Myotragus balearicus
Encyclopedia
Myotragus balearicus also known as the Balearic Islands Cave Goat, a species of the subfamily Caprinae which lived on the islands of Majorca and Minorca
until its extinction
around 5,000 years ago. This animal was previously described as an 'odd goat,' but since the genetic analyses done at the University of Pompeu Fabra of Barcelona
, it seems that Myotragus was more closely related to sheep than to goat
s.
s, but towards the front, granting them stereoscopic vision. The lower jaw contained two perennial-growth incisors in the lower jaw, like rodent
s and lagomorphs, but not other ungulates. The lower jaw usually lacked other incisors, though some jaws have been found with vestigial second incisors. The upper jaw lacked incisors. The rest of its teeth were molars and premolars adapted to the crushing of vegetal matter. The nose was short in comparison with the rest of the skull, similar to the noses of rabbits and hares. Finally, both sexes had at the top of the head two very short horns. It is possible these horns were longer, having short bone-bases and long horn-covers, but no complete horns have been found.
Myotragus balearicus was quite small in size (standing about 50 centimetres high at the shoulder) and weighed between 50 and 70 kilograms. The legs were proportionately shorter than those of other related and less flexible bovids, which did not make Myotragus balearicus exceptionally fast. This was not a serious problem because on the islands there were no predators except for some birds of prey, from which they probably hid in the vegetation. On the shoulders they had a pronounced hump, while the back was bent in the hindquarters. The legs, like many from the order Artiodactyla, had four fingers of which only two were used to walk. The tail was rather long in comparison to the rest of the body.
The bone histology of Myotragus shows lamellar-zonal tissue throughout the cortex, a feature peculiar to ectothermic reptiles
. The growth of bones in Myotragus is unlike any other mammal and similar to crocodilians in showing slow and adaptive rates, intermittently ceasing growth altogether, and reaching somatic maturity by about 12 years. This pattern of growth indicates that Myotragus, in the same way as extant reptiles, adapted its metabolism to changing food and water availability, and ambient temperatures.
in the northeast of Majorca. It was found that a Myotragus newborn was quite large in proportion to the size of the mother, and probably it could walk and follow its progenitor around soon after being born. It seems that it did not take a long time maturing, perhaps only a year or two.
The fact that the species conserved the horns is a possible indication that the males used them to fight for their right to reproduce, but the lack of sexual dimorphism
invites one to think this species was not polygamous or, at least, the males did not build "harems." Given the ostensibly short length of its horns, in combat Myotragus had to punch more towards the flanks (as do many small antelope) than to fight head to head (more typical of larger ungulates).
The Mediterranean climate is seasonal; thus, it is thought that Myotragus had an annual mating season, but it is not known in what part of the year this occurred. It is thought that the seasonal differences, especially in rainfall, were somewhat less pronounced during the animal's existence than they are today, and that the period of gestation
cannot be deduced with certainty.
s and lagomorphs increase their size, as happened to the Hypnomys
, the giant dormouse
that shared a habitat with Myotragus. Such species also tend to lose their fear reaction towards predators if none occur on the islands. A clear example of this is the loss of the capacity to run at high speed, the development of stereoscopic vision (which is useful to calculate distances, but not so to watch for predators) and the proportional reduction of the brain, something which has also been observed in the Homo floresiensis
, a newly discovered dwarf-like human species on the island of Flores
, Indonesia.
The analyses of DNA
and the oldest fossils (Pliocene
5.7 million years ago) of the island of Majorca (Myotragus pepgonellae) indicate that Myotragus balearicus, in spite of being a browsing animal, descended originally from grazers. The closest related species to Myotragus are ovine, such as the extinct Nesogoral of the Plio-Pleistocene
of Sardinia
, the old Gallogoral of France (possible mainland ancestor of both Myotragus and Nesogoral), Ovis (present sheep and mouflon
) and the mountain goats of Central Asia
. The last ancestor common to Myotragus and Nesogoral arrived at Majorca and Sardinia around 6 million years ago, a time at which the Straits of Gibraltar
were closed and the Mediterranean Sea
was a small collection of salty lakes. Later on, the opening of the straits and the massive salt water inflow isolated the animal populations, which diversified in the new Mediterranean islands created by tectonic forces. At the same time, climatic change replaced the vegetation of subtropical type with the present one of Mediterranean type, forcing Myotragus to develop drastic changes in its feeding and set of teeth.
Strangely, Myotragus initially only colonized the island of Majorca. On Ibiza
a strange ecosystem without terrestrial mammals developed in which birds and bats were the main vertebrates, while in Minorca a giant rabbit evolved that covered the same niche as Myotragus in Majorca. With the level of the sea falling in the glacial era, Majorca and Minorca were united and Myotragus replaced the great Minorcan lagomorphs. Both islands separated again at the beginning of the Holocene
.
During years of continued discussion between scientists, some said the extinction was caused by climate change, while others maintained they were exterminated by the first human settlers of the Balearic Islands. Various evidence could support both opinions; as a result, this question is still not answered unequivocally.
The dominant theory is the one that postulates an extinction by human causes. Traditional methods had dated the first human colonization of the Balearic Islands towards 5000 BC or even before, but subsequent tests with modern methods of dating clearly indicate that there was no human presence before 3000 BC. This date agrees very closely with the fast decline of the three forms.
The first Balearic settlers had a Neolithic
culture, although they continued living in caves, which are plentiful on the islands. In these have been found numerous animal bones, especially those of Myotragus, with evidence of carving and denting by humans. Most surprising is that not all Myotragus arrived dead at the caves, but seem to have been kept alive for some time there. Many had their horns trimmed, which healed later. This may mean that their captors were attempting to domesticate them. Domestication ultimately did not succeed, probably because Myotragus would not reproduce in captivity or not at a suitable speed, as only remains of adult individuals have been found.
Human hunting, the failure of domestication
, the introduction of domestic animals like goats (that competed with Myotragus for the same food), cows, pigs and sheep (and consequently, the destruction of the forests to create places for them to pasture) and dogs (which could have preyed on 'Myotragus) were the probable causes for the extinction of this animal.
.
Minorca
Min Orca or Menorca is one of the Balearic Islands located in the Mediterranean Sea belonging to Spain. It takes its name from being smaller than the nearby island of Majorca....
until its extinction
Extinction
In biology and ecology, extinction is the end of an organism or of a group of organisms , normally a species. The moment of extinction is generally considered to be the death of the last individual of the species, although the capacity to breed and recover may have been lost before this point...
around 5,000 years ago. This animal was previously described as an 'odd goat,' but since the genetic analyses done at the University of Pompeu Fabra of Barcelona
Barcelona
Barcelona is the second largest city in Spain after Madrid, and the capital of Catalonia, with a population of 1,621,537 within its administrative limits on a land area of...
, it seems that Myotragus was more closely related to sheep than to goat
Goat
The domestic goat is a subspecies of goat domesticated from the wild goat of southwest Asia and Eastern Europe. The goat is a member of the Bovidae family and is closely related to the sheep as both are in the goat-antelope subfamily Caprinae. There are over three hundred distinct breeds of...
s.
Description
Its eyes were not directed towards the sides, as are those of nearly all the herbivorous mammalMammal
Mammals are members of a class of air-breathing vertebrate animals characterised by the possession of endothermy, hair, three middle ear bones, and mammary glands functional in mothers with young...
s, but towards the front, granting them stereoscopic vision. The lower jaw contained two perennial-growth incisors in the lower jaw, like rodent
Rodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s and lagomorphs, but not other ungulates. The lower jaw usually lacked other incisors, though some jaws have been found with vestigial second incisors. The upper jaw lacked incisors. The rest of its teeth were molars and premolars adapted to the crushing of vegetal matter. The nose was short in comparison with the rest of the skull, similar to the noses of rabbits and hares. Finally, both sexes had at the top of the head two very short horns. It is possible these horns were longer, having short bone-bases and long horn-covers, but no complete horns have been found.
Myotragus balearicus was quite small in size (standing about 50 centimetres high at the shoulder) and weighed between 50 and 70 kilograms. The legs were proportionately shorter than those of other related and less flexible bovids, which did not make Myotragus balearicus exceptionally fast. This was not a serious problem because on the islands there were no predators except for some birds of prey, from which they probably hid in the vegetation. On the shoulders they had a pronounced hump, while the back was bent in the hindquarters. The legs, like many from the order Artiodactyla, had four fingers of which only two were used to walk. The tail was rather long in comparison to the rest of the body.
The bone histology of Myotragus shows lamellar-zonal tissue throughout the cortex, a feature peculiar to ectothermic reptiles
Ectotherm
An ectotherm, from the Greek εκτός "outside" and θερμός "hot", refers to organisms that control body temperature through external means. As a result, organisms are dependent on environmental heat sources and have relatively low metabolic rates. For example, many reptiles regulate their body...
. The growth of bones in Myotragus is unlike any other mammal and similar to crocodilians in showing slow and adaptive rates, intermittently ceasing growth altogether, and reaching somatic maturity by about 12 years. This pattern of growth indicates that Myotragus, in the same way as extant reptiles, adapted its metabolism to changing food and water availability, and ambient temperatures.
Feeding
The fossil remains of Myotragus balearicus seem to indicate that this animal was a browser, like the present goats. It fed on all kinds of shrub vegetation and low branches of the trees of the Mediterranean climate, although it had a special predilection to endemic Balearic shrubs. The fossil record of Majorca and Minorca, as well as the absence of grazing animals, seem to indicate that the primitive Balearic Islands were covered by forests before human colonisation and that herbaceous grassland of appreciable size did not exist. In this habitat, Myotragus would move about in solitude or in small groups.Reproduction
Not much is known about the reproductive habits of this species. In 1999 the skeleton of a newly born individual was found near ManacorManacor
Manacor is a town and municipality on the Mediterranean island of Majorca, part of the Spanish autonomous community of the Balearic Islands. It is one of the biggest municipalities in Majorca. It has tourist areas like Porto Cristo, site of the famous Caves of Drach, and Calas de Mallorca. Manacor...
in the northeast of Majorca. It was found that a Myotragus newborn was quite large in proportion to the size of the mother, and probably it could walk and follow its progenitor around soon after being born. It seems that it did not take a long time maturing, perhaps only a year or two.
The fact that the species conserved the horns is a possible indication that the males used them to fight for their right to reproduce, but the lack of sexual dimorphism
Sexual dimorphism
Sexual dimorphism is a phenotypic difference between males and females of the same species. Examples of such differences include differences in morphology, ornamentation, and behavior.-Examples:-Ornamentation / coloration:...
invites one to think this species was not polygamous or, at least, the males did not build "harems." Given the ostensibly short length of its horns, in combat Myotragus had to punch more towards the flanks (as do many small antelope) than to fight head to head (more typical of larger ungulates).
The Mediterranean climate is seasonal; thus, it is thought that Myotragus had an annual mating season, but it is not known in what part of the year this occurred. It is thought that the seasonal differences, especially in rainfall, were somewhat less pronounced during the animal's existence than they are today, and that the period of gestation
Gestation
Gestation is the carrying of an embryo or fetus inside a female viviparous animal. Mammals during pregnancy can have one or more gestations at the same time ....
cannot be deduced with certainty.
Origins
The unique characters of Myotragus balearicus are a consequence of a prolonged process of evolution on the islands (a clear example of island dwarfing). In this type of isolation, the ungulates tend to become smaller while rodentRodent
Rodentia is an order of mammals also known as rodents, characterised by two continuously growing incisors in the upper and lower jaws which must be kept short by gnawing....
s and lagomorphs increase their size, as happened to the Hypnomys
Majorcan Giant Dormouse
The Majorcan Giant Dormouse, scientifically known as Hypnomys morphaeus or Eliomys morpheus , is an extinct animal from Europe. It is considered an example of island gigantism. The closest extant relative is considered to be the garden dormouse, genus Eliomys. It is believed to have had an...
, the giant dormouse
Dormouse
Dormice are rodents of the family Gliridae. Dormice are mostly found in Europe, although some live in Africa and Asia. They are particularly known for their long periods of hibernation...
that shared a habitat with Myotragus. Such species also tend to lose their fear reaction towards predators if none occur on the islands. A clear example of this is the loss of the capacity to run at high speed, the development of stereoscopic vision (which is useful to calculate distances, but not so to watch for predators) and the proportional reduction of the brain, something which has also been observed in the Homo floresiensis
Homo floresiensis
Homo floresiensis is a possible species, now extinct, in the genus Homo. The remains were discovered in 2003 on the island of Flores in Indonesia. Partial skeletons of nine individuals have been recovered, including one complete cranium...
, a newly discovered dwarf-like human species on the island of Flores
Flores
Flores is one of the Lesser Sunda Islands, an island arc with an estimated area of 14,300 km² extending east from the Java island of Indonesia. The population was 1.831.000 in the 2010 census and the largest town is Maumere. Flores is Portuguese for "flowers".Flores is located east of Sumbawa...
, Indonesia.
The analyses of DNA
DNA
Deoxyribonucleic acid is a nucleic acid that contains the genetic instructions used in the development and functioning of all known living organisms . The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes, or are involved in...
and the oldest fossils (Pliocene
Pliocene
The Pliocene Epoch is the period in the geologic timescale that extends from 5.332 million to 2.588 million years before present. It is the second and youngest epoch of the Neogene Period in the Cenozoic Era. The Pliocene follows the Miocene Epoch and is followed by the Pleistocene Epoch...
5.7 million years ago) of the island of Majorca (Myotragus pepgonellae) indicate that Myotragus balearicus, in spite of being a browsing animal, descended originally from grazers. The closest related species to Myotragus are ovine, such as the extinct Nesogoral of the Plio-Pleistocene
Pleistocene
The Pleistocene is the epoch from 2,588,000 to 11,700 years BP that spans the world's recent period of repeated glaciations. The name pleistocene is derived from the Greek and ....
of Sardinia
Sardinia
Sardinia is the second-largest island in the Mediterranean Sea . It is an autonomous region of Italy, and the nearest land masses are the French island of Corsica, the Italian Peninsula, Sicily, Tunisia and the Spanish Balearic Islands.The name Sardinia is from the pre-Roman noun *sard[],...
, the old Gallogoral of France (possible mainland ancestor of both Myotragus and Nesogoral), Ovis (present sheep and mouflon
Mouflon
The mouflon is a subspecies group of the wild sheep Ovis aries. Populations of Ovis aries can be partitioned into the mouflons and urials or arkars...
) and the mountain goats of Central Asia
Central Asia
Central Asia is a core region of the Asian continent from the Caspian Sea in the west, China in the east, Afghanistan in the south, and Russia in the north...
. The last ancestor common to Myotragus and Nesogoral arrived at Majorca and Sardinia around 6 million years ago, a time at which the Straits of Gibraltar
Gibraltar
Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...
were closed and the Mediterranean Sea
Mediterranean Sea
The Mediterranean Sea is a sea connected to the Atlantic Ocean surrounded by the Mediterranean region and almost completely enclosed by land: on the north by Anatolia and Europe, on the south by North Africa, and on the east by the Levant...
was a small collection of salty lakes. Later on, the opening of the straits and the massive salt water inflow isolated the animal populations, which diversified in the new Mediterranean islands created by tectonic forces. At the same time, climatic change replaced the vegetation of subtropical type with the present one of Mediterranean type, forcing Myotragus to develop drastic changes in its feeding and set of teeth.
Strangely, Myotragus initially only colonized the island of Majorca. On Ibiza
Ibiza
Ibiza or Eivissa is a Spanish island in the Mediterranean Sea 79 km off the coast of the city of Valencia in Spain. It is the third largest of the Balearic Islands, an autonomous community of Spain. With Formentera, it is one of the two Pine Islands or Pityuses. Its largest cities are Ibiza...
a strange ecosystem without terrestrial mammals developed in which birds and bats were the main vertebrates, while in Minorca a giant rabbit evolved that covered the same niche as Myotragus in Majorca. With the level of the sea falling in the glacial era, Majorca and Minorca were united and Myotragus replaced the great Minorcan lagomorphs. Both islands separated again at the beginning of the Holocene
Holocene
The Holocene is a geological epoch which began at the end of the Pleistocene and continues to the present. The Holocene is part of the Quaternary period. Its name comes from the Greek words and , meaning "entirely recent"...
.
Extinction
Diverse datings indicate that the three native terrestrial mammals of Majorca (Myotragus, Hypnomys and the giant shrew Nesiosites) disappeared all in the same very short period of time, during the third millennium BC.During years of continued discussion between scientists, some said the extinction was caused by climate change, while others maintained they were exterminated by the first human settlers of the Balearic Islands. Various evidence could support both opinions; as a result, this question is still not answered unequivocally.
The dominant theory is the one that postulates an extinction by human causes. Traditional methods had dated the first human colonization of the Balearic Islands towards 5000 BC or even before, but subsequent tests with modern methods of dating clearly indicate that there was no human presence before 3000 BC. This date agrees very closely with the fast decline of the three forms.
The first Balearic settlers had a Neolithic
Neolithic
The Neolithic Age, Era, or Period, or New Stone Age, was a period in the development of human technology, beginning about 9500 BC in some parts of the Middle East, and later in other parts of the world. It is traditionally considered as the last part of the Stone Age...
culture, although they continued living in caves, which are plentiful on the islands. In these have been found numerous animal bones, especially those of Myotragus, with evidence of carving and denting by humans. Most surprising is that not all Myotragus arrived dead at the caves, but seem to have been kept alive for some time there. Many had their horns trimmed, which healed later. This may mean that their captors were attempting to domesticate them. Domestication ultimately did not succeed, probably because Myotragus would not reproduce in captivity or not at a suitable speed, as only remains of adult individuals have been found.
Human hunting, the failure of domestication
Domestication
Domestication or taming is the process whereby a population of animals or plants, through a process of selection, becomes accustomed to human provision and control. In the Convention on Biological Diversity a domesticated species is defined as a 'species in which the evolutionary process has been...
, the introduction of domestic animals like goats (that competed with Myotragus for the same food), cows, pigs and sheep (and consequently, the destruction of the forests to create places for them to pasture) and dogs (which could have preyed on 'Myotragus) were the probable causes for the extinction of this animal.
Discovery
Myotragus balearicus was first excavated and identified in Majorca in 1909 by the archaeozoologist Dorothea BateDorothea Bate
Dorothea Minola Alice Bate FGS , also known as Dorothy Bate, was a British palaeontologist, a pioneer of archaeozoology...
.