Portrait of Jessica Haysom

Jessica Haysom

PhD student
Conservation Biology


PhD project: Borneo’s arboreal mammals: diversity and vulnerability to habitat change

Tropical arboreal mammals, except primates, are extremely diverse but critically understudied. Borneo’s non-flying mammal community has over 130 species, from Ranee mice (Haeromys spp.) weighing less than 50g to the island’s largest land predator, the Clouded Leopard (Neofelis diardi). More than half are thought to be at least semi-arboreal, but in practice almost nothing is known about this side of their ecology. Borneo also has one of the highest deforestation rates in the tropics due to logging for timber and clear-felling to meet the world’s increasing demand for palm oil. As a result, much of the island is now a matrix of oil palm plantations interspersed with pockets of logged or primary forest.

While studies have shown that logged and fragmented forests retain a high level of terrestrial biodiversity, the impacts of habitat disturbance on arboreal species are unclear. Logging alters the 3D structure of the forest canopy and fragmentation removes the canopy entirely, therefore it is highly likely that arboreal mammals will be adversely affected. This in turn may have consequences for ecosystem-functioning, as mammals play an important role in crucial processes such as seed predation and dispersal, and predator–prey interactions. 

Jessica’s study will be the first in-depth investigation into the identity and ecology of Borneo’s arboreal mammals and their vulnerability to habitat change. Fieldwork will be based at the Stability of Altered Forest Ecosystems (SAFE) project in Sabah, Malaysian Borneo, with replicated sites in primary rainforest, logged secondary forest and oil palm plantations. Jessica will set live traps, fur traps and camera traps along vertical gradients from ground level to the high canopy across all three habitat types and will also record detailed vegetation characteristics for each site. 

Jessica’s main aims are to: 

  • identify which mammal species use the arboreal space in Borneo’s primary rainforests 
  • discover how community composition changes with habitat disturbance 
  • correlate community diversity with habitat features (eg tree height, tree species, number of branch connections) in order to develop enlightened landscape management policies 
  • optimise arboreal sampling techniques that can be replicated across the tropics to facilitate further research 

With this work she hopes to produce novel insights into the arboreal aspect of rainforest mammal communities which, despite their diversity and functional importance, is currently missing from most tropical studies. 

Jessica Haysom is a member of the Durrell Institute of Conservation and Ecology


Dr Matthew Struebig
Professor Jim Groombridge
Professor Stephen Rossiter (Queen Mary, University of London)


NERC EnvEast Research Scholarship

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