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This study evaluates the hypothesis that some documented cases of long-distance sea crossing by the Late Pleistocene Homo sapiens occurred as a result of accidental drifting, rather than by intentional seafaring. For that purpose, we use an existing computer simulation framework, with some modifications, to investigate the likelihood that a planned or unplanned island colonization by a small group of individuals will persist to establish a viable population. Within the original framework, planned colonization was operationally characterized as being initiated by equal numbers of unrelated young men and women, whereas for unplanned colonization, those who migrate inadvertently were regarded in effect as a random sample of the whole population. Here, we consider a different scenario for unplanned colonization, which we believe is more relevant to sea crossing by the Late Pleistocene humans, that is, we assume that unplanned colonization occurs when members of households on watercrafts with limited voyaging capabilities are drifted away by ocean currents and washed up on a distant island. We also extend the previous analysis by considering a broader range of combinations of fertility and mortality schedules that individuals are assumed to follow. Our simulations suggest the following: (1) colonization of an island by ten or fewer unrelated young men and women can be successful within the feasible range of fertility and mortality levels; (2) in comparison, the likelihood of success for unplanned colonization is considerably smaller for the same range of fertility and mortality levels; and (3) there exists a small range of parameter combinations for which unplanned colonization has a non-negligible prospect of success even without assuming recurrent accidental drifts to the same island, and thus, the accidental colonization scenario cannot be totally excluded. In addition, we find that the minimum founding population required for successful colonization varies substantially depending on the fertility and mortality levels.

Gayal (Bos frontalis) is a semi domesticated and endangered bovine species in Bangladesh. This study was conducted to know the present distribution, performances and utility of gayal in the home tract. Bandarban Hill district was found the home tract of gayal in Bangladesh. Gayals were reared under extensive management system in the forest of Bandarban Hill district. They browsed forest herbs and grass freely in the forest and came to human dwelling for salt licking. Total number of gayal was counted between 800- 900. The average number of gayal per farmer was 5.01. The coat color of adult gayal was black. White stocking was very prominent in adult gayal. The height at wither and weight for adult males ranged from 126 to 136 cm and 490 to 577 kg, respectively. Reproductive efficiency was high and calving interval was 402 days. They exhibited high disease resistant. The PVC (Pack Cell Volume) and hemoglobin value was 33.5±5.71% and 13.43±2.9 g/dl, respectively. Gayal was used only as meat animal. The high growth rate and reproductive efficiency of gayal in the home tract indicates that this species can be utilized economically if proper breeding plan and sound extension service can be adopted.DOI: http://dx.doi.org/10.3329/bjas.v44i1.23147Bang. J. Anim. Sci. 2014. 44 (1): 75-84

アフロ・ユーラシアにおける牧畜を対象にした人間生態学・生態人類学的研究では，これまでウシ，ヒツジ，ヤギ，ラクダ，トナカイなどの群居性の有蹄類に属する哺乳動物を対象にして，家畜と人との相互のかかわり方が把握されてきた。しかし，ブタの牧畜に関しては，国内外をとおして先行研究がまったくみられない。そこで本研究は，バングラデシュの中央部に位置するベンガルデルタにおけるブタを対象にした遊牧の実態を把握することを目的とする。筆者は，2007 年12 月以降現在まで，おのおのは短期間ではあるが9 回にわたりバングラデシュ国内において絶えず移動中のブタの群れを探し求めること，群れのなかのブタの年齢や性別構成を聞き取ることなど，飼育技術や移動形態などの生産に関する直接観察を行った。ここでは，「大規模所有者」（約800 ～1000 頭のブタを所有）に焦点を当てることを通して遊牧の実際が把握される。その結果は，以下のとおりである。 遊牧されるブタは，一部のゴミ捨て場でのブタを除いて，1 年を通してデルタに分布する野生タロを中心とした野生植物に全面的に依存する。とりわけ乾季にはブタは収穫後の農地に入いり，農民にとっては雑草と評価されている植物を掘り起こして根の部分を食べる。収穫後の水田では，稲の収穫の際にこぼれ落ちた米粒が残っており，それが利用される。また，ブタの群れは，常に移動しているのできめ細かい移動の範囲を確定できないが，およそ10 ～ 20 平方km の遊動域を見出すことができる。ブタは，群れの移動と採食のための一時的滞在とを繰り返す。2 時間弱のなかで母豚による授乳の時間が4 回みられた。この授乳活動は，牧夫がそれぞれの子ブタを誘導するのではなくて，子ブタの方が積極的に働きかけて群れのなかで自主的に開始される行動である。さらに，牧夫による群れの管理には音声が使われる。牧夫は生後まもない子ブタを殺すこと，別の母親への子ブタの移出などによって各母ブタへの負担を均等にする努力をしている。同時に，ブタの年齢に応じて群れを変えるなどして群れ全体の管理がなされている。他のブタ飼育者からブタが購入されることなどによっても，ブタの所有頭数が維持される。 以上のように，バングラデシュのブタを対象にした遊牧は，年中群れとともに移動をして自然資源を利用する点，100 ～ 200 頭の単位ごとの群れで分散飼育して多様な環境を季節や微地形に応じてきめ細かく利用する点など，熱帯モンスーンアジアのデルタにおける自然特性に応じた資源利用の形をよく示している。, Previous studies of the interaction between pigs and humans haveemphasized house pigs, which are managed by keepers in sedentary settlements.On the other hand, no ethnological studies have been made ofnomadic native pigs. Therefore, it remains unclear whether these pig groupsare nomadic or semi-nomadic in different study areas. Nobody knows whokeeps these pigs, how they are cared for and controlled, or for what purposethey are being kept. Many anthropological studies of nomadic pastoralismhave been made, with the noteworthy exception of such pigs: a lone study ofpigs in Bangladesh is available in the literature. To investigate the actual conditionsof this type of nomadic pig husbandry, the author conducted ethnologicalfield research during the dry season (December 2007–February 2008) andthe rainy season (July–August, 2008). First, nomadic pig herds were sought inthe Dhaka area, Tangail District, and Gazipur District in the Bengal delta ofBangladesh. The herds were then followed and observed to discover how theyfed and their routes of movement.In Bangladesh, pigs are raised by humans. They are seasonally nomadicwhile their owners seek grazing land and fodder for them. Each herd studiedincluded approximately 100–200 pigs. The herds move over vast areas whileseeking food in cultivated field lands. The movements very according to theseasons, the routes chosen according to food availability. Regarding the dailyroutine of nomadic pig husbandry, pig keepers depart from their camp in themorning and return to it in the evening. While herding their pigs, they diligentlyprevent the pigs from entering cultivated fields. Each herd occupies awide area while seeking food in the open fields. By calling the pigs, the keeperscan reduce the area that the animals occupy: that is to say the pigs payattention to the commands of their handlers.The route of movement of the pigs and the seasonal change of land useare illustrative. Pig groups moved according to the season, depending on theavailability of food resources. During the rainy season (June–September), theyare able to live near flooded rivers. In years with large-scale flooding, theyare reportedly kept in the forest, where they can eat trees roots. During thedry season, they are kept in cultivated fields after harvest. By digging in thesoil, pigs are able to eat some plants that are considered noxious weeds by thefarmers. The pigs can also eat rice grain remaining in paddy fields after harvest.However, when farmers began using a field for wheat and maize, thepigs had to be moved to other areas.The seasonal change in feeding resources was as follows. During thedry season, wild plants such as taro were the most important feeding resourcesupporting nomadic pig husbandry. Crops were also used. During the rainyseason, earthworms were used as fodder. I observed cases of pigs kept in rubbishdisposal areas for a few months near the main road of the city. In thiscase, two keepers made a camp and cared for their pigs. The rubbish site wasconstantly supplied from the city with kitchen refuse, which the pigs werekeen to eat. In February 2008, two handlers were keeping their pigs in thesame refuse area. However, in August 2008, they lost this resource because alocal government office prohibited use of the land as a rubbish dump. No furtherinformation relating to how they cared for their pigs was obtainable afterthat.Nomadic pig pastoralism in Bangladesh depends on the seasonal use ofnatural resources and on less-seasonal kitchen refuse when available. The significanceof this case study, for interactions between pigs and humans in tropicalmonsoon Asia, will be explored further in the near future.

山と森の環境史

環境と歴史学 : 歴史研究の新地平.水島司編.

野生と環境

特集 生き物文化誌学とは何か : 生き物文化誌学会設立5周年記念. 『ビオストーリー』編集委員会編