Population abundance and age structure of Critically Endangered Long-billed (Gyps indicus) and White-rumped Vultures (Gyps bengalensis) at Breeding Colonies in Mudumalai Tiger Reserve, Southern India

Iranian Journal of Animal Biosystematics

مقالات آماده انتشار، پذیرفته شده، انتشار آنلاین از تاریخ 15 مهر 1404

نوع مقاله: Original Article

شناسه دیجیتال (DOI): 10.22067/ijab.2025.92760.1096

نویسندگان

Manigandan Selvaraj^{* 1}؛ Byju H²

¹Director, Eco Voice Foundation, 5/70, Sivakumar Colony, Masinagudi, The Nilgiri -643223, TamilNadu, India

²Centre of Advanced Study in Marine Biology, Annamalai University, Parangipettai 608502, Tamil Nadu, India. Email- [e-mail]

چکیده

The White-rumped Vulture (Gyps bengalensis, WRV) and Long-billed Vulture (Gyps indicus, LBV) are critically endangered species requiring urgent conservation focus. This study assesses population abundance, age structure, and inter-annual trends of WRV and LBV breeding colonies in Mudumalai Tiger Reserve (MTR) over three breeding seasons (2018–2021). Field surveys were conducted monthlytwice during the breeding season (October–June) across nesting colonies:Anaikatty, Jakalikadavu, and Gudalpatty for WRV, and Ebbanad, Kallampalayam, and Kodanadu for LBV. Standardized direct counts and age classification were used to assess population structure and trends.Results show a decline in WRV populations at Anaikatty and Jakalikadavu, coinciding with the establishment of a new breeding colony at Gudalpatty in 2020–2021, which recorded the highest WRV density (77.1 individuals/visit). This shift suggests a response to habitat disturbances, including increased cattle grazing and anthropogenic activities near Anaikatty and Jakalikadavu. Bayesian mixed effect modelconfirmed significant inter-annual variation in WRV abundance (credible interval range -0.29 to 0.57), indicatingthat environmental factors and habitat suitability influence breeding site selection.In contrast, LBV populations remained stable across sites and years, with the highest abundance at Kallampalayam, likely due to minimal human disturbance. Age structure analysis showed adult WRVs comprised 50–70% of the population, with a notable decline in adults at Anaikatty from 2019–2020 to 2020–2021, potentially due to reduced survival or emigration. The highest proportion of chicks in 2020–2021 suggests reproductive compensation.LBV incubation periods varied with elevation and sunlight exposure, with Kallampalayam initiating incubation earliest. The findings highlight the importance of long-term monitoring and site-specific conservation measures to mitigate anthropogenic threats and support vulture recovery. Protecting emerging colonies such as Gudalpatty, alongside habitat restoration and disturbance management at established sites, is critical for sustaining WRV and LBV populations in MTR. These insights contributeto targeted conservation strategies for vultures in southern India.

کلیدواژه‌ها

Age؛ breeding colonies؛ critically endangered؛ Gyps؛ population trend؛ population decline