopards , pythons and crocodiles . It is not known what influence these predators have on the life expectancy of the pygmy hippopotamus.

The life expectancy of pygmy hippos in captivity is between 42 and 55 years. Basically, breeding in zoos works well. Between 1970 and 1991, the number of pygmy hippos born in captivity more than doubled.

Systematics

Systematic classification

The pygmy hippopotamus and the (large) hippopotamus are the only two species of the hippopotamus (Hippopotamidae), a family of the ungulates that still exist today . The pygmy hippopotamuses , which were once native to Mediterranean islands such as Sicily , Crete , Malta and Cyprus and which were extinct before humans settled the islands, are probably not close relatives of Choeropsis liberiensis . As far as we know today, these species are dwarfed island forms of the large species that used to be found on mainland Europe.

The systematic classification of the pygmy hippopotamus has changed several times since it was first described scientifically. Samuel George Morton originally called the pygmy hippopotamus together with the large hippopotamus in the genus Hippopotamus . Later, however, the conclusion was reached that it differs so strongly from the hippopotamus that the classification in its own genus with the name Choeropsis was justified. In 1977, the scientist Coryndon suggested that the pygmy hippopotamus was closely related to the representatives of the genus Hexaprotodon , which comprises a group of prehistoric hippos that were mostly native to Asia. This changed classification was largely accepted until 2005. In 2005 Jean-Renaud Boisserie was able to prove that the degree of relationship to Hexaprotodon is low and that the previous classification in a separate genus was justified. Since then, the species bears the generic name Choeropsis again and is the only living representative of this genus.

Among the extinct Malagasy hippos , there may have been a close relative of the pygmy hippopotamus . Hippopotamus madagascariensis , also according to the taxonomic uncertainty of the pygmy hippopotamus as Hexaprotodon m. or Choeropsis m. referred to, corresponded in size to the pygmy hippopotamus and lived similarly to this in wooded river regions. It is believed to have become extinct from excessive hunting and habitat destruction over the past 500 years.

Conservation breeding

Mother and cub at the Guangzhou Zoo

The Basel Zoo , where since 1959 53 dwarf hippos were born and were successfully reared, is an international studbook keeper and coordinator of the European Endangered Species Program (EEP), the dwarf hippos. The 2007 studbook lists 316 pygmy hippopotamuses in human care worldwide (this corresponds to more than ten percent of the natural population estimated by the IUCN). 118 of them belong to the European Endangered Species Program.

literature

  • Phillip T. Robinson et al. : The Pygmy Hippo Story. Oxford University Press, New York 2017, ISBN 978-0-19-061185-9 .
  • Annika Hillers et al .: Pygmy Hippo Research and Conservation project: Gola Rainforest National Park May 2013 – April 2014. Basel Zoo, July 2015. (PDF)
  • Annika Hillers, Andrew Muana: Pygmy Hippo Conservation Project: Final Report July 2010 – June 2011. Across the River - A Transboundary Peace Park for Sierra Leone and Liberia (ARTP) Research Unit, Basel Zoo, 2010/11. (PDF)
  • Chris Stuart, Tilde Stuart: Field Guide to the Larger Mammals of Africa. 2nd Edition. Struik, Cape Town 2000, ISBN 1-86872-534-0 .
  • Ronald M. Nowak: Walker's Mammals of the World. 6th edition. Johns Hopkins University Press, Baltimore 1999, ISBN 0-8018-5789-9 .
  • Wolfram Bell: keeping, breeding, behavior and diseases of hippos. Schüling, Münster 2007, ISBN 978-3-86523-086-7 .
  • F. von Houwald et al. (Ed.): EAZA Husbandry Guidelines for the Pygmy Hippopotamus. Basel Zoo, 2007.
  • Herbert Wendt: In Noah's footsteps. Grote, Hamm 1956.
  • Hans Schomburgk: My Africa. Experienced and heard from the interior of Africa. Juncker, Berlin 1928.

Web links

Commons : Hexaprotodon liberiensis  - collection of images, videos and audio files

Individual evidence

  1. ^ SG Morton: Additional Observations on a new living species of Hippopotamus. In: Journal of the Academy of Natural Sciences of Philadelphia. Series 2, Volume 1, August 1849, pp. 231-235. (biodiversitylibrary.org)
  2. ^ J. Leidy: On the Osteology of the Head of Hippopotamus, and a Description of the Osteological Characters of a new Genus of Hippopotamidae. In: Journal of the Academy of Natural Sciences of Philadelphia. Series 2, Volume 2, January 1853, pp. 207-224. (biodiversitylibrary.org)
  3. ↑ a b c d e f Choeropsis liberiensis in the endangered Red List species the IUCN 2010. Posted by: R. Lewison, W. Oliver, 2008. Accessed April 26 of 2010.
  4. ↑ a b c d e f g h i j k l m n Stewart Keith Eltringham: The Hippos . Poyser, London 1999, ISBN 0-85661-131-X .
  5. ↑ a b c Pygmy Hippo Fact Sheet. (No longer available online.) In: Smithsonian National Zoological Park. Archived from the original on August 25, 2008 ; accessed on May 22, 2007 (English).
  6. ↑ a b Samuel Zschokke: Distorted Sex Ratio at Birth in the Captive Pygmy Hippopotamus, Hexaprotodon Liberiensis . In: Journal of Mammalogy . tape 83 , no. 3 , 2002, p. 674-681 , doi : 10.1644 / 1545-1542 (2002) 083 <0674: DSRABI> 2.0.CO; 2 .
  7. ↑ Stewart Keith Eltringham: The Pygmy Hippopotamus . In: IUCN (ed.): Pigs, Peccaries and Hippos: Status Survey and Action Plan . S. 87-94 ( iucn.org [PDF; 7.0 MB ]).
  8. ↑ David Quammen: The Song of the Dodo. List, Berlin 2004, ISBN 3-548-60040-9 , p. 206.
  9. ^ A b S. C. Coryndon: The taxonomy and nomenclature of the Hippopotamidae (Mammalia, Artiodactyla) and a description of two new fossil species . In: Proceedings of the Koninklijke Nederlandse Akademie van Wetenschappen . tape 80 , no. 2 , 1977, p. 61-88 .
  10. ^ A b Jean-Renaud Boisserie: The phylogeny and taxonomy of Hippopotamidae (Mammalia: Artiodactyla): a review based on morphology and cladistic analysis . In: Zoological Journal of the Linnean Society . tape 143 , no. 1 , 2005, p. 1–26 , doi : 10.1111 / j.1096-3642.2004.00138.x .
  11. ↑ JM Harris: Family Hippopotamidae. In: J. M. Harris (Ed.) The Fossil Ungulates. Geology, Fossil Artiodactyls and Paleoenvironments. (= Koobi Fora Research Project. Volume 3). Clarendon, Oxford 1991, ISBN 0-19-857399-5 , pp. 31-85.
  12. ^ WLR Oliver: Taxonomy and Conservation Status of the Suiformes - an Overview . In: IBEX Journal of Mountain Ecology . No. 3 , 1996, p. 3–5 ( mountainecology.org [PDF; 820 kB ]).
  13. ↑ Hippopotamus madagascariensis in the Red List of Endangered Species of the IUCN 2010. Posted by: J.-R. Boisserie, 2008. Retrieved April 26, 2010.