The planet is undergoing a major loss of biodiversity, driven by a range of threats operating at various scales. Understanding species’ vulnerability to these threats can help inform conservation policy and practice. This thesis combines three approaches to explore the vulnerability of red colobus monkeys (Piliocolobus spp.) to population declines and extinction.

First, I use correlative species distribution modelling to investigate how climate and land use determine current and future red colobus species distributions. I found that predicted loss of suitable habitat in the future varied between species (range -100% to +10%) and differed between models produced using different land use datasets. Generally, the most optimistic future for red colobus was predicted in scenarios with the highest mitigation of climate change and land use change. This highlights the importance of implementing mitigation strategies for these threats for the long-term survival of red colobus.

Second, I determine whether one intrinsic trait, niche breadth, can explain vulnerability to future habitat loss in red colobus. In the four species for which I could conduct this analysis, I found this not to be the case, suggesting that other factors, such as niche position and level of exposure to climate change and land use change, might be more important in determining the vulnerability of red colobus than niche breadth.

Third, I investigate oxidative stress as a potential mechanistic link between anthropogenic disturbance and recruitment in the Zanzibar red colobus (Piliocolobus kirkii) using a non- invasive approach to measure oxidative stress in urine. Given the novelty of measuring urinary oxidative stress in wild animals, I first carry out a methodological investigation. I found that time of day and the time between sample collection and freezing had some effect on oxidative stress measurements but that the collection method (pipetting from leaves vs. plastic catchpole) and the length of long-term storage time did not. This implies that oxidative stress markers are stable enough for application in field studies with consideration of a few methodological constraints. I then investigate the link between two aspects of anthropogenic disturbance (habitat degradation and tourist exposure), and four markers of oxidative stress (malondialdehyde, 8-OHdG, neopterin, total antioxidant capacity) in six groups of Zanzibar red colobus monkeys. I found that colobus experiencing higher levels of habitat degradation had higher antioxidant capacity but showed no difference in any of the other oxidative stress markers. I also found no relationship between tourist exposure and any of the oxidative stress markers. I found no link between any of the oxidative stress markers and the juvenile to adult
female ratio (a proxy of recruitment) of each group. These results suggest that the monkeys experience oxidative stress when exposed to habitat degradation but that they may prevent downstream consequences for reproduction by increasing their antioxidant response.

Overall, in this thesis, I make two substantial contributions. Firstly, I provide a critical examination of some of the methodological approaches for investigating species vulnerability to extinction using correlative and mechanistic methods. Secondly, I demonstrate that, red colobus monkeys have some capacity to cope with small-scale anthropogenic disturbance but large-scale shifts in climate and land use are likely to have detrimental effects on their survival. Conservation action should focus on tackling immediate threats, such as hunting, but should not neglect the importance and urgency of mitigation strategies for climate change and land use change.