Millions of years ago, the ancestors of the deer, in addition to the antlers on the skull, also had tusks . A pair of canines that emerged from the upper jaw, which could appear through the lip. Most modern cervids retain their antlers, but have lost their tusks or occasionally retain them as vestigial organs.
Although not all. There is a small group of deer, native to Southeast Asia, that retains the tusks of their ancestors: the muntíacos or barking deer.
The muntíaco or barking deer
The genus Muntiacus is currently represented by twelve species that inhabit from India to the islands of Indonesia and southeastern China. They come from a lineage that is estimated to be between 15 and 35 million years old , and they occupied European territories during the Miocene. As good cervids, the males have a pair of antlers that they renew every year.
They are animals of a relatively small size, especially for cervids; most species are around half a meter tall, no more than 1.30 long, and adults weigh between 10 and 20 kilos.
Like all cervids, they are herbivores; they graze on herbaceous plants and browse bushes, although they can feed on fruits, seeds, mushrooms, and frequently, also on tree bark that they pluck thanks to their fangs. When they have it, they can eat eggs or carrion, a behavior that, although it may seem surprising, is not uncommon among cervids.
These teeth are also used by males during mating matches ; they first lunge at each other with their antlers, and when knocked down, they attack with bites. Sometimes, they cause serious injuries to each other.
A chromosomal oddity
Among the different species of muntíacos a curious oddity occurs, and it is not only that each species has a different number of chromosomes, but, in some cases, the males have one more pair of chromosomes than the females .
For example, the Indian muntjac ( M. muntjac ) is the mammal with the lowest known number of chromosomes: the female has 6 pairs of chromosomes and the male has 7. The black muntjac ( M. crinifons ) or Gongshan’s ( M. gongshanensis ) have 8 pairs for the female and 9 for the male; Fea’s muntiaco ( M. feae ) has 13 pairs the female and 14 the male; while the Chinese muntjac ( M. reevesi ) has, in both males and females, 46 chromosomes.
These peculiarities become even more complex when discovering that the Chinese and Indian muntjacs, the species that have the most and the fewest chromosomes, respectively, can hybridize, resulting in animals with 27 pairs of chromosomes.
This wide variation in the number of chromosomes according to the species has been the source of scientific discussion. The currently most accepted hypothesis indicates that the ancestors of the muntíacos had a high number of chromosomes, and that in the evolutionary process they merged into some species.
The barking of the muntíaco
One of the most striking features of the muntíacos, apart from their fangs, is their particular sound. Their calls are reminiscent of dog barks . The reasons why they emit these peculiar sounds are very varied, in studies up to 13 different vocalizations have been identified. Not only barks —which express alarm or anguish—, but also moans, squeals, bleats, screams, chattering and whistles of different tones, associated above all with social behaviors, such as the mother-child relationship, grooming between equals or submission.
In many species of cervids, it is common for the mother and young to mutually recognize their specific sounds, as well as the meaning of the different calls—for help, alert, etc. In the muntíacos, this repertoire is much more extensive, and may be related to individual recognition, the cohesion of the family unit or of small social groups , in areas where the vegetation is dense and generally higher than the height of the animals, and therefore where visual cues are ineffective.
The Chinese Muntiaco, an invader in Europe
In the 1970s, the presence of Chinese muntjacs ( M. reeves ) was reported for the first time in the British Isles, specifically in the Monks Wood National and Nature Reserve in Cambridgeshire. In 1985, the population was already causing serious damage to the renewal of the area’s vegetation, especially hazel, maple and ash trees. It became an invasive species.
In recent years, the species has made the leap to the continent. To prevent the serious impact it caused in Britain, and its spread throughout Europe, the European Commission included the species on its list of invasive alien species of Union importance .
The Commission recommends the prohibition of the sale of this species , the gradual elimination of zoos and collections as the animals die naturally, avoiding their reproduction, a rapid eradication of any emerging population in the natural environment, and effective management of established populations.
These measures should be sufficient to prevent the species from becoming established and causing further damage to European biodiversity.
References:
Barrette, C. 1977. Fighting Behavior of Muntjac and the Evolution of Antlers. Evolution, 31(1), 169-176. DOI: 10.2307/2407555
European Commission. 2020. Invasive Alien Species for Union Concern. Publications Office of the European Union.
Odden, M. et al. 2007. Predicting spacing behavior and mating systems of solitary cervids: A study of hog deer and Indian muntjac. Zoology, 110(4), 261-270. DOI: 10.1016/j.zool.2007.03.003
Oli, M. K. et al. 1995. Vocalizations of barking deer (Muntiacus muntjak) in Nepal. 59(2), 179-186. DOI: 10.1515/mamm.1995.59.2.179
Wang, W. et al. 2000. Rapid and Parallel Chromosomal Number Reductions in Muntjac Deer Inferred from Mitochondrial DNA Phylogeny. Molecular Biology and Evolution, 17(9), 1326-1333. DOI: 10.1093/oxfordjournals.molbev.a026416
Ward, A. I. et al. 2021. Reeves’ muntjac populations continue to grow and spread across Great Britain and are invading continental Europe. European Journal of Wildlife Research, 67(3), 34. DOI: 10.1007/s10344-021-01478-2
