Altered food habits? Understanding the feeding preference of free-ranging Grey langurs within an urban settlement

Urbanization affects concurrent human-animal interactions as a result of altered resource availability and land use pattern, which leads to considerable ecological consequences. While some animals have lost their habitat due to urban encroachment, few of them managed to survive within the urban ecosystem by altering their natural behavioural patterns. The feeding repertoire of folivorous colobines, such as grey langur, largely consists of plant parts. However, these free-ranging langurs tend to be attuned to the processed high-calorie food sources to attain maximum benefits within the concrete jungle having insignificant greenery. Therefore, besides understanding their population dynamics, the effective management of these urbanized, free-ranging, non-human primate populations also depends on their altered feeding habits. Here, we have used a field-based experimental setup that allows grey langurs to choose between processed and unprocessed food options, being independent of any inter-specific conflicts over resources due to food scarcity. The multinomial logit model reveals the choice-based decision-making of these free-ranging grey langurs in an urban settlement of West Bengal, India, where they have not only learned to recognize the human-provisioned processed food items as an alternative food source but also shown a keen interest in it. However, such a mismatch between the generalized feeding behaviour of folivorous colobines and their specialized gut physiology reminds us of Liem’s paradox and demands considerable scientific attention. While urbanization imposes tremendous survival challenges to these animals, it also opens up for various alternative options for surviving in close proximity to humans which is reflected in this study, and could guide us for the establishment of a sustainable urban ecosystem in the future.

Methods
Kindly refer to the manuscript titled "Altered food habits? Understanding the feeding preference of free-ranging Grey langurs within an urban settlement" for further details.

城市化通过改变资源可获取性与土地利用格局，影响了同步发生的人与动物交互行为，进而引发显著的生态效应。尽管部分动物因城市扩张侵占而丧失栖息地，但仍有少数物种通过调整自身自然行为模式，得以在城市生态系统中存续。叶食性疣猴科动物（folivorous colobines，如灰叶猴（grey langur））的取食谱主要由植物组织构成。然而，这些自由活动的灰叶猴往往会适应加工过的高能量食物来源，以在绿植稀少的水泥丛林中获取最大化的收益。因此，除了掌握它们的种群动态之外，对这些城市化、自由活动的非人灵长类种群的有效管理，也有赖于其改变后的取食习性。本研究采用野外实验设置，让灰叶猴可在加工与未加工的食物选项间进行选择，该设置排除了因食物短缺引发的种间资源竞争干扰。多项logit模型（multinomial logit model）分析结果显示，在印度西孟加拉邦的一处城市定居点中，这些自由活动的灰叶猴展现出基于选择的决策行为：它们不仅已学会将人类投喂的加工食物视为替代食物来源，还对此表现出浓厚兴趣。然而，叶食性疣猴科动物的泛化取食行为与其特化的肠道生理之间的这种不匹配，让我们联想到利姆悖论（Liem’s paradox），亟需学界给予充分的科学关注。尽管城市化给这些动物带来了巨大的生存挑战，但也为它们在人类周边存续提供了多种替代途径，本研究即印证了这一点，该研究成果或可为未来可持续城市生态系统的构建提供参考。

方法：如需获取更多细节，请参阅题为《改变的取食习性？探究城市定居点内自由活动灰叶猴的取食偏好（Altered food habits? Understanding the feeding preference of free-ranging Grey langurs within an urban settlement）》的手稿。