Population dynamics of the Manyara monkey (Cercopithecus mitis manyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania

Christian Kiffner; John Kioko; Thomas M Butynski; Yvonne A de Jong; Dietmar Zinner

doi:10.5194/pb-9-33-2022

Population dynamics of the Manyara monkey (Cercopithecus mitis manyaraensis) and vervet monkey (Chlorocebus pygerythrus) in Lake Manyara National Park, Tanzania

Primate Biol. 2022 Oct 5;9(2):33-43. doi: 10.5194/pb-9-33-2022. eCollection 2022.

Authors

Christian Kiffner^{1

2

3}, John Kioko¹, Thomas M Butynski⁴, Yvonne A de Jong⁴, Dietmar Zinner^{5

6

7}

Affiliations

¹ Center for Wildlife Management Studies, The School for Field Studies, 23601, Karatu, Tanzania.
² Department of Human Behavior, Ecology and Culture, Max Planck Institute for Evolutionary Anthropology, 04103 Leipzig, Germany.
³ Human-Wildlife Conflict & Coexistence in Agricultural Landscapes Group, Leibniz Centre for Agricultural Landscape Research (ZALF), 15374 Müncheberg, Germany.
⁴ Eastern Africa Primate Diversity and Conservation Program, Nanyuki 10400, Kenya.
⁵ Cognitive Ethology Laboratory, German Primate Center, Leibniz Institute for Primate Research, 37077 Göttingen, Germany.
⁶ Department of Primate Cognition, Georg-August-Universität Göttingen, 37083 Göttingen, Germany.
⁷ Leibniz Science Campus Primate Cognition, 37077 Göttingen, Germany.

Abstract

Estimating population densities and their trends over time is essential for understanding primate ecology and for guiding conservation efforts. From 2011 through to 2019, we counted two guenon species during seasonal road transect surveys in Lake Manyara National Park: the Tanzania-endemic Manyara monkey Cercopithecus mitis manyaraensis (International Union for Conservation of Nature and Natural Resources, IUCN, Red List category of "endangered") and the vervet monkey Chlorocebus pygerythrus (Red List category of "least concern"). To account for imperfect detectability, we analysed the data in a line distance sampling framework, fitted species-specific detection functions, and subsequently estimated seasonal densities. To test for seasonal differences and yearly trends in the species-specific density estimates, we fitted generalized additive models. Seasonal point density estimates fluctuated considerably during the 9 years (2011-2019) of our study, ranging from 3 to 29 individuals km $^{- 2}$ for Manyara monkeys and from 19 to 83 individuals km $^{- 2}$ for vervet monkeys. Densities of both taxa did not differ seasonally, and we did not detect marked directional population trends. Our study illustrates the utility and limitations of line distance sampling for long-term primate monitoring. Beyond informing primate ecology and management, our results highlight the conservation importance of Lake Manyara National Park for primate conservation.